Kidney, Ureter, and Bladder (KUB): A Novel Grading System for Encrusted Ureteral Stents

OBJECTIVE: To introduce a grading system (kidney, ureter, and bladder [KUB]) to identify encrusted stents that may require multiple surgeries, multimodal surgery, and operative time > 180 minutes for successful removal.

METHODS: One hundred ten retained encrusted ureteral stents were retrospectively scored using the KUB grading system and this score was correlated with operative time, need for multiple surgeries or multimodal surgery, and stone-free rate. Data analysis was performed with t test, Mann-Whitney U test, and chi-square tests. A P value of <0.05 was considered statistically significant.

RESULTS: Average indwelling stent time was 17.2 months (0.7-139.0). There were 83.6% of stents removed in a single surgery, with 63.0% of these requiring multimodal surgery. K score ≥ 3 was associated with multiple surgeries (odds ratio [OR] 3.59, P = .006), multimodal surgery (OR 2.44, P = .04), operative time > 180 minutes (OR 3.80, P = .001), and lower stone-free rate (OR 0.23, P = .02). U score ≥ 3 was associated with operative time > 180 minutes (OR 3.28, P = .003). B score ≥ 3 was associated with lower stone-free rate (OR 0.23, P = .020). Total score ≥ 9 was associated with multiple surgeries (OR 4.19, P = .001), operative time > 180 minutes (OR 3.45, P = .002), and lower stone-free rate (OR 0.13, P = .001).

CONCLUSION: The KUB system identifies stents at risk for requiring multiple surgeries, multimodal surgery, and operative time > 180 minutes. It also correlates with stone-free rate. This grading system can help surgeons manage patient expectations and predict surgical complexity.