Differential Diagnosis of Abdominal Masses in the Neonate

Symposium on The Newborn

Differential Diagnosis of Abdominal Masses in the Neonate Kenneth C. Henderson, MD.,':' and Evan M. Torch, MD.t

Management of an infant with an abdominal mass requires a rational approach to diagnostic evaluation to prevent wasted time, unnecessary trauma to the patient, and needless expense to the family. Evaluation of the mass requires cooperation between the pediatrician, neonatologist, surgeon, and radiologist. In examining the newborn, close attention should be paid to the genetic history of the parents and the clinical condition of the mother. These can often provide clues to diagnosis. Palpation may lead the examining physician to radiologic examination, ultrasound, or radioisotope scanning as indicated for the findings of a particular patient.

RENAL DISEASE

Physical Examination There are several good methods for manually exammmg the abdomen in the newborn. The procedure should call for a general examination and then a more specific palpation of the masses of renal origin. The Schaffer method is perhaps the preferred technique for a general comprehensive examination of the entire abdomen. 41 Palpation, percussion, and auscultation are used to determine whether abdominal distention is due to an excess of air within or outside of the bowel, to excess fluid which might be clear chylous exudate, pus or blood, to an enlarged viscus or viscera, or to the presence of a cystic or solid tumor. By careful palpation the size of the liver is determined, the edge of which is normally palpable just below the right costal margin, and the kidneys whose lower poles can be felt in the flanks. Distended veins over the abdomen are a sign of venous obstruction. Visible gastric or bowel patterns may be considered an almost unimpeacha':'Chief of Pediatrics and Director of Intensive Care Nurseries, Medical Center of Central Georgia, Macon, Georgia; Assistant Professor of Pediatrics, Medical College of Georgia, Augusta, Georgia tResident, Medical College of Georgia, Augusta, Georgia

Pediatric Clinics of North America- Vol. 24, No.3, August 1977

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ble mark of infection, bleeding, or abnormal communication with intraabdominal viscera. Masses of renal origin are spherical, movable, and confined to the flank. 32 Masses of extragenitourinary origin usually extend beyond the midline and are nodular and fixed. Retroperitoneal lesions such as lymphomas and lymphosarcomas are nodular, often in midabdomen, and at times are diffuse or multicentric. In order to locate the kidneys the examiner must use deep bimanual palpation of the abdomen. 44 When palpating the left kidney, the right hand is placed under the left lumbar region while the left hand explores deeply the left flank and up under the costal margin along the spinal column. Museles34 advocates the reversal of this technique for the detection of the right kidney. The normal kidney is situated above the level of the umbilicus. If the lower poles are found closer to the midline than are the upper poles, the possibility of a horseshoe kidney is suggested. The fingers are run lightly over the vertebral column from the level of the umbilicus to that of the xiphoid process. Finally the examiner digitally compresses the abdomen from the sides, raises his hands, and allows the abdominal contents to slip through the fingers. This is helpful in detecting a mobile mass such as a duplication of the intestine or an ovarian cyst.

Laboratory Diagnosis Since the majority of masses in the newborn are of renal origin, the following general description deals specifically with evaluation of the urinary tract; however, these descriptions in general apply to techniques used for a complete abdominal examination. The plain roentgenogram of the abdomen supplies information about the size and position of abdominal organs and can demonstrate abnormal deposits of calcium. The intravenous pyelogram and associated bodygram and nephrotomogram are highly diagnostic tools. Bodygrams and nephrotomograms are made during the early phase of intravenous urographic examination. The pyelographic phase demonstrates the calyceal system. Tomograms may provide clear definition of renal structures. Ultrasonography is a noninvasive method of delineating~he gross anatomy of the kidneys and can be used to verify and clarify\the solid or cystic nature of a renal lesion. Radioactive isotopic scanning is the most accurate procedure for differentiating a renal pseudotumor from a true tumor. The bodygram, made during the early phase of urographic examination, allows differentiation of solid and cystic structures, whereas the nephrotomogram demonstrates renal outline. Together with the pyelogram, they supply more information than any single procedure for evaluating renal masses in the newborn. These enable correct preoperative diagnosis in the majority of patients with multicystic kidney, hydronephrosis, and renal tumor. Unless a mass is considered to originate from the intestinal tract, intravenous pyelography should be the initial contrast study. During the early phase solid structures with normal or increased vascularity appear opaque, whereas cystic structures are radiolucent. This effect can usually differentiate the cystic or hydronephrotic kidney from a solid mass. If necrosis or hemorrhage has occurred in a solid mass, the mass

