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Essentials of Genitourinary Disorders in Children: Imaging Evaluation
Essentials of Genitourinary Disorders in Children: Imaging Evaluation Grace S. Phillips, MD, and Angelisa Paladin, MD
T
here is a relatively high incidence of congenital anomalies of the urogenital tract (UGT) in the pediatric population. Imaging plays a key role in the diagnosis of UGT abnormalities, but given the inherent risks of ionizing radiation, care must be taken when choosing the particular modality and protocol to image children with suspected pathology. We review the imaging techniques commonly in practice for imaging the pediatric UGT and describe imaging features of common congenital anomalies. In addition, we also discuss a brief review of acquired abnormalities, with an emphasis on testicular and ovarian torsion, infections, and tumors.
Imaging Techniques Ultrasound Ultrasound (US) is the quickest, easiest, and least-invasive method of imaging the urogenital tract (UGT). US has several advantages as a modality, including the absence of ionizing radiation, portability, and the ability to assess both overall morphology and blood supply of lesions. With the advent of US contrast agents, functional information may also be obtained by US, although use of US contrast agents in the United States is currently limited. One main disadvantage of US is that it is operator dependent. A common finding on renal sonography is dilation of the renal collecting system. The Society for Fetal Urology grading system is a commonly accepted method for describing hydronephrosis or pelviectasis, which categorizes the degree of dilation and associated parenchymal changes on a scale of 0 to 4.1
Fluoroscopy A common fluoroscopic method for evaluating the UGT is the voiding cystourethrogram (VCUG). Detailed anatomic as well as functional information may be gathered by VCUG. Because of the invasive nature of placing a bladder catheter, sedation is sometimes warranted in children to optimize the Department of Radiology, University of Washington School of Medicine, Seattle Children’s Hospital, Seattle, WA. Address reprint requests to Grace S. Philips, MD, Department of Radiology, University of Washington School of Medicine, Seattle Children’s Hospital, Seattle, WA 98105. E-mail: [email protected].
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0037-198X/12/$-see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1053/j.ro.2011.07.006
examination, particularly in the 3- to 6-year-old age range. The principle drawback of VCUG is its use of ionizing radiation. Patient radiation dose may be minimized with the use of pulsed fluoroscopy and last-image capture.
Nuclear Medicine Scintigraphy Nuclear medicine scintigraphy (NM) may also be used to evaluate the UGT. Although NM also uses ionizing radiation, in the form of radiopharmaceuticals, the radiation dose is typically lower than that of fluoroscopy. However, the examinations may also require placement of a bladder catheter, and anatomic detail is inferior to fluoroscopy. Furthermore, because of the length of the NM examinations, sedation of the patient may be required to achieve diagnostic-quality images. Technetium (Tc)-99m mercaptoacetyltriglycine is commonly used for diuretic renal scintigraphy becayuse it yields better images in infants and patients with decreased renal function compared with Tc99m diethylenetriaminepentaacetic acid, which is excreted by filtration.2 Renal cortical imaging can be accomplished by Tc(99m) dimercaptosuccinic acid scintigraphy, which can be used to image patients in the acute setting to evaluate for pyelonephritis, as well as in the quiescent period (greater than three months after a urinary tract infection) to evaluate for renal scarring.3
Magnetic Resonance Imaging Magnetic resonance imaging (MRI) has become an increasingly valuable imaging tool in the evaluation of the UGT because of the absence of ionizing radiation, as well as its ability to render both superior anatomical, temporal and functional detail. The authors of several recent articles have reviewed techniques for optimizing MRI of the pediatric UGT.4-7 Because of the typical length of MRI examinations, sedation of the patient may be necessary.
Congenital Anomalies Anomalies That May Present with Hydronephrosis Five main disorders that cause nearly all cases of hydronephrosis in pediatric patients include ureteropelvic junction
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obstruction (UPJO), ureterovesicle junction (UVJ) obstruction and megaureter, vesicoureteral reflux, renal duplication anomalies with an obstructed moiety, and posterior ureteral valves. Ureteropelvic Junction Obstruction UPJO is a common cause of hydronephrosis, and accounts for 44%-65% of infants with prenatally diagnosed hydronephrosis.8 Obstruction at the level of the ureteropelvic junction may be caused by an intrinsic lesion, such as a stenotic or aperistaltic segment of the ureter or persistent fetal folds, or by an extrinsic lesion, such as a crossing vessel. Intrinsic lesions are more common in the neonate that typically presents with prenatally diagnosed hydronephrosis, whereas extrinsic lesions become more common in older children.9 Vesicoureteral reflux (VUR) may coexist in up to 25% of obstructed systems.2 Surgical treatment for UPJO consists of either laparoscopic dismembered pyeloplasty or vascular hitch procedure.10 UPJO may be suspected at US when the degree of pelviectasis is out of proportion to calyceal dilatation; the ureter is also typically nondilated. At renal scintigraphy, UPJO typically manifests as accumulation of activity within a patulous renal collecting system without alteration in the time-activity curve in response to diuretic administration (furosemide).11 Although computed tomography (CT) may be used to assess for crossing vessels in the adult population,12 its use in children is limited by the relatively high inherent radiation dose. Magnetic resonance urography shows delayed renal transit time, with persistence of contrast within a dilated pelvicalyceal system (Fig. 1). Decreased function may also be seen of the affected kidney.5,13,14 Crossing vessels and fetal folds causing the UPJO may also be reliably detected by MR.15 When patients with surgically corrected UPJO are followed sonographically, it is important to recognize that fewer than half will have improvement in pelvicaliectasis within the first 6 months,16 and some degree of pelvicaliectasis typically persists indefinitely.16 Ureterovesicle Junction Obstruction (UVJO) and Megaureter Congenital dilation of the ureter, or megaureter, may be classified as primary or secondary. Primary megaureter denotes dilatation of the ureter in the absence of additional underlying abnormalities and may be associated with obstruction at the level of the UVJ. Of note, primary megaureter is often used synonymously with primary obstructive megaureter, regardless of whether an obstruction at the UVJ actually exists. Secondary megaureter is defined as dilation of the ureter in association with other conditions, such as posterior urethral valves, prune belly syndrome, and VUR. Children with primary megaureter most commonly come to medical attention because of an abnormal screening prenatal ultrasound. Patients with primary megaureter are at increased risk for urinary tract infection, at a rate of 0.94/year in the first year of life.17 Although the authors of recent literature support conservative management for the majority of patients with primary megaureter, surgery may be contemplated in the setting
Figure 1 UPJO in a 6-year-old girl with left upper quadrant pain. Maximum intensity projection image obtained from a magnetic resonance urogram demonstrates marked dilatation of the left renal pelvis and calyces with an abrupt transition to a normal caliber left ureter.
of higher grades of hydronephrosis, ureteral diameter ⬎11.33 cm, and decreasing renal function.18,19 On sonography, the megaureter is seen as a tubular anechoic structure that can become increasingly tortuous as it enlarges. Similar findings may be seen on excretory urogram (ie, intravenous pyelogram; Fig. 2). Varying degrees of pelviectasis may be present. The presence of internal echoes or urothelial thickening within the collecting system raises the possibility of a urinary tract infection. Either Lasix renogram or magnetic resonance urography may be used to evaluate for obstruction. Vesicoureteral Reflux VUR is a frequently encountered entity in the pediatric population, with an incidence of 1%.20 VUR may be suspected in several different clinical scenarios, including in a patient with hydronephrosis detected on screening prenatal ultrasound as well as in a child who presents with a urinary tract infection. VUR may also be suspected from family history of VUR.21 The treatment of VUR with long-term antibiotic prophylaxis to prevent urinary tract infections remains controversial although published guidelines do exist.22-26 Although even high-grade VUR may spontaneously resolve,27 the likelihood of resolution beyond infancy generally decreases with increasing severity of VUR.28 Surgical or endoscopic intervention is sometimes considered for patients with recurrent urinary tract infections despite prophylactic antibiotics, poor
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58 compliance with prophylactic antibiotics, and new renal scarring while on prophylactic antibiotics.20 On VCUG, contrast within the urinary bladder abnormally refluxes into the ureter and renal collecting system (Fig. 3). Variable degrees of tortuosity and dilation of the ureter and collecting system may be present on the basis of the degree of reflux (Table 1). Radionuclide voiding cystography may be used to follow patients with VUR in lieu of VCUG to minimize radiation exposure. Contrast-enhanced sonography has been used to evaluate for VUR in Europe, although sonographic contrast agents are not currently widely available in the United States. Renal Duplication Duplication of the renal collecting system is a common congenital anomaly with an incidence of 0.8%.29,30 Varying degrees of duplication may occur, ranging from a bifid renal pelvis that joins a single ureter to complete duplication of the pelvis and ureter with 2 separate ureteral orifices. When duplication is complete, the site of insertion of the upper and lower pole moiety ureters into the urinary bladder follows the
Figure 3 VUR in a 2-month-old girl with recurrent urinary tract infections. Anteroposterior image of the abdomen and pelvis from a VCUG demonstrates duplicated collecting systems bilaterally. There is grade 4 and grade 2 VUR in the right upper and lower moieties, respectively. There is grade 5 and grade 3 VUR in the left upper and lower moieties, respectively.
