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: Pathology
[{'content': 'An impoant factor for chronic pyelonerphritis is ? \nSelect and explain. \nA. Obstruction, B. Vesico-ureteral reflux, C. Pelvi-ureteric junction obstruction, D. Catheter induced', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans is \'b\' i.e., Vesico-Ureteral refluxAll factors mentioned as options play an impoant role in the genesis of Chronic Pyelonephritis.However, if asked to choose one, I will go with Vesico-Ureteral Reflux."Although obstruction is an impoant predisposing factor in the pathogenesis of ascending infection, it is the incompetence of the vesico-ureteral valve that allows bacteria to ascend the crater into the pelvis"- Robbins 6th / 973 Obstruction and catheterization will both contribute to infection in the region of urethra & bladder. These form source of infection into the the pelvis but "in the absence of vesico-ureteral reflux, infection would remain confined to the bladder". Thus majority of patients without VUR suffer from urethritis and cystitis but not pyelonephritis.', 'role': 'assistant'}]