AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Background

A posterior urethral valve is an abnormal congenital obstructing membrane that is located within the posterior male urethra; this valve is the most common cause of bladder outlet obstruction in male children.

The valve is believed to result from abnormal embryologic development of the fetal posterior urethra. The classic categorization of posterior urethral valves into types I, II, and III was developed by Young et al in 1919¹ (see Anatomy, Types of posterior urethral valves) and has undergone modification over time based on clinical observation and better understanding of the embryologic events that lead to normal urethral development.

Regardless of the type of valve, however, all valves essentially obstruct normal bladder emptying. This mechanical obstruction increases voiding pressures and may alter normal development of the fetal bladder and kidneys. Typically, children with higher degrees of obstruction present earlier with the most severe symptoms. A spectrum of signs and symptoms ranging from severe obstruction with resultant renal failure and pulmonary hypoplasia to mild obstructive symptoms of voiding dysfunction may be noted.

With routine obstetric ultrasonography, the prenatal diagnosis of posterior urethral valve is becoming increasingly common, leading to investigative efforts at improving bladder drainage in utero. Postnatal diagnostic modalities and treatment algorithms are fairly well established, and valve management has become less invasive with the development of pediatric endoscopic instruments. The final goal of all therapeutic intervention for posterior urethral valve is proper urinary tract function with protection of the renal units. As a result of progress in the diagnosis, treatment, and surveillance of this condition, morbidity and mortality rates have markedly diminished over the past several decades.

For excellent patient education resources, visit eMedicine's Men's Health Center. Also, see eMedicine's patient education article Understanding the Male Anatomy.

Pathophysiology

Posterior urethral valves can appear at the earliest stage of urinary tract development; therefore, the entire urinary tract develops in an abnormal environment of high intraluminal pressure due to the mechanical obstruction. Permanent defects in the function of the kidneys, ureters, and bladder may result from prenatal maldevelopment—despite adequate decompression of the urinary tract after birth.

Renal function may be impaired for several reasons. Renal parenchymal dysplasia is common and may be related to maldevelopment of the metanephric blastema (renal precursor tissue) in an environment of high intraluminal pressure. In other cases, renal tubular function may be affected by high pressures that result in poor urinary concentrating ability, with resultant diuresis and the development of ureteral and bladder dysfunction due to high urinary production. The affected kidneys may function well initially, but they have a reduced renal reserve. Renal deterioration may also occur due to hyperfiltration injury that causes glomerulosclerosis, chronic pyelonephritis associated with vesicoureteral reflux, urinary stasis, or incomplete bladder emptying—all of which are common in boys with posterior urethral valves and which can cause further insult to the developing kidneys.

Hydronephrosis is common and may be due to a variety of causes. First, bladder dysfunction with high back pressures on the ureter may be causative. Second, the ureter itself may develop an abnormally deficient musculature due to chronic distention from high pressure or high urine flow. Third, high urinary flow due to the lack of urinary concentrating ability of the nephron can dilate the kidneys and ureters. Finally, there may be abnormalities of the vesicoureteral junction such as reflux or, rarely, ureterovesical obstruction.

Vesicoureteral reflux is present in one half of male patients with posterior urethral valves and is often thought to be physiologic as a result of high bladder pressures that overcome the competence of the ureterovesical junction. Reflux may also be anatomic, secondary to abnormal ureteral orifice position that is caused by an abnormal ureteral bud development during embryogenesis.

Bladder dysfunction is thought to be caused by alterations in collagen deposition and the development of detrusor smooth muscle cells. Several authors have noted high pressure due to poor compliance or uninhibited contraction of the detrusor muscle and eventual myogenic failure. In mild cases, incontinence may be present; in severe cases, ongoing deterioration of renal function occurs. Bladder dysfunction often improves over time after definitive treatment of the obstruction. Management of the persistently hostile bladder is imperative to diminish further renal impairment and the risk of urinary tract infection (UTI), persistent hydronephrosis or vesicoureteral reflux, and incontinence.

