The aim of preoperative treatment of infantile hypertrophic pyloric stenosis (IHPS) is to restore dehydration and metabolic alkaosis. One hundred and eighty-three cases of IHPS treated at Tokyo Metropolitan Kiyose Childre's Hospital were reviewed, and the relationship between serum electrolites, urinary electrolites and blood pH, BE and HCO_3~ were studied. Even if serum chloride concentration were 95mEq/ l or more (52 patients) , urinary chloride concentration were below 25mEq/ l in 46 (88.5%). Urinary sodium excretion was also low, and those results suggested the depletion of electrolites and persistent dehydration. When urinary chloride concentration was 25mEq/l or more, blood pH, BE, and HCO_3~ became normal. It is recommended that pyloromyoromy is planned when urinary chloride concentration is 25mEq/l or more.
