Posterior Urethral Valves:
COPUM
 
 
A. Bladder diverticuli
B. Dilated posterior urethra
C. Thin membrane ballooned and compressing urethra just distal to prostate
D. Normal distal urethra and urine beneath the foreskin
E. Ureteric reflux
 
The nomenclature, classification and embryology of posterior urethral valves have been long debated, with controversy persisting to today. The classically described entity of PUV is the most common cause of urethral obstruction in the male infant, child and adolescent. Because of the severity of the obstruction and the resulting renal damage, PUV patients represent 10-15% of pediatric renal transplants. Up to 1/3 will develop end stage renal disease. Though etiology of PUV remains unknown, it is generally believed to be a primary mesonephric anomaly involving androgenic differentiation of the prostatic and membranous portions of the male urethra. Historically, three types of PUV have been described, with the nomenclature of PUV unchallenged until the early 1990s when Dewan et al coined the term Congenital Obstructing Posterior Urethral Membrane, or COPUM, to take the place of the more classic term Posterior Urethral Valves. Their endoscopic, dissection and autopsy studies demonstrated that the usual posterior urethral lesion is infact not valvular, rather consists of a persistent membrane distal to the verumontanum that remains connected to the verumontanum by urothelial folds. They also concluded that this congenital obstructing membrane of the posterior urethra appears to exist in a spectrum of severity, with early presentation correlating with a higher degree of obstruction. Clinical presentation is classically age dependent, with the majority of infants with severe obstruction due to PUV or COPUM recognized on prenatal ultrasound. Typically they demonstrate bilateral hydronephrosis, a distended and thickened bladder, and oligohydramnios. Potter’s syndrome may be present. Palpable abdominal masses, ascites or respiratory distress suggest severe bladder outlet obstruction. Neonates who are not recognized at birth most commonly present within several weeks with urosepsis, dehydration and electrolyte abnormalities. Patients presenting during toddler and school-aged years may exhibit a dribbling urinary stream or voiding dysfunction as their primary complaint. VCUG is the gold standard for imaging this entity. The classic imaging appearance is an abrupt transition from the dilated posterior urethra to a small bulbous urethra at the level of the obstructing membrane. Actual obstructing tissue may not be visible. Associated findings include bladder wall trabeculation/muscular hypertrophy, vesicoureteral reflux, reflux into a utricle or other ducts, urinary ascites and urinoma and/or a perinephric urine collection. The top differential diagnoses include anterior urethral valves, voiding dysfunction, cecoureterocele, and post-surgical or post-traumatic urethral stricture. The ultimate goal of management of PUV or COPUM is to maximize and preserve GFR, and depends on the degree of renal insufficiency and the age of the child. The older child who presents with voiding dysfunction or urinary tract infection but satisfactory renal function is effectively treated initially by endoscopic membrane ablation. In the very young infant, the placement of a urethral catheter and initiation of prophylactic antibiotics allow assessment of baseline renal function during the first few days after birth. Further management is dictated by the level of renal function, and can include elective vesicostomy and high-loop temporizing ureteral diversion. The prognosis for children with PUV or COPUM has improved dramatically, and relates most closely to the nadir serum creatinine level. With earlier recognition, control of infection, appropriate and selective surgery, recognition of harmful urodynamic abnormalities and nephrologic management, survival rates have significantly increased. References: Campbell’s Urology, 8th ed, pp 2209-2213. Diagnostic Imaging: Pediatrics, pp 5:28-30. Krishnan A, deSouza A, Konijeti R, Baskin LS (2006) The Anatomy and Embryology of Posterior Urethral Valves. J Urol 175: 1214-1220. Imagi R, Moon DA, Dewan PA (2001) Congenital Posterior Urethral Membrane: Variable Morphological Expression. J Urol 165: 1240-1243.
 
 
 
Differential Diagnosis
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Cobb’s collar
Urethral diaphragm
Plicae colliculi
A
E
B
C
D