This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urinary tract, Subject name: Pathology
[{'content': 'Xanthogranulomatous pyelonephritis is often associated with infection by - \nSelect and explain. \nA. proteus, B. E. coli, C. H. influenzae, D. Klebsiella', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Xanthogranulomatous pyelonephritis It is an unusual and rare form of chronic pyelonephritis associated with Proteus infections. MORPHOLOGY Gross: Cut surface shows large, yellowish-orange nodules, which may be confused with renal cell carcinoma. Microscopy: Interstitium shows foamy macrophages, plasma cells, and lymphocytes Clinical Features Chronic pyelonephritis associated with reflux may be silent onset. Usual symptoms are back-pain, fever, pyuria, and bacteriuria Ref: RAM DAS NAYAK EXAM PREPARATORY MANUAL FOR UNDERGRADUATES 2nd ed. pg no: 619', 'role': 'assistant'}]