What are the classic electrolyte changes seen with ruptured bladder in foals?

• A. Hyponatremia, hypochloremia, hyperkalemia
• B. Hypernatremia, hyperchloremia, hypokalemia
• C. Hyperkalemia only
• D. Hyponatremia only

Answer: (A)

When a foal’s bladder ruptures, urine accumulates in the peritoneal cavity (uroperitoneum). The peritoneum then allows solutes from the urine to diffuse back into the bloodstream. Urine typically has higher potassium and relatively lower sodium and chloride compared with plasma, so as these solutes are absorbed, potassium rises while sodium and chloride fall. This pattern—hyponatremia, hypochloremia, and hyperkalemia—is the classic electrolyte finding with uroperitoneum. The hyperkalemia is particularly dangerous because it can affect heart rhythm, so recognizing this combination is key.