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Neonatal Gastrointestinal Imaging
NEON AT AL GASTROENTEROLOGY
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NEONATAL GASTROINTESTINAL IMAGING William A. Cumming, MD, and Jonathan L. Williams MD
Imaging, with all its different modalities, is an important and expensive element in the process leading to diagnosis and management of the anomalies and diseases of the neonatal gastrointestinal tract. Conventional radiography, computed tomography (CT), ultrasonography (US), magnetic resonance (MR) imaging, and nuclear medicine all have roles to play. Often, the problem is to decide whether and when to ask for an imaging study and which one to choose. Factors in this decision will include the nature and urgency of the problem, the clinical condition of the patient, the availability of equipment and skilled personnel, the expense in time and money, and sometimes the financial resources of the patient's family. We will review the various gastrointestinal conditions encountered in newborn infants and recommend the efficient use of imaging in each.
ESOPHAGUS Esophageal Atresia and Tracheoesophageal Fistula
The commonest esophageal anomaly is atresia (EA), occurring with or without a tracheoesophageal fistula (TEF) in 2 to 3 infants per 10,000 births. Today, 95% of these children should survive, although prematurity, ventilator dependence, and severe associated anomalies are significant risk factors that affect the outcomes. The diagnosis of EA is made
From the Departments of Radiology and Pediatrics, University of Florida, Gainesville, Florida
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clinically when a tube cannot be passed from the infant's mouth to its stomach. A chest film with a feeding tube secured with its tip as far down the esophagus as it will go provides all the necessary information about the site of the atresia. Very rarely is there a reason or need to add a contrast agent to the proximal esophageal pouch, a practice we discourage because of the real risk of aspiration. If EA is known on clinical grounds and a chest or abdominal film shows air in the stomach and bowel, then there must be a distal TEF. No other imaging of the esophagus is necessary before surgical intervention, but a search should be made for those anomalies in the heart, lungs, kidneys, brain, and skeleton that we know to be associated with EA and TEF. 26 Even chromosomal abnormalities, trisomies 21 and 18, should be considered. 8, 11 US is probably the most efficient way to look at the brain and kidneys, whereas limb and vertebral anomalies will be obvious on conventional radiographs. Surgical repair will usually be carried out early in low-risk infants but may be staged and delayed in those with higher risk. 1 After the EA is repaired, postoperative complications to be watched for are early anastomotic leaks, later anastomotic strictures, and recurrent fistulas at any time. Leaks may cause a pneumothorax, which will be obvious on chest films, or they may only be seen during barium swallow, which is usually done at about 10 days after the operation and before feeding. These leaks usually heal spontaneously but are reason to postpone oral feeding. Anastomotic strictures will obstruct the esophagus, interfere with swallowing, and may cause aspiration of milk or formula. They require dilatation to ensure satisfactory esophageal function. Recurrent TEFs, occurring in 3% to 7% of patients, cause chronic aspiration and pneumonia.11 They will not heal without surgical intervention. TEFs connecting the proximal esophageal pouch to the trachea are uncommon, occurring in about 4% of all EA and TEF patients. They are almost never diagnosed preoperatively, but they are usually found and closed at operation. Occasionally one is missed and is discovered postoperatively by barium examination (Fig. 1). It is important to remember that all patients with repaired EA and TEF can have recurrent TEFs or missed proximal TEFs that will be diagnosed with barium studies and will require additional surgery. Tracheomalacia almost always coexists with EA and TEF, although, interestingly, it does not accompany EA without TEF. 21 It allows tracheal collapse and luminal narrowing that can be seen at fluoroscopy, on CT, or on lateral chest films. The trachea, soft and lacking adequate resilience, collapses on expiration, obstructs the airway, and may cause apnea. There is some controversy over the need for surgical aortopexy to maintain a good tracheal lumen in such cases, but most affected children survive on their own without further operation.7, 12 Although EA with a distal TEF comprises almost 90% of all the EA and TEF cases, the 8% or so of patients with EA without TEF have a unique problem: esophageal segments that are widely separated and not easily brought together for anastomosis. In addition, a significant number of them have Down syndrome. 8 Various procedures have been tried
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Figure 1. Lateral view of a barium-filled esophagus 3 weeks after repair of esophageal atresia shows a fistula from the proximal esophageal pouch to the trachea. Note the tight anastomotic stricture just below the fistula.
to encourage the esophageal segments to grow closer together without much success. Radiologists can estimate the gap between the segments by passing radiopaque tubes or implements from above and below under fluoroscopic control. Repair is usually delayed in the hope that the segments will somehow be attracted to each other, but if they cannot be brought together, esophageal replacement with colon or stomach will be necessary. A long-term problem for some infants with repaired EA is gastroesophageal reflux causing chronic esophagitis and sometimes aspiration of gastric contents. Some of these children eventually require antireflux surgery. All patients with repaired EA will have a characteristic disorder of esophageal motility: absence of contraction on either side of the anastomosis, and absent peristalsis of the distal esophagus. Despite this, swallowing is usually functionally adequate as long as there is not an anastomotic stricture. Antireflux surgery, however, has the potential to interfere with the passage of swallowed food to the stomach in patients with the disordered motility of repaired EA. Other
Malformations
Other uncommon foregut malformations include esophageal duplication cysts, which may become very large mediastinal masses, and
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esophageal bronchi that lead into sequestered pulmonary segments. Barium examinations and CT are effective in diagnosing and managing these anomalies. Congenital esophageal stenosis, also shown with barium, is a rare finding. It may accompany EA or it may be alone, but it will resist dilatation. 31 Aortic Rings
Vascular rings are anomalies of the aortic arch that result in a ring of vessels encircling and obstructing the trachea and esophagus. In some cases the ring is formed by a double aortic arch, one with both right and left arches, whereas others are made up of the aortic arch, a ductus or ligarnenturn arteriosurn, and an anomalous subclavian artery corning off the arch as the last branch rather than the first. The common features of almost all of them are a predominant right-sided aortic arch and an anomalous vessel passing behind the esophagus that can be seen during barium swallow. MR imaging, CT, or aortography are appropriate for defining their anatomy and planning surgical treatrnent. 29 Hiatal Hernia
When part of the stomach passes up through the esophageal hiatus to lie above the diaphragm, a hiatal hernia exists. If filled with air, it may be seen on a chest film, but it will be obvious on a barium swallow. Although often asymptomatic, they may cause reflux and they will usually be repaired surgically. Hiatal hernias often appear in children who have had antireflux surgery. Functional Disorders
Functional disorders of the pharynx and esophagus include dysphagia, laryngotracheal aspiration, and gastroesophageal reflux (GER). Sucking and swallowing in an infant are easily examined with barium and fluoroscopy and can be recorded on videotape for detailed review. Dysphagia may be due to anatomic anomalies of the pharynx or esophagus or to neurologic disorders of the tenth nerve or the brain stern. Aspiration into the larynx and trachea can occur in three different ways: food can pass through a TEF; food can enter the larynx during swallowing; or gastric contents can enter the larynx as a result of GER. Each of these possjbilities must be carefully looked for whenever an infant has chronic or recurrent pulmonary disease. Reflux can be sought and the related anatomy and function of the gastroesophageal junction can be examined with barium, endoscopy, scintigraphy, pH probe, and rnanornetry. Each has its admirers. Unfortunately, all infants reflux some of the time, and it is difficult to select
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those who will benefit from medical or surgical treatment. 4 Life-threatening apneic events or recurrent aspiration pneumonia are usually considered reasons for treatment. Achalasia
Achalasia occasionally occurs in infants and is recognized by absence of peristalsis during barium swallow accompanied by failure of the lower esophageal sphincter to relax when swallowed food arrives. The esophagus of these patients is of normal size, not dilating until later in life. Cricopharyngeal achalasia is a rare cause of dysphagia in the newborn. 25 Fluoroscopy with barium is the most efficient way to study disorders of esophageal motility, and manometry can be used to confirm the diagnosis. 18 STOMACH Gastric
These lie in the wall of the stomach, where they are well shown with CT or US. They are of little clinical importance but are usually removed surgically (Fig. 2).
Figure 2. A CT scan through the upper abdomen shows a cystic mass in the posterior wall of the stomach. This is a gastric duplication cyst.
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Antral and Pyloric Webs
These rare congenital membranes may obstruct gastric emptying and cause vomiting. They are diagnosed with barium studies and, when discovered, are excised.
Gastric Perforation
Spontaneous or iatrogenic perforation of the stomach in newborn infants causes a pneumoperitoneum that is readily shown with conventional abdominal films. Because air in the peritoneum will rise to the highest possible site, it is best shown with a horizontal x-ray beam. The infant can lie on its back or side, and the air will be seen at the highest point in the peritoneal cavity. In the left lateral decubitus position it will be clearly seen lying along the right flank and between the liver and the abdominal wall (Fig. 3). With use of a vertical x-ray beam, a large pneumoperitoneum may be visible as a football-shaped collection on a supine radiograph (Fig. 4), but films taken with a horizontal beam will be much more sensitive to small amounts of air. Whatever the cause, perforation of the stomach is a surgical emergency requiring immediate repair.
Figure 3. Left lateral decubitus film of the abdomen shows a large collection of free peritoneal air outlining the right flank. This is a large pneumoperitoneum that resulted from a spontaneous gastric perforation. The air/fluid level indicates a considerable quantity of peritoneal fluid.
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Figure 4. A vertical beam, supine abdominal film shows a "football-shaped" pneumoperitoneum nearly filling the peritoneal space. The falciform ligament is clearly outlined by air on both sides. This is the same patient seen in figure 3.