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may appear lucent on the bodygram. Complications from pyelography are rare. The newborn should be well hydrated. Hypaque or Renografin is used in a dose range of 2.5 to 5 ml per kg. given as bolus injection. Since the concentrating ability of the kidneys may be poor in newborns, it may be advisable to wait five or more days if possible, then to repeat the urographic studies. A prolonged nephrogram lasting many days may be seen in neonates who are dehydrated or oliguric prior to excretory urography. It is postulated the renal tubules are blocked by mucoproteins. The main purpose of cystourethrography is to determine whether reflux occurs. Contrast material is usually introduced into the bladder in a retrograde manner through a catheter. Water-soluble contrast material is used which is hypertonic and may irritate the bladder and cause trabeculations. Ultrasound is a beam of nonionizing energy propagated through tissue as a mechanical pressure wave. It travels through liquids and solids, but cannot pass through air or a vacuum. Sound reflections occur at tissue interfaces and depend on the density and elasticity of the tissue as well as on the angle of incidence of tissue interface to beam. No significant functional or morphologic effects are known to occur in the patient at the energies employed. B-mode ultrasonography can be used to .' form actual images of cross sections of the body and its contents. Bmode is less subject to error than the A-mode technique, and should be used to evaluate abdominal masses in the newborn. Ultrasound may serve to outline the non visualized kidney. Angiography (arteriography, aortography, cavography) is often advocated for detection of Wilms' tumor. The information provided by intravenous urography and ultrasonography is usually ample for diagnosis and preoperative evaluation. In the newborn the incidence of malignancy in Wilms' tumor approaches zero, and arteriography is virtually never indicated. Renal Masses There seems to be little difference of opinion as to which masses are the most common in the neonate. Most studies or articles dealing with intraabdominal masses designate those tumors arising from the kidney the predominant intraabdOIninal masses in the newborn. In one study,32 of 653 patients reviewed, fully 49.5 per cent of their tumors consisted of abdominal masses of genitourinary tract origin, with hydronephrosis representing 40 per cent of tumors (Fig. 1). Obstruction may be due to several sources including aberrant vessels. In fact, Nixon's36 studies showed that in about one-third of cases, aberrant vessels were at least a contributory cause. The aberrant vessels usually pass in front of the pelvic-ureteric junction, most often causing the upper 1 to 2 cm of the ureter to be kinked up against the distended pelvis.52 Intrinsic abnormalities may include congenital stenosis of the same ureteropelvic junction, and functional and organic obstruction resulting from adhesions between the upper pelvis and the ureter. In Melicow and Uson's32 breakdown of the causes of neonatal hydronephrosis, obstrpction of the ureteropelvic junction is represented in 34

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Figure 1. struction.

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Hydronephrosis of the right kidney secondary to ureteropelvic junction ob-

patients, congenital bladder neck obstruction in 12, and ureterocele in 10 (Fig. 2). In most cases, fever, pyuria, flank or lateral abdominal pain, pyuria, and some degree of albuminuria are present. Often repalpation will reveal a mass where none was found originally, if the examiner keeps in mind that in many cases the presenting sign is urinary infection. Pain, always difficult to evaluate, mayor may not present as loin pain, as is so often the case in older children. Transillumination will detect masses representing hydronephrosis in 4 of 5 cases. 32 However, intravenous pyelogram is far more widely used and seems to be the diagnostic tool of choice. Retrograde pyelography or arteriography is rarely indicated. 17 Ordinary roentgenographic findings vary with the cause and severity of hydronephrosis.1 4 Early urograms in severe hydronephrosis show a thin and dilated kidney which is in effect a urine-filled cyst. With slightly less severe hydronephrosis, contrast material within the tubules of the remaining renal parenchyma can be seen outlining the hydronephrotic sac. 28 Ultrasonography, which will likely be the diagnostic tool of the future, is almost 100 per cent accurate in identifying whether suspected cases of hydronephrosis are cystic or solid in nature. Cystic disease of the kidney may be divided into three basic types: type I-dilation of the collecting tubules; type II-nonfunction in part

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of the kidney; and type III-normally functioning tissue intermixed with nonfunctioning cystic areas. Type I consists of that which is often known as a medullary sponge kidney, a nonhereditary disease affecting only the kidney, also called microcystic kidney disease and infantile polycystic disease. There are also numerous congenital cystic malformations which are usually autosomal recessive conditions accompanied by equally characteristic malformations of the intrahepatic biliary tree. It is well to speak of types II and III together, as they are often clinically inseparable. Benign cysts of the kidney in the neonate present either as solitary multilobular or as polycystic cysts; the latter includes both the adult and infantile forms. Haller and Talbert 19 present an excellent review of polycystic kidney disease in the neonate, a hereditary disorder in which both kidneys are diffusely cystic. This form does not have a strong familial incidence and usually presents with hypertension, bilateral kidney enlargement, and progressive insufficiency. Early death is the usual outcome. 38 Intravenous pyelogram usually confirms bilateral involvement with distortion of the renal pelvis. On ultrasonography,14 polycystic kidneys usually present as neither cystic nor solid, but more commonly as complex. Sherwood et al. 44 found no polycystic or multicystic kidney disease by palpation, whereas Stevenson found only t.wo instances of polycystic kidney disease of 468 infants examined. According to Flanagan and Kozah,13 congenital multicystic kidney is the most common intraabdominal mass in the newborn. Multicystic kidney can usually be distinguished from polycystic disease, as emphasized by Spence,48 as multicystic kidney is usually unilateral, whereas polycystic is usually bilateral and has a much more favorable prognosis. Most importantly it is commonly present as a mass in the abdomen, it appears to elicit no pain upon palpation, and it is usually moveable and nontender. On intravenous pyelogram multicystic kidneys appear as functionless with partial or complete atresia or fibrosis of the ureter. Ultrasonography demonstrates uniformly cystic as opposed to solid structure.

Figure 2.

Congenital bladder neck obstruction from posterior urethral valves.

