Anterior Urethral Valves
Though uncommon, congenital obstruction of the anterior urethra can be caused by anterior urethral valves. These account for the second most common cause of congenital urethral obstruction in boys. This entity consists of a prominent semilunar fold in the ventral male urethra either bulbous or penile urethra. Of variable severity and often obstructing they may result in the same sequelae as posterior urethral valves. There is frequently dilatation of the anterior urethra proximal to the valve. This may mimic a diverticulum, though presence of an obstructing anterior urethral membrane without diverticulum has been described. Though the patho-etiology is not entirely clear, accepted hypotheses suggest that this anomaly may represent incomplete fusion of a segment of the urethral plate, or focal incomplete development of the corpus spongiosum with ballooning of the urethral mucosa due to inadequate support. During micturation, urine fills the ventral urethral sacculation and/or diverticulum proximal to the valve, elevating the lip of the valve and pressing it against the dorsal wall of the urethra, limiting the flow of urine. Clinically, patients may present with penis swelling noted during micturation, caused by dilatation of the saccule and/or obstructive dilatation of the urethra. Infants may present with urosepsis and/or renal insufficiency if the valve is obstructing. Small, non-obstructing lesions often appear stable for many years and do not show continuous enlargement and worsening obstruction. Voiding cystourethrography confirms anterior urethral valves, and demonstrates contrast filling an oval ventral out pouching of the anterior urethra. Difficulties with catheterization may occur because the catheter preferentially enters the saccule and/or diverticulum. A coude-tipped catheter can be used to glide past the valve lip and saccule, into the proximal urethra and bladder. Renal sonography and scintigraphy can be used as adjunct imaging to assess anatomy and function of the upper urinary tract. Initial management of this anomaly parallels that for posterior urethral valves, with transurethral or suprapubic catheter drainage, antibiotic therapy, electrolyte management and assessment of renal function in infants who present with obstruction. Diversion, such as loop ureterostomy or vesicostomy might be chosen depending on clinical circumstances. Surgical management may involve endoscopic or open treatment. Electrocautery can be directed toward the distal margin of the diverticulum, versus open resection and reconstruction of the diverticulum. Some advocate the latter technique for more homogeneous reconstruction of urethra diameter. Patch graft urethroplasty is completed as well, in which grafting of penile shaft skin from the corona is used for urethroplasty. Primary differential diagnostic considerations for this anomaly include congenital anterior urethral diverticulum, dilatation of a Cowper gland duct, post-surgical or post-traumatic urethral stricture. Reference: Campbell’s Urology, 8th ed, pp 2225-2226. Diagnostic Imaging: Pediatrics, pp 5:29-30. Practical Pediatric Imaging; Diagnostic Radiology of Infants and Children, 3rd ed, pp1059.
A. Anterior urethral valves
B. Associated dilatation of anterior and posterior urethra proximal to obstructing valves
A
B
Differential Diagnosis
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Urethral diverticulum
Posterior valve
Urethral stricture