Ulcer Disease
Peptic ulcer disease in the newborn occurs more commonly in the stomach than in the duodenum. Symptoms are minimal, but the bleeding may be severe. These ulcers are rarely seen on barium examinations, but they are well shown by endoscopy.
This common gastric outlet obstruction occurs with a frequency of 1 in 500 live term births. Patients usually present between the ages of 3 and 6 weeks and are most often male. The affected infants develop projectile vomiting that does not contain bile. Careful palpation of the right upper abdomen may reveal the olive-shaped mass of the hypertro-
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phied pyloric sphincter. If definitely felt, further diagnostic imaging is not necessary, but most clinicians today rely on US to confirm the diagnosis. If skilled sonography is unavailable, barium will also make the diagnosis. Careful US examination of the gastric outlet will show a relatively hypoechoic, hypertrophic pyloric sphincter. Surgical myotomy is curative. If the US examination of a vomiting infant fails to show pyloric stenosis, then barium examination should probably be undertaken to determine the cause. SMALL BOWEL Duodenal Atresia
Polyhydramnios and a dilated stomach and duodenum found on a prenatal US examination indicate duodenal obstruction due to atresia. After delivery the infant will vomit unless the stomach is kept empty. Vomitus will be bilious if the atresia is distal to the papilla of Vater. A supine abdominal film will show a dilated, air-filled stomach and duodenum ("double bubble") with no air in bowel beyond the duodenum. Barium examination is never necessary. The treatment is surgical. Duodenal Stenosis
Incomplete obstruction by a web or annular pancreas will be shown with barium. The treatment is surgical. Midgut Malrotation and Volvulus
During embryologic development, the midgut migrates out of the abdominal cavity and into the umbilical cord. Here it rotates counterclockwise about 90 degrees. Later it returns to the abdomen, where it rotates another 180 degrees and becomes fixed in the situation that we recognize as normal, with the cecum in the right lower quadrant and the duodenojejunal junction in the left upper quadrant. Any deviation from this normal rotational pattern is considered to be malrotation with an abnormal attachment of the midgut mesentery to the posterior abdominal wall. A short mesenteric attachment permits twisting around the mesenteric axis. When this happens, first the venous drainage is occluded causing edema and mucosal bleeding, and later the arterial supply is cut off and infarction occurs. The bowel lumen at the duodenojejunal junction becomes twisted and obstructed as well. This process can occur rapidly and early surgical intervention is essential. Because most cases of volvulus secondary to malrotation occur in the first days of life, any neonate with bilious vomiting should be carefully examined with volvulus in mind. Plain films of the abdomen are rarely
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helpful in volvulus but should be taken to look for other causes of obstruction and for perforation. The diagnosis depends on identifying the locations of the cecum and the duodenojejunal junction. An air enema usually locates the cecum quickly, and barium in the stomach and duodenum will show a displaced duodenojejunal junction or a "corkscrew" deformity of the twisted bowel (Fig. 5). A US examination of the abdomen of a patient with malrotation may show reversal of the normal relationship of the superior mesenteric artery and vein, but few would rely on this to select patients for emergency surgery. Meconium Peritonitis
During fetal life, bowel perforation from any cause allows spillage of intestinal contents into the peritoneal space. The material can cause peritonitis that results in calcifications, both on the parietal and visceral peritoneum. The calcifications are characteristically sharp, linear, punctuate, or plaque-like. If the processus vaginalis is open, they may be seen in the scrotum. Cystic fibrosis and ileal atresia are the commonest causes of peritoneal calcification, but whatever the cause, peritoneal calcification in the newborn is considered to be evidence of antenatal bowel perforation.
Figure 5. A barium-filled stomach and duodenum shows the "corkscrew" appearance of the twisted duodenojejunal junction in a patient with midgut volvulus.
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Meconium lleus
Small bowel obstruction due to sticky meconium that occludes the lumen completely occurs almost entirely in infants with cystic fibrosis. Abdominal films show air-filled, dilated loops of bowel proximal to the obstruction, sometimes with air I fluid levels. Air mixed with the thick meconium may produce a bubbly pattern in the distal small bowel or right colon. An enema with either barium or water-soluble contrast will show a microcolon containing a plug of meconium, and reflux of contrast into the terminal ileum will show more meconium plugging the lumen there. Perseverance with the enema will usually result in contrast passing around the plug to reach the dilated bowel proximal to the obstruction. When this occurs, the obstructing meconium will usually start to move, the infant will no longer be obstructed, and no further treatment will be necessary. Enemas used to try to clear the terminal ileum of thick meconium are usually hypertonic and water-soluble. Wetting agents or mucolytic drugs have been added to enemas to help clear the meconium. Multiple enemas may be necessary to clear the obstructing meconium, often under fluoroscopic control.
Meckel Diverticulum
A remnant of the embryonic omphalomesenteric duct, this true diverticulum of the ileum is found along the antimesenteric border. It is the most common abnormality of the GI tract but seldom causes symptoms, although inflammation, perforation, intussusception, bowel obstruction, and bleeding are known to occur. The diverticulum may contain ectopic gastric mucosa producing hydrochloric acid to cause a bleeding peptic ulceration of the adjacent ileal mucosa. This is uncommon in newborns but a possible cause of rectal bleeding. A technetium pertechnetate scan will show the gastric mucosal excretion, usually in the right lower quadrant. Very rarely, the omphalomesenteric duct remains patent and connects the umbilicus with the terminal ileum, causing air and intestinal contents to leak from the umbilicus. Water-soluble contrast material can be injected into the sinus at the umbilicus to demonstrate the connection to the ileum.
Pneumoperitoneum
As already discussed under gastric perforation, pneumoperitoneum can be due to any bowel or stomach perforation. Small bowel perforations in infants are usually of unknown cause, but they require diagnosis with horizontal beam x-rays, as well as prompt surgical treatment.
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and lleal Stenosis and Atresia
Small bowel atresia in the neonate is thought to be the result of focal ischemia during intrauterine life. The affected neonate will have the signs and symptoms of a complete small bowel obstruction. Plain films will show dilated, air-filled bowel that cannot be identified with certainty as large or small, but the more distal the atresia, the more loops of dilated bowel will be present (Fig. 6). The differential diagnosis at this point will usually include ileal atresia, meconium ileus, meconium plug syndrome, and Hirschsprung disease. An enema with water-soluble contrast will help sort out the diagnosis. If it shows a microcolon containing little or no meconium and the contrast stops abruptly in the terminal ileum, then atresia is the diagnosis. On the other hand, if it shows a microcolon with meconium plugging the terminal ileum, then the patient has meconium ileus, probably due to cystic fibrosis. If the colon caliber is near normal and it contains a long plug of meconium, then it is either Hirschsprung disease or meconium plug syndrome. Stenosis of small bowel is much less common than atresia and is usually
Figure 6. Supine film of an infant with a distended abdomen shows many loops of dilated, air-filled bowel with no air in the rectum. The differential diagnosis includes ilea/ atresia, meconium i/eus, Hirschsprung disease, and meconium plug syndrome. An enema with water-soluble contrast showed a meconium plug that was promptly evacuated to allow a diagnosis of meconium plug syndrome.
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not diagnosed until later, when it causes chronic incomplete bowel obstruction. Small Bowel Duplications
These can occur anywhere along the length of the small bowel, from duodenum to ileum. If they are open and communicate with the lumen of the bowel, they will be collapsed and empty. If they are closed and do not communicate, they will be cystic masses. US or CT will detect closed cystic duplications, but open duplications tend to be invisible. Some open duplications contain ectopic gastric mucosa and can cause bleeding just as a Meckel diverticulum does. These can be shown with scintigraphy. Closed cystic duplications may cause obstruction or act as lead points of an intussusception. COLON
lmperforate Anus
Anorectal atresia, often called imperforate anus (IA), is a relatively common anomaly, although atresia elsewhere in the colon is very rare. IA occurs more often in males than in females and is often associated with other anomalies. Those that are generally well known are the same ones associated with EA and TEF, whereas others, perhaps less well known, include cryptorchidism, spinal dysraphism, single umbilical artery, cloacal exstrophy, omphalocele, and sacral agenesis. 2 Imaging is not necessary to diagnose IA, but it is important in defining the anatomy, detecting associated anomalies, diagnosing complications, and planning treatment. Soon after noting that an infant has IA, US should be used to look at the abdomen for renal abnormalities, and the lumbar spinal canal for dysraphism. It may also be helpful to examine the head for hydrocephalus or hemorrhage. Chest and abdominal films will show the heart size and shape, vertebral and sacral anomalies, and calcification of bowel or peritoneum. 27, 28 As soon as possible and prior to surgical treatment, a decision must be made as to the height of the atresia, because this decides the surgical management. High anorectal atresias are those that have a rectal pouch lying above the puborectalis muscle, whereas low atresias have rectal pouches that come through the muscle to lie close to the skin of the anal dimple. High atresias will usually be managed in stages by an early colostomy and late formal repair, whereas low atresias get an early and definitive anoplasty. Therefore, to separate the "highs" from the "lows," it has been considered important to estimate the gap between the rectum and the anal dimple by some sort of imaging. It is no longer appropriate to take radiographs of upside-down infants, because that method was notoriously inaccurate. US has been advocated and can be quite effective,
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but we have seen some serious errors that have led to inappropriate treatment. Therefore, we do not recommend reliance on US to make the differentiation between high and low atresia, although we sometimes use it to confirm our clinical impression. The general rule is that the rectal pouch, as measured by US, should be 1 cm or more from the anal dimple in patients with high atresia, and less than 1 cm in those with low. Both CT and MR imaging have been used to examine infants with IA to look at pelvic muscles, particularly the levator sling and the external anal sphincter. Although both methods produce excellent images and may accurately identify the pelvic muscles, their use is rarely necessary. Careful clinical examination of the perineum is usually all that is required. Female infants with low atresia will have rectocutaneous fistulas to the skin between the vaginal introitus and the anal dimple. These fistulas are usually capable of passing meconium and can function as ectopic anuses until repair is carried out later. Males with low atresias will have very small rectocutaneous fistulas opening to the midline of the perineum, anterior to the anal dimple, sometimes as far forward as the scrotum or even the underside of the penis. These fistulas are rarely able to pass more than a few drops of meconium, and they cannot function as ectopic anuses. When present, dark meconium in the fistula makes it easily visible, but sometimes only pearly squamous debris is present, making them more difficult to identify. The presence of a cutaneous fistula is proof that the atresia is low, and no further imaging examinations are necessary to make this determination. Absence, on the other hand, is presumptive evidence of a high atresia. In females with high atresia there will usually be a rectovaginal fistula with passage of meconium into the vagina. Males with high atresias will have rectourethral or occasionally rectovesical fistulas that can be shown with conventional cystourethrography (Fig. 7). A small number of atresias are considered to be of intermediate height, but they are treated like the highs. A few infants with IA do not seem to have patent fistulas to skin or to the genitourinary tract, but they are exceptional. It may be that their fistulas have not been adequately looked for, because we know that extra effort may show fistulas not seen on conventional examinations. 13
Hirschsprung disease is a congenital disorder of unknown etiology, characterized by absent ganglion cells in the myenteric plexus of the distal bowel. It affects boys four times as often as girls. 20 It has a poorly defined familial occurrence, an occasional association with trisomy 21, and also with Ondine's curse (central congenital hypoventilation). 9 • 23 • 24 The result of the anomaly is absence of peristalsis of the affected distal bowel and consequent functional obstruction. The length of the aganglionic segment is variable, ranging from a short segment of rectum adjacent to the anal canal to a long segment involving the entire colon and distal
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Figure 7. A voiding cystourethrogram shows contrast passing from the urethra to the rectum through a rectourethral fistula in a newborn boy with imperforate anus. This is evidence of a high anorectal atresia.