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Abdominal Tumors Neonatal renal neoplasms are rare. They are now believed to be a distinct entity 39 (as opposed to Wilms' tumors of older children), but this is certainly not the majority view. Williams52 regards them as a separate entity and terms them fibrosarcomas. The characteristic Wilms' tumor in infancy presents as a unicentric, encapsulated embryoma arising from mesodermal cell nests within the kidney.19 On palpation the kidney is usually felt to be enlarged and firmer in consistency than normal and is usually readily apparent. Most renal neoplasms of the newborn, however, are not typical Wilms' tumors, but rather are diffuse, nonencapsulated, mesenchymal proliferations which envelop islands of normal renal parenchyma. 39 , 50 These neoplasms have been referred to as hemartomas, leiomyomas, fibromas, and congenital mesoblastic nephromas. According to Waisman and Cooper,50 many of these tumors are included under the designation of Wilms' tumor and are treated as such. The gross appearance of this group of renal neoplasms occurring during the neonatal period is similar to that of a typical leiomyoma with masses occurring at either pole of the kidney, distorting the normal renal configuration and usually compressing the renal pelvis. 50 In a review of the literature, it was shown that 13.4 per cent of 1351 cases of Wilms' tumor reported between 1940 and 1958 were in patients less than one year of age. 5 These patients had a 30 per cent better cure rate compared with all patients with Wilms' tumor.25 Addition of modalities of treatment other than surgical excision results in a significant increase in mortality and side effects.2o Arteriography is not part of the Wilms' study protocol,14 but when it is obtained it is likely to show the vena cava displaced to one side in the venous phase. In the arteriographic phase the renal arteries may be displaced upward and be seen to given off many pathological vessels throughout the tumor. 7 Ultrasonography usually shows a complex pattern (combination of a cystic and solid component) inside the kidney. Ectopic ureters and duplications of the kidneys and ureters should be considered. Whereas the normal ureter inserts into the posterior bladder wall at the superior lateral margin of the trigone, the ectopic ureter inserts more medially and caudally into the bladder, urethra, or genital tract. Usually an ectopic ureter drains the upper portion of a double renal system. In the newborn with a flank mass associated with hematuria and thrombocytopenia, renal vein thrombosis must be suspected. This diagnosis is especially warranted in infants of diabetic mothers. Urologic culture will usually be negative, with azotemia and proteinuria rarely seen. This condition seems to be more common in boys, and the left kidney is involved more frequently than the right. The physician may also note elevated hematocrit values secondary to dehydration. In complete venous obstruction the intravenous pyelogram will not visualize on the affected side. Retrograde pyelograms will fill incompletely if done early in the course of the disease or demonstrate parenchymal extravasation or venous backflow if done later.6 Inferior venacavography can be accomplished with ease and may be helpful in ascertaining the extent of thrombosis. 3 Arteriography is an accurate way of diagnosing vascular

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accident and determining the degree of injury. This is accomplished through the umbilical artery in newborns. Surgical exploration and renal biopsy may be necessary if the results are equivocal.3 Transrenal venography has been suggested as a follow-up tool. 4 Adrenal hemorrhage may present as an abdominal mass in many instances. One or both glands may be enlarged and the architecture of both the cortex and medulla may be totally disrupted. There is a high incidence in infants of either diabetic or hypertensive mothers, but the primary etiologic factor seems to be traumatic delivery and placental hemorrhage. These infants will likely exhibit a sudden collapse with cyanosis, irregular respiration, weakness, subnormal temperature, failure to suck, and a possible flank mass, and infants are usually afebrile. The key factors in suspecting this diagnosis are (1) difficult delivery, (2) limpness and cyanosis, (3) tachycardia, (4) tachy'pnea, and (5) signs of peripheral collapse. The general incidence in postmortem studies of newborns is over 1 per cent. 15 The incidence may actually be much higher if one considers those asymptomatic hemorrhages in the newborn discovered in later life by roentgenographic evidence of calcification of the adrenal gland or adrenal cortical insufficiencyY On x-ray examination calcification may be seen in the mass. Lateral x-rays show a retroperitoneal- mass displacing the stomach and intestines forward. 30 Urography reveals a downwardly displaced kidney with the upper pole tilted laterally and compression of the upper calycesY In differentiating between neuroblastomas and adrenal hemorrhage, both of which may present as suprarenal masses, it is well to remember that adrenal hemorrhage is usually a sudden event. The finding of elevated urinary catecholamines, HVA, or VMA is suggestive of a neuroblastoma. 43

NONRENAL MASSES Neuroblastoma may arise anywhere that deviations of the neural crest ectoderm exist. 26 Accordingly, neuroblastomas may arise in the embryo at any point along the sympathetic chain of ganglia extending from the neck to the pelvis. Histologically, the neoplasm varies from an undifferentiated highly malignant form to a more mature lesion. 19 In a review for the American Academy of Pediatrics comprising a study and report of 217 cases, Gross, Farber, and Martin16 give a comprehensive listing of the characteristics of neuroblastomas. Neuroblastoma is one of four types of tumor (that is, pheochromocytoma, ganglioneuroma, sympathogonioma, and neuroblastoma) which may arise from the sympathetic nervous system of any part of the body. The neuroblastoma is a rapidly growing neoplasm with great infiltrative qualities; blood vessel invasion is common. Occasionally the cells take on an elongated or spindle form producing neurofibrillae and rosettes. The site of primary neuroblastoma in the abdomen may be either adrenal, pelvic, kidney, sacrococcygeal, or, in one-fourth of the cases, the site is unknown. The adrenal gland is the most commonly affected. If the tumor resembles a teratoma or occurs in the sacrococcygeal area, metastasis is not common. 16 Multiple neuroblastomas were encountered