Weigert–Meyer rule. The upper pole ureter inserts medially and caudally, and occasionally ectopically at the trigone, bladder neck, or urethra.31 The lower pole ureter inserts laterally and cranially. The upper pole moiety can be associated with a ureterocele, which may be associated with hydronephrosis of the upper pole collecting system.31 The ureterocele may also cause bladder outlet obstruction. The lower pole moiety ureter is more prone to VUR, although VUR may be seen into both the upper and lower pole moiety ureters (Fig. 3). Duplication of the collecting system may be suspected at ultrasound when a parenchymal band is seen dividing the Table 1 Grade of VUR on the Basis of VCUG Findings Grade I II III
IV
V Figure 2 UVJO in an 8-year-old boy with intermittent right-sided abdominal pain. Right anterior oblique image from an intravenous pyelogram demonstrates moderate right hydroureteronephrosis with smooth tapering of the right distal ureter (arrow) at the ureterovesicular junction.
Findings Contrast column extends from the urinary bladder into a nondilated ureter Contrast column opacifies a nondilated ureter and renal collecting system Contrast opacifies a mildly dilated ureter and renal collecting system with blunting of calyceal fornices. Contrast opacifies an increasingly dilated and tortuous ureter and renal collecting system. Contrast opacifies a severely dilated and tortuous ureter and renal collecting system. There is loss of papillary impressions, and intrarenal reflux may be seen.
VCUG, voiding cystourethrogram; VUR, vesicoureteral reflux.
Evaluating genitourinary disorders in children
Figure 4 Renal duplication in a 1-month-old girl with history of prenatal hydronephrosis. Sagittal ultrasound image of the left kidney (demarcated by cursors) shows a parenchymal band dividing the upper and lower pole consistent with duplication of the collecting system. There is marked upper (U) and mild lower (L) moiety hydronephrosis, raising the possibility of upper moiety obstruction and lower moiety vesicoureteral reflux.
renal collecting system (Fig. 4). Variable amounts of pelvicaliectasis may be present. Upper and lower pole moiety ureters may be difficult to trace throughout their course even when hydroureter is present. A ureterocele associated with the upper pole moiety ureter typically manifests as an intravesicle cystic structure at the UVJ on ultrasound, and as a filling defect on VCUG, particularly on early filling images. When VUR is seen only into the lower pole moiety ureter and renal collecting system, a characteristic “drooping lily” configuration of the lower pole moiety pelvis may result.
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Figure 6 MCDK in a 2-month-old boy with prenatal diagnosis of hydronephrosis. Sagittal ultrasound image of the left kidney (demarcated by cursors) demonstrates multiple noncommunicating cysts with no intervening parenchyma. The ureter is not dilated.
Posterior Urethral Valves Posterior urethral valves are the most common cause of lower urinary obstruction in boys.32 The primary abnormality is a mucosal membrane in the prostatic urethra; however, the exact embryology of this disease is still not known. The secondary effects of this membrane from outlet obstruction result in injuries to the bladder and kidneys. Despite current aggressive medical and surgical therapies, 24%-45% of patients with posterior urethral valves still progress to renal insufficiency in their lifetime.33 Factors associated with poor long-term outcome include the presence of bilateral VUR, delayed detection, recurrent urinary infections, incontinence in patients older than 5 years and a serum creatinine of ⬎1 mg/dL at 1 year of age.34 Endoscopic valve ablation relieves the urethral obstruction and is usually performed in the first week of life. Patients with extremely dilated upper tracts sometimes require upper tract reconstruction.33 Posterior urethral valves may be suspected on prenatal ultrasound in the setting of persistent bladder distention, olioghydramnios, and urinary ascites.35 The diagnosis of posterior urethral valves is best confirmed by VCUG (Fig. 5). Findings include dilation and elongation of the posterior urethra, bladder trabeculation, and hypertrophy of the bladder neck. Other common findings shown on VCUG or ultrasound include VUR, bladder diverticula, and renal dysplasia. Occasionally, forniceal rupture, perinephric urinomas, and urine ascites are demonstrated.
Multicystic Dysplastic Kidney
Figure 5 Posterior urethral valves in a 1-day-old boy with prenatal diagnosis of hydronephrosis. Right anterior oblique image of the pelvis during the voiding phase of a VCUG demonstrates a dilated posterior urethra (arrow), narrowed bladder neck, and right vesicoureteral reflux.
Multicystic dysplastic kidney (MCDK) is a developmental abnormality of the kidney that typically results in negligible function of the affected kidney. The incidence of unilateral MCDK is approximately 1 in 4300 live births.36,37 Bilateral MCDK is rare and may result in fetal demise. Given the widespread use of prenatal sonography, most cases of MCDK are diagnosed prenatally. Historically, there was concern regarding a possible increased risk of Wilms tumor in the affected kidney and hypertension, for which prophylactic nephrectomy was typically performed. However, more recent studies found that the risk of Wilms tumor in MCDK is 1:2000 or
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Figure 7 Renal fusion anomaly: horseshoe kidney in a 10-year-old girl with myelomenigocele. Axial T2-weighted MRI image of the abdomen demonstrates fused kidneys with a parenchymal isthmus (arrow) at the lower poles overlying the spine.
less.38 Furthermore, the risk of hypertension is not greater than the general population, although when present, may be attributed to MCDK 25%-50% of the time.39 Therefore, a conservative approach regarding surgery and imaging for MCDK is currently advocated. On ultrasound, MCDK typically shows a conglomeration of noncommunicating, simple-appearing cysts in the ipsilateral renal fossa (Fig. 6). Little, if any, surrounding parenchyma is seen. Variable rates and degree of involution of MCDK over time have been reported,37 which on imaging manifests as decreased size and/or number of the multiple cysts. Compensatory hypertrophy of the unaffected kidney may also be seen. There is a 19% risk of VUR in the contralateral kidney.40 Therefore, VCUG may be appropriate if contralateral pelviectasis is detected by ultrasound, or if the patient develops a urinary tract infection.39
Renal Fusion Anomalies and Ectopia Renal fusion anomalies and ectopia both have embryologic origins relating to aberrations in the normal ascension and rotation of the bilateral kidneys during the eighth and ninth
weeks of gestation.31 Horseshoe kidney is the most common renal fusion anomaly with an estimated incidence of 1 in 400-500 live births31,41 and is often asymptomatic. In symptomatic patients, horseshoe kidney may present with urinary tract infection, or less commonly, with a mass, hematuria, or abdominal pain.31 A pelvic kidney is the most common form of renal ectopia. Less frequently, the ectopic kidney can traverse midline while ascending and fuse to the contralateral, normally located kidney, which is termed “crossed-fused” renal ectopia. On ultrasound, a horseshoe kidney may be suspected when the lower poles of the bilateral kidneys are angled medially. Cross-sectional imaging of the midline, either with ultrasound, MR (Fig. 7), or CT, may detect either a parenchymal or fibrous band of tissue joining the lower poles of the bilateral kidneys anterior to the spine. In pelvic kidney, ultrasound may show an empty renal fossa and the ectopic kidney in the ipsilateral pelvis. Crossed-fused renal ectopia may have a variety of configurations, most commonly with the superior pole of the ectopic kidney fused to the lower pole of the normally located kidney. VUR is seen in as many as 20%-30% of patients with renal fusion anomalies or ectopias.42 Hypospadias and cryptorchidism may be present in up to 5%.43
Acquired Abnormalities Scrotal Abnormalities Testicular Torsion There are 2 types of testicular torsion, extravaginal and intravaginal. Extravaginal testicular torsion is seen in neonates and may occur in utero or shortly after birth. Extravaginal testicular torsion accounts for 10% of all testicular torsions. Sonographic features of extravaginal testicular torsion vary depending on the acuity of presentation and follow a predict-
Figure 8 Testicular torsion in a 17-year-old boy with severe left testicular pain. Transverse ultrasound image of the right and left testicle demonstrates no detectable color Doppler flow within the enlarged left testicle. The echotexture of both testes are homogeneous. The patient subsequently underwent emergency surgery, which showed left testicular torsion. The left testicle was detorsed and orchipexy was performed.
