Can the degree of ureteral stone impaction better predict surgical success and complications? a new classification system.

Background: According to our hypothesis, a classification system that grades stone impaction may better predict surgical success and complications. Therefore, we developed a new classification system, and in this study, we aimed to evaluate the effect of stone impaction and its degree on success and complications of ureteroscopic lithotripsy (URS-L), as well as to investigate preoperative factors predicting stone impaction and its degree.

Methods: Data of patients over the age of 18 years who underwent URS-L for a single ureteral stone were prospectively collected. First, stone impaction was determined by the primary surgeon using a Likert scale. Subsequently, non-impacted and impacted stones were further divided into two subgroups and classified according to the degree of stone impaction between Grades 1 and 4. Patient characteristics, preoperative non-contrast computed tomography (CT) findings, laboratory values, and intraoperative and postoperative outcomes were analyzed. Stone-free status was defined as the absence of residual stones > 2 mm on non-contrast CT at postoperative month 1.

Results: The study included a total of 211 patients. Operative time, ureteral injury, degree of ureteral injury, failure (nephrostomy placement), hospital stay, and stone-free rates differed significantly between impacted and non-impacted stones. When evaluated by degree of impaction, significant differences were identified in operative time, presence of pyuria, ureteral injury, degree of ureteral injury, failure, hospital stay, and stone-free status. Colic severity, time from pain onset to surgery, location (upper ureter), stone volume, peri-calculus ureteral wall thickness (PUWT), and presence of severe hydronephrosis were found to be predictive factors of stone impaction, while female gender, stone location (upper ureter), and PUWT were independent predictors of Grade 4 stones.

Conclusions: This study showed that stone impaction and the new classification system are associated with surgical outcomes. Not all non-impacted or impacted stones are the same, and grading according to the interaction of the stone with the ureteral wall can better predict surgical outcomes.