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in 4 of 217 cases. Metastatic spread is usually to blood and bone, but secondary lesions occur in a variety of locations. Distribution of metastasis includes bones, regional lymph nodes, liver, and brain as the predominant acceptor sites. Neuroblastomas share many characteristics with other retroperitoneal tumors. 46 The initial manifestation in one-half the children studied was swelling of the abdomen with a mass palpated in a high percentage of cases. The one characteristic laboratory finding in almost all patients was an abnormal intravenous or retrograde pyelogram. The usual findings were distention or displacement of the kidney, pelvis, or ureter in about 75 per cent of neuroblastomas. Seventy-five per cent of patients had elevated vanillylmandelic acid levels in the urine. 27 Haller and Talbert 19 differentiate neuroblastomas from primary renal neoplasms in that neuroblastomas tend to involve midline structures, have a firm, finely nodular consistency, and are calcified on x-ray examination. Extrinsic compression and displacement of the bladder is often demonstrated with intravenous pyelograms as compared with the characteristic calyceal and pelvic distortion which results from an intrinsic renal tumor. Aortography shows ranges of tumor vascularity and is often instrumental in demonstrating hepatic metastases. The renal outline is usually displaced inferiorly, but remains intact. Angiography, which consists of injecting media in the femoral vein, can provide information such as whether or not renal vein invasion has occurred and whether or not the tumor has crossed the midline and involved contralateral organs. 19 Lymphography seems to be the best tool for demonstrating field size. 7 Sonographic examination may demonstrate a clear cleavage plane between mass and renal outline and echoes seen within the mass indicate the solid nature of this tumor. 40 Teratomas are curious lesions which contain an assemblage of tissues foreign to the part in which they arise. 1 The typical teratoma contains tissues or tissue elements whose embryologic origin can be traced to all three of the germ layers. The degree of malignant potential varies widely. These masses are often situated near the midline and most commonly present as sacrococcygeal growths in newborns. 23 Although teratomas may attain enormous size, they are usually encapsulated and can be separated from adjacent structures. Where these tumors arise from the stomach, it has often been necessary to remove a section of contiguous, involved gastric wall. 19 Teratomas are three times more common in girls than in boys and are often found with a family history of twinning. 52 The tumors, although well encapsulated as a rule, are often vascular and hemorrhage may occur. Large intrapelvic components often cause rectal or urinary tract obstruction. It is important to note that retroperitoneal tumors are still a rather rare entity in the newborn. When they do occur the symptoms are much like those of neuroblastomas and Wilms' tumor due to the size of the mass and its juxtaposition to other important structures. 35 They have a great tendency to displace or distort the urinary system and gastrointestinal viscera. Hydronephrosis from ureteral obstruction is a presenting problem in many patients whose tumors lie in the retroperitoneal space or in the pelvis. Downward displacement of the kidney is common, as the site of the teratoma is often superior and paramedian.

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Gastric teratomas are also rare occurrences, yet their malignant potential requires the physician to consider the entities. Perhaps the most comprehensive review to date is that of Morrison et al.,;);) who describe 39 cases and report that gastric teratomas are a distinctly male phenomenon in contrast to the female predominance in other teratomas. The most frequent single finding was a palpable abdominal mass with location usually being the posterior wall of the lesser curvature. Respiratory embarrassment as a result of abdominal distention is a common finding, as is vomiting and occasional melena. Table 1 may help differentiate abdominal teratomas' from neuroblastomas and Wilms' tumor.33 In using instrumentation to delineate teratomas, whether retroperitoneal or gastric, one finds, especially in x-ray studies, a wide diversity of disease and esoteric landmarks. In retroperitoneal teratomas the presence of bone or teeth is almost pathognomonic.;)5 Scattered ill-defined calcification may be observed, rendering differentiation from neuroblastomas difficult. Neuroblastomas characteristically have punctate calcifications, whereas calcium in teratomas usually is conglomerate. The gastric teratomas also call for extensive radiologic evaluation. Plain films will usually reveal a soft tissue mass. Intravenous pyelograms may be helpful in demonstrating extrarenal origins for the mass and may show nonfunction due to compression on one side or the other. Barium contrast studies often demonstrate gastric deformities, extrinsic pressure on the intestines, or a filling defect of nonspecific type. Since 6 to 10 per cent of retroperitoneal teratomas are already malignant, and any element may undergo malignant changes,35 one would not be remiss in obtaining skull and long bone series. Soft tissue sarcomas are usually of muscle or fibrous tissue origin and tend to be undifferentiated. They may arise from any lymph node or lymphoid tissue; lymph nodes of the retroperitoneal areas are common sites. In contrast to Hodgkin's disease, localized lymphosarcoma is usually not characterized by systemic manifestation. 45 Rhabdomyosarcomas occur with greater frequency than fibrosarcomas, although both types are rare. 22 , 49 Quite often with retroperitoneal sarcomas, it is the site of metastasis which alerts the physician to the possible diagnosis. Prune belly syndrome is found almost exclusively in boys. The principal manifestations are generally hypoplasia of the abdominal muscle, dilation of the urinary system, and undescended testes. Skeletal anomalies, especially of the feet, may be associated. Some patients have Table 1.

