In a foal with ruptured bladder, which pattern of potassium, sodium, and chloride would you expect?

• A. High K, Low Na, Low Cl
• B. Low K, High Na, High Cl
• C. High K, High Na, High Cl
• D. Low K, Low Na, Low Cl

Answer: (A)

When the bladder ruptures, urine leaks into the peritoneal cavity and the peritoneum acts like a dialysis membrane, allowing diffusion between urine in the abdomen and the blood. Urine typically has relatively high potassium and relatively low sodium and chloride compared with plasma. Through diffusion, potassium moves from the urine (peritoneal fluid) into the bloodstream, raising serum potassium, while sodium and chloride move from the blood into the peritoneal space, lowering serum sodium and chloride. So the expected pattern is high potassium with low sodium and low chloride. This electrolyte profile is a classic clue of uroperitoneal leakage in foals.