ileum. Affected infants do not have a normal meconium stool in the first days of life. They become distended, may vomit, and sometimes may become acutely ill when enterocolitis occurs. Diagnosis is almost always made by barium enema and rectal biopsy, although manometry of the internal sphincter is sometimes helpful. Today most cases are diagnosed soon after birth, with only a few remaining undiagnosed for months or years. Plain films of the abdomen will show distended loops of air-filled bowel but, typically, no air in the rectum (see Fig. 6). Barium enema in the infant will show a distal aganglionic segment that is of normal caliber, perhaps containing a meconium plug. The bowel proximal to this segment will not be dilated as it would be in an older child. The infant will not evacuate the enema normally, and barium may persist in the colon for days. Any suspicion of Hirschsprung disease should lead to biopsy of rectal mucosa for definitive diagnosis. Enterocolitis can complicate this disease before or after surgery and can be lethal. It is characterized by abdominal distension and bloody diarrhea and is often caused by Clostridium difficile. Diagnosis can be assisted by a supine abdominal radiograph showing absence of gas in the rectum despite gaseous distension of the rest of the colon (intestinal cutoff sign). An uncommon but important complication of this disease is appendicitis in the newborn, and this association should be remembered whenever neonatal appendicitis is suspected. 3 Surgery is the treatment of Hirschsprung disease and may consist of staged operations or early definitive repair using one of several techniques. 6
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Meconi um
This is probably the same condition as small left colon syndrome or immature colon, although these may be other poorly defined disorders of colonic motility that occur sporadically. MPS typically presents in a newborn who fails to pass a meconium stool for a day or two and who begins to get distended. Suspecting Hirschsprung disease or meconium ileus, a clinician requests an enema. Plain films may be helpful but will not be diagnostic in differentiating MPS, Hirschsprung disease, ileal atresia, and meconium ileus 14 (see Fig. 6). For the enema, water-soluble contrast such as that used for cystography is usually selected in preference to barium. In a patient with MPS, the enema shows a slightly narrow left colon containing a long column of meconium and results in the evacuation of a long, snake-like black meconium plug. The infant usually has normal stools thereafter, and no further examinations are necessary. Unfortunately, there is some overlap with Hirschsprung disease, and a few infants pass only a small amount of meconium immediately after the enema but have normal stools later. Any uncertainty about the diagnosis should result in a rectal mucosal biopsy.
Contrast Media
Diagnostic enemas given to newborn infants are an important tool in the identification of atresias, malrotation and volvulus, Hirschsprung disease, meconium ileus, and meconium plug syndrome. The contrast medium used can be air, barium mixture, or an aqueous solution of various ionic iodine-containing salts. Air is usually an effective contrast agent for enemas when looking for malrotation or intussusception, because it allows localization of the cecum without leaving a lot of opaque medium to spoil any further examination of the upper gastrointestinal tract. Meglumine iothalamate or diatrizoate solutions in a concentration of about 17% such as those used for cystography are readily available and often chosen for enemas if there is a risk of perforation or the possibility of meconium ileus. Although they are somewhat hypertonic as compared with body fluids, they are safer than the very hypertonic solutions recommended by others. Hypertonicity is thought to facilitate loosening of meconium plugs by osmotically drawing water into the bowel lumen. Whether this is true or not, the solutions are certainly effective in clinical practice and are readily available and conveniently packaged for use. An inverted bottle hung from an intravenous stand, a length of intravenous tubing, and an 8 Fr feeding tube as an enema tip represent all the equipment necessary. Occasionally a bowel perforation will become apparent during an enema, and the contrast medium will flow into the peritoneum. Air is nontoxic and will be quickly absorbed. Water-soluble contrast will be absorbed promptly but may cause some fluid balance problems because of hypertonicity. These must be antici-
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pated and treated. Barium will cause peritonitis and will remain in the peritoneum for years. It should not be used if perforation is likely. Necrotizing Enterocolitis (NEC)
This may affect any part of the colon or small bowel, but it seems to occur most often in the region of the cecum and ascending colon. Although the etiology is obscure and probably multifactorial, many associations have been described including prematurity, congenital heart disease, and oral feeding. Most patients with NEC are premature, although many are full term. The term infants tend to get NEC earlier, at about 5 days on average, than do the premature infants, who get it at an average of about 2 weeks. 15 Clinically, the diagnosis is suspected when the abdomen becomes distended, gastric residuals increase, and there is red rectal bleeding. Radiologic diagnosis is suspected when loops of bowel become dilated, and confirmed when intramural gas is seen. Intramural gas can enter the portal venous system where it is easily seen with US, and often it is visible in the liver on conventional abdominal films. Although this portal gas is evidence of serious NEC, it does not seem to be particularly ominous in practice. The serious complication of NEC is perforation, which will usually lead to emergency surgery. Left lateral decubitus views of the abdomen taken with a horizontal beam will show free intraperitoneal air, which is diagnostic of bowel perforation. Most radiologists are unwilling to do barium enemas on infants suspected of having NEC because of the risk of perforation and leakage of barium into the peritoneum. The late complication of NEC is stricture, which can be shown by barium enema or follow through weeks or months after the acute disease. LIVER
Cholestasis
Jaundice in the newborn is usually a medical problem not requiring any imaging procedures, but the importance of early treatment of biliary atresia makes it important to identify those patients who will require surgery. 10 Contemporary practice consists of relatively early examinations with hepatobiliary scintigraphy, US, and liver biopsy. These three will usually provide information sufficient to select patients requiring surgical intervention. At operation, examination and intraoperative cholangiography will determine the treatment. US has limited usefulness in diagnosing biliary atresia, although it is superb in detecting dilated common bile ducts and choledochal cysts. It easily determines the presence or absence of a gallbladder, but this information is not helpful in separating surgical from nonsurgical causes of jaundice. The most important imaging study is probably hepatobiliary scintigraphy to deter-
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mine whether or not bile reaches the intestine. This nuclear medicine examination should not be undertaken prior to 6 weeks of age because of frequent false positives earlier. Failure of the agent to reach the intestine in 24 hours is usually enough evidence of biliary obstruction to warrant surgery, although a few cases of hepatitis and occasional cases of cystic fibrosis may be included. 5 Portal Vein Thrombosis
An uncommon complication of umbilical venous catheterization, portal vein thrombosis can be determined by Doppler study of portal venous blood flow. There is a report of successful treatment by infusion of streptokinase through the catheter, which was left in position. 19 Unfortunately, most portal thrombosis is probably not recognized at the time, but inferred only in retrospect when the complications of portal hypertension lead to a diagnosis of cavernous transformation of the portal vein. Any suspicion of thrombosis related to an umbilical venous catheter should lead to a Doppler examination so that thrombolytic therapy can be initiated. Tumors
Congenital hemangiomas or hemangioendotheliomas of the liver are large, vascular, benign tumors that can have devastating consequences: arteriovenous shunting sufficient to cause heart failure, hepatomegaly making breathing impossible, and platelet consumption that can lead to lethal hemorrhage or prevent life-saving surgical intervention. Biopsy is generally considered to be dangerous because of the vascular nature of the tumor and the usual thrombocytopenia. If no complications intervene, these tumors tend to resolve spontaneously, but when they become life-threatening, treatment must be undertaken. Embolization, radiation, resection, cyclophosphamide, and steroids have all been tried and results have been mixed. 16• 17• 22 Diagnosis of a neonatal liver tumor with US or CT is usually not difficult, but they all tend to look alike (Figs. 8 and 9). If US, Doppler, laboratory, and clinical examinations exclude a hemangioma, then biopsy can be carried out to determine malignancy. Hepatoblastomas are malignant liver tumors occasionally presenting in the newborn period. They are usually large and solid, seen easily with US or CT, but often are confused with other liver tumors. 30 They may contain some areas of necrosis and some calcification, particularly after chemotherapy. Treatment is surgical resection, sometimes only possible after reduction of tumor size by chemotherapy. Mesenchymal hamartomas are benign liver tumors seen with US or CT. They may be quite large and may be cystic. Treatment is usually surgical resection. A most unusual liver tumor is the metastatic neuroblastoma seen in young infants and known as stage IV special (IVS) because their
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Figure 8. A CT scan through the liver of an infant with cardiomegaly, hepatomegaly, and a bruit heard over the liver. The patient has a large hepatic hemangioendothelioma with multiple small calcifications. Doppler study showed considerable vascularity and blood flow.
