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 a case of hyperophic pyloric stenosis, which of the following metabolic disturbance is found? 
Select and explain. 
A. Respiratory alkalosis, B. Metabolic acidosis, C. Metabolic alkalosis with paradoxical aciduria, D. Metabolic alkalosis with alkaline urine
C: Metabolic alkalosis with paradoxical aciduria
Answer: C: Metabolic alkalosis with paradoxical aciduria 
Explanation: Due to vomiting of the gastric contents, infants develop a hypochloremic, hypokalemic metabolic alkalosis. The urine pH is high initially but eventually drops because hydrogen ions are preferentially exchanged for sodium ions in the distal tubule of the kidney as the hypochloremia becomes severe. Ref: Schwaz's Principles of Surgery, 9th Edition, Chapter 39