This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
In pyloric stenosis, the following changes are seen: March 2011 
Select and explain. 
A. Hypokalemic hyponatremic alkalosis, B. Hyperkalemia, C. Acidosis with hyponatremic alkalosis, D. Hyperchloremic acidosis
A: Hypokalemic hyponatremic alkalosis
Answer: A: Hypokalemic hyponatremic alkalosis 
Explanation: Ans. A: Hypokalemic hyponatremic alkalosis The 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