Several protective mechanisms may develop in boys with posterior urethral valves, which may lower intraluminal pressures and allow at least one renal unit to develop more normally. These mechanisms include massive unilateral vesicoureteral reflux (usually associated with an ipsilateral dysplastic kidney, known as vesicoureteral reflux and dysplasia syndrome), bladder diverticula, and urinary ascites.

Frequency

United States

A posterior urethral valve occurs in approximately 1 in 5000 live male births. The prevalence is in the range of 1:2375 to 1:8000.

International

The incidence rates are similar in countries worldwide.

Mortality/Morbidity

The early diagnosis and management of posterior urethral valves in boys has led to significant improvements in the morbidity and mortality rates for this condition.

• Perinatal mortality, formerly around 50%, was usually secondary to pulmonary hypoplasia and sepsis. Mortality rates have declined to <10% with improvements in perinatal care, as well as increases in the elective termination of pregnancies following prenatal detection of the condition.
• The long-term prognosis and morbidity of affected boys depend on the degree of parenchymal dysfunction, which may be prenatally determined. In addition, one frequently cited indicator is a nadir serum creatinine level less than 0.8 mg/dL at age 1 year; this suggests a good prognosis for long-term renal function. Proper management of the adverse urinary tract characteristics is critical to optimize renal function, even when renal function is impaired.
• Renal transplantation has been instrumental in the treatment of patients with posterior urethral valve and end-stage renal disease. Several studies have shown that transplantation is an effective therapy; however, hostile bladder parameters should be ruled out or corrected to ensure allograft survival.

Race

No defined racial predilection has been identified.

Sex

Posterior urethral valve affects only males.

Age

The posterior urethral valve defect is congenital, and as noted previously (see Introduction, Background), those males with more serious obstruction manifest symptoms earlier. If the condition is not diagnosed during prenatal ultrasonography, patients with severe obstruction present within days of birth, or toddlers present with voiding dysfunction and UTI. Incontinence is a rare presenting symptom in older boys with mild obstruction.

Anatomy

Structure and development of posterior urethral valves

The male urethra is composed of posterior and anterior urethral segments. The posterior urethra consists of the prostatic urethra (the urethra that traverses the prostate from the bladder neck to the urogenital diaphragm) and the membranous urethra (the segment that traverses the urogenital diaphragm).

Embryologically, posterior urethral valves are thought to arise due to an abnormally anterior insertion of the mesonephric (wolffian) duct on the cloaca before its division into the urogenital sinus and the anorectal canal. Remnants of normal insertion are noted in normal male urethras as plicae colliculi, folds that run distal and lateral to the verumontanum (a midline prominence in the midprostatic urethra where the ejaculatory ducts enter). This anterior insertion is thought to exaggerate the normal folds, with the distinction of being thicker, more prominent, and fused anteriorly.

Types of posterior urethral valves

Young et al initially categorized posterior urethral valves into 3 types.¹

The type I valve is a bicuspid valve that radiates distally from the posterior edge of the verumontanum to the anterior proximal membranous urethra. There is a variable aperture to allow urine flow during voiding; however, the fused portion fills with urine and bulges into the membranous urethra. This gives the characteristic sail-in-the-wind finding commonly seen on voiding cystourethrography (VCUG). Type I valves account for 95% of all valves.

The type II valve is no longer considered an obstructing valve; rather, it is thought to be a sequela of voiding dysfunction. It was described as a hypertrophic band of superficial muscle that runs along the posterolateral wall of the urethra from the ureteral orifice to the verumontanum. Therefore, these valves can be differentiated from type I and type III valves by their location proximal to the verumontanum. However, although this muscular hypertrophy may present with the anatomic obstruction of a posterior urethral valve, it may also occur with other nonobstructive causes of high-pressure voiding.

