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: Medicine
Which of the following urinary findings is most characteristic of acute glomerulonephritis? 
Select and explain. 
A. Proteinuria, B. Granular casts, C. Erythrocyte casts, D. Hyaline casts
C: Erythrocyte casts
Answer: C: Erythrocyte casts 
Explanation: Hematuria with dysmorphic RBCs, RBC casts, and protein excretion >500 mg/d is virtually diagnostic of glomerulonephritis. RBC casts form as RBCs that enter the tubule fluid and become trapped in a cylindrical mold of gelled Tamm-Horsfall protein.
Harrisson’s Principles of Internal Medicine Ed 19 Pg 294