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
Metabolic abnormality seen in gastric outlet obstruction is 
Select and explain. 
A. Hypochloremic, hypokalemic acidosis, B. Hypochloremic, hypokalemic alkalosis, C. Hyperchloremic, hypokalemic acidosis, D. Hypochloremic, hyperkalemic alkalosis
B: Hypochloremic, hypokalemic alkalosis
Answer: B: Hypochloremic, hypokalemic alkalosis 
Explanation: Ans. is 'b' i.e. Hypochloremic, hypokalemic alkalosis Repetitive vomiting leads to hypochloremic, hypokalemic metabolic alkalosis. The urine is alkaline initially but eventually it becomes acidic (paradoxical aciduria)Cause of paradoxical aciduriaInitially the kidney compensate for metabolic alkalosis by reabsorbing hydrogen and chloride ions in exchange for sodium, potassium and bicarbonate. But gradually as the body stores of sodium and especially potassium become depleted, kidney starts retaining these ions in exchange of hydrogen ions. Thus the urine becomes acidic and the metabolic alkaline state is further aggravated.