VARIABLES

Frequency Peak age Size Calcification Evidence of metastasis

Differentiation of Abdominal Teratomas from Neuroblastomas and Wilms' Tumor TERATOMA

Least common First few months Intermediate Common None

NEUROBLASTOMA

Intermediate 1112 years Smallest Common "flecks" Present early

WILMS' TUMOR

Most common 3 years Largest Rare (10 to 15%) Present later

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Patent urachal cyst.

malrotation of the gastrointestinal tract and urachal cysts (Fig. 3) or diverticula. The prognosis is poor. Chronic renal disease or sepsis causes death ..The urinary tract may also be normal. The pathogenesis is unknown for the syndrome of renal agenesis and pulmonary hypoplasia with characteristic facies in the newborn. Oligohydramnios may be associated with renal anomalies. These newborns usually have respiratory distress from spontaneous pneumomediastinum, pneumothorax, and large palpable kidneys. Hydronephrotic kidneys may be due to ureteropelvic obstruction. These infants may have micro cystic kidney disease. Hepatic tumors in the majority are malignant. Most are malignant parenchymal neoplasms of embryonal deviation, but benign tumors are also common. 8 Malignant primary liver tumors constitute 8 per cent of the cancer fatalities in the first months of life. 12 The primary malignant tumor of this age is the hepatoblastoma. It is usually unicentric in origin and surrounded by pseudocapsule. 19 Often these tumors are seen in conjunction with certain congenital malformations such as hemihypertrophy and extensive hemangiomata. 2 The most frequent presenting sign is asymptomatic abdominal enlargement with poor appetite, failure

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to gain weight, and pallor. Jaundice is rarely seen, but evidence of bleeding in the skin or abdominal cavity may be present because of platelet trapping and secondary thrombocytopenia. 2 There is frequently a disturbance of mineral and lipid metabolism which can lead to demineralization of the skeleton. The only test of value in the laboratory seems to be the alpha-I-fetal globulin. This test, like VMA in determining neuroblastoma, is also valuable in following the course of malignant liver tumors. lla Although benign liver tumors in the newborn are rare,11 the presenting signs and symptoms are similar to those seen in infants with malignant tumors. The presenting benign liver tumor in the newborn is usually the hemangioma. The newborn usually has an upper abdominal mass which mayor may not become symptomatic. The presentation may be that of a distended abdomen which represents shock requiring immediate surgical intervention. The infantile hemagioma is more properly designated as an hemangioendothelioma. Curiously, these lesions are often accompanied by cutaneous hemangiomas. Because of the large capillary bed, they may lead directly to heart failure on a he'modynamic basis35 or they may trap platelets in such numbers that a full blown picture of thrombocytopenic purpura appears. The tumors are usually diffuse throughout the liver. Occasionally, anemia may be I!resent. X-ray films of the abdomen demonstrate an enlarged liver, sometimes with areas of calcification and displacement of abdominal contents. An hepatic angiogram and a liver scan are also important in determining degree of involvement, although liver scans are not always able to differentiate whether or not the tumor is vascular. Needle biopsy is contraindicated. Ultrasonography is also valuable because it demonstrates echo face areas where tumor is present. 1S Thermography can detect even subtle temperature changes, with neoplastic liver tissue emitting more energy than surrounding regions. The major tumor arising from the biliary tract of newborns is the congenital choledochal cyst.42 In the newborn, however, vomiting as a result of partial intestinal obstruction and a palpable mass in the right upper quadrant are more usual. This lesion usually develops as a ballooning of the distal common bile duct and represents a retroperitoneal swelling associated with intermittent jaundice.42 The condition is more common in female infants by a ratio of 3.8 to 1. Differential diagnosis is most complex because symptoms duplicate those found in congenital cystic dilation of the common duct, duodenal duplication, and solid tumors of the liver and retroperitoneum. Plain films of the abdomen and contrast studies of the gastrointestinal tract reveal a radiolucent mass displacing duodenum, colon, and liver.19 Intravenous pyelogram will illustrate a downward displacement of the right kidney, though the kidney is usually normal and is seen through the mass. Ultrasonogram may demonstrate a right anterior cystic mass. In evaluating pelvic masses, sex of the patient becomes important because, as contrasted to the male infant who is more likely to present with urinary tract obstruction and distended bladder, the female can develop a unique pelvic mass as a result of imperforate hymen, vaginal atresia, or ovarian tumor. Any mass that originates between the rectum

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and the displaced bladder in the female infant is most likely to represent hydrometrocolpos resulting from the accumulation of vagin~ and cervical secretions stimulated by maternal estrogen (Fig. 4). When large quantities of this fluid accumulate, cystic tumors of large size may grow within the pelvis and abdomen. 24 Signs of obstructed venous return may then appear, such as edema and bluish discoloration of the legs and lower part of the abdomen, with visible dilatation of the veins and capillary network. Rarely do these tumors produce hydronephrosis or intestinal obstruction secondary to pressure. In addition to outlining the mass through carefully exposed anteroposterior and lateral films of the abdomen after drainage of the bladder, a cystogram will usually show anterior displacement and compression of the bladder, further identifying the nature of the lesion and ruling out obstructive anomalies of the urinary tract.24 The latter is more likely to be encountered with the inherited form of hydrometrocolpos. In addition to voiding difficulties there may be a delay in expelling meconium or frank intestinal obstruction. 19 On rectal examination the little finger is forced posteriorly into the hollow of the sacrum through the hugely distended proximal vagina and uterus. Intravenous pyelogram will verify kidney function as normal. These tests should verify the palpated fixed anterior midline suprapubic mass.

