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
Organ which is commonly involved in Retroperitoneal fibrosis is 
Select and explain. 
A. Large intestine, B. Pancreas, C. Ureter, D. Kidney
C: Ureter
Answer: C: Ureter 
Explanation: Ureter is involved in Retro peritoneal fibrosis leading to Hydro Ureteno Nephrosis.