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: Gynaecology & Obstetrics
Which of the following tubal obstruction locations is least amenable to surgical repair? 
Select and explain. 
A. Fimbrial, B. Interstitial, C. Ampullary, D. Isthmic
B: Interstitial
Answer: B: Interstitial 
Explanation: Proximal obstruction of Fallopian tube especially Interstitial part is very prone to repeated obstruction post-operatively. So it cannot be treated with cannulation.