Figure 4.

Hydrometrocolpos.

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Tumors of the ovary are rare in infancy and childhood. These include teratoma, dysgerminoma, lymphosarcoma, granulosa cell tumor and simple cyst of graafian or germinal epithelial origin. Mainolfi29 noted that of 30 ovarian tumors reported in the first 36 days of life, 28 represented simple cysts. Up to 50 per cent of newborn females examined at autopsy possessed cystic ovaries. 29 Marshall also produced statistics to confirm the benign nature of these tumors occurring in the newborn31 and goes on to describe a classic picture of proper therapeutic appraisal, the usual ovarian enlargement in the first year of life presenting as an asymptomatic abdominal mass. Larger masses cause increasing symptoms of poor feeding, pain and vomiting. The ovaries of infant girls are high in the pelvis, close to the general abdominal cavity, and the pedicles are long. Therefore ovarian masses in the newborn are often low-abdominal in location. Rarely, these tumors precipitate an abdominal emergency as a result of traumatic rupture or hemorrhage, or ischemic infarction secondary to a twisting of the pedicle. 19 As in all suspected pelvic masses, bimanual palpation through the rectum should be done, as well as inspection of the perineum to exclude a diagnosis of hydrometrocolpos. An intravenous pyelogram and anteroposterior and lateral abdominal x-rays should be done to rule out urinary tract obstruction.

MASSES OF THE GASTROINTESTINAL TRACT Abdominal distention in the newborn period enters into the differential diagnosis of abdominal masses. Some of the more common causes of abdominal distention are mentioned here for completeness. However, no attempt is made to cover the subject in detail.

Duplication Cysts The most frequent tumors of the gastrointestinal tract in the newborn are cysts. There are a variety of solid neoplasms emphasized by previous studies mentioned in this paper, such as gastric teratomas. Lymphomas, though rare, may present as malignant masses in the gastrointestinal tract, as well as sarcomas which are also rare. Duplication cysts of the gastrointestinal tract can occur anywhere between the mouth and the rectum, but are most commonly associated with the terminal ileum and cecum. 19 They may present clinically as asymptomatic palpable' masses, as gastrointestinal obstruction resulting from intrinsic obstruction of adjacent intestine, or as intestinal bleeding resulting from peptic ulceration from ectopic gastric mucosa. Cystic duplication of the intestine may present with intestinal obstruction, but more often is found as tense, mobile cystic lesions on ballottment of the peritoneal cavity. Unlike tubular duplications, these possess no communication with the intestine proper and gradually swell with their own secretions. They are usually located on the mesenteric side and share a common blood supply with the bowel they subtend.51 Duplication cysts of the colon may be associated with anomalies of the external genitalia. 9 The palpable masses are usually round but some-

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times are tubular, often being mobile. A mobile elongated mass stretching across the abdomen is likely to be a duplication. These masses are usually softer than malignant tumors, with intestinal obstruction being the cardinal symptom.

Volvulus If, during the fifth week of fetal life, the intestine returns improperlyfrom the umbilicus, or rotates abnormally, there is likely to be volvulus. Midgut volvulus presents with mild dilation of the proximal duodenum and with an abrupt partial obstruction at the middle of the third portion. No ligament of Treitz is present and the proximal jejunum is found in the right upper quadrant rather than in the left upper quadrant. The midgut is the portion of the bowel that extends from the distal descending duodenum to the midtransverse colon. It is supplied by the superior mesenteric artery. Under normal circumstances of fetal rotation, there is broad mesenteric fixation from the duodenojejunal junction at the ligament of Treitz in the left upper quadrant down to the region of the iliocecal valve in the right lower quadrant. Neonatal Gastric Perforation Spontaneous perforation of the stomach is occasionally observed in newborns. These perforations characteristically occur within the first week of life causing sudden distress with tachypnea, abdominal distention, and vomiting. Controversy exists regarding the etiology of neonatal gastric perforation. Congenital defects in the gastric musculature, peptic ulceration, and ischemic necrosis secondary to shunting of blood away from the visceral bed are incriminated. Spontaneous pneumoperitoneum in a neonate who does not have necrotizing enterocolitis should suggest the possibility of gastric perforation (Fig. 5).