The type III valve is a circumferential membrane or diaphragm that is located at the membranous urethra, which is thought to result from the incomplete regression of the urogenital membrane during embryogenesis. There is a central aperture, and the central portions of the ring may prolapse into the more distal urethra during voiding, which results in a wind-sock appearance on VCUG. Type III valves account for almost 5% of all valves.

Despite the former classification of posterior urethral valves, a theory holds that there is most likely a single obstructive membrane that is altered by the passage of urethral catheters or cystoscopes, which results in variable tears of the membrane; these membranes may be perceived as a type I or type III valve. This concept of a single type of valve is referred to as congenital obstructing posterior urethral membrane.²

Clinical Details

The clinical presentation of posterior urethral valve is extremely variable. Increasingly, these valves are identified on antenatal ultrasonography. A history of oligohydramnios, bilateral hydronephrosis, and incomplete emptying of a thick-walled bladder may be elicited. Severely affected newborns may exhibit respiratory difficulties due to pulmonary hypoplasia, Potter facies, ascites, and a palpable abdominal mass (eg, involving the bladder or ureter).

It is common for newborns to not void for the first 24 hours of life; thus, a history of anuria may be misleading. A presentation in the neonatal period of abdominal distention due to a dilated bladder, ureters, and kidneys or due to urinary ascites has also been recognized.

If the diagnosis of posterior urethral valve is not recognized at birth, within weeks of birth, severely affected boys often present with urosepsis, dehydration, electrolyte abnormalities, or failure to thrive. A poor, dribbling urine stream may be noted. Toddlers often present with voiding dysfunction or UTI, and school-aged boys usually come to the clinician's attention because of urinary incontinence.

Preferred Examination

Renal ultrasonography in the male newborn can confirm the antenatal findings of hydroureteronephrosis with a dilated, thick-walled bladder and a dilated posterior urethra. In symptomatic older boys, ultrasonography is useful to screen for these findings of posterior urethral valves. VCUG is necessary to confirm the diagnosis and to assess the bladder for associated findings of trabeculation, diverticula, and vesicoureteral reflux.

Limitations of Techniques

VCUG is considered the diagnostic criterion standard imaging modality for posterior urethral valves, but normal mucosal folds (plicae colliculi) may appear as lucencies on VCUG and suggest the presence of valve leaflets. Conversely, valve leaflets may not be visible on VCUG; however, other associated findings with valves should raise suspicions. Also, improper VCUG technique can cause the diagnosis to be missed by omission of adequate urethral views during voiding or failure to remove the urinary catheter, which can stent the valves open during voiding.

Findings from renal ultrasonography, computed tomography (CT) scanning, intravenous pyelography (IVP), and renal scanning are not diagnostic for posterior urethral valves, although each modality may add details regarding the structure or function of the urinary tract.

DIFFERENTIALS

Section 3 of 11  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Other Problems to Be Considered

Anatomic obstructive disorders

Urethral atresia
Anterior urethral valves
Syringocele
Megalourethra
Congenital urethral polyp
Urethral duplication
Congenital urethral stricture (Cobb collar)
Prune-belly syndrome (Eagle-Barrett syndrome or triad syndrome)
Plicae colliculi (normal anatomic structure)

Functional voiding disorders

Neuropathic bladder
Detrusor sphincter dyssynergy/dyssynergia
Small-capacity hypertonic bladder
Detrusor hyperreflexia
Nonneurogenic neurogenic bladder (Hinman syndrome)

RADIOGRAPH

Section 4 of 11  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

Plain radiographs do not add to the actual diagnosis of posterior urethral valves; however, chest radiography may be useful in the evaluation of pulmonary hypoplasia, and images of the kidneys, ureters, and bladder (KUB images) may show the ground-glass appearance of urinary ascites, if present.

