This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Benign Gastric Disease, Subject name: Surgery
Most common biochemical abnormality in congenital pyloric stenosis. 
Select and explain. 
A. Hyperkalemic metabolic acidosis, B. Hypokalemic metabolic acidosis, C. Hyperkalemic metabolic alkalosis, D. Hypokalemic metabolic alkalosis
D: Hypokalemic metabolic alkalosis
Answer: D: Hypokalemic metabolic alkalosis 
Explanation: Ans. is 'd' i.e. Hypokalemic metabolic alkalosis Repeated vomiting leads to hypochloremic, hypokalemic metabolic alkalosis. The urine is alkaline initially but eventually it becomes acidic (paradoxical aciduria)