Duodenal Atresia In duodenal atresia the radiograph of the abdomen demonstrates a moderately dilated stomach and a markedly dilated duodenal bulb, the so-called "double bubble," with no air in the bowel distally (Fig. 6). This pattern is diagnostic of duodenal obstruction in the majority of instances and the introduction of barium may be unnecessary. The obvious clinical stigmata of Down's syndrome may be present. The cause of duodenal atresia may be the failure of normal bowel recanalization. The infants present with bile-stained vomiting during the first 24 hours of life. The zone atresia is usually below the ampulla of Vater. Duodenal stenosis and intraluminal diaphragm may be considered. Angular pancreas presents with the same clinical and radiological findings of duodenal atresia. In this anomaly, arms of pancreatic tissue extend out from the normally positioned head of the pancreas and encircle the second portion of the duodenum. The obstruction may be partial or complete. Intrinsic duodenal stenosis or atresia may accompany the annular pancreas.

DIFFERENTIAL DIAGNOSIS OF ABDOMINAL MASSES

Figure 5.

Gastric perforation.

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Figure 6.

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Duodenal atresia.

Small Bowel Atresia Atresia of the small bowel is now thought to occur secondary to an intrauterine vascular accident rather than abnormal recanalization. The obstruction of the bowel lumen may be by a thin membrane, a narrow strand of fibrotic tissue representing the atretic segment, or there may be an obvious break in continuity with the two blind ends of the bowel being completely separated from one another. Proximal small bowel obstruction with the "triple bubble" pattern analogous to the "double bubble" versus duodenal obstruction may be seen. Distinction between what might be small bowel and what might be colon is exceedingly difficult when the abdominal radiograph shows dilation of multiple loops of bowel. A diagnostic enema may establish the diagnosis. A typical unused microcolon may be seen with ileal atresia (Fig. 7). Pancreatic Cyst Congenital cysts of the pancreas in infants are most common in the body and tail of the pancreas and may attain considerable size. They contain cloudy yellow fluid which is usually sterile on culture and does not demonstrate high enzyme activity.35 A developmental cyst seldom

DIFFERENTIAL DIAGNOSIS OF ABDOMINAL MASSES

Figure 7.

573

Ileal atresia with unused colon.

gives rise to symptoms until it is quite large. As the cyst enlarges it presses through the gastrohepatic or gastrocolic omentum. The stomach is forced upward and anteriorly, while the transverse colon is pushed downward and anteriorly. This is readily demonstrated in barium x-ray studies. 35 Symptoms are due to extrinsic pressure on neighboring organs, but the function of the pancreas is not compromised. Differential diagnosis includes renal or ovarian cysts, intestinal duplication, and retroperitoneal tumors.

Meconium Ileus About 10 per cent of patients with cystic fibrosis present with meconium ileus in the newborn period. The supine abdominal radiograph shows multiple loops of dilated bowel within which can be seen many small bubbles created by the mixing of the thick, tenacious meconium with intestinal gas (Fig. 8). This so-called "soap bubble" appearance is suggestive of meconium ileus. Air fluid levels are seen not infrequently in meconium ileus. Gastrografin enemas may dislodge the

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Figure 8.

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Meconium ileus.

impacted meconium. Meconium peritonitis, which commonly undergoes calcification, may be seen and microcolon may be present. Meconium cyst formation is the result of perforation of the fetal intestine resulting in postnatal intestinal obstruction. Once meconium reaches the peritoneal cavity it produces an intense peritoneal reaction which may be localized with formations of adhesions, fibrosis, and calcifications. lo Occasionally symptoms may be delayed as long as three weeks. Necrotizing Enterocolitis Abdominal distention and diarrhea containing blood may alert us to the pressure of necrotizing enterocolitis in the sick premature or term infant. The plain film of the abdomen demonstrates widespread intramural air which may lead to pneumoperitoneum. Widespread bowel necrosis may be present. This disease is thought to result from bowel ischemia due to shunting of blood away from the gut during periods of

DIFFERENTIAL DIAGNOSIS OF ABDOMINAL MASSES

Figure 9.

575

Aganglionic megacolon.

hypoxia and shock. Air may be seen in the portal venous system. Portal venous gas is usually a transient phenomenon, originating from the intramural air.

'I

i

Low Colonic Obstruction The pattern of disparity in size of bowel loops suggests low colonic obstruction and is an indication for barium enema. It is seen in patients with Hirschsprung's disease, meconium plug syndrome, and neonatal small left colon syndrome. Infants with aganglionic megacolon present in the first two or three days of life with failure to pass meconium, abdominal distention, and vomiting. Barium enema examination shows a narrow irregular, contracted rectum with a sharp zone of transition in the rectosigmoid area (Fig. 9). The colon proximal to this transition is dilated. Rectal biopsy shows no ganglionic cells. Follow-up films at 18 to 24 hours show little evacuation of barium due to ineffective peristalsis (Fig. 10). When no meconium is passed in 48 hours, meconium plug syn-

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drome may be considered. Barium enema may show a large meconium plug present in the rectum, sigmoid, and distal descending colon. The plug may be expelled following barium enema. Hirschsprung's disease must be considered. Repeat symptoms after discharge from the nursery must alert one to further workup. The infant of a diabetic mother who presents with abdominal distention, vomiting, and signs of low colonic obstruction may have neonatal small left colon syndrome. Barium enema examination show!,! colon distal to the splenic flexure to be of small caliber with smooth edges. The precise relationship between this syndrome and maternal diabetes is not known. The colon may eventually become normal in size.