Figure 9. A CT scan through the liver of an asymptomatic infant with hepatomegaly shows a large hepatic tumor that was relatively avascular. Biopsy showed it to be a benign mesenchymal hamartoma. Its appearance is identical to that of a hepatoblastoma.
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clinical course is unique. These tumors arise in an adrenal and metastasize to liver, marrow, and skin. The liver is diffusely involved and may become large enough to interfere with breathing. If left alone, these tumors tend to disappear spontaneously. MISCELLANEOUS CONDITIONS
Hernia Most congenital diaphragmatic hernias occur through the foramen of Bochdalek, a persistent pleuroperitoneal canal located posterolaterally in each hemidiaphragm. They are more frequently found on the left than the right. Abdominal contents pass up into the chest, where they compress the developing lung. Fortunately, these hernias can be seen on antenatal US, because these are high-risk babies and it is important to know the diagnosis before they are born. After delivery, plain films will show the abdominal contents lying in the chest. Following surgical repair of the hernia, and replacement of the abdominal contents below the diaphragm, these infants have abnormal midgut rotation, but their clinical problems are more respiratory than gastrointestinal.
During fetal development, the midgut lies, for a time, in the umbilical cord in the extraembryonic coelom. If it fails to return and remains in a dilated cord, the resulting anomaly is known as an omphalocele. There is little imaging to be done in these patients except perhaps to investigate associated anomalies, which are common. Gastroschisis A defect in the anterior abdominal wall above and to the right of the umbilicus allows escape of bowel into the amniotic fluid. The bowel is bare, not covered by skin or peritoneum, and the base of the umbilicus is intact. After surgical repair, these infants often have intestinal obstructions, stenoses, and atresias that require barium examinations, but no imaging is usually necessary in the early days of life. Visceral Situs Abnormalities Mirror image abdominal visceral situs inversus associated with dextroposition of the heart is usually not associated with any gastrointestinal problems, but other abnormalities of abdominal situs are more complicated. When the liver is horizontal or its situs is indeterminate,
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the stomach may be on the right, the left, or in the midline. Affected infants have a high incidence of cardiosplenic abnormalities, either asplenia or polysplenia with complex congenital heart disease, and they often have midgut malrotation. Umbilical Catheters
Umbilical arterial and venous catheterization are essential in neonatal intensive care, and abdominal films are essential in determining the location of these catheters. The umbilicus projects over the fourth lumbar vertebral body in the frontal view of the abdomen. Venous catheters ascend cephalad from the umbilicus, traveling through the umbilical vein to the left portal vein, to the ductus venosus, and to the inferior vena cava. The entire course of an umbilical venous catheter is just to the right of the midline and parallel to it. Misplacements occur when the catheter turns to the right or left in the liver to lie in the right or left portal veins. Introducing the catheter too far may place it in the right atrium, the superior vena cava, through the foramen ovale to the left atrium, or sometimes out into the lung in the left superior pulmonary vein. Umbilical arterial catheters pass down the umbilical arteries to the superior vesical arteries the internal iliac arteries, up to the common iliacs, and to the aorta. Common misplacements of these catheters are into pelvic branches of the internal iliac arteries or occasionally up into the left subclavian artery if introduced too far. Whenever an umbilical catheter is placed, its final position should be determined with plain films. References 1. Alexander F, Johanningman J, Martin LW: Staged repair improves outcome of highrisk premature infants with esophageal atresia and tracheoesophageal fistula. J Pediatr Surg 28:151-154, 1993 2. Appignani BA, Jaramillo D, Barnes PD, et al: Dysraphic myelodysplasias associated with urogenital and anorectal anomalies: Prevalence and types seen with MR imaging. Am J Roentgenol 163:1199-1203, 1994 3. Arliss J, Holgersen LO: Neonatal appendiceal perforation and Hirschsprung's disease. J Pediatr Surg 25:694-695, 1990 4. Bagwell CE: Gastroesophageal reflux in children. Surg Annu 27:133-163, 1995 5. Ben Haim S, Seabold JE, Kao SC, et al: Utility of Tc-99m mebrofen scintigraphy in the assessment of infantile jaundice. Clin Nucl Med 20:153-163, 1995 6. Carcassone M: Hirschsprung's disease: Editorial. Ann Pediatr Paris 38:133-136, 1991 7. Clevenger FW, Othersen HB, Smith CD: Relief of tracheal compression by aortopexy. Ann Thorac Surg 50:524-528, 1990 8. Ein SH, Shandling B, Heiss K: Pure esophageal atresia: Outlook in the 1990s. J Pediatr Surg 28:1147-1150, 1993 9. El Halaby E, Coran AG: Hirschsprung's disease associated with Ondine's Curse: Report of three cases and review of the literature. J Pediatr Surg 29:530-535, 1994 10. Emblem R, Stake G, Monclair T: Progress in the treatment of biliary atresia: A plea for
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12. 13. 14.
15. 16. 17.
18. 19. 20. 21.
22. 23. 24. 25. 26. 27. 28.
29. 30. 31.
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surgical intervention within the first two months of life in infants with persistent cholestasis. Acta Pediatr 82:971-974, 1993 Engum SA, Grosfeld JL, West KW, et al: Analysis of the morbidity and mortality in 227 cases of esophageal atresia and/ or tracheoesophageal fistula over two decades. Arch Surg 130:502-508, 1995 Filler RM, Messineo A, Vinograd I: Severe tracheomalacia associated with esophageal atresia: Results of surgical treatment. J Pediatr Surg 27:1136-1140, 1992 Gross GW, Wolfson PJ, Pena A: Augmented-pressure colostogram in imperforate anus with fistula. Pediatr Radio! 21:560-562, 1991 Hussain SM, Meradji M, Robben SB, et al: Plain film diagnosis in meconium plug syndrome, meconium ileus, and neonatal Hirschsprung's disease. A scoring system. Pediatr Radio! 21:556-559, 1991 Kabeer A, Gunnlaugsson S, Coren C: Neonatal necrotizing enterocolitis. A 12 year review at a county hospital. Dis Colon Rectum 38:866-872, 1995 Manglani M, Chari G, Sharma U, et al: Successful treatment with cyclophosphamide in a large hepatic hemangioendothelioma. Indian Pediatr 31:875-877, 1994 McHugh K, Burrows PE: Infantile hepatic hemangioendotheliomas: Significance of portal venous and systemic collateral arterial supply. J Vase Interv Radio! 3:337-344, 1992 Myers NA, Jolley SG, Taylor R: Achalasia of the cardia in children: A world survey. J Pediatr Surg 29:1375-1379, 1994 Rehan VI<, Cronin CM, Bowman JM: Neonatal portal vein thrombosis successfully treated by regional streptokinase infusion. Eur J Pediatr 153:456-459, 1994 Rescorla FJ, Morrison AM, Engles D, et al: Hirschsprung's disease. Evaluation of mortality and long-term function in 260 cases. Arch Surg 1127:934-941, 1992 Rideout DT, Hayashi AH, Gillis DA, et al: The absence of clinically significant tracheomalacia in patients having esophageal atresia without tracheoesophageal fistula. J Pediatr Surg 26:1303-1305, 1991 Robbins RC, Chin C, Yun KL, et al: Arterial switch and resection of hepatic hemangioendothelioma. Ann Thorne Surg 59:1575-1577, 1995 Russell MB, Russell CA, Fenger K, et al: Familial occurrence of Hirschsprung's disease. Clin Genet 45:23-25, 1994 Russell MB, Russell CA, Niebuhr E: An epidemiological study of Hirschsprung's disease and additional anomalies. Acta Paediatr 83:68-71, 1994 Skinner MA, Shorter NA: Primary neonatal cricopharyngeal achalasia: A case report and review of the literature. J Pediatr Surg 27:1509-1511, 1992 Spitz L, Kiely EM, Morecroft JA, et al: Oesophageal atresia: At-risk groups for the 1990s. J Pediatr Surg 29:723-725, 1994 Stephenson CA, Ball TI, Ricketts RR: An unusual case of meconium peritonitis associated with perforated hydrocolpos. Pediatr Radio! 22:2279-2280, 1992 Taccone A, Marzoli A, Martucciello G, et al: Intraabdominal calcifications in the newborn: An unusual case with anorectal malformation and other anomalies. Pediatr Radio! 22:309-310, 1992 Van Son JA, Julsrud PR, Hagler DJ, et al: Imaging strategies for vascular rings. Aim Thorne Surg 57:604-610, 1994 Von Schweinitz D, Gluer S, Mildenberger H: Liver tumors in neonates and very young infants: Diagnostic pitfalls and therapeutic problems. Eur J Pediatr Surg 5:72-76, 1995 Yeung CK, Spitz L, Brereton RJ, et al: Congenital esophageal stenosis due to tracheobronchial remnants: A rare but important association with esophageal atresia. J Pediatr Surg 27:852-855, 1992
Address reprint requests to William A. Cumming, MD Department of Radiology Shands Hospital Gainesville, FL 32610
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NEONATAL GASTROINTESTINAL IMAGING William A. Cumming, MD, and Jonathan L. Williams MD
Imaging, with all its different modalities, is an important and expensive element in the process leading to diagnosis and management of the anomalies and diseases of the neonatal gastrointestinal tract. Conventional radiography, computed tomography (CT), ultrasonography (US), magnetic resonance (MR) imaging, and nuclear medicine all have roles to play. Often, the problem is to decide whether and when to ask for an imaging study and which one to choose. Factors in this decision will include the nature and urgency of the problem, the clinical condition of the patient, the availability of equipment and skilled personnel, the expense in time and money, and sometimes the financial resources of the patient's family. We will review the various gastrointestinal conditions encountered in newborn infants and recommend the efficient use of imaging in each.
