THE MERCK VETERINARY MANUAL
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Urethral Anomalies

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Congenital or hereditary urethral anomalies are uncommon in all domestic species; they include urethral agenesis, imperforate urethra, hypospadias, epispadias in combination with bladder exstrophy, urethral duplication, urethral diverticula, urethrorectal fistula, and urethral stenosis.

This developmental defect results from failure of the urethral grooves to fuse during phallus elongation. The urethral opening is ventral and caudal to the tip of the penis and is classified on the basis of anatomic localization as glandular, penile, scrotal, perineal, or anal. The penis or scrotum may be underdeveloped as well. This uncommon anomaly is most frequently seen in male dogs; the highest prevalence is seen in Boston Terriers, suggesting a genetic basis. The condition is also rarely seen in bulls. Clinical signs depend on the site of the urethral meatus and include urine scalding and complications of increased susceptibility to urinary tract infection. Although surgical correction also depends on the site of the urethral meatus, a modification of the prescrotal urethrostomy is generally useful.

These congenital anomalies predominantly affect dogs, cats, and horses. The anomalies are more common in males than females; males are more likely to develop urethrorectal fistulas, whereas in females the rectovaginal fistulas predominate. In dogs, English Bulldogs seem to have a breed predisposition, possibly as a congenital defect due to abnormal separation of the embryonal cloaca into the urethra and rectum. Clinical signs include hematuria and dysuria secondary to urinary tract infection. Simultaneous passage of urine from the anus and urethra during micturition may be noted. Appropriate therapy consists of surgical correction and concurrent management of urinary tract infection.

Last full review/revision July 2013 by Scott D. Fitzgerald, DVM, PhD, DACVP, DACPV

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