This review describes causes, clinical signs, metabolic changes in serum and peritoneal fluid, diagnosis and treatment of uroperitoneum. Rupture of the bladder or urachus is the most common cause of uroperitoneum. The main clinical sign is a pear-shaped enlargement of the abdomen accompanied by gradual deterioration in demeanour and appetite. Ultrasonography shows massive accumulation of anechoic abdominal fluid and organs suspended in the fluid. Bladder defects may be seen cystoscopically and the proximal part of a persistent urachus can be explored endoscopically. Abdominocentesis yields light yellow fluid. A peritoneal-to-serum creatinine concentration ratio of 2 or greater is diagnostic of uroperitoneum. Treatment consists of surgical repair of the defect.