ESOPHAGUS Esophageal Atresia and Tracheoesophageal Fistula
The commonest esophageal anomaly is atresia (EA), occurring with or without a tracheoesophageal fistula (TEF) in 2 to 3 infants per 10,000 births. Today, 95% of these children should survive, although prematurity, ventilator dependence, and severe associated anomalies are significant risk factors that affect the outcomes. The diagnosis of EA is made
From the Departments of Radiology and Pediatrics, University of Florida, Gainesville, Florida
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clinically when a tube cannot be passed from the infant's mouth to its stomach. A chest film with a feeding tube secured with its tip as far down the esophagus as it will go provides all the necessary information about the site of the atresia. Very rarely is there a reason or need to add a contrast agent to the proximal esophageal pouch, a practice we discourage because of the real risk of aspiration. If EA is known on clinical grounds and a chest or abdominal film shows air in the stomach and bowel, then there must be a distal TEF. No other imaging of the esophagus is necessary before surgical intervention, but a search should be made for those anomalies in the heart, lungs, kidneys, brain, and skeleton that we know to be associated with EA and TEF. 26 Even chromosomal abnormalities, trisomies 21 and 18, should be considered. 8, 11 US is probably the most efficient way to look at the brain and kidneys, whereas limb and vertebral anomalies will be obvious on conventional radiographs. Surgical repair will usually be carried out early in low-risk infants but may be staged and delayed in those with higher risk. 1 After the EA is repaired, postoperative complications to be watched for are early anastomotic leaks, later anastomotic strictures, and recurrent fistulas at any time. Leaks may cause a pneumothorax, which will be obvious on chest films, or they may only be seen during barium swallow, which is usually done at about 10 days after the operation and before feeding. These leaks usually heal spontaneously but are reason to postpone oral feeding. Anastomotic strictures will obstruct the esophagus, interfere with swallowing, and may cause aspiration of milk or formula. They require dilatation to ensure satisfactory esophageal function. Recurrent TEFs, occurring in 3% to 7% of patients, cause chronic aspiration and pneumonia.11 They will not heal without surgical intervention. TEFs connecting the proximal esophageal pouch to the trachea are uncommon, occurring in about 4% of all EA and TEF patients. They are almost never diagnosed preoperatively, but they are usually found and closed at operation. Occasionally one is missed and is discovered postoperatively by barium examination (Fig. 1). It is important to remember that all patients with repaired EA and TEF can have recurrent TEFs or missed proximal TEFs that will be diagnosed with barium studies and will require additional surgery. Tracheomalacia almost always coexists with EA and TEF, although, interestingly, it does not accompany EA without TEF. 21 It allows tracheal collapse and luminal narrowing that can be seen at fluoroscopy, on CT, or on lateral chest films. The trachea, soft and lacking adequate resilience, collapses on expiration, obstructs the airway, and may cause apnea. There is some controversy over the need for surgical aortopexy to maintain a good tracheal lumen in such cases, but most affected children survive on their own without further operation.7, 12 Although EA with a distal TEF comprises almost 90% of all the EA and TEF cases, the 8% or so of patients with EA without TEF have a unique problem: esophageal segments that are widely separated and not easily brought together for anastomosis. In addition, a significant number of them have Down syndrome. 8 Various procedures have been tried
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Figure 1. Lateral view of a barium-filled esophagus 3 weeks after repair of esophageal atresia shows a fistula from the proximal esophageal pouch to the trachea. Note the tight anastomotic stricture just below the fistula.
to encourage the esophageal segments to grow closer together without much success. Radiologists can estimate the gap between the segments by passing radiopaque tubes or implements from above and below under fluoroscopic control. Repair is usually delayed in the hope that the segments will somehow be attracted to each other, but if they cannot be brought together, esophageal replacement with colon or stomach will be necessary. A long-term problem for some infants with repaired EA is gastroesophageal reflux causing chronic esophagitis and sometimes aspiration of gastric contents. Some of these children eventually require antireflux surgery. All patients with repaired EA will have a characteristic disorder of esophageal motility: absence of contraction on either side of the anastomosis, and absent peristalsis of the distal esophagus. Despite this, swallowing is usually functionally adequate as long as there is not an anastomotic stricture. Antireflux surgery, however, has the potential to interfere with the passage of swallowed food to the stomach in patients with the disordered motility of repaired EA. Other
Malformations
Other uncommon foregut malformations include esophageal duplication cysts, which may become very large mediastinal masses, and
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esophageal bronchi that lead into sequestered pulmonary segments. Barium examinations and CT are effective in diagnosing and managing these anomalies. Congenital esophageal stenosis, also shown with barium, is a rare finding. It may accompany EA or it may be alone, but it will resist dilatation. 31 Aortic Rings
Vascular rings are anomalies of the aortic arch that result in a ring of vessels encircling and obstructing the trachea and esophagus. In some cases the ring is formed by a double aortic arch, one with both right and left arches, whereas others are made up of the aortic arch, a ductus or ligarnenturn arteriosurn, and an anomalous subclavian artery corning off the arch as the last branch rather than the first. The common features of almost all of them are a predominant right-sided aortic arch and an anomalous vessel passing behind the esophagus that can be seen during barium swallow. MR imaging, CT, or aortography are appropriate for defining their anatomy and planning surgical treatrnent. 29 Hiatal Hernia
When part of the stomach passes up through the esophageal hiatus to lie above the diaphragm, a hiatal hernia exists. If filled with air, it may be seen on a chest film, but it will be obvious on a barium swallow. Although often asymptomatic, they may cause reflux and they will usually be repaired surgically. Hiatal hernias often appear in children who have had antireflux surgery. Functional Disorders
Functional disorders of the pharynx and esophagus include dysphagia, laryngotracheal aspiration, and gastroesophageal reflux (GER). Sucking and swallowing in an infant are easily examined with barium and fluoroscopy and can be recorded on videotape for detailed review. Dysphagia may be due to anatomic anomalies of the pharynx or esophagus or to neurologic disorders of the tenth nerve or the brain stern. Aspiration into the larynx and trachea can occur in three different ways: food can pass through a TEF; food can enter the larynx during swallowing; or gastric contents can enter the larynx as a result of GER. Each of these possjbilities must be carefully looked for whenever an infant has chronic or recurrent pulmonary disease. Reflux can be sought and the related anatomy and function of the gastroesophageal junction can be examined with barium, endoscopy, scintigraphy, pH probe, and rnanornetry. Each has its admirers. Unfortunately, all infants reflux some of the time, and it is difficult to select
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those who will benefit from medical or surgical treatment. 4 Life-threatening apneic events or recurrent aspiration pneumonia are usually considered reasons for treatment. Achalasia
Achalasia occasionally occurs in infants and is recognized by absence of peristalsis during barium swallow accompanied by failure of the lower esophageal sphincter to relax when swallowed food arrives. The esophagus of these patients is of normal size, not dilating until later in life. Cricopharyngeal achalasia is a rare cause of dysphagia in the newborn. 25 Fluoroscopy with barium is the most efficient way to study disorders of esophageal motility, and manometry can be used to confirm the diagnosis. 18 STOMACH Gastric
These lie in the wall of the stomach, where they are well shown with CT or US. They are of little clinical importance but are usually removed surgically (Fig. 2).
Figure 2. A CT scan through the upper abdomen shows a cystic mass in the posterior wall of the stomach. This is a gastric duplication cyst.
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Antral and Pyloric Webs
These rare congenital membranes may obstruct gastric emptying and cause vomiting. They are diagnosed with barium studies and, when discovered, are excised.
Gastric Perforation
Spontaneous or iatrogenic perforation of the stomach in newborn infants causes a pneumoperitoneum that is readily shown with conventional abdominal films. Because air in the peritoneum will rise to the highest possible site, it is best shown with a horizontal x-ray beam. The infant can lie on its back or side, and the air will be seen at the highest point in the peritoneal cavity. In the left lateral decubitus position it will be clearly seen lying along the right flank and between the liver and the abdominal wall (Fig. 3). With use of a vertical x-ray beam, a large pneumoperitoneum may be visible as a football-shaped collection on a supine radiograph (Fig. 4), but films taken with a horizontal beam will be much more sensitive to small amounts of air. Whatever the cause, perforation of the stomach is a surgical emergency requiring immediate repair.
Figure 3. Left lateral decubitus film of the abdomen shows a large collection of free peritoneal air outlining the right flank. This is a large pneumoperitoneum that resulted from a spontaneous gastric perforation. The air/fluid level indicates a considerable quantity of peritoneal fluid.
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Figure 4. A vertical beam, supine abdominal film shows a "football-shaped" pneumoperitoneum nearly filling the peritoneal space. The falciform ligament is clearly outlined by air on both sides. This is the same patient seen in figure 3.
