Congenital urachal and urinary bladder defects leading to uroperitoneum in a neonatal quarter horse colt.

A newborn (5 h old) quarter horse colt was presented because of lethargy and severe abdominal distention. Uroperitoneum was suspected during initial workup, based on sonographic imaging and peritoneal fluid analysis. Definitive diagnosis was confirmed during exploratory celiotomy. Surgery revealed a congenitally abnormal allantoic stalk/urachal remnant and a failure of embryological fusion of the dorsal bladder wall. Recovery was successful and the animal is now a healthy, 4-year-old western performance gelding. These specific congenital abnormalities have not been previously documented in the peer-reviewed literature. Key clinical message: Congenital abnormalities of the urachus and the urinary bladder should be suspected in foals with uroperitoneum at birth. Cases involving congenital abnormalities of the urachus and urinary bladder might have favorable prognoses if animals retain adequate function of the urogenital tract and do not have secondary complications before and following surgery.