Evaluating genitourinary disorders in children
Figure 9 Torsion of the testicular appendage in a 10-year-old boy with 4-day history of intermittent right scrotal pain. Sagittal ultrasound image of the right testicle demonstrates a round, hyperechoic avascular soft tissue mass (arrows) adjacent to the right epididymal head.
able evolution.44 In the acute phase, the affected testicle is enlarged, heterogeneous, and without Doppler flow. Subsequently, the testicle becomes more normal in size with persistent heterogeneity, sometimes accompanied by hydrocele. Finally, the testicle becomes small with areas of increased echogenicity.44 Intravaginal testicular torsion is typically seen in pubertal boys. The bell-clapper deformity is a predisposing condition, in which the tunica vaginalis completely surrounds the testicle, allowing for its increased mobility. Patients typically present with acute-onset scrotal pain, nausea, and vomiting. Prompt diagnosis is essential for testicular salvage, which is nearly 100% if treated within 6 hours of initial symptoms and only 20% if treated 12-24 hours after onset of symptoms.45,46 Grayscale imaging of the testicle can be normal immediately after torsion,45 with subsequent enlargement and heterogeneity of the affected testicle. A twisting of the spermatic cord may also be seen. The absence of intratesticular flow (Fig. 8) is 86% sensitive and 100% specific for testicular torsion.47 A pitfall to diagnosis is incomplete torsion, which may result in normal testicular blood flow. With spontaneous or manual detorsion, Doppler evaluation of the testicle may show normal or increased testicular blood flow.48
61 Torsion of a Testicular or Epididymal Appendage The testicular and epididymal appendages are normal structures that represent the embryologic remnants of the paramesonephric and mesonephric ducts, respectively. When torsion of either of these structures occurs, the resultant testicular pain can mimic the presentation of testicular torsion. Treatment of torsion of the testicular or epididymal appendage is generally conservative, with a goal of pain management. The normal testicular appendage may be visible by ultrasound as an ovoid, isoechoic structure along the superior pole of the testes, adjacent to the epididymis. The normal epididymal appendage may also be visible by ultrasound, as an ovoid, isoechoic structure arising from the epididymal head. The typical sonographic findings of torsion of the testicular appendage are an ovoid, hyperechoic, avascular mass (Fig. 9) measuring 5.6 mm or greater, along the superior pole of the testes adjacent to the epididymal head.49 Less frequently the mass may be hypoechoic or isoechoic.49 There is often associated testicular and epididymal hyperemia and enlargement, scrotal wall thickening, and a reactive hydrocele.50 The sonographic diagnosis of torsion of the testicular or epididymal appendage remains challenging for several reasons. First, the ultrasound findings of adjacent epididymal and testicular hyperemia seen in torsion of the testicular or epididymal appendage may mimic epididymitis.50 Second, the ovoid, avascular mass representing the torsed appendix is sometimes not evident by ultrasound. Third, the normal appendages also often appear avascular on color Doppler evaluation. Furthermore, it is often difficult to distinguish the torsed testicular appendage from a torsed epididymal appendage, although both are typically treated conservatively. Epididymitis/Epididymo-Orchitis Epididymitis and epididymoorchitis are common causes of testicular pain and are therefore important differential considerations in patients with suspected testicular torsion. Epididymitis and epididymoorchitis may be related to bacterial infection, although Somekh et al51 have suggested a postinfectious etiology. Treatment therefore may include antibiotics or supportive care. Patients with epididymitis may have
Figure 10 Epididymoorchitis in a 20-year-old male patient with right testicular pain. Sagittal ultrasound image of the right and left testicle demonstrates hyperemia of the right testis and epididymis compared to the left. The right testis is mildly heterogeneous in echogenicity and larger in size than the left testis.
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Figure 11 Seminoma in a 14-year-old boy with enlarged left testicle. Sagittal ultrasound image of the right testicle demonstrates a predominately solid, heterogeneous mass (arrow) occupying most of the mid- and inferior pole. There are some regions of cystic change within the mass and well-defined punctate calcifications at the margins.
associated genitourinary abnormalities, such as ectopic ureter and VUR, for which additional radiological evaluation may be warranted.48 On ultrasound, epididymitis typically manifests as focal or diffuse hyperemia and enlargement of the epididymis (Fig. 10). With epididymoorchitis, similar sonographic findings may be seen in the ipsilateral testicle. A reactive hydrocele and scrotal wall thickening may also be present. Of note, detorsion of a previously torsed testicle may also result in testicular and epididymal hyperemia; however, clinical correlation should be made because detorsion of the torsed testicle should result in dramatic relief of testicular pain. Testicular Neoplasm The incidence of testicular tumors in children follows a bimodal distribution, with a small peak occurring in the first three years of life and a second, larger peak occurring in
Figure 13 Tuboovarian abscess in a 17-year-old girl with worsening left lower pelvic pain, fever, and purulent vaginal discharge. Sagittal ultrasound image of the pelvis shows enlarged left ovary (Lt Ov). Also noted is a complex cystic mass (black arrow) with irregular walls and internal debris likely representing infected and enlarged left fallopian tube. The patient’s vaginal discharge was positive for Chlamydia infection. The patient was subsequently treated with a triple antibiotic regimen of ampicillin, clindamycin, and flagyl.
adults. Testicular tumors in the prepubescent child are more likely to be benign, and have a different distribution of histologic types than in adults. Teratomas, which are typically benign, are the most common testicular tumor in prepubescent boys.52 The most common malignant tumor in prepubescent males is the malignant yolk sac tumor, in contrast to seminomas in young adults.53 Metastatic leukemia may also present as a testicular mass, and is often bilateral.53,54 Ultrasound is the primary modality for screening and characterizing suspected testicular tumors (Fig. 11). An associated hydrocele is present in 15%-50% of patients with a testicular tumor.54 Staging for distant metastases is typically accomplished with CT. Common routes of metastatic spread are to the retroperitoneal lymph nodes, and for malignant yolk sac tumors, to the lungs (20%).54
Ovarian Abnormalities
Figure 12 Ovarian torsion in a 9-year-old girl with severe right-sided abdominal pain. Axial transabdominal image of the pelvis demonstrates marked enlargement of the right ovary (RT OV) compared with the left (LT OV). The patient underwent laparoscopic surgery which confirmed the diagnosis of right ovarian torsion.
Ovarian Torsion Ovarian torsion remains a difficult diagnosis for radiologists and referring clinicians. A recent large, multiinstitutional study found the annual rate of ovarian torsion similar to testicular torsion (4-5 per 100,000); however, the salvage rate much lower (40% compared with 65%).55 Ovarian torsion has a bimodal distribution with peaks occurring at ⬍1 year of age and 11-18 years of age, likely related to ovarian enlargement and cyst formation related to hormonal stimulation. In neonates with ovarian torsion, the diagnosis is sometimes suggested by prenatal imaging. After birth, infants may present with a mass or feeding intolerance.56 Common presenting symptoms in girls ⬎1 year of age include abdominal pain, nausea and vomiting, fever, and leukocytosis,57 which may mimic other genitourinary or gastrointestinal pathologies and hamper accurate, timely diagnosis. In children, ovarian torsion is most often associated with normal ovaries
Evaluating genitourinary disorders in children
63 The diagnosis of TOA may be confirmed with either CT or ultrasound (Fig. 13). However, given the radiation dose and greater cost of CT, ultrasound is the preferred initial imaging modality. Sonographic findings include a cystic or multiseptated mass with multiple internal echoes correlating with purulent fluid.61 The involved adenexa is typically undistinguishable from the mass. Most common findings on contrastenhanced CT include a multilocular inflammatory mass with a thick, enhancing abscess wall.61 Additional findings include thickening of the mesosalpinx, adjacent pelvic fat stranding, bowel wall thickening, and thickening of the uterosacral ligaments.62
Figure 14 Ovarian teratoma in a 9-year-old girl with abdominal pain and distension. Coronal image from an abdominal computed tomographic image with intravenous and oral contrast demonstrates a large, heterogeneous pelvis mass (black arrow) with areas of dense calcification and surrounding intraperitoneal fluid.
