Vesicourachal diverticulum in a Santa Ines lamb: a rare congenital anomaly

ABSTRACT: The urachus is a canal that connects the urinary bladder with the allantoic sac through the umbilical cord in the prenatal period, transporting urine from the embryo or the fetus to the placenta and involuting after birth. Vesicourachal diverticulum occurs when the obliteration of the urachal lumen is incomplete, resulting in a discontinuity in the muscular layer of the bladder. A 3-month-old male Santa Inês lamb, weighing 20.5 kg, presented bilateral ventral abdominal distension, inappetence, severe apathy, mixed dyspnea, bruxism and an estimated degree of dehydration of 10%. On ultrasound examination, a marked accumulation of free fluid was observed in the abdominal cavity, and paracentesis revealed uroperitoneum. Due to the severity of the clinical condition the animal was euthanized. Necropsy revealed 8 liters of peritoneal fluid and a conical structure with approximately 1 cm diameter located at the apex of the bladder that was ruptured. The histopathological evaluation was consistent with a vesicourachal diverticulum. This congenital anomaly is considered rare in small ruminants, and this is the first report in the literature of a vesicourachal diverticulum in a lamb.