With an ultrasound finding of free fluid and no other obvious abnormalities, which condition is most likely the cause of colic?

• A. Ruptured urinary bladder
• B. Meconium impaction
• C. Gastric ulcers
• D. Intestinal obstruction

Answer: (A)

Free fluid in the abdomen on ultrasound, when there are no other obvious intra-abdominal abnormalities, points to urine in the peritoneal cavity from a ruptured urinary bladder (uroperitoneum). This condition releases urine into the abdomen, creating a clear ultrasound finding of free fluid even when other structures look normal. Other causes would typically present with different ultrasound signs: meconium impaction usually shows fecal material and distended bowel segments; gastric ulcers are not typically seen as a cause of free abdominal fluid and would not produce that fluid signal; intestinal obstruction would more likely reveal dilated loops, gas patterns, or localized distension rather than just free fluid. Thus, the presence of free intraperitoneal fluid with otherwise unremarkable findings makes bladder rupture the most likely cause of colic in this scenario.