41%, followed by ovarian cysts (35%) or a benign tumor (23%). Malignancy and thromboembolic events are very rare (⬍0.5%).55 Current preferred treatment of ovarian torsion is laporoscopic detorsion. In neonates, the typical sonographic finding of ovarian torsion is a pelvic cystic mass. In girls ⬎1 year of age, the most sensitive radiologic finding of ovarian torsion is ovarian enlargement ⬎5 cm (Fig. 12) with a reported sensitivity of 83%.56 Other findings that have been described on Doppler ultrasound include small peripheral cysts secondary to edema from venous and lymphatic stasis, a spiral appearance of the torsed adnexa, and the absence of ovarian venous flow. Several studies have shown that the presence of arterial flow does not exclude the diagnosis of ovarian torsion.58 Tubo-Ovarian Abscess (TOA) TOA is a serious complication of pelvic inflammatory disease (PID) and is typically caused by an ascending sexually transmitted infection, most commonly Neisseria gonorrhoeae or Chlamydia trachomatis. The rate of TOA in patients with PID is 15%-20%.59 The most common clinical symptoms include abdominal pain, followed in descending order by vaginal discharge, vomiting, diarrhea, and fever. The most common physical examination findings are lower abdominal and cervical motion tenderness. Clinically, it is difficult to differentiate patients with TOA from PID based on laboratory studies and clinical assessment alone. Imaging is therefore often critical to diagnosis. Initially, patients are treated with broadspectrum antibiotics. Drainage or surgery is usually considered if the patient fails to respond within 48-72 hours. In a recent study, DeWitt et al60 showed that abscesses ⬎8 cm were associated with increased need for surgery or drainage.
Ovarian Neoplasm Ovarian neoplasms are rare in childhood and most commonly benign, with the risk of malignancy reported to range from 10% to 35%.63 Fortunately, childhood ovarian malignancies often are found at early stages and respond favorably to chemotherapy. Germ cell tumors (Fig. 14) are the most common ovarian tumor in children and adolescents, followed by sex cord stromal and epithelial neoplasms. Conversely, in adults, epithelial tumors are most common.64 Clinical presentation is similar with benign and malignant tumors and in descending order of frequency includes: abdominal pain, palpable mass and abdominal distension. Other symptoms include nausea, vomiting, and urinary symptoms if the tumor is large.65 Surgical treatment for benign ovarian tumors is conservative. Partial oopherectomy is preferred when possible. Malignant tumors are treated with chemotherapy and unilateral salpingooopherectomy with close follow-up of the contralateral ovary and abdomen.66
Benign Tumors Benign teratomas account for two-thirds of all pediatric ovarian tumors. The tumor markers alpha fetoprotein (AFP) and human chorionic gonadotropin-beta (B-HCG) are typically normal. US imaging predominately demonstrates a cystic mass with one or more mural nodules. Other sonographic features of ovarian teratomas are related to the presence of calcifications, and fat-fluid levels or fat.
Malignant Tumors A total of 85% of malignant ovarian tumors in childhood are of germ cell origin and are predominately malignant teratomas and dysgerminomas. The tumor markers AFP and BHCG are often elevated. Malignant teratomas and dysgerminomas are typically solid masses on diagnostic imaging. Coarse calcifications can be seen in malignant teratomas and fine stippled calcifications in dysgerminomas. Less common malignant ovarian tumors are sex cord stromal tumors (10%) and epithelial carcinomas (5%). Imaging characteristics of these tumors are highly variable and include complex masses with fluid in the cul-de-sac in 50% of cases.61
Conclusions Congenital anomalies of the UGT are relatively common disorders in children. Children with anomalies of the UGT
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64 may present because of an abnormal prenatal screening sonogram, or with symptoms, such as a urinary tract infection, typically in early childhood. Radiological imaging remains the basis for accurate diagnosis. Children may also present with acquired anomalies of the UGT, such as gonadal torsion, infections, and tumors, many of which are amenable to sonographic diagnosis. Care must be taken to follow the “as low as reasonably achievable” (ALARA) principle regarding radiation exposure in children when selecting the modality and protocol for imaging children with suspected UGT anomalies.
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term outcome of primary obstructive megaureter in childhood. Pediatr Nephrol 25:1679-1686, 2010 Chertin B, Pollack A, Koulikov D, et al: Long-term follow up of antenatally diagnosed megaureters. J Pediatr Urol 4:188-191, 2008 McLellan DL, Retik AB, Bauer SB, et al: Rate and predictors of spontaneous resolution of prenatally diagnosed primary nonrefluxing megaureter. J Urol 168:2177-2180, 2002; discussion: 80 Perez-Brayfield M, Kirsch AJ, Hensle TW, et al: Endoscopic treatment with dextranomer/hyaluronic acid for complex cases of vesicoureteral reflux. J Urol 172:1614-1616, 2004 Skoog SJ, Peters CA, Arant BS Jr, et al: Pediatric vesicoureteral reflux Guidelines Panel Summary Report: Clinical Practice Guidelines for Screening Siblings of Children with vesicoureteral reflux and neonates/ Infants with prenatal hydronephrosis. J Urol 184:1145-1151, 2010 Craig JC, Simpson JM, Williams GJ, et al: Antibiotic prophylaxis and recurrent urinary tract infection in children. N Engl J Med 361:17481759, 2009 Kallen R: Antibiotic prophylaxis and recurrent urinary tract infection in children. N Engl J Med 362:555, 2010; author reply: 6-7 Peters CA, Skoog SJ, Arant BS Jr, et al: Summary of the AUA Guideline on Management of Primary Vesicoureteral Reflux in Children. J Urol 184:1134-1144, 2010 Skurnik D, Pier GB, Andremont A: Antibiotic prophylaxis and recurrent urinary tract infection in children. N Engl J Med 362:555-556, 2010; author reply: 6-7 Szmigielska A, Krzemien G, Roszkowska-Blaim M: Antibiotic prophylaxis and recurrent urinary tract infection in children. N Engl J Med 362:556, 2010; author reply ⫺7 Sjöström S, Sillén U, Bachelard M, et al: Spontaneous resolution of high grade infantile vesicoureteral reflux. J Urol 172:694-698, 2004; discussion: 9 Fernbach SK, Feinstein KA, Schmidt MB: Pediatric voiding cystourethrography: A pictorial guide. RadioGraphics 20:155-168, 2000; discussion: 68-71 Privett JT, Jeans WD, Roylance J: The incidence and importance of renal duplication. Clin Radiol 27:521-530, 1976 Siomou E, Papadopoulou F, Kollios KD, et al: Duplex collecting system diagnosed during the first 6 years of life after a first urinary tract infection: A study of 63 children. J Urol 175:678-681, 2006; discussion: 81-82 Decter RM: Renal duplication and fusion anomalies. Pediatr Clin North Am 44:1323-1341, 1997 Otukesh H, Sharifiaghdas F, Hoseini R, et al: Long-term upper and lower urinary tract functions in children with posterior urethral valves. J Pediatr Urol 2009 (Epub ahead of print) Yohannes P, Hanna M: Current trends in the management of posterior urethral valves in the pediatric population. Urology 60:947953, 2002 Ylinen E, Ala-Houhala M, Wikström S: Prognostic factors of posterior urethral valves and the role of antenatal detection. Pediatr Nephrol 19:874-879, 2004 Berrocal T, López-Pereira P, Arjonilla A, et al: Anomalies of the distal ureter, bladder, and urethra in children: Embryologic, radiologic, and pathologic features. RadioGraphics 22:1139-1164, 2002 Gordon AC, Thomas DF, Arthur RJ, et al: Multicystic dysplastic kidney: Is nephrectomy still appropriate? J Urol 140:1231-1234, 1988 Onal B, Kogan BA: Natural history of patients with multicystic dysplastic kidney-what followup is needed? J Urol 176:1607-1611, 2006 Homsy YL, Anderson JH, Oudjhane K, et al: Wilms tumor and multicystic dysplastic kidney disease. J Urol 158:2256-2259, 1997; discussion: 9-60 Hains DS, Bates CM, Ingraham S, et al: Management and etiology of the unilateral multicystic dysplastic kidney: A review. Pediatr Nephrol 24: 233-241, 2009 Aslam M, Watson AR, Trent & Anglia MCDK Study Group: Unilateral multicystic dysplastic kidney: Long term outcomes. Arch Dis Child 91:820-823, 2006 Segura JW, Kelalis PP, Burke EC: Horseshoe kidney in children. J Urol 108:333-336, 1972