Omental and Vitelline Cysts Omental cysts may cause difficulty in the form of enlarging abdominal masses or are discovered as asymptomatic masses with only a relatively small percentage of patients presenting with acute symptoms. 37 The tumors seem to arise as mesodermal abnormalities of either embryonic or benign neoplastic character, possibly related to the lymphatic system. They are usually multilocular and invade most of the omental apron. Vitelline duct cysts or cysts of the omphalomesenteric duct occur when both the proximal and distal ends of the vitelline duct become obliterated, leaving a middle segment patent. They usually present as

Figure 10. Total aganglionosis.

I,

Ii I

DIFFERENTIAL DIAGNOSIS OF ABDOMINAL MASSES

577

visible palpable masses in the abdomen just beneath the umbilicus tied to the navel. When grasped and moved from side to side or pressed inward, the umbilicus can be seen to pucker in conformity with their movement. 21 They are spherical or ovoid and feel distinctly cystic. Injection of contrast media into an umbilical sinus may identify a communicating vitelline cYSt. 19

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26. Koop, C. E.: Current management of neophroblastoma and neuroblastoma. Am. J. Surg., 107:497-501,1964. 27. Koop, C. E., and Schnaufer, L.: The management of abdominal neuroblastoma. Cancer, 35:905-907, 1975. 28. Lattimer, J. K., Melicow, M. M., and U son, A. C.: Nephroblastoma (Wilms' tumor). J.A.M.A., 171 :2163-2168,1959. 29. Mainolfi, F. G., Standiford, J. W., mid Hubbard, T. B.: Ruptured ovarian cyst in the newborn. J. Pediat. Surg., 3:612-616, 1968. 30. Marin, H. M.: Adrenal hematoma simulating tumor in a newborn. Arch. Surg., 71 :941945, 31. Marshall, J. R.: Ovarian enlargements in the first year of life. Review of 45 cases. Ann. Surg., 161 :372-377, 1965. 32. Melicow, M. M., and Uson, A. C.: Palpable abdominal masses in infants and children. A report based on a review of 653 cases. J. Urol., 81 :705-710. 1»')9. 33. Morrison, L., Snodgrass, P., and Wiseman, H.: Gastric teratoma, Report of a case and a review of the literature. Clin. Pediat., 14:712-718, 1975. 34. Museles, M., Gaudry, C. L., and Bason, M. W.: Renal anomalies in the newborn found by deep palpation. Pediatrics, 47:97-100,1971. 35. Mustard, W. T., Ravitch, M. W., Synder, W. H., Jr., et. al.: Pediatric Surgery. Edition 2. Chicago, Year Book Medical Publishers, Inc., 1969. 36. Nixon, H. H.: Hydronephrosis in children. Brit. J. Surg., 40:601,1953. 37. Oliver, G. A.: The omental cyst: A rare cause of acute abdominal crisis. Surgery, 56: 588-593, 1964. 38. Osanthanonch, V., and Potter, E. L.: Pathogenesis of polycystic kidneys. Arch. Pathol., 77:466. 1964. 39. Richmond, H., and Dougall, A. J.: Neonatal renal tumors. J. Pediat., 5 :413-417, 1970. 40. Rose, J. S., Becker, J. A., Staiano, S. J., et. al.: B-mode sonography of abdominal masses. Am. J. Roentgenol. Radium Ther. Nuc!. Med., 120:691-698, 1974. 41. Schaffer, A. J.: Diseases of the newborn. Edition 2. Philadelphia, W. B. Saunders Co., 1965, p. 481. 42. Scharli, A., and Bettex, M.: Congenital choledochal cyst: reconstruction of the normal anatomy. J. Pediat. Surg., 3:604-607,1968. 43. Schneider, K. M.: Neonatal neuroblastoma. Pediatrics, 36:359-376,1965. 44. Sherwood, D. W., Smith, R. C., Lemmon, R. H., et al.: Abnormalties of the genitourinary tract discovered by palpation of the abdomen of the newborn. Pediatrics, 36: 127-131, 1956. 45. Smith, C. H., and Miller, D. R.: Blood Disease in Infancy and Childhood. Edition 3. St. Louis, C. V. Mosby Co., 1972, p. 639. 46. Snyder, W. H., Jr., Kruse, C. A., Greaney, E. M., et al.: Retroperitoneal tumors in infants and children. Arch. Surg., 63:26-38, 1951. 47. Sober, 1., and Hirsh, M.: Unilateral massive adrenal hemorrhage in newborn infants. J. Urol., 93:430-434,1965. 48. Spence, H. M.: Congenital unilateral multicystic kidney. An entity to be distinguished from polycystic kidney disease and other disorders. J. Urol., 74:693-706,1955. 49. Sulamaa, M., and Moller, C.: Soft tissue sarcoma in children. J. Pediat. Surg., 4 :520-525, 1969. 50. Waisman, J., and Cooper, P. H.: Renal neoplasms of the newborn. J. Pediat. Surg., 5:407411,1970. 51. White, J. J.: Surgical emergencies in infancy and childhood. Surg. Clin. North Am., 50:877-884,1970. 52. Williams, D. 1. (ed.): Pediatric Urology. London, Butterworths, 1970, p. 150. Department of Pediatrics Medical Center of Central Georgia 777 Hemlock Street Hospital Box 95 Macon, Georgia 31201