VCUG is considered the diagnostic study of choice (see Images 1-5) for the evaluation of posterior urethral valves. The bladder is typically thickened with trabeculae and may exhibit vesicoureteral reflux or, less commonly, diverticula. The bladder neck is typically hypertrophic, leading to a lucent ring or collar. On voiding, the posterior urethra is dilated (ie, shield shaped), and valve leaflets may be seen as lucencies, giving the appearance of a spinning top. If leaflets are not visible, a commonly associated finding of posterior urethral bulging distally over the bulbar urethra may be noted. The anterior urethra is typically underfilled, and voiding is incomplete.

IVP is not routinely used in children because the contrast agent is poorly concentrated and visualized in newborn kidneys, particularly if renal function is diminished. Elevated serum creatinine levels may preclude the use of intravenous (IV) contrast material. IVP can show an absent kidney in the case of renal dysplasia or delayed renal function with persistent high intraluminal pressures. Hydroureteronephrosis may be seen. Delayed images may show bladder or urethral pathology, but the lower urinary tract is better visualized with VCUG.

Degree of Confidence

Again, VCUG is the criterion standard diagnostic test for posterior urethral valves. The constellation of bladder and urethral abnormalities with or without valve identification typically confirms the presence of valves. Cystourethroscopy with the patient under general anesthesia may be required to formally confirm the presence of posterior urethral valves at the time of intervention.

False Positives/Negatives

Regarding false-positive findings, any of the obstructive etiologies listed in the Differentials section above may show bladder and upper-tract changes that are typical of posterior urethral valves. However, most of the listed conditions have significant differences in imaging that separate them from posterior valves, such as the location of involvement (anterior valves, syringocele), associated anomalies (prune-belly syndrome), and degree of impairment (plicae colliculi). False-positive results should not be seen with functional disorders because the posterior urethra should not be dilated, except potentially in detrusor sphincter dyssynergy/dyssynergia.

False-negative results are rarely noted in cases of posterior urethral valve that have minimal anatomic obstruction and, thus, limited functional impairment and upper-tract changes. In boys with these findings, VCUG may not show valve leaflets. However, in a boy with the clinical stigmata of a posterior valve in whom definitive visualization of the valve is lacking, cystourethroscopy may be indicated to rule out urethral pathology. It is important to obtain voiding images in the lateral view with—and, ideally, without—the catheter in situ, because the images with the catheter removed optimally demonstrate the valves (see Images 3-5). It has long been believed that leaving the urethral catheter in place may hold the valves open and prevent proper visualization, but that does not happen in practice if good urethral distention is achieved.

In the postoperative setting after valve ablation, some posterior urethral dilatation usually persists, with secondary bladder changes. However, if incomplete valve ablation is suspected, then repeating cystourethroscopy rather than VCUG is recommended.

CT SCAN

Section 5 of 11  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

Rarely necessary in neonates, CT scans with IV contrast enhancement may reveal dysplastic and/or dilated kidneys with delayed renal function and excretion, hydroureter, dilated bladder with wall thickening, trabeculation, and diverticula. A dilated posterior urethra might be seen, although leaflets may be easily missed. Elevated serum creatinine levels generally preclude use of IV contrast material.

Degree of Confidence

CT scans cannot reliably depict valves, although they should reveal the sequelae of bladder outlet obstruction.

False Positives/Negatives

False findings are identical to those for radiography. An exception is that plicae colliculi, which might be seen on VCUG studies, should not be noted on CT scans.

MRI

Section 6 of 11  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

MRI findings are similar to those of CT scanning except that enhancement with IV gadolinium-based contrast agents may allow functional as well as anatomic assessment.

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving  or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.

Degree of Confidence

The degree of confidence is similar to that with CT scanning.

False Positives/Negatives

False findings are similar to those observed with CT scanning.

ULTRASOUND

Section 7 of 11  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

A proper ultrasonographic study to evaluate the urinary tract must include images of both kidneys, the ureters, and the bladder. Hydroureteronephrosis with or without cortical thinning, a thick-walled bladder with trabeculation and diverticula, and a dilated posterior urethra with a hypertrophic bladder neck are usually seen. In the setting of renal dysplasia, the renal parenchyma is typically hyperechogenic with visible small cysts (<10 mm), but in the most mildly affected cases, renal ultrasound findings may be normal (see Images 6-10). Echogenic lines that are the actual valve leaflets might be seen. The combination of the dilated, thick-walled bladder and dilated posterior urethra has been described as a keyhole appearance (see Image 11).