Evaluating genitourinary disorders in children 42. Donnelly LF: Diagnostic Imaging. Pediatrics (ed 1). Salt Lake City, UT, Amirsys, 2005 43. Guarino N, Tadini B, Camardi P, et al: The incidence of associated urological abnormalities in children with renal ectopia. J Urol 172: 1757-1759, 2004; discussion: 9 44. Traubici J, Daneman A, Navarro O, et al: Original report. Testicular torsion in neonates and infants: Sonographic features in 30 patients. AJR Am J Roentgenol 180:1143-1145, 2003 45. Dogra VS, Gottlieb RH, Oka M, et al: Sonography of the scrotum. Radiology 227:18-36, 2003 46. Patriquin HB, Yazbeck S, Trinh B, et al: Testicular torsion in infants and children: Diagnosis with Doppler sonography. Radiology 188:781785, 1993 47. Burks DD, Markey BJ, Burkhard TK, et al: Suspected testicular torsion and ischemia: Evaluation with color Doppler sonography. Radiology 175:815-821, 1990 48. Baldisserotto M: Scrotal emergencies. Pediatr Radiol 39:516-521, 2009 49. Baldisserotto M, de Souza JC, Pertence AP, et al: Color Doppler sonography of normal and torsed testicular appendages in children. AJR Am J Roentgenol 184:1287-1292, 2005 50. Karmazyn B, Steinberg R, Livne P, et al: Duplex sonographic findings in children with torsion of the testicular appendages: Overlap with epididymitis and epididymoorchitis. J Pediatr Surg 41:500504, 2006 51. Somekh E, Gorenstein A, Serour F: Acute epididymitis in boys: Evidence of a post-infectious etiology. J Urol 171:391-394, 2004; discussion: 4 52. Pohl HG, Shukla AR, Metcalf PD, et al: Prepubertal testis tumors: Actual prevalence rate of histological types. J Urol 172:2370-2372, 2004 53. Carkaci S, Ozkan E, Lane D, et al: Scrotal sonography revisited. J Clin Ultrasound 38:21-37, 2010
65 54. Ahmed HU, Arya M, Muneer A, et al: Testicular and paratesticular tumours in the prepubertal population. Lancet Oncol 11:476-483, 2010 55. Guthrie BD, Adler MD, Powell EC: Incidence and trends of pediatric ovarian torsion hospitalizations in the United States, 2000-2006. Pediatrics 125:532-538, 2010 56. Oltmann SC, Fischer A, Barber R, et al: Cannot exclude torsion—A 15-year review. J Pediatr Surg 44:1212-1216, 2009; discussion: 7 57. Chang YJ, Yan DC, Kong MS, et al: Adnexal torsion in children. Pediatr Emerg Care 24:534-537, 2008 58. Stark JE, Siegel MJ: Ovarian torsion in prepubertal and pubertal girls: Sonographic findings. AJR Am J Roentgenol 163:1479-1482, 1994 59. Paik CK, Waetjen LE, Xing G, et al: Hospitalizations for pelvic inflammatory disease and tuboovarian abscess. Obstet Gynecol 107:611-616, 2006 60. Dewitt J, Reining A, Allsworth JE, et al: Tuboovarian abscesses: Is size associated with duration of hospitalization & complications?. Obstet Gynecol Int 2010;2010:847041 61. Surratt JT, Siegel MJ: Imaging of pediatric ovarian masses. RadioGraphics 11:533-548, 1991 62. Wilbur AC, Aizenstein RI, Napp TE: CT findings in tuboovarian abscess. AJR Am J Roentgenol 158:575-579, 1992 63. Diamond MP, Baxter JW, Peerman CG Jr, et al: Occurrence of ovarian malignancy in childhood and adolescence: A community-wide evaluation. Obstet Gynecol 71:858-860, 1988 64. Panteli C, Curry J, Kiely E, et al: Ovarian germ cell tumours: A 17-year study in a single unit. Eur J Pediatr Surg 19:96-100, 2009 65. Schultz KA, Sencer SF, Messinger Y, et al: Pediatric ovarian tumors: A review of 67 cases. Pediatr Blood Cancer 44:167-173, 2005 66. Vaysse C, Delsol M, Carfagna L, et al: Ovarian germ cell tumors in children. Management, survival and ovarian prognosis. A report of 75 cases. J Pediatr Surg 45:1484-1490, 2010
T
here is a relatively high incidence of congenital anomalies of the urogenital tract (UGT) in the pediatric population. Imaging plays a key role in the diagnosis of UGT abnormalities, but given the inherent risks of ionizing radiation, care must be taken when choosing the particular modality and protocol to image children with suspected pathology. We review the imaging techniques commonly in practice for imaging the pediatric UGT and describe imaging features of common congenital anomalies. In addition, we also discuss a brief review of acquired abnormalities, with an emphasis on testicular and ovarian torsion, infections, and tumors.
Imaging Techniques Ultrasound Ultrasound (US) is the quickest, easiest, and least-invasive method of imaging the urogenital tract (UGT). US has several advantages as a modality, including the absence of ionizing radiation, portability, and the ability to assess both overall morphology and blood supply of lesions. With the advent of US contrast agents, functional information may also be obtained by US, although use of US contrast agents in the United States is currently limited. One main disadvantage of US is that it is operator dependent. A common finding on renal sonography is dilation of the renal collecting system. The Society for Fetal Urology grading system is a commonly accepted method for describing hydronephrosis or pelviectasis, which categorizes the degree of dilation and associated parenchymal changes on a scale of 0 to 4.1
Fluoroscopy A common fluoroscopic method for evaluating the UGT is the voiding cystourethrogram (VCUG). Detailed anatomic as well as functional information may be gathered by VCUG. Because of the invasive nature of placing a bladder catheter, sedation is sometimes warranted in children to optimize the Department of Radiology, University of Washington School of Medicine, Seattle Children’s Hospital, Seattle, WA. Address reprint requests to Grace S. Philips, MD, Department of Radiology, University of Washington School of Medicine, Seattle Children’s Hospital, Seattle, WA 98105. E-mail: [email protected].
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0037-198X/12/$-see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1053/j.ro.2011.07.006
examination, particularly in the 3- to 6-year-old age range. The principle drawback of VCUG is its use of ionizing radiation. Patient radiation dose may be minimized with the use of pulsed fluoroscopy and last-image capture.
Nuclear Medicine Scintigraphy Nuclear medicine scintigraphy (NM) may also be used to evaluate the UGT. Although NM also uses ionizing radiation, in the form of radiopharmaceuticals, the radiation dose is typically lower than that of fluoroscopy. However, the examinations may also require placement of a bladder catheter, and anatomic detail is inferior to fluoroscopy. Furthermore, because of the length of the NM examinations, sedation of the patient may be required to achieve diagnostic-quality images. Technetium (Tc)-99m mercaptoacetyltriglycine is commonly used for diuretic renal scintigraphy becayuse it yields better images in infants and patients with decreased renal function compared with Tc99m diethylenetriaminepentaacetic acid, which is excreted by filtration.2 Renal cortical imaging can be accomplished by Tc(99m) dimercaptosuccinic acid scintigraphy, which can be used to image patients in the acute setting to evaluate for pyelonephritis, as well as in the quiescent period (greater than three months after a urinary tract infection) to evaluate for renal scarring.3
Magnetic Resonance Imaging Magnetic resonance imaging (MRI) has become an increasingly valuable imaging tool in the evaluation of the UGT because of the absence of ionizing radiation, as well as its ability to render both superior anatomical, temporal and functional detail. The authors of several recent articles have reviewed techniques for optimizing MRI of the pediatric UGT.4-7 Because of the typical length of MRI examinations, sedation of the patient may be necessary.