Ulcer Disease
Peptic ulcer disease in the newborn occurs more commonly in the stomach than in the duodenum. Symptoms are minimal, but the bleeding may be severe. These ulcers are rarely seen on barium examinations, but they are well shown by endoscopy.
This common gastric outlet obstruction occurs with a frequency of 1 in 500 live term births. Patients usually present between the ages of 3 and 6 weeks and are most often male. The affected infants develop projectile vomiting that does not contain bile. Careful palpation of the right upper abdomen may reveal the olive-shaped mass of the hypertro-
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phied pyloric sphincter. If definitely felt, further diagnostic imaging is not necessary, but most clinicians today rely on US to confirm the diagnosis. If skilled sonography is unavailable, barium will also make the diagnosis. Careful US examination of the gastric outlet will show a relatively hypoechoic, hypertrophic pyloric sphincter. Surgical myotomy is curative. If the US examination of a vomiting infant fails to show pyloric stenosis, then barium examination should probably be undertaken to determine the cause. SMALL BOWEL Duodenal Atresia
Polyhydramnios and a dilated stomach and duodenum found on a prenatal US examination indicate duodenal obstruction due to atresia. After delivery the infant will vomit unless the stomach is kept empty. Vomitus will be bilious if the atresia is distal to the papilla of Vater. A supine abdominal film will show a dilated, air-filled stomach and duodenum ("double bubble") with no air in bowel beyond the duodenum. Barium examination is never necessary. The treatment is surgical. Duodenal Stenosis
Incomplete obstruction by a web or annular pancreas will be shown with barium. The treatment is surgical. Midgut Malrotation and Volvulus
During embryologic development, the midgut migrates out of the abdominal cavity and into the umbilical cord. Here it rotates counterclockwise about 90 degrees. Later it returns to the abdomen, where it rotates another 180 degrees and becomes fixed in the situation that we recognize as normal, with the cecum in the right lower quadrant and the duodenojejunal junction in the left upper quadrant. Any deviation from this normal rotational pattern is considered to be malrotation with an abnormal attachment of the midgut mesentery to the posterior abdominal wall. A short mesenteric attachment permits twisting around the mesenteric axis. When this happens, first the venous drainage is occluded causing edema and mucosal bleeding, and later the arterial supply is cut off and infarction occurs. The bowel lumen at the duodenojejunal junction becomes twisted and obstructed as well. This process can occur rapidly and early surgical intervention is essential. Because most cases of volvulus secondary to malrotation occur in the first days of life, any neonate with bilious vomiting should be carefully examined with volvulus in mind. Plain films of the abdomen are rarely
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helpful in volvulus but should be taken to look for other causes of obstruction and for perforation. The diagnosis depends on identifying the locations of the cecum and the duodenojejunal junction. An air enema usually locates the cecum quickly, and barium in the stomach and duodenum will show a displaced duodenojejunal junction or a "corkscrew" deformity of the twisted bowel (Fig. 5). A US examination of the abdomen of a patient with malrotation may show reversal of the normal relationship of the superior mesenteric artery and vein, but few would rely on this to select patients for emergency surgery. Meconium Peritonitis
During fetal life, bowel perforation from any cause allows spillage of intestinal contents into the peritoneal space. The material can cause peritonitis that results in calcifications, both on the parietal and visceral peritoneum. The calcifications are characteristically sharp, linear, punctuate, or plaque-like. If the processus vaginalis is open, they may be seen in the scrotum. Cystic fibrosis and ileal atresia are the commonest causes of peritoneal calcification, but whatever the cause, peritoneal calcification in the newborn is considered to be evidence of antenatal bowel perforation.
Figure 5. A barium-filled stomach and duodenum shows the "corkscrew" appearance of the twisted duodenojejunal junction in a patient with midgut volvulus.
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Meconium lleus
Small bowel obstruction due to sticky meconium that occludes the lumen completely occurs almost entirely in infants with cystic fibrosis. Abdominal films show air-filled, dilated loops of bowel proximal to the obstruction, sometimes with air I fluid levels. Air mixed with the thick meconium may produce a bubbly pattern in the distal small bowel or right colon. An enema with either barium or water-soluble contrast will show a microcolon containing a plug of meconium, and reflux of contrast into the terminal ileum will show more meconium plugging the lumen there. Perseverance with the enema will usually result in contrast passing around the plug to reach the dilated bowel proximal to the obstruction. When this occurs, the obstructing meconium will usually start to move, the infant will no longer be obstructed, and no further treatment will be necessary. Enemas used to try to clear the terminal ileum of thick meconium are usually hypertonic and water-soluble. Wetting agents or mucolytic drugs have been added to enemas to help clear the meconium. Multiple enemas may be necessary to clear the obstructing meconium, often under fluoroscopic control.
Meckel Diverticulum
A remnant of the embryonic omphalomesenteric duct, this true diverticulum of the ileum is found along the antimesenteric border. It is the most common abnormality of the GI tract but seldom causes symptoms, although inflammation, perforation, intussusception, bowel obstruction, and bleeding are known to occur. The diverticulum may contain ectopic gastric mucosa producing hydrochloric acid to cause a bleeding peptic ulceration of the adjacent ileal mucosa. This is uncommon in newborns but a possible cause of rectal bleeding. A technetium pertechnetate scan will show the gastric mucosal excretion, usually in the right lower quadrant. Very rarely, the omphalomesenteric duct remains patent and connects the umbilicus with the terminal ileum, causing air and intestinal contents to leak from the umbilicus. Water-soluble contrast material can be injected into the sinus at the umbilicus to demonstrate the connection to the ileum.
Pneumoperitoneum
As already discussed under gastric perforation, pneumoperitoneum can be due to any bowel or stomach perforation. Small bowel perforations in infants are usually of unknown cause, but they require diagnosis with horizontal beam x-rays, as well as prompt surgical treatment.
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and lleal Stenosis and Atresia
Small bowel atresia in the neonate is thought to be the result of focal ischemia during intrauterine life. The affected neonate will have the signs and symptoms of a complete small bowel obstruction. Plain films will show dilated, air-filled bowel that cannot be identified with certainty as large or small, but the more distal the atresia, the more loops of dilated bowel will be present (Fig. 6). The differential diagnosis at this point will usually include ileal atresia, meconium ileus, meconium plug syndrome, and Hirschsprung disease. An enema with water-soluble contrast will help sort out the diagnosis. If it shows a microcolon containing little or no meconium and the contrast stops abruptly in the terminal ileum, then atresia is the diagnosis. On the other hand, if it shows a microcolon with meconium plugging the terminal ileum, then the patient has meconium ileus, probably due to cystic fibrosis. If the colon caliber is near normal and it contains a long plug of meconium, then it is either Hirschsprung disease or meconium plug syndrome. Stenosis of small bowel is much less common than atresia and is usually
Figure 6. Supine film of an infant with a distended abdomen shows many loops of dilated, air-filled bowel with no air in the rectum. The differential diagnosis includes ilea/ atresia, meconium i/eus, Hirschsprung disease, and meconium plug syndrome. An enema with water-soluble contrast showed a meconium plug that was promptly evacuated to allow a diagnosis of meconium plug syndrome.
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not diagnosed until later, when it causes chronic incomplete bowel obstruction. Small Bowel Duplications
These can occur anywhere along the length of the small bowel, from duodenum to ileum. If they are open and communicate with the lumen of the bowel, they will be collapsed and empty. If they are closed and do not communicate, they will be cystic masses. US or CT will detect closed cystic duplications, but open duplications tend to be invisible. Some open duplications contain ectopic gastric mucosa and can cause bleeding just as a Meckel diverticulum does. These can be shown with scintigraphy. Closed cystic duplications may cause obstruction or act as lead points of an intussusception. COLON
lmperforate Anus
Anorectal atresia, often called imperforate anus (IA), is a relatively common anomaly, although atresia elsewhere in the colon is very rare. IA occurs more often in males than in females and is often associated with other anomalies. Those that are generally well known are the same ones associated with EA and TEF, whereas others, perhaps less well known, include cryptorchidism, spinal dysraphism, single umbilical artery, cloacal exstrophy, omphalocele, and sacral agenesis. 2 Imaging is not necessary to diagnose IA, but it is important in defining the anatomy, detecting associated anomalies, diagnosing complications, and planning treatment. Soon after noting that an infant has IA, US should be used to look at the abdomen for renal abnormalities, and the lumbar spinal canal for dysraphism. It may also be helpful to examine the head for hydrocephalus or hemorrhage. Chest and abdominal films will show the heart size and shape, vertebral and sacral anomalies, and calcification of bowel or peritoneum. 27, 28 As soon as possible and prior to surgical treatment, a decision must be made as to the height of the atresia, because this decides the surgical management. High anorectal atresias are those that have a rectal pouch lying above the puborectalis muscle, whereas low atresias have rectal pouches that come through the muscle to lie close to the skin of the anal dimple. High atresias will usually be managed in stages by an early colostomy and late formal repair, whereas low atresias get an early and definitive anoplasty. Therefore, to separate the "highs" from the "lows," it has been considered important to estimate the gap between the rectum and the anal dimple by some sort of imaging. It is no longer appropriate to take radiographs of upside-down infants, because that method was notoriously inaccurate. US has been advocated and can be quite effective,
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but we have seen some serious errors that have led to inappropriate treatment. Therefore, we do not recommend reliance on US to make the differentiation between high and low atresia, although we sometimes use it to confirm our clinical impression. The general rule is that the rectal pouch, as measured by US, should be 1 cm or more from the anal dimple in patients with high atresia, and less than 1 cm in those with low. Both CT and MR imaging have been used to examine infants with IA to look at pelvic muscles, particularly the levator sling and the external anal sphincter. Although both methods produce excellent images and may accurately identify the pelvic muscles, their use is rarely necessary. Careful clinical examination of the perineum is usually all that is required. Female infants with low atresia will have rectocutaneous fistulas to the skin between the vaginal introitus and the anal dimple. These fistulas are usually capable of passing meconium and can function as ectopic anuses until repair is carried out later. Males with low atresias will have very small rectocutaneous fistulas opening to the midline of the perineum, anterior to the anal dimple, sometimes as far forward as the scrotum or even the underside of the penis. These fistulas are rarely able to pass more than a few drops of meconium, and they cannot function as ectopic anuses. When present, dark meconium in the fistula makes it easily visible, but sometimes only pearly squamous debris is present, making them more difficult to identify. The presence of a cutaneous fistula is proof that the atresia is low, and no further imaging examinations are necessary to make this determination. Absence, on the other hand, is presumptive evidence of a high atresia. In females with high atresia there will usually be a rectovaginal fistula with passage of meconium into the vagina. Males with high atresias will have rectourethral or occasionally rectovesical fistulas that can be shown with conventional cystourethrography (Fig. 7). A small number of atresias are considered to be of intermediate height, but they are treated like the highs. A few infants with IA do not seem to have patent fistulas to skin or to the genitourinary tract, but they are exceptional. It may be that their fistulas have not been adequately looked for, because we know that extra effort may show fistulas not seen on conventional examinations. 13
Hirschsprung disease is a congenital disorder of unknown etiology, characterized by absent ganglion cells in the myenteric plexus of the distal bowel. It affects boys four times as often as girls. 20 It has a poorly defined familial occurrence, an occasional association with trisomy 21, and also with Ondine's curse (central congenital hypoventilation). 9 • 23 • 24 The result of the anomaly is absence of peristalsis of the affected distal bowel and consequent functional obstruction. The length of the aganglionic segment is variable, ranging from a short segment of rectum adjacent to the anal canal to a long segment involving the entire colon and distal
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Figure 7. A voiding cystourethrogram shows contrast passing from the urethra to the rectum through a rectourethral fistula in a newborn boy with imperforate anus. This is evidence of a high anorectal atresia.