The bladder may be of large or small volume, but it is invariably thick-walled. Urinary ascites or perinephric collections due to urinomas may also be seen, most commonly soon after birth, and are caused by rupture of the urinary tract, typically at the level of the calyces. A suggestive prenatal sonogram reveals a male fetus with bilateral hydroureteronephrosis; a dilated and thickened bladder with poor emptying; and, possibly, oligohydramnios (see Images 12-24). After the diagnosis has been established and initial management has begun, ultrasonography is useful to follow up on the degree of hydronephrosis and parenchymal integrity after treatment, as well as the adequacy of bladder evacuation with voiding and the resolution of any urinomas.

Degree of Confidence

The sum of the ultrasonographic findings with clinical correlates, combined with the rarity of other obstructive lesions, is highly indicative of posterior urethral valves. The valves typically cannot be seen on sonograms, and VCUG is required to make the definitive diagnosis.

False Positives/Negatives

False-positive results may be seen with other obstructive and functional disorders of bladder emptying. The ultrasonographic findings are the final common signs of most of the conditions in the differential diagnosis (see Differentials). False-negative results may be seen in mild cases without upper-tract abnormality and an essentially normal bladder. In a study by Williams et al, the reported sensitivity of renal and bladder ultrasonography for valves was 87% in patients younger than 4 years and 98% for those age 4 years or older.³

NUCLEAR MEDICINE

Section 8 of 11  

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• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

Nuclear cystography has no role in the diagnosis of posterior urethral valves because of the poor anatomic detail, but this modality can depict the presence of vesicoureteral reflux. However, grading of such reflux is not as accurate as with contrast VCUG.

Nuclear renography may be used to assess upper-tract consequences of bladder outlet obstruction. A urethral catheter must be placed before the study to eliminate the effect of a distended, high-pressure bladder on renal function and drainage. An absent or dysplastic kidney is seen as a photopenic area in the renal fossa. Delayed visualization of a renal unit with a slow rise to peak activity suggests altered renal function. Differential renal function is important to estimate relative renal impairment and is based on activity at 1-2 minutes after injection of a tracer. Hydronephrosis with ureteral dilatation can represent ureterovesical obstruction or chronic nonobstructive changes of posterior urethral valves; the latter should demonstrate washout after furosemide administration, if renal function is adequate (see Images 25-26).

Degree of Confidence

Nuclear medicine study is poor for the specific diagnosis of posterior urethral valves, but it is excellent for assessment of the upper-tract consequences (see Nuclear Medicine, Findings).

False Positives/Negatives

False-positive findings can result when a urethral catheter is not used. High bladder storage pressure or vesicoureteral reflux can prevent drainage from the kidney and ureter. Distal ureteral obstruction by ureterovesical junction obstruction or a ureterocele can mimic the changes of valves. False-negative findings can be seen in cases in which there is normal renal function and drainage.

INTERVENTION

Section 9 of 11  

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• Introduction
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• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Prenatal intervention is essentially experimental and limited to a few centers. Options include percutaneous placement of a vesicoamniotic shunt, open fetal surgery, and fetal cystoscopic ablation. Significant complications may occur, resulting in maternal or fetal morbidity, as well as fetal loss. It is unclear whether prenatal intervention has a significant effect on the long-term prognosis of males with posterior urethral valves. Pulmonary function has been shown to benefit from the reversal of oligohydramnios, but no renal benefit has been noted.

