A 70-year-old man visited our hospital with the complaint of appetite loss. He had undergone an ileal conduit reconstruction due to bilateral ileo-ureteral stenosis 3 months before. Blood gas analysis showed metabolic acidosis (pH 7.091, pO2 120.5 mmHg, pCO2 20.9 mmHg, HCO3 6.1 mmHg), and blood analysis revealed serum chloride 121 mmol/l (normal range: 99-110). Sodium bicarbonate was immediately administered, his condition improved. We concluded that reabsorption of urine from the ileal conduit due to dehydration had caused hyperchloremic metabolic acidosis. He was given sodium bicarbonate 2 g per day, and his blood gas analysis and serum electrolytes remained within normal limits.