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
Following is true of Pyonephrosis except - 
Select and explain. 
A. Commonly associated with Renal calculi, B. Always unilateral, C. Is a complication of Hydronephrosis, D. Follows acute pyelonephritis
B: Always unilateral
Answer: B: Always unilateral 
Explanation: None