Clinical Factors to Predict Difficult Ureter during Ureteroscopic Lithotripsy

OBJECTIVE: To identify risk factors for difficult ureters during ureteroscopic lithotripsy and to determine the appropriate indications for preoperative stenting. METHODS: We retrospectively analyzed 156 ureteroscopic procedures for upper urinary tract stones after excluding those with preoperative stenting or percutaneous nephrostomy. Traceability of the ureter was assessed by two urologists. Traceability was defined as positive if either or both urologists discerned the ureter in all slices on preoperative plain computed tomography. Patients' backgrounds were compared between the nondifficult ureter and difficult ureter groups. A multivariate logistic regression model was used to evaluate the relationships between difficult ureters and other clinical factors. RESULTS: Of 156 patients, 31 (19.9%) were classified into the difficult ureter group. The positive traceability was higher in the nondifficult ureter group (48.3% vs. 83.2%, P < 0.001). The major axis was smaller in the difficult ureter group than in the nondifficult ureter group (8.8 ± 3.9 mm vs. 10.9 ± 4.5 mm, P < 0.018). A major axis <8 mm (odds ratio: 4.495, 95% confidence interval: 1.791–11.278, and P=0.001), negative traceability (odds ratio: 7.565, 95% confidence interval: 2.693–21.248, and P < 0.001), smoking status (odds ratio: 3.196, 95% confidence interval: 1.164–8.773, and P=0.024), and absence of diabetes mellitus (odds ratio: 5.813, 95% confidence interval: 1.121–30.142, and P=0.036) were identified as independent predictors of difficult ureters on multivariate logistic regression analysis. CONCLUSION: Patients with smaller stones, negative traceability, ongoing tobacco consumption, and absence of diabetes mellitus were at higher risk of difficult ureters. In these patients, preoperative stenting may be considered.