Diagnosis of ruptured urinary bladder in a foal by the identification of calcium carbonate crystals in the peritoneal fluid.

A 3-day-old Quarter Horse colt was examined because of signs of severe depression, discomfort, and abdominal straining. The foal seemed disoriented, and the abdomen was tense and distended ventrally. The differential diagnoses included ruptured urinary bladder, retained meconium, septicemia/bacteremia, and neonatal maladjustment syndrome. Serum biochemical analysis revealed marked hyponatremia, hypochloremia, and moderate hyperkalemia, as well as mildly high urea, creatinine, and phosphorus concentrations. The primary differential diagnosis at this time was ruptured urinary bladder. Abdominocentesis was performed to confirm this diagnosis. Microscopic examination of abdominal fluid revealed calcium carbonate crystals, which originated from the urine of the foal. Biochemical analysis also confirmed the diagnosis of ruptured urinary bladder, because the ratio of peritoneal fluid creatinine to serum creatinine was 2.8:1. The foal died before surgical correction could be attempted.