Perineal urinary bladder diverticulum resulting in partial urinary obstruction in a rhesus monkey.

A 16-year-old rhesus monkey with perineal swelling and urinary obstruction was found to have a congenital urinary bladder diverticulum. Because the diverticulum was located at the trigone, its distention partially obstructed the urethra, resulting in incomplete voiding. The diverticulum was resected and did not redevelop.