This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fluid, Electrolyte and Nutrition, Subject name: Surgery
Condition which does not cause metabolic acidosis:- 
Select and explain. 
A. Renal failure, B. Ureterosigmoidostomy, C. Pancreatic or biliary fistula, D. Pyloric stenosis
D: Pyloric stenosis
Answer: D: Pyloric stenosis 
Explanation: Hyperophic pyloric stenosis causes hypokalemia, hypochloremia metabolic alkalosis with paradoxical aciduria. CAUSES OF NON-ANION GAP ACIDOSIS Mnemonic- USED CARP U-Ureteraldiversion S-Small Bowel Fistula E-Extra Chloride (ammonium chloride, Calcium Chloride) D-Diarrhea C-Carbonic anhydrase inhibitors (Acetazolamide, Mefenamic acid) A-Adrenal Insufficiency R-Renal Tubular Acidosis P-Pancreatic Fistula CAUSES OF NORMAL-ANION GAP ACIDOSIS Mnemonic- MUD PILERS M Methanol, Metformin U Uremia D Diabetic Ketoacidosis (DKA), Alcoholic Ketoacidosis or Starvation Ketosis P Paraldehyde, Phenformin I Iron, Isopropyl Alcohol, and Isoniazid (due to Seizures) L Lactic Acidosis E Ethylene Glycol, Ethyl Alcohol R Rhabdomyolysis S Salicylates (do not miss Chronic Salicylate Poisoning)