Screening of clinical indicators for evaluation of incarcerated stone before operation

Objective To investigate the clinical indicators which could be used to differentiate incarcerated stones from unincarcerated stones by comparing clinical characteristics of patients. Methods 96 patients who were diagnosed as ureteral stones treated by ureteroscopic lithotripsy (URSL) from June 2017 to November 2017 were selected in the study. Clinical characteristics of patients were collected. The total study consisted of 62 male and 34 female patients. The patients’ age ranged from 24 to 78 years old and average age was (54.5±12.7) years old. There were 35 patients were diagnosed as ureteral stones with hypertension, 9 patients with diabetes, 85 patients with hydronephrosis, respectively. The number of patients, whose stone located in upper ureters, middle ureters and lower ureters were 49, 19, 28, respectively. The average of maximum stone diameter, maximum cross-sectional area of the stone, stone volume, hounsfield units of stone and maximum ureteral wall thickness (UWTmax) at the stone site were(7.75±2.68)mm, (36.12±24.43)mm2, (304.06±303.39)mm3, (755.75±318.05) HU, and (3.18±1.13)mm, respectively. Percussion tenderness over kidney region were positive in 11 cases, weak positive in 64 cases and negative in 21 cases, respectively. Stone-free rate after operation were 93.8%. Patients were divided into two groups, incarcerated or unincarcerated, and statistical differences between clinical characteristics of the two groups were analyzed by univariate analysis. The differences were further compared by multivariate logistic regression analysis to find independent predictors of impacted stones. The ROC curve was used to find the optimal UWTmax for diagnosis of impacted stone. The accuracy of this value was evaluated and patients were grouped by this value to compare the differences between groups. Results The operation and follow-up were successfully performed in all patients. Univariate analysis showed there were no statistical significance differences in gender[(24 males and 16 females)vs. (38 males and 18 females)], age [(53.4±12.3) years vs.(48.7±12.7) years], previous history of diabetes (4 cases vs. 5 cases) and stone location[(19 upper stones, 9 middle stones, 12 lower stones) vs. (30 upper stones, 10 middle stones, 16 lower stones)], between the two groups(P>0.05). Among the clinical characteristics of patients in incarcerated and unincarcerated groups, UWTmax were (4.15±0.94)mm and (2.58±0.76)mm, previous history of hypertension were 20 cases and 15 cases, ipsilateral URSL history were 14 cases and 10 cases, hounsfield units of stone were (847.66±282.39)HU and (698.65±325.50) HU, hydronephrosis were 40 cases and 50 cases, maximum stone diameter were (8.67±2.28)mm and (7.17±2.75)mm, maximum cross-sectional area of the stone were (43.83±23.65)mm2 and (31.14±23.64)mm2, stone volume were (386.20±296.60)mm3 and (253.04±296.29)mm3, percussion tenderness over kidney region were positive in 8 cases(20.0%), weak positive in 27 cases, negative in 5 cases and positive in 3 cases, weak positive in 37 cases, negative in 16 cases, respectively. The difference was statistically significant(P<0.05). Multivariate logistic regression analysis showed UWTmax (OR=10.40, P<0.001) at the stone site was significantly correlated with impacted ureteral stones and it was an independent predictor of impacted stones. ROC curve analysis showed that the optimal cut-off value of UWTmax was 3.26 mm. The sensitivity of the value to predict impacted stone is 82.5% and the specificity is 87.5%. Depending on the cut off value of 3.26 mm, cases were divided into two groups, 40 cases were in high UWTmax(≥3.26 mm)group and 56 cases were in low UWTmax(<3.26 mm)group. Higher UWTmax was accompanied with a higher incidence of ureteral edema[77.5%(31/40) vs. 32.1%(18/56)], polyps[30.0%(12/40)vs. 7.1%(4/56)], strictures[37.5%(15/40)vs. 12.5%(7/56)] and a lower stone-free rate[87.5%(35/40)vs. 98.2%(55/56)]. The difference was statistically significant(P<0.05). Conclusions UWTmax can be used to differentiate impacted stones from unimpacted stones before surgery. The patients with Higher UWTmax(≥3.26 mm) was accompanied with a higher incidence of stone impacted, ureteral edema, polyps, and strictures, and a lower rate of stone clearance. Key words: Ureteral wall thickness; Ureteral calculi; Impacted stone