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: Surgery
A young bank manager presented with acute severe lower abdominal pain which is radiating towards inguinal region. USG shows renal stones. Conservative management in this patient is indicated when: 
Select and explain. 
A. A stone less than 6 mm in size, B. Hydronephrosis and infection is present, C. Associated congenital anomalies of kidney, D. Stone does not descend for 2 weeks of follow up
A: A stone less than 6 mm in size
Answer: A: A stone less than 6 mm in size 
Explanation: Most ureteral calculi pass and do not require intervention. Spontaneous passage depends on stone size, shape, location, and associated ureteral edema (which is likely to depend on the length of time that a stone has not progressed). Ureteral calculi 4-5 mm in size have a 40-50% chance of spontaneous passage. In contrast, calculi >6 mm have a The vast majority of stones that pass do so within a 6-week period after the onset of symptoms. All other options are indications for intervention. Ref: Stoller M.L. (2008). Chapter 16. Urinary Stone Disease. In E.A. Tanagho, J.W. McAninch (Eds), Smith's General Urology, 17e.