Congenital Anomalies Anomalies That May Present with Hydronephrosis Five main disorders that cause nearly all cases of hydronephrosis in pediatric patients include ureteropelvic junction
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obstruction (UPJO), ureterovesicle junction (UVJ) obstruction and megaureter, vesicoureteral reflux, renal duplication anomalies with an obstructed moiety, and posterior ureteral valves. Ureteropelvic Junction Obstruction UPJO is a common cause of hydronephrosis, and accounts for 44%-65% of infants with prenatally diagnosed hydronephrosis.8 Obstruction at the level of the ureteropelvic junction may be caused by an intrinsic lesion, such as a stenotic or aperistaltic segment of the ureter or persistent fetal folds, or by an extrinsic lesion, such as a crossing vessel. Intrinsic lesions are more common in the neonate that typically presents with prenatally diagnosed hydronephrosis, whereas extrinsic lesions become more common in older children.9 Vesicoureteral reflux (VUR) may coexist in up to 25% of obstructed systems.2 Surgical treatment for UPJO consists of either laparoscopic dismembered pyeloplasty or vascular hitch procedure.10 UPJO may be suspected at US when the degree of pelviectasis is out of proportion to calyceal dilatation; the ureter is also typically nondilated. At renal scintigraphy, UPJO typically manifests as accumulation of activity within a patulous renal collecting system without alteration in the time-activity curve in response to diuretic administration (furosemide).11 Although computed tomography (CT) may be used to assess for crossing vessels in the adult population,12 its use in children is limited by the relatively high inherent radiation dose. Magnetic resonance urography shows delayed renal transit time, with persistence of contrast within a dilated pelvicalyceal system (Fig. 1). Decreased function may also be seen of the affected kidney.5,13,14 Crossing vessels and fetal folds causing the UPJO may also be reliably detected by MR.15 When patients with surgically corrected UPJO are followed sonographically, it is important to recognize that fewer than half will have improvement in pelvicaliectasis within the first 6 months,16 and some degree of pelvicaliectasis typically persists indefinitely.16 Ureterovesicle Junction Obstruction (UVJO) and Megaureter Congenital dilation of the ureter, or megaureter, may be classified as primary or secondary. Primary megaureter denotes dilatation of the ureter in the absence of additional underlying abnormalities and may be associated with obstruction at the level of the UVJ. Of note, primary megaureter is often used synonymously with primary obstructive megaureter, regardless of whether an obstruction at the UVJ actually exists. Secondary megaureter is defined as dilation of the ureter in association with other conditions, such as posterior urethral valves, prune belly syndrome, and VUR. Children with primary megaureter most commonly come to medical attention because of an abnormal screening prenatal ultrasound. Patients with primary megaureter are at increased risk for urinary tract infection, at a rate of 0.94/year in the first year of life.17 Although the authors of recent literature support conservative management for the majority of patients with primary megaureter, surgery may be contemplated in the setting
Figure 1 UPJO in a 6-year-old girl with left upper quadrant pain. Maximum intensity projection image obtained from a magnetic resonance urogram demonstrates marked dilatation of the left renal pelvis and calyces with an abrupt transition to a normal caliber left ureter.
of higher grades of hydronephrosis, ureteral diameter ⬎11.33 cm, and decreasing renal function.18,19 On sonography, the megaureter is seen as a tubular anechoic structure that can become increasingly tortuous as it enlarges. Similar findings may be seen on excretory urogram (ie, intravenous pyelogram; Fig. 2). Varying degrees of pelviectasis may be present. The presence of internal echoes or urothelial thickening within the collecting system raises the possibility of a urinary tract infection. Either Lasix renogram or magnetic resonance urography may be used to evaluate for obstruction. Vesicoureteral Reflux VUR is a frequently encountered entity in the pediatric population, with an incidence of 1%.20 VUR may be suspected in several different clinical scenarios, including in a patient with hydronephrosis detected on screening prenatal ultrasound as well as in a child who presents with a urinary tract infection. VUR may also be suspected from family history of VUR.21 The treatment of VUR with long-term antibiotic prophylaxis to prevent urinary tract infections remains controversial although published guidelines do exist.22-26 Although even high-grade VUR may spontaneously resolve,27 the likelihood of resolution beyond infancy generally decreases with increasing severity of VUR.28 Surgical or endoscopic intervention is sometimes considered for patients with recurrent urinary tract infections despite prophylactic antibiotics, poor
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58 compliance with prophylactic antibiotics, and new renal scarring while on prophylactic antibiotics.20 On VCUG, contrast within the urinary bladder abnormally refluxes into the ureter and renal collecting system (Fig. 3). Variable degrees of tortuosity and dilation of the ureter and collecting system may be present on the basis of the degree of reflux (Table 1). Radionuclide voiding cystography may be used to follow patients with VUR in lieu of VCUG to minimize radiation exposure. Contrast-enhanced sonography has been used to evaluate for VUR in Europe, although sonographic contrast agents are not currently widely available in the United States. Renal Duplication Duplication of the renal collecting system is a common congenital anomaly with an incidence of 0.8%.29,30 Varying degrees of duplication may occur, ranging from a bifid renal pelvis that joins a single ureter to complete duplication of the pelvis and ureter with 2 separate ureteral orifices. When duplication is complete, the site of insertion of the upper and lower pole moiety ureters into the urinary bladder follows the
Figure 3 VUR in a 2-month-old girl with recurrent urinary tract infections. Anteroposterior image of the abdomen and pelvis from a VCUG demonstrates duplicated collecting systems bilaterally. There is grade 4 and grade 2 VUR in the right upper and lower moieties, respectively. There is grade 5 and grade 3 VUR in the left upper and lower moieties, respectively.
Weigert–Meyer rule. The upper pole ureter inserts medially and caudally, and occasionally ectopically at the trigone, bladder neck, or urethra.31 The lower pole ureter inserts laterally and cranially. The upper pole moiety can be associated with a ureterocele, which may be associated with hydronephrosis of the upper pole collecting system.31 The ureterocele may also cause bladder outlet obstruction. The lower pole moiety ureter is more prone to VUR, although VUR may be seen into both the upper and lower pole moiety ureters (Fig. 3). Duplication of the collecting system may be suspected at ultrasound when a parenchymal band is seen dividing the Table 1 Grade of VUR on the Basis of VCUG Findings Grade I II III
IV
V Figure 2 UVJO in an 8-year-old boy with intermittent right-sided abdominal pain. Right anterior oblique image from an intravenous pyelogram demonstrates moderate right hydroureteronephrosis with smooth tapering of the right distal ureter (arrow) at the ureterovesicular junction.
Findings Contrast column extends from the urinary bladder into a nondilated ureter Contrast column opacifies a nondilated ureter and renal collecting system Contrast opacifies a mildly dilated ureter and renal collecting system with blunting of calyceal fornices. Contrast opacifies an increasingly dilated and tortuous ureter and renal collecting system. Contrast opacifies a severely dilated and tortuous ureter and renal collecting system. There is loss of papillary impressions, and intrarenal reflux may be seen.
VCUG, voiding cystourethrogram; VUR, vesicoureteral reflux.
Evaluating genitourinary disorders in children
Figure 4 Renal duplication in a 1-month-old girl with history of prenatal hydronephrosis. Sagittal ultrasound image of the left kidney (demarcated by cursors) shows a parenchymal band dividing the upper and lower pole consistent with duplication of the collecting system. There is marked upper (U) and mild lower (L) moiety hydronephrosis, raising the possibility of upper moiety obstruction and lower moiety vesicoureteral reflux.
renal collecting system (Fig. 4). Variable amounts of pelvicaliectasis may be present. Upper and lower pole moiety ureters may be difficult to trace throughout their course even when hydroureter is present. A ureterocele associated with the upper pole moiety ureter typically manifests as an intravesicle cystic structure at the UVJ on ultrasound, and as a filling defect on VCUG, particularly on early filling images. When VUR is seen only into the lower pole moiety ureter and renal collecting system, a characteristic “drooping lily” configuration of the lower pole moiety pelvis may result.
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Figure 6 MCDK in a 2-month-old boy with prenatal diagnosis of hydronephrosis. Sagittal ultrasound image of the left kidney (demarcated by cursors) demonstrates multiple noncommunicating cysts with no intervening parenchyma. The ureter is not dilated.
Posterior Urethral Valves Posterior urethral valves are the most common cause of lower urinary obstruction in boys.32 The primary abnormality is a mucosal membrane in the prostatic urethra; however, the exact embryology of this disease is still not known. The secondary effects of this membrane from outlet obstruction result in injuries to the bladder and kidneys. Despite current aggressive medical and surgical therapies, 24%-45% of patients with posterior urethral valves still progress to renal insufficiency in their lifetime.33 Factors associated with poor long-term outcome include the presence of bilateral VUR, delayed detection, recurrent urinary infections, incontinence in patients older than 5 years and a serum creatinine of ⬎1 mg/dL at 1 year of age.34 Endoscopic valve ablation relieves the urethral obstruction and is usually performed in the first week of life. Patients with extremely dilated upper tracts sometimes require upper tract reconstruction.33 Posterior urethral valves may be suspected on prenatal ultrasound in the setting of persistent bladder distention, olioghydramnios, and urinary ascites.35 The diagnosis of posterior urethral valves is best confirmed by VCUG (Fig. 5). Findings include dilation and elongation of the posterior urethra, bladder trabeculation, and hypertrophy of the bladder neck. Other common findings shown on VCUG or ultrasound include VUR, bladder diverticula, and renal dysplasia. Occasionally, forniceal rupture, perinephric urinomas, and urine ascites are demonstrated.