In newborn males with suspected posterior urethral valves, ultrasonography should be performed in the first 24 hours to document bladder dilatation and changes in the upper tract. After the study, a 5F feeding tube may be placed as a urethral catheter. Some pediatric urologists favor a suprapubic catheter for the initial bladder drainage; however, urethral catheterization may be difficult because the valves obstruct retrograde passage of the catheter or the catheter may obliterate more flimsy valves, making later VCUG more difficult to interpret.

When VCUG is performed, ideally the urethral catheter should be removed during voiding to optimally demonstrate the valves. When the valves are diagnosed, the urethral catheter should then be replaced to continue decompression of the bladder. A serum creatinine level is determined to assess renal function. If the renal function is stable, transurethral valve ablation is performed through a cystoscope with a cold knife, electrocautery, or laser energy. If the serum creatinine level does not stabilize and if the upper tracts show no improvement, more drastic measures for bladder drainage may be required. Vesicostomy may be performed in such cases or if the urethra is too small to accept the small cystoscope. Routine performance of more proximal upper-tract diversion (pyelostomy, cutaneous ureterostomy) is reserved for rare circumstances.

The symptomatic older child usually undergoes cystoscopy for diagnosis with endoscopic ablation of the valves, if seen.

Medical/Legal Pitfalls

• Despite antenatal diagnosis of posterior urethral valves, severely affected male fetuses may die in utero or early in life. Early diagnosis may require the clinician to make recommendations regarding the potential viability and quality of life for an affected male fetus so that parents may make informed decisions regarding the elective termination of pregnancy. The upper gestational age limit for elective termination varies among states and countries.
• Lack of definitive documentation of the valves on radiologic studies does not rule out their presence. Newborns with suspected lower tract obstruction and findings on VCUG should undergo decompression with a catheter until definitive therapy is performed. Ultimate renal function may improve as long as the obstruction is relieved early. Cystourethroscopy may ultimately be required to make the diagnosis.
• Cystourethroscopy and endoscopic management may lead to urethral stricture formation. Incontinence of urine due to iatrogenic sphincter injury may not be seen until the boy reaches the normal age of continence. Retrograde ejaculation after puberty may be seen and be a cause of infertility.
• Voiding dysfunction (urgency, frequency, and enuresis) is not uncommon in boys and typically improves spontaneously. If the symptoms are severe or do not improve, obstruction due to posterior urethral valve must be ruled out with VCUG. A missed diagnosis of obstruction may result in permanent bladder dysfunction, with possible renal failure.

MULTIMEDIA

Section 10 of 11  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Media file 1:  Anteroposterior view of the abdomen during a voiding cystourethrographic study. This image demonstrates a dilated bladder with trabeculation, diverticula, and bilateral massive reflux.
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Media file 2:  Anteroposterior view of the abdomen during a voiding cystourethrographic study. This image demonstrates bilateral grade 4 vesicoureteral reflux. No intrarenal reflux is noted.
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Media file 3:  Sagittal voiding image of the bladder and urethra that was obtained from a voiding cystourethrographic study before catheter removal. This image demonstrates a trabeculated, hypertrophied bladder. The bladder neck is hypertrophied and well demarcated between the body of the bladder and the dilated posterior urethra, the latter of which has the classic spinnaker-sail appearance.
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Media file 4:  Late anteroposterior image from a voiding cystourethrographic study. This image demonstrates a small, trabeculated bladder with bilateral diverticula. The posterior urethra is dilated.
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Media file 5:  Lateral view of a voiding cystourethrographic study during voiding after catheter removal. The dilated posterior urethra is highly suggestive of a posterior urethral valve, which is seen as the nonopacified line that separates the dilated posterior urethra from the normal-caliber distal urethra. The absence of the urethral catheter may be critical to demonstrate the valve, as good urethral distention is mandatory.
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Media type:  Radiograph

Media file 6:  Longitudinal sonogram of the right kidney in a 1-day-old male infant (same patient as in Images 7-10). This image demonstrates grade 4 hydronephrosis, with thinning of the renal parenchyma.
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Media file 7:  Longitudinal sonogram of the right kidney (same patient as in Images 6, 8-10). This image shows that the hypoechoic areas interconnect, a finding that is consistent with hydronephrosis rather than multiple distinct renal cysts, which do not interconnect.
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Media type:  Ultrasound

