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
Urinalysis shows RBC casts; likely source is - 
Select and explain. 
A. Kidney, B. Ureter, C. Bladder, D. Urethra
A: Kidney
Answer: A: Kidney 
Explanation: 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.