McKittrick-Wheelock Syndrome, a Rare Cause of Nonresponsive Persistent Dyselectrolytemia.

Case Presentation: A 67-year-old man presented with transient loss of consciousness and dizziness after weeks of vomiting, weakness, and recurrent syncopal episodes. Initial laboratory findings showed hyponatremia (Na 125 mEq/L), severe hypokalemia (K 2.3 mEq/L), hypochloremia (Cl 77 mEq/L), metabolic alkalemia (pH 7.5; HCO₃^- 34 mEq/L), low serum osmolality (263 mOsm/L) with inappropriately concentrated urine (332 mOsm/kg), and prerenal azotemia (creatinine 3.4 mg/dL; eGFR 19 mL/min/1.73 m²; blood urea 209 mg/dL). Contrast-enhanced CT, along with colonoscopy, identified a large mucus-secreting villous adenoma in the upper rectum. After fluid and electrolyte replacement, the patient underwent surgical resection with complete remission of symptoms and correction of electrolyte abnormalities on follow-up. Conclusion: Rectal villous adenomas should be considered in older adults with unexplained hypovolemia, hypokalemic hyponatremia, and metabolic alkalemia. Early recognition and definitive resection are curative and prevent kidney injury.