Media file 8:  Renal sonogram (same patient as in Images 6-7, 9-10). This image shows grade 4 hydronephrosis of the left kidney.
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Media file 9:  Renal sonogram (same patient as in Images 6-8, 10). This image shows grade 4 hydronephrosis of the left kidney.
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Media file 10:  Renal sonogram (in the same patient as in Images 6-9). This image shows grade 4 hydronephrosis of the left kidney.
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Media file 11:  Longitudinal sonogram of the bladder. This image demonstrates a distended bladder, with the classic keyhole appearance of the posterior urethra seen distally (on the right).
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Media file 12:  Prenatal longitudinal sonogram of the right kidney. This image demonstrates significant hydronephrosis with possible renal cortical thinning. The kidney is larger than expected for the patient's gestational age.
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Media file 13:  Prenatal longitudinal sonogram of the left kidney. This image demonstrates significant hydronephrosis with possible renal cortical thinning. As is the case with the right kidney, the left kidney is longer than expected for the patient's gestational age (same patient as in Image 12).
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Media file 14:  Prenatal axial sonogram of the abdomen. This image demonstrates bilateral hydronephrosis. (The spine is the echogenic ring near the top of the image.)
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Media file 15:  Prenatal sonogram almost in the coronal plane. A distended urinary bladder is depicted throughout this image as well as previous prenatal ultrasonographic studies. The bladder wall may be thickened (see Image 16).
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Media file 16:  Prenatal sonogram almost in the coronal plane (same patient as in Image 15). A distended urinary bladder is depicted throughout this image as well as previous prenatal ultrasonographic studies. The bladder wall may be thickened.
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Media file 17:  An initial prenatal sonogram. This image demonstrates a distended urinary bladder and oligohydramnios.
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Media file 18:  A first prenatal sonogram. This image demonstrates a cystic area in the region of the left renal fossa. This cystic area appears to be separate from the left kidney, which is located just to the left of the fluid collection on the image. The fluid collection was thought to represent a urinoma.
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Media file 19:  Sonogram. This image demonstrates mild pelvocaliectasis that involves the right kidney (same patient as in Images 20-24).
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Media file 20:  A second prenatal sonogram (same patient as in Images 19 and 21-24). This image demonstrates interval resolution of the fluid collection in the left renal fossa and a left kidney with pelvocaliectasis.
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Media file 21:  A second prenatal sonogram (same patient as in Images 19-20, 22-24). This image also demonstrates pelvocaliectasis that involves the right kidney.
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Media file 22:  A second prenatal sonogram, transverse view (same patient as in Images 19-21, 23-24). This image of the abdomen demonstrates bilateral pelvocaliectasis.
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Media file 23:  Postnatal sonogram on the first day of life (same patient as in Images 19-22, 24). This sagittal image of the bladder demonstrates bladder wall thickening and prominence of the distal left ureter.
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Media file 24:  Transverse sonogram of the bladder (same patient as in Images 19-23). Bladder wall thickening is again demonstrated.
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Media file 25:  Excretory images obtained from renal scanning that was performed with diethylenetriaminepentaacetic acid. This study demonstrates radiotracer accumulation within the dilated renal collecting systems and dilated ureters. The bladder remains empty because of catheter drainage.
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Media file 26:  Renal scanning images performed with diethylenetriaminepentaacetic acid. This study demonstrates accumulation of radiotracer within the renal collecting systems bilaterally; within the dilated ureters bilaterally; and within a small, irregular-appearing bladder. Renograms (top right and bottom left) demonstrate poor clearance of contrast material from the renal collecting systems. The relatively poorer function in the left kidney reflects congenital renal dysplasia.
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Media type:  Image

REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• MRI
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

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Article Last Updated: Aug 7, 2007