This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Medicine
[{'content': 'Urinalysis shows RBC casts; likely source is - \nSelect and explain. \nA. Kidney, B. Ureter, C. Bladder, D. Urethra', 'role': 'user'}, {'content': 'Answer: A \nExplanation: RBC casts are indicative of glomerular disease , i.e, the source is from kidney. WBC casts are strongly suggestive of pyelonephritis. Ref : Davidson - 22nd edn - pg no. 468.', 'role': 'assistant'}]