ileum. Affected infants do not have a normal meconium stool in the first days of life. They become distended, may vomit, and sometimes may become acutely ill when enterocolitis occurs. Diagnosis is almost always made by barium enema and rectal biopsy, although manometry of the internal sphincter is sometimes helpful. Today most cases are diagnosed soon after birth, with only a few remaining undiagnosed for months or years. Plain films of the abdomen will show distended loops of air-filled bowel but, typically, no air in the rectum (see Fig. 6). Barium enema in the infant will show a distal aganglionic segment that is of normal caliber, perhaps containing a meconium plug. The bowel proximal to this segment will not be dilated as it would be in an older child. The infant will not evacuate the enema normally, and barium may persist in the colon for days. Any suspicion of Hirschsprung disease should lead to biopsy of rectal mucosa for definitive diagnosis. Enterocolitis can complicate this disease before or after surgery and can be lethal. It is characterized by abdominal distension and bloody diarrhea and is often caused by Clostridium difficile. Diagnosis can be assisted by a supine abdominal radiograph showing absence of gas in the rectum despite gaseous distension of the rest of the colon (intestinal cutoff sign). An uncommon but important complication of this disease is appendicitis in the newborn, and this association should be remembered whenever neonatal appendicitis is suspected. 3 Surgery is the treatment of Hirschsprung disease and may consist of staged operations or early definitive repair using one of several techniques. 6
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Meconi um
This is probably the same condition as small left colon syndrome or immature colon, although these may be other poorly defined disorders of colonic motility that occur sporadically. MPS typically presents in a newborn who fails to pass a meconium stool for a day or two and who begins to get distended. Suspecting Hirschsprung disease or meconium ileus, a clinician requests an enema. Plain films may be helpful but will not be diagnostic in differentiating MPS, Hirschsprung disease, ileal atresia, and meconium ileus 14 (see Fig. 6). For the enema, water-soluble contrast such as that used for cystography is usually selected in preference to barium. In a patient with MPS, the enema shows a slightly narrow left colon containing a long column of meconium and results in the evacuation of a long, snake-like black meconium plug. The infant usually has normal stools thereafter, and no further examinations are necessary. Unfortunately, there is some overlap with Hirschsprung disease, and a few infants pass only a small amount of meconium immediately after the enema but have normal stools later. Any uncertainty about the diagnosis should result in a rectal mucosal biopsy.
Contrast Media
Diagnostic enemas given to newborn infants are an important tool in the identification of atresias, malrotation and volvulus, Hirschsprung disease, meconium ileus, and meconium plug syndrome. The contrast medium used can be air, barium mixture, or an aqueous solution of various ionic iodine-containing salts. Air is usually an effective contrast agent for enemas when looking for malrotation or intussusception, because it allows localization of the cecum without leaving a lot of opaque medium to spoil any further examination of the upper gastrointestinal tract. Meglumine iothalamate or diatrizoate solutions in a concentration of about 17% such as those used for cystography are readily available and often chosen for enemas if there is a risk of perforation or the possibility of meconium ileus. Although they are somewhat hypertonic as compared with body fluids, they are safer than the very hypertonic solutions recommended by others. Hypertonicity is thought to facilitate loosening of meconium plugs by osmotically drawing water into the bowel lumen. Whether this is true or not, the solutions are certainly effective in clinical practice and are readily available and conveniently packaged for use. An inverted bottle hung from an intravenous stand, a length of intravenous tubing, and an 8 Fr feeding tube as an enema tip represent all the equipment necessary. Occasionally a bowel perforation will become apparent during an enema, and the contrast medium will flow into the peritoneum. Air is nontoxic and will be quickly absorbed. Water-soluble contrast will be absorbed promptly but may cause some fluid balance problems because of hypertonicity. These must be antici-
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pated and treated. Barium will cause peritonitis and will remain in the peritoneum for years. It should not be used if perforation is likely. Necrotizing Enterocolitis (NEC)
This may affect any part of the colon or small bowel, but it seems to occur most often in the region of the cecum and ascending colon. Although the etiology is obscure and probably multifactorial, many associations have been described including prematurity, congenital heart disease, and oral feeding. Most patients with NEC are premature, although many are full term. The term infants tend to get NEC earlier, at about 5 days on average, than do the premature infants, who get it at an average of about 2 weeks. 15 Clinically, the diagnosis is suspected when the abdomen becomes distended, gastric residuals increase, and there is red rectal bleeding. Radiologic diagnosis is suspected when loops of bowel become dilated, and confirmed when intramural gas is seen. Intramural gas can enter the portal venous system where it is easily seen with US, and often it is visible in the liver on conventional abdominal films. Although this portal gas is evidence of serious NEC, it does not seem to be particularly ominous in practice. The serious complication of NEC is perforation, which will usually lead to emergency surgery. Left lateral decubitus views of the abdomen taken with a horizontal beam will show free intraperitoneal air, which is diagnostic of bowel perforation. Most radiologists are unwilling to do barium enemas on infants suspected of having NEC because of the risk of perforation and leakage of barium into the peritoneum. The late complication of NEC is stricture, which can be shown by barium enema or follow through weeks or months after the acute disease. LIVER
Cholestasis
Jaundice in the newborn is usually a medical problem not requiring any imaging procedures, but the importance of early treatment of biliary atresia makes it important to identify those patients who will require surgery. 10 Contemporary practice consists of relatively early examinations with hepatobiliary scintigraphy, US, and liver biopsy. These three will usually provide information sufficient to select patients requiring surgical intervention. At operation, examination and intraoperative cholangiography will determine the treatment. US has limited usefulness in diagnosing biliary atresia, although it is superb in detecting dilated common bile ducts and choledochal cysts. It easily determines the presence or absence of a gallbladder, but this information is not helpful in separating surgical from nonsurgical causes of jaundice. The most important imaging study is probably hepatobiliary scintigraphy to deter-
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mine whether or not bile reaches the intestine. This nuclear medicine examination should not be undertaken prior to 6 weeks of age because of frequent false positives earlier. Failure of the agent to reach the intestine in 24 hours is usually enough evidence of biliary obstruction to warrant surgery, although a few cases of hepatitis and occasional cases of cystic fibrosis may be included. 5 Portal Vein Thrombosis
An uncommon complication of umbilical venous catheterization, portal vein thrombosis can be determined by Doppler study of portal venous blood flow. There is a report of successful treatment by infusion of streptokinase through the catheter, which was left in position. 19 Unfortunately, most portal thrombosis is probably not recognized at the time, but inferred only in retrospect when the complications of portal hypertension lead to a diagnosis of cavernous transformation of the portal vein. Any suspicion of thrombosis related to an umbilical venous catheter should lead to a Doppler examination so that thrombolytic therapy can be initiated. Tumors
Congenital hemangiomas or hemangioendotheliomas of the liver are large, vascular, benign tumors that can have devastating consequences: arteriovenous shunting sufficient to cause heart failure, hepatomegaly making breathing impossible, and platelet consumption that can lead to lethal hemorrhage or prevent life-saving surgical intervention. Biopsy is generally considered to be dangerous because of the vascular nature of the tumor and the usual thrombocytopenia. If no complications intervene, these tumors tend to resolve spontaneously, but when they become life-threatening, treatment must be undertaken. Embolization, radiation, resection, cyclophosphamide, and steroids have all been tried and results have been mixed. 16• 17• 22 Diagnosis of a neonatal liver tumor with US or CT is usually not difficult, but they all tend to look alike (Figs. 8 and 9). If US, Doppler, laboratory, and clinical examinations exclude a hemangioma, then biopsy can be carried out to determine malignancy. Hepatoblastomas are malignant liver tumors occasionally presenting in the newborn period. They are usually large and solid, seen easily with US or CT, but often are confused with other liver tumors. 30 They may contain some areas of necrosis and some calcification, particularly after chemotherapy. Treatment is surgical resection, sometimes only possible after reduction of tumor size by chemotherapy. Mesenchymal hamartomas are benign liver tumors seen with US or CT. They may be quite large and may be cystic. Treatment is usually surgical resection. A most unusual liver tumor is the metastatic neuroblastoma seen in young infants and known as stage IV special (IVS) because their
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Figure 8. A CT scan through the liver of an infant with cardiomegaly, hepatomegaly, and a bruit heard over the liver. The patient has a large hepatic hemangioendothelioma with multiple small calcifications. Doppler study showed considerable vascularity and blood flow.
