*2.2. Ureteral Calculi*

Urinary tract stones are very common. The prevalence is 1–19.1% in Asia, 5–9% in Europe, and 7–13% in North America [4,5]. Although most small stones pass spontaneously, some do not, causing UUTO with or without infection. Surgical intervention (shock wave or ureteroscopic lithotripsy) is required to prevent the impairment of renal function [6]. Even after stones are removed, some patients develop ureteral strictures that may continue to impair renal function.
