In pyloric stenosis, the following changes are seen:March 2011

Ans. A: Hypokalemic hyponatremic alkalosisThe vomiting of hydrochloric acid results in hypochloraemic alkalosis but, initially sodium and potassium levels may be relatively normal, but later on bicarbonate is excreted along with sodium and so, with time, the patient becomes progressively hyponatremic and more profoundly dehydrated.Because of dehydration, a phase of sodium retention follows and potassium and hydrogen are excreted in preference. This results in the urine becoming paradoxically acidic and hypokalemia ensues