Development of a nomogram predicting the probability of stone free rate in patients with ureteral stones eligible for semi-rigid primary laser uretero-litothripsy

Abstract

Purpose Few tools are available to predict uretero-lithotripsy outcomes in patients with ureteral stones. Aim of our study was to develop a nomogram predicting the probability of stone free rate in patients undergoing semi-rigid uretero-lithotripsy (ULT) for ureteral stones. Methods From January 2014 onwards, patients undergoing semi-rigid Ho: YAG laser uretero-lithotripsy for ureteral stones were prospectively enrolled in two centers. Patients were preoperatively evaluated with accurate clinical history, urinalysis and renal function. Non-contrast CT was used to define number, location and length of the stones and eventually the presence of hydronephrosis. A nomogram was generated based on the logistic regression model used to predict ULT success. Results Overall, 356 patients with mean age of 54 years (IQR 44/65) were enrolled. 285/356 (80%) patients were stone free at 1 month. On multivariate analysis single stone (OR 1.93, 95% CI 1.05–3.53, p = 0.034), stone size (OR 0.92, 95% CI 0.87–0.97, p = 0.005), distal position (OR 2.12, 95% CI 1.29–3.48, p = 0.003) and the absence of hydronephrosis (OR 2.02, 95% CI 1.08–3.78, p = 0.029) were predictors of success and these were used to develop a nomogram. The nomogram based on the model presented good discrimination (area under the curve [AUC]: 0.75), good calibration (Hosmer–Lemeshow test, p > 0.5) and a net benefit in the range of probabilities between 15 and 65%. Internal validation resulted in an AUC of 0.74. Conclusions The implementation of our nomogram could better council patients before treatment and could be used to identify patients at risk of failure. External validation is warranted before its clinical implementation.

A simple predictive model with internal validation for assessment of stone-left after ureteroscopic lithotripsy in upper ureteral stones

“…Studies have demonstrated that the surgical methods can greatly affect the outcomes, four times of stone-left incidence of flexible ureteroscopy less than ureteroscopy in this paper. In addition, there were also lots of researches that includes all ureteral stones, which in our opinion was meaningless (16). Unless those rare stones, nearly all distal and middle ureteral stones can reach a high SFR under standard skilled procedures.…”

A retrospective comparison of Sun’s tip-flexible semirigid ureterorenoscopy, super-mini percutaneous nephrolithotomy and flexible ureteroscopy applied to treat upper urinary tract calculi

“…Operation time referred to a period from the time when the scope was inserted into the body to the time when the scope was removed from the body. For the definitions on stone-free status, different studies [ 10 , 11 ] has some differences on the size of stone fragments. In this study, stone-free status referred to the scope smoothly reaching target calices and pulverizing calculi into small fragments less than 2 mm [ 11 ].…”

What are the predictors of residual stone after ureteroscopy for urolithiasis?

“…Stone length and location, number of stones, and the presence of pyuria were significant independent factors correlated with SFR. Meanwhile, single stone, stone size, distal position, and absence of hydronephrosis, which are significant predictive factors of stone-free status, were used in another nomogram for predicting the outcome of rigid URS for ureteral stones (13) (15). This study revealed that stone volume, presence of lower pole stone, operator with an experience of >50 flexible URS, stone number, and presence of hydronephrosis were stone-free status.…”