Multicystic Dysplastic Kidney
Figure 5 Posterior urethral valves in a 1-day-old boy with prenatal diagnosis of hydronephrosis. Right anterior oblique image of the pelvis during the voiding phase of a VCUG demonstrates a dilated posterior urethra (arrow), narrowed bladder neck, and right vesicoureteral reflux.
Multicystic dysplastic kidney (MCDK) is a developmental abnormality of the kidney that typically results in negligible function of the affected kidney. The incidence of unilateral MCDK is approximately 1 in 4300 live births.36,37 Bilateral MCDK is rare and may result in fetal demise. Given the widespread use of prenatal sonography, most cases of MCDK are diagnosed prenatally. Historically, there was concern regarding a possible increased risk of Wilms tumor in the affected kidney and hypertension, for which prophylactic nephrectomy was typically performed. However, more recent studies found that the risk of Wilms tumor in MCDK is 1:2000 or
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Figure 7 Renal fusion anomaly: horseshoe kidney in a 10-year-old girl with myelomenigocele. Axial T2-weighted MRI image of the abdomen demonstrates fused kidneys with a parenchymal isthmus (arrow) at the lower poles overlying the spine.
less.38 Furthermore, the risk of hypertension is not greater than the general population, although when present, may be attributed to MCDK 25%-50% of the time.39 Therefore, a conservative approach regarding surgery and imaging for MCDK is currently advocated. On ultrasound, MCDK typically shows a conglomeration of noncommunicating, simple-appearing cysts in the ipsilateral renal fossa (Fig. 6). Little, if any, surrounding parenchyma is seen. Variable rates and degree of involution of MCDK over time have been reported,37 which on imaging manifests as decreased size and/or number of the multiple cysts. Compensatory hypertrophy of the unaffected kidney may also be seen. There is a 19% risk of VUR in the contralateral kidney.40 Therefore, VCUG may be appropriate if contralateral pelviectasis is detected by ultrasound, or if the patient develops a urinary tract infection.39
Renal Fusion Anomalies and Ectopia Renal fusion anomalies and ectopia both have embryologic origins relating to aberrations in the normal ascension and rotation of the bilateral kidneys during the eighth and ninth
weeks of gestation.31 Horseshoe kidney is the most common renal fusion anomaly with an estimated incidence of 1 in 400-500 live births31,41 and is often asymptomatic. In symptomatic patients, horseshoe kidney may present with urinary tract infection, or less commonly, with a mass, hematuria, or abdominal pain.31 A pelvic kidney is the most common form of renal ectopia. Less frequently, the ectopic kidney can traverse midline while ascending and fuse to the contralateral, normally located kidney, which is termed “crossed-fused” renal ectopia. On ultrasound, a horseshoe kidney may be suspected when the lower poles of the bilateral kidneys are angled medially. Cross-sectional imaging of the midline, either with ultrasound, MR (Fig. 7), or CT, may detect either a parenchymal or fibrous band of tissue joining the lower poles of the bilateral kidneys anterior to the spine. In pelvic kidney, ultrasound may show an empty renal fossa and the ectopic kidney in the ipsilateral pelvis. Crossed-fused renal ectopia may have a variety of configurations, most commonly with the superior pole of the ectopic kidney fused to the lower pole of the normally located kidney. VUR is seen in as many as 20%-30% of patients with renal fusion anomalies or ectopias.42 Hypospadias and cryptorchidism may be present in up to 5%.43
Acquired Abnormalities Scrotal Abnormalities Testicular Torsion There are 2 types of testicular torsion, extravaginal and intravaginal. Extravaginal testicular torsion is seen in neonates and may occur in utero or shortly after birth. Extravaginal testicular torsion accounts for 10% of all testicular torsions. Sonographic features of extravaginal testicular torsion vary depending on the acuity of presentation and follow a predict-
Figure 8 Testicular torsion in a 17-year-old boy with severe left testicular pain. Transverse ultrasound image of the right and left testicle demonstrates no detectable color Doppler flow within the enlarged left testicle. The echotexture of both testes are homogeneous. The patient subsequently underwent emergency surgery, which showed left testicular torsion. The left testicle was detorsed and orchipexy was performed.
Evaluating genitourinary disorders in children
Figure 9 Torsion of the testicular appendage in a 10-year-old boy with 4-day history of intermittent right scrotal pain. Sagittal ultrasound image of the right testicle demonstrates a round, hyperechoic avascular soft tissue mass (arrows) adjacent to the right epididymal head.
able evolution.44 In the acute phase, the affected testicle is enlarged, heterogeneous, and without Doppler flow. Subsequently, the testicle becomes more normal in size with persistent heterogeneity, sometimes accompanied by hydrocele. Finally, the testicle becomes small with areas of increased echogenicity.44 Intravaginal testicular torsion is typically seen in pubertal boys. The bell-clapper deformity is a predisposing condition, in which the tunica vaginalis completely surrounds the testicle, allowing for its increased mobility. Patients typically present with acute-onset scrotal pain, nausea, and vomiting. Prompt diagnosis is essential for testicular salvage, which is nearly 100% if treated within 6 hours of initial symptoms and only 20% if treated 12-24 hours after onset of symptoms.45,46 Grayscale imaging of the testicle can be normal immediately after torsion,45 with subsequent enlargement and heterogeneity of the affected testicle. A twisting of the spermatic cord may also be seen. The absence of intratesticular flow (Fig. 8) is 86% sensitive and 100% specific for testicular torsion.47 A pitfall to diagnosis is incomplete torsion, which may result in normal testicular blood flow. With spontaneous or manual detorsion, Doppler evaluation of the testicle may show normal or increased testicular blood flow.48
61 Torsion of a Testicular or Epididymal Appendage The testicular and epididymal appendages are normal structures that represent the embryologic remnants of the paramesonephric and mesonephric ducts, respectively. When torsion of either of these structures occurs, the resultant testicular pain can mimic the presentation of testicular torsion. Treatment of torsion of the testicular or epididymal appendage is generally conservative, with a goal of pain management. The normal testicular appendage may be visible by ultrasound as an ovoid, isoechoic structure along the superior pole of the testes, adjacent to the epididymis. The normal epididymal appendage may also be visible by ultrasound, as an ovoid, isoechoic structure arising from the epididymal head. The typical sonographic findings of torsion of the testicular appendage are an ovoid, hyperechoic, avascular mass (Fig. 9) measuring 5.6 mm or greater, along the superior pole of the testes adjacent to the epididymal head.49 Less frequently the mass may be hypoechoic or isoechoic.49 There is often associated testicular and epididymal hyperemia and enlargement, scrotal wall thickening, and a reactive hydrocele.50 The sonographic diagnosis of torsion of the testicular or epididymal appendage remains challenging for several reasons. First, the ultrasound findings of adjacent epididymal and testicular hyperemia seen in torsion of the testicular or epididymal appendage may mimic epididymitis.50 Second, the ovoid, avascular mass representing the torsed appendix is sometimes not evident by ultrasound. Third, the normal appendages also often appear avascular on color Doppler evaluation. Furthermore, it is often difficult to distinguish the torsed testicular appendage from a torsed epididymal appendage, although both are typically treated conservatively. Epididymitis/Epididymo-Orchitis Epididymitis and epididymoorchitis are common causes of testicular pain and are therefore important differential considerations in patients with suspected testicular torsion. Epididymitis and epididymoorchitis may be related to bacterial infection, although Somekh et al51 have suggested a postinfectious etiology. Treatment therefore may include antibiotics or supportive care. Patients with epididymitis may have
Figure 10 Epididymoorchitis in a 20-year-old male patient with right testicular pain. Sagittal ultrasound image of the right and left testicle demonstrates hyperemia of the right testis and epididymis compared to the left. The right testis is mildly heterogeneous in echogenicity and larger in size than the left testis.
