Purpose: After treatment for kidney stones, residual fragments with a diameter of ≤ 4 mm are traditionally referred to as ‘clinically insignificant residual fragments’. We hypothesize that patients with these fragments are at an increased risk for stone-related morbidity, such as complaints, hydronephrosis, and stone regrowth, when compared to stone-free patients. This study aimed to investigate the relevance of complete stone clearance in surgical treatment of urolithiasis. Methods: We conducted a single-center retrospective cohort study. Patients who underwent percutaneous nephrolithotomy between 2015 and 2020 were included if a CT-scan was available within 6 months after the procedure, and the follow-up duration was at least 1 year. The stone-free status at the end of the first stone episode during the study period was categorized as fully stone-free, not stone-free with small residual fragments (≤ 4 mm) and not stone-free with large residual fragments (> 4 mm). Follow-up data were collected, including stone-related events and re-intervention rates. Results: A total of 103 subjects were included with a median follow-up of 21.4 months. Stone-related events occurred in 10 (29.4%) of the fully stone-free subjects, 20 (58.8%) of the subjects with small residual fragments and 25 (71.4%) of the subjects with large residual fragments. The stone-related event-free survival per subgroup resulted in a significantly different survival distribution in a log rank test (p = 0.008). Conclusion: A complete stone-free status seems to be of fundamental importance for decreasing stone-related morbidity. Further developments and research should focus on optimizing the full clearance of stone material during PCNL.

Background: Cone beam computed tomography (CBCT) enables intraoperative cross-sectional and three-dimensional imaging of the urinary tract. CBCT in a hybrid operating room can be used for intraoperative detection of residual stones and potential additional stone extraction at the end of percutaneous nephrolithotomy (PCNL). This study describes our initial experience with intraoperative CBCT during PCNL and analyzes its role in potentially improving its outcomes. Methods: We conducted a single-center retrospective cohort study at a tertiary referral hospital between 2018 and 2021. The study aimed to evaluate the outcome of patients who underwent intraoperative noncontrast CBCT scan during PCNL. The CBCT scan was performed when the urologist determined the kidney to be endoscopically stone-free. In case any residual fragments were imaged, an additional effort was made to extract them. Patients were divided into three groups based on treatment outcome: stone-free upon CBCT, not stone-free with additional stone extraction after CBCT, and not stone-free without additional stone extraction. Procedure and patient characteristics were recorded to identify factors associated with additional stone extraction during CBCT-assisted PCNL. Results: A total of 102 procedures were included in this study. Intraoperative CBCT scans showed residual calcifications in 58 (57%) cases. In 39 cases, which is 38% of the total population and 61% of the cases with residual calcifications, one or more residual fragments imaged on the intraoperative CBCT-scan were extracted additionally within the same procedure. A higher Guy's Stone Score was associated with a higher likelihood of additionally extracting stones as a result of the CBCT. Conclusions: CBCT-assisted PCNL in a hybrid operating room can lead to additional stone extraction in the same procedure in 37% of all cases and in over 60% of the cases in which residual fragments are imaged. The value of CBCT-assisted PCNL appears to increase in the case of more complex stone surgery cases.

Background: Percutaneous nephrolithotomy (PCNL) often fails to achieve complete stone clearance with a single procedure. Residual fragments, irrespective of size, are associated with increased stone‐related morbidity and a higher likelihood of re‐intervention. Endoscopic combined intrarenal surgery (ECIRS), which integrates PCNL with retrograde ureterorenoscopy, may improve stone‐free rates and reduce morbidity. However, given the potential for increased risks and greater resource utilisation, a comprehensive randomised controlled trial is warranted. The ‘PRECISE’ trial is designed to compare ECIRS and PCNL in terms of efficacy, safety, stone‐related morbidity, and resource utilisation. Study Design: The PRECISE is a prospective, non‐blinded, randomised, parallel‐group, multicentre interventional trial involving patients eligible for percutaneous kidney stone surgery. Patients will be randomised in a 1:1 ratio to undergo either ECIRS or standard PCNL. Endpoints: The primary endpoint is the Grade A (0 mm) stone‐free rate on postoperative computed tomography (CT) at 4 weeks. Secondary radiological endpoints include Grade B (≤2 mm) and Grade C (≤4 mm) stone‐free rates at 4 weeks, stone volume reduction, 1‐year stone‐free rates, and radiation exposure. Additional outcomes include complications, operative duration, stone‐related events (SREs), health‐related quality of life (HRQoL), cost differences, cost‐effectiveness and environmental impact, assessed up to 5 years postoperatively. Patients and Methods: Adults (aged ≥18 years) eligible for percutaneous kidney stone surgery, where retrograde access is feasible, will be recruited. The main exclusion criteria comprise papillary calcifications, renal transplant procedures, and (suspected) pregnancy. A total of 350 patients (175 per arm) will be recruited. Follow‐up includes CT imaging with clinical consultations at 4 weeks and 1 year to evaluate radiological outcomes, complications, SREs, and HRQoL. Telephone interviews at 3 and 5 years will assess long‐term SREs and HRQoL. We aim to retrospectively evaluate cost differences, cost‐effectiveness, and environmental impact. Trial Registration: The PRECISE study: an investigation into combined kidney stone surgery, Dutch Trial Registry, NL‐009577.

Background/Objectives: Intraoperative cone-beam computed tomography (CBCT) can detect residual fragments (RFs) during percutaneous nephrolithotomy (PCNL), enabling immediate removal and improving stone-free status. However, CBCT requires a hybrid operating room (OR), which is often limited in availability. This study explores patient and stone characteristics associated with CBCT eligibility and develops an exploratory treatment-selection model estimating stone-free probabilities conditional on CBCT use. Methods: We performed a retrospective study of a previously conducted randomized controlled trial evaluating intraoperative CBCT during PCNL in a tertiary care center. We compared CBCT-eligible cases versus ineligible cases, and cases achieving grade C (≤4 mm) stone-free status versus those with RFs. A multivariate exploratory treatment-selection model was developed using the strongest potential predictors of stone-free status. Internal validation was performed using bootstrapping. The model was also assessed for predicting grade A (0 mm) stone-free status. Results: The only significant difference between CBCT-eligible (n = 160) and ineligible (n = 60) cases was stone composition (p = 0.022). The final model included intraoperative CBCT (p = 0.003), stone size (p = 0.024), and composition (p = 0.044). Model-based estimates suggested smaller differences in predicted stone-free probabilities with CBCT in solitary stones. The AUC was 0.81 (95% CI: 0.73–0.88) for grade C and 0.75 for grade A (95% CI: 0.67–0.82) outcomes. Internal validation demonstrated moderate optimism, indicating potential overfitting. Conclusions: This exploratory treatment-selection model estimates conditional stone-free probabilities with and without CBCT. The findings suggest variation in expected benefit across stone characteristics but should be considered hypothesis-generating. The model is not intended for clinical decision-making and requires external validation before implementation.