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
Medical therapy can be tried in gallstone patients with: 
Select and explain. 
A. Contracted and small non functioning gallbladder, B. Radiolucent gallstones, C. Gallstones of size < 30 mm in diameter, D. Gallstone pancreatitis
B: Radiolucent gallstones
Answer: B: Radiolucent gallstones 
Explanation: Ursodeoxycholic acid (UDCA) decreases cholesterol saturation of bile. In carefully selected patients with functioning gallbladder and with radiolucent stones <10 mm in diameter, complete dissolution with UDCA can be achieved in 50% of patients within 6 months to 2 years. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 2621