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
A patient who is being treated for leukemia develops unilateral flank pain. Radiologic studies demonstrate a dilated renal pelvis and dilation of the upper one-third of the corresponding ureter. A stone with which of the following compositions is most likely causing this patient's problems? 
Select and explain. 
A. Calcium salts, B. Cholesterol, C. Cystine, D. Uric acid
D: Uric acid
Answer: D: Uric acid 
Explanation: Patients prone to develop uric acid stones include those with gout, leukemia (paicularly during chemotherapy, which releases large amounts of nucleic acids from dying leukemia cells), and acidic urine. Calcium-containing stones are the most common kind in the general population. Cholesterol stones are found in the gallbladder. Cystine stones are a rare form of renal stone seen in patients with cystinuria. Ref: Wyatt C., Butterwoh IV J.F., Moos P.J., Mackey D.C., Brown T.G. (2008). Chapter 16. Pathology of the Kidney and Bladder. In C. Wyatt, J.F. Butterwoh IV, P.J. Moos, D.C. Mackey, T.G. Brown (Eds), Pathology: The Big Picture.