This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney Stones & Renal Tubular Acidosis, Subject name: Medicine
Nephrocalcinosis is seen in all except? 
Select and explain. 
A. Polycystic kidney, B. Hyperparathyroidism, C. Medullary sponge kidney, D. Renal tubular acidosis
A: Polycystic kidney
Answer: A: Polycystic kidney 
Explanation: Causes of Nephrocalcinosis Medullary sponge kidney Hyperparathyroidism/ Hypoparathyroidism Renal tubular acidosis Renal tuberculosis Hyperoxaluria Milk-alkali syndrome Sarcoidosis