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Figure 11 Seminoma in a 14-year-old boy with enlarged left testicle. Sagittal ultrasound image of the right testicle demonstrates a predominately solid, heterogeneous mass (arrow) occupying most of the mid- and inferior pole. There are some regions of cystic change within the mass and well-defined punctate calcifications at the margins.
associated genitourinary abnormalities, such as ectopic ureter and VUR, for which additional radiological evaluation may be warranted.48 On ultrasound, epididymitis typically manifests as focal or diffuse hyperemia and enlargement of the epididymis (Fig. 10). With epididymoorchitis, similar sonographic findings may be seen in the ipsilateral testicle. A reactive hydrocele and scrotal wall thickening may also be present. Of note, detorsion of a previously torsed testicle may also result in testicular and epididymal hyperemia; however, clinical correlation should be made because detorsion of the torsed testicle should result in dramatic relief of testicular pain. Testicular Neoplasm The incidence of testicular tumors in children follows a bimodal distribution, with a small peak occurring in the first three years of life and a second, larger peak occurring in
Figure 13 Tuboovarian abscess in a 17-year-old girl with worsening left lower pelvic pain, fever, and purulent vaginal discharge. Sagittal ultrasound image of the pelvis shows enlarged left ovary (Lt Ov). Also noted is a complex cystic mass (black arrow) with irregular walls and internal debris likely representing infected and enlarged left fallopian tube. The patient’s vaginal discharge was positive for Chlamydia infection. The patient was subsequently treated with a triple antibiotic regimen of ampicillin, clindamycin, and flagyl.
adults. Testicular tumors in the prepubescent child are more likely to be benign, and have a different distribution of histologic types than in adults. Teratomas, which are typically benign, are the most common testicular tumor in prepubescent boys.52 The most common malignant tumor in prepubescent males is the malignant yolk sac tumor, in contrast to seminomas in young adults.53 Metastatic leukemia may also present as a testicular mass, and is often bilateral.53,54 Ultrasound is the primary modality for screening and characterizing suspected testicular tumors (Fig. 11). An associated hydrocele is present in 15%-50% of patients with a testicular tumor.54 Staging for distant metastases is typically accomplished with CT. Common routes of metastatic spread are to the retroperitoneal lymph nodes, and for malignant yolk sac tumors, to the lungs (20%).54
Ovarian Abnormalities
Figure 12 Ovarian torsion in a 9-year-old girl with severe right-sided abdominal pain. Axial transabdominal image of the pelvis demonstrates marked enlargement of the right ovary (RT OV) compared with the left (LT OV). The patient underwent laparoscopic surgery which confirmed the diagnosis of right ovarian torsion.
Ovarian Torsion Ovarian torsion remains a difficult diagnosis for radiologists and referring clinicians. A recent large, multiinstitutional study found the annual rate of ovarian torsion similar to testicular torsion (4-5 per 100,000); however, the salvage rate much lower (40% compared with 65%).55 Ovarian torsion has a bimodal distribution with peaks occurring at ⬍1 year of age and 11-18 years of age, likely related to ovarian enlargement and cyst formation related to hormonal stimulation. In neonates with ovarian torsion, the diagnosis is sometimes suggested by prenatal imaging. After birth, infants may present with a mass or feeding intolerance.56 Common presenting symptoms in girls ⬎1 year of age include abdominal pain, nausea and vomiting, fever, and leukocytosis,57 which may mimic other genitourinary or gastrointestinal pathologies and hamper accurate, timely diagnosis. In children, ovarian torsion is most often associated with normal ovaries
Evaluating genitourinary disorders in children
63 The diagnosis of TOA may be confirmed with either CT or ultrasound (Fig. 13). However, given the radiation dose and greater cost of CT, ultrasound is the preferred initial imaging modality. Sonographic findings include a cystic or multiseptated mass with multiple internal echoes correlating with purulent fluid.61 The involved adenexa is typically undistinguishable from the mass. Most common findings on contrastenhanced CT include a multilocular inflammatory mass with a thick, enhancing abscess wall.61 Additional findings include thickening of the mesosalpinx, adjacent pelvic fat stranding, bowel wall thickening, and thickening of the uterosacral ligaments.62
Figure 14 Ovarian teratoma in a 9-year-old girl with abdominal pain and distension. Coronal image from an abdominal computed tomographic image with intravenous and oral contrast demonstrates a large, heterogeneous pelvis mass (black arrow) with areas of dense calcification and surrounding intraperitoneal fluid.
41%, followed by ovarian cysts (35%) or a benign tumor (23%). Malignancy and thromboembolic events are very rare (⬍0.5%).55 Current preferred treatment of ovarian torsion is laporoscopic detorsion. In neonates, the typical sonographic finding of ovarian torsion is a pelvic cystic mass. In girls ⬎1 year of age, the most sensitive radiologic finding of ovarian torsion is ovarian enlargement ⬎5 cm (Fig. 12) with a reported sensitivity of 83%.56 Other findings that have been described on Doppler ultrasound include small peripheral cysts secondary to edema from venous and lymphatic stasis, a spiral appearance of the torsed adnexa, and the absence of ovarian venous flow. Several studies have shown that the presence of arterial flow does not exclude the diagnosis of ovarian torsion.58 Tubo-Ovarian Abscess (TOA) TOA is a serious complication of pelvic inflammatory disease (PID) and is typically caused by an ascending sexually transmitted infection, most commonly Neisseria gonorrhoeae or Chlamydia trachomatis. The rate of TOA in patients with PID is 15%-20%.59 The most common clinical symptoms include abdominal pain, followed in descending order by vaginal discharge, vomiting, diarrhea, and fever. The most common physical examination findings are lower abdominal and cervical motion tenderness. Clinically, it is difficult to differentiate patients with TOA from PID based on laboratory studies and clinical assessment alone. Imaging is therefore often critical to diagnosis. Initially, patients are treated with broadspectrum antibiotics. Drainage or surgery is usually considered if the patient fails to respond within 48-72 hours. In a recent study, DeWitt et al60 showed that abscesses ⬎8 cm were associated with increased need for surgery or drainage.
Ovarian Neoplasm Ovarian neoplasms are rare in childhood and most commonly benign, with the risk of malignancy reported to range from 10% to 35%.63 Fortunately, childhood ovarian malignancies often are found at early stages and respond favorably to chemotherapy. Germ cell tumors (Fig. 14) are the most common ovarian tumor in children and adolescents, followed by sex cord stromal and epithelial neoplasms. Conversely, in adults, epithelial tumors are most common.64 Clinical presentation is similar with benign and malignant tumors and in descending order of frequency includes: abdominal pain, palpable mass and abdominal distension. Other symptoms include nausea, vomiting, and urinary symptoms if the tumor is large.65 Surgical treatment for benign ovarian tumors is conservative. Partial oopherectomy is preferred when possible. Malignant tumors are treated with chemotherapy and unilateral salpingooopherectomy with close follow-up of the contralateral ovary and abdomen.66
Benign Tumors Benign teratomas account for two-thirds of all pediatric ovarian tumors. The tumor markers alpha fetoprotein (AFP) and human chorionic gonadotropin-beta (B-HCG) are typically normal. US imaging predominately demonstrates a cystic mass with one or more mural nodules. Other sonographic features of ovarian teratomas are related to the presence of calcifications, and fat-fluid levels or fat.
Malignant Tumors A total of 85% of malignant ovarian tumors in childhood are of germ cell origin and are predominately malignant teratomas and dysgerminomas. The tumor markers AFP and BHCG are often elevated. Malignant teratomas and dysgerminomas are typically solid masses on diagnostic imaging. Coarse calcifications can be seen in malignant teratomas and fine stippled calcifications in dysgerminomas. Less common malignant ovarian tumors are sex cord stromal tumors (10%) and epithelial carcinomas (5%). Imaging characteristics of these tumors are highly variable and include complex masses with fluid in the cul-de-sac in 50% of cases.61
Conclusions Congenital anomalies of the UGT are relatively common disorders in children. Children with anomalies of the UGT
G.S. Phillips and A. Paladin
64 may present because of an abnormal prenatal screening sonogram, or with symptoms, such as a urinary tract infection, typically in early childhood. Radiological imaging remains the basis for accurate diagnosis. Children may also present with acquired anomalies of the UGT, such as gonadal torsion, infections, and tumors, many of which are amenable to sonographic diagnosis. Care must be taken to follow the “as low as reasonably achievable” (ALARA) principle regarding radiation exposure in children when selecting the modality and protocol for imaging children with suspected UGT anomalies.
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