Figure 9. A CT scan through the liver of an asymptomatic infant with hepatomegaly shows a large hepatic tumor that was relatively avascular. Biopsy showed it to be a benign mesenchymal hamartoma. Its appearance is identical to that of a hepatoblastoma.
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clinical course is unique. These tumors arise in an adrenal and metastasize to liver, marrow, and skin. The liver is diffusely involved and may become large enough to interfere with breathing. If left alone, these tumors tend to disappear spontaneously. MISCELLANEOUS CONDITIONS
Hernia Most congenital diaphragmatic hernias occur through the foramen of Bochdalek, a persistent pleuroperitoneal canal located posterolaterally in each hemidiaphragm. They are more frequently found on the left than the right. Abdominal contents pass up into the chest, where they compress the developing lung. Fortunately, these hernias can be seen on antenatal US, because these are high-risk babies and it is important to know the diagnosis before they are born. After delivery, plain films will show the abdominal contents lying in the chest. Following surgical repair of the hernia, and replacement of the abdominal contents below the diaphragm, these infants have abnormal midgut rotation, but their clinical problems are more respiratory than gastrointestinal.
During fetal development, the midgut lies, for a time, in the umbilical cord in the extraembryonic coelom. If it fails to return and remains in a dilated cord, the resulting anomaly is known as an omphalocele. There is little imaging to be done in these patients except perhaps to investigate associated anomalies, which are common. Gastroschisis A defect in the anterior abdominal wall above and to the right of the umbilicus allows escape of bowel into the amniotic fluid. The bowel is bare, not covered by skin or peritoneum, and the base of the umbilicus is intact. After surgical repair, these infants often have intestinal obstructions, stenoses, and atresias that require barium examinations, but no imaging is usually necessary in the early days of life. Visceral Situs Abnormalities Mirror image abdominal visceral situs inversus associated with dextroposition of the heart is usually not associated with any gastrointestinal problems, but other abnormalities of abdominal situs are more complicated. When the liver is horizontal or its situs is indeterminate,
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the stomach may be on the right, the left, or in the midline. Affected infants have a high incidence of cardiosplenic abnormalities, either asplenia or polysplenia with complex congenital heart disease, and they often have midgut malrotation. Umbilical Catheters
Umbilical arterial and venous catheterization are essential in neonatal intensive care, and abdominal films are essential in determining the location of these catheters. The umbilicus projects over the fourth lumbar vertebral body in the frontal view of the abdomen. Venous catheters ascend cephalad from the umbilicus, traveling through the umbilical vein to the left portal vein, to the ductus venosus, and to the inferior vena cava. The entire course of an umbilical venous catheter is just to the right of the midline and parallel to it. Misplacements occur when the catheter turns to the right or left in the liver to lie in the right or left portal veins. Introducing the catheter too far may place it in the right atrium, the superior vena cava, through the foramen ovale to the left atrium, or sometimes out into the lung in the left superior pulmonary vein. Umbilical arterial catheters pass down the umbilical arteries to the superior vesical arteries the internal iliac arteries, up to the common iliacs, and to the aorta. Common misplacements of these catheters are into pelvic branches of the internal iliac arteries or occasionally up into the left subclavian artery if introduced too far. Whenever an umbilical catheter is placed, its final position should be determined with plain films. References 1. Alexander F, Johanningman J, Martin LW: Staged repair improves outcome of highrisk premature infants with esophageal atresia and tracheoesophageal fistula. J Pediatr Surg 28:151-154, 1993 2. Appignani BA, Jaramillo D, Barnes PD, et al: Dysraphic myelodysplasias associated with urogenital and anorectal anomalies: Prevalence and types seen with MR imaging. Am J Roentgenol 163:1199-1203, 1994 3. Arliss J, Holgersen LO: Neonatal appendiceal perforation and Hirschsprung's disease. J Pediatr Surg 25:694-695, 1990 4. Bagwell CE: Gastroesophageal reflux in children. Surg Annu 27:133-163, 1995 5. Ben Haim S, Seabold JE, Kao SC, et al: Utility of Tc-99m mebrofen scintigraphy in the assessment of infantile jaundice. Clin Nucl Med 20:153-163, 1995 6. Carcassone M: Hirschsprung's disease: Editorial. Ann Pediatr Paris 38:133-136, 1991 7. Clevenger FW, Othersen HB, Smith CD: Relief of tracheal compression by aortopexy. Ann Thorac Surg 50:524-528, 1990 8. Ein SH, Shandling B, Heiss K: Pure esophageal atresia: Outlook in the 1990s. J Pediatr Surg 28:1147-1150, 1993 9. El Halaby E, Coran AG: Hirschsprung's disease associated with Ondine's Curse: Report of three cases and review of the literature. J Pediatr Surg 29:530-535, 1994 10. Emblem R, Stake G, Monclair T: Progress in the treatment of biliary atresia: A plea for
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surgical intervention within the first two months of life in infants with persistent cholestasis. Acta Pediatr 82:971-974, 1993 Engum SA, Grosfeld JL, West KW, et al: Analysis of the morbidity and mortality in 227 cases of esophageal atresia and/ or tracheoesophageal fistula over two decades. Arch Surg 130:502-508, 1995 Filler RM, Messineo A, Vinograd I: Severe tracheomalacia associated with esophageal atresia: Results of surgical treatment. J Pediatr Surg 27:1136-1140, 1992 Gross GW, Wolfson PJ, Pena A: Augmented-pressure colostogram in imperforate anus with fistula. Pediatr Radio! 21:560-562, 1991 Hussain SM, Meradji M, Robben SB, et al: Plain film diagnosis in meconium plug syndrome, meconium ileus, and neonatal Hirschsprung's disease. A scoring system. Pediatr Radio! 21:556-559, 1991 Kabeer A, Gunnlaugsson S, Coren C: Neonatal necrotizing enterocolitis. A 12 year review at a county hospital. Dis Colon Rectum 38:866-872, 1995 Manglani M, Chari G, Sharma U, et al: Successful treatment with cyclophosphamide in a large hepatic hemangioendothelioma. Indian Pediatr 31:875-877, 1994 McHugh K, Burrows PE: Infantile hepatic hemangioendotheliomas: Significance of portal venous and systemic collateral arterial supply. J Vase Interv Radio! 3:337-344, 1992 Myers NA, Jolley SG, Taylor R: Achalasia of the cardia in children: A world survey. J Pediatr Surg 29:1375-1379, 1994 Rehan VI<, Cronin CM, Bowman JM: Neonatal portal vein thrombosis successfully treated by regional streptokinase infusion. Eur J Pediatr 153:456-459, 1994 Rescorla FJ, Morrison AM, Engles D, et al: Hirschsprung's disease. Evaluation of mortality and long-term function in 260 cases. Arch Surg 1127:934-941, 1992 Rideout DT, Hayashi AH, Gillis DA, et al: The absence of clinically significant tracheomalacia in patients having esophageal atresia without tracheoesophageal fistula. J Pediatr Surg 26:1303-1305, 1991 Robbins RC, Chin C, Yun KL, et al: Arterial switch and resection of hepatic hemangioendothelioma. Ann Thorne Surg 59:1575-1577, 1995 Russell MB, Russell CA, Fenger K, et al: Familial occurrence of Hirschsprung's disease. Clin Genet 45:23-25, 1994 Russell MB, Russell CA, Niebuhr E: An epidemiological study of Hirschsprung's disease and additional anomalies. Acta Paediatr 83:68-71, 1994 Skinner MA, Shorter NA: Primary neonatal cricopharyngeal achalasia: A case report and review of the literature. J Pediatr Surg 27:1509-1511, 1992 Spitz L, Kiely EM, Morecroft JA, et al: Oesophageal atresia: At-risk groups for the 1990s. J Pediatr Surg 29:723-725, 1994 Stephenson CA, Ball TI, Ricketts RR: An unusual case of meconium peritonitis associated with perforated hydrocolpos. Pediatr Radio! 22:2279-2280, 1992 Taccone A, Marzoli A, Martucciello G, et al: Intraabdominal calcifications in the newborn: An unusual case with anorectal malformation and other anomalies. Pediatr Radio! 22:309-310, 1992 Van Son JA, Julsrud PR, Hagler DJ, et al: Imaging strategies for vascular rings. Aim Thorne Surg 57:604-610, 1994 Von Schweinitz D, Gluer S, Mildenberger H: Liver tumors in neonates and very young infants: Diagnostic pitfalls and therapeutic problems. Eur J Pediatr Surg 5:72-76, 1995 Yeung CK, Spitz L, Brereton RJ, et al: Congenital esophageal stenosis due to tracheobronchial remnants: A rare but important association with esophageal atresia. J Pediatr Surg 27:852-855, 1992
Address reprint requests to William A. Cumming, MD Department of Radiology Shands Hospital Gainesville, FL 32610