Y-duplication of the Urethra with an Unusual Morphology (Type A4D10): Insight into the Pathogenesis.

Y-Duplication of the male urethra is a rare malformation with little more than 140 cases reported in the world literature. Usually, the penile urethra is hypoplastic, and urine is passed through the perineal channel. A 12-year-old boy with Y-duplication urethra presented with well-developed penile and perineal channels. The perineal channel was opening within the anal sphincter instead of opening within the rectum. It appears that high resistance offered by the anal sphincter redirected the urinary stream through the penile channel, thereby leading to its adequate development. On this basis, we propose a new hypothesis of "siphoning-disuse atrophy" to explain the morphogenesis of Y-duplication of the urethra. Clinical significance of distinguishing between pre- and postsphincteric opening of the perineal channel is emphasized.