Mini and Standard Percutaneous Nephrolithotomy in Obese Patients. Results from a Single-surgeon Large Series

Background and objective

Percutaneous nephrolithotomy (PCNL) is the recommended treatment for large or complex renal stones. This study aims to evaluate the outcomes of mini PCNL in obese and nonobese patients and to compare the outcomes of mini and standard PCNL in the obese population.

Methods

We retrospectively reviewed our PCNL database to identify patients who had undergone mini (Amplatz sheath size 17.5Ch) or standard (Amplatz sheath size ≥26Ch) PCNL between 2005 and 2022. First, we compared the outcomes of the two procedures in the obese (body mass index [BMI] ≥30) and nonobese (BMI<30) patients. Second, we compared the outcomes of mini and standard PCNL in the obese population. A multivariable logistic regression analysis was performed to assess the variables associated with stone-free rate (SFR) and complications.

Key findings and limitations

A total of 781 patients underwent mini PCNL; there was no difference between nonobese (578) and obese (133) patients in surgical time, number of tubeless procedures, postoperative stay, SFR, and overall complication rates. Similar outcomes were also seen in the 356 patients who had undergone standard PCNL, including 276 nonobese and 80 obese patients. The comparison of mini and standard PCNL in the obese population (213 patients) showed that mini PCNL provided significant benefits in surgical time (60 vs 94 min), SFR (85% vs 63.8%), and blood transfusion rate (2% vs 10%). The multivariable analysis confirmed that mini PCNL resulted in significantly higher odds of being stone free (odds ratio [OR] 1.79) and lower odds of having a blood transfusion (OR 0.28).

Conclusions and clinical implications

Obese patients can safely undergo either mini or standard PCNL; in this series, mini performed better than standard PCNL in terms of SFR and blood transfusion rates.

Patient summary

In this study, we compared the outcomes of mini and standard percutaneous nephrolithotomy (PCNL) in the obese population. We found that mini PCNL had lower surgical time and blood transfusion rate, and better stone-free rate than its standard counterpart in obese patients.

The effect of bioelectric impedance analysis on the success of extracorporeal shock wave lithotripsy

Bioelectric impedance analysis (BIA) is a non-invasive method that can show the distribution of fatty and lean mass of the body. In this study, we aimed to determine the effect of BIA on extracorporeal shock wave lithotripsy (SWL) success. Our secondary aim was to determine the factors predicting transition from a single SWL session to multiple sessions. Patients who underwent SWL due to kidney stones were prospectively included. Demographics, pre-procedural BIA parameters (fat percentage, obesity degree, muscle mass, total water and metabolic rate), stone parameters, and number of SWL sessions were recorded. Univariate and multivariate regression analyzes were made to determine independent risk factors for success. Then, the successful group was divided into two subgroups according to their SWL session number as one session or multiple sessions and multivariate regression analysis was made to determine independent risk factors. Stone-free status was achieved in 114 (61.2%) of 186 patients. Stone Hounsfield Unit (HU) (OR: 0.998, p = 0.004), stone volume (OR: 0.999, p = 0.023) and fat percentage (OR: 0.933, p = 0.001) were independent risk factors for stone-free status in multivariate analysis. HU value of the stone (OR: 1.003, p = 0.005) and age (OR: 1.032, p = 0.031) were determined as independent risk factors for transition to multiple sessions in the subgroup analysis of the successful group. Fat percentage, stone volume, and stone density were determined as factors affecting success in SWL. Routine use of BIA may be considered to predict success before SWL. The probability of SWL success in a single session decreases as the age and stone's HU value increase.

Prospective Comparison of Thulium and Holmium Laser Lithotripsy for the Treatment of Upper Urinary Tract Lithiasis

Background

Lithotripsy with holmium:yttrium-aluminum-garnet (Ho:YAG) laser is the current gold standard for treating stones of the upper urinary tract (UUT). The recently introduced thulium fiber laser (TFL) has the potential to be more efficient and as safe as Ho:YAG.

Objective

To compare the performance and complications between Ho:YAG and TFL for UUT lithotripsy.

Design setting and participants

This was a prospective single-center study of 182 patients treated between February 2021 and February 2022. In a consecutive approach, laser lithotripsy was performed via ureteroscopy with Ho:YAG for 5 mo, and then with TFL for 5 mo.

Outcome measurements and statistical analysis

Our primary outcome was stone-free (SF) status at 3 mo after ureteroscopy with Ho:YAG versus TFL lithotripsy. Secondary outcomes were complication rates and results regarding the cumulative stone size. Patients were followed at 3 mo with abdominal imaging (ultrasound or computed tomography).

Results and limitations

The study cohort comprised 76 patients treated with Ho:YAG laser and 100 patients treated with TFL. Cumulative stone size was significantly higher in the TFL than in the Ho:YAG group (20.4 vs 14.8 mm; p = 0.01). SF status was similar in both groups (68.4% vs 72%; p = 0.06). Complication rates were comparable. In subgroup analysis, the SF rate was significantly higher (81.6% vs 62.5%; p = 0.04) and the operative time was shorter for stones measuring 1-2 cm, whereas the results were similar for stones <1 cm and >2 cm. The lack of randomization and single-center design are the main limitations of the study.

Conclusions

TFL and Ho:YAG lithotripsy are comparable in terms of the SF rate and safety for the treatment of UUT lithiasis. According to our study, for a cumulative stone size of 1-2 cm, TFL is more effective than Ho:YAG.

Patient summary

We compared the efficiency and safety of two laser types for the treatment of stones in the upper urinary tract. We found that stone-free status at 3 months did not significantly differ between the holmium and thulium lasers.

Development and validation of a predictive model for stone-free failure after extracorporeal shockwave lithotripsy in patients with ureteral stone in a large prospective cohort

PURPOSE

To develop and validate a nomogram for predicting stone-free failure after shock wave lithotripsy (SWL) guided by ultrasound in patients with ureteral stones.

METHODS

The development cohort consisted of 1698 patients who underwent SWL guided by ultrasound at our center from June 2020 through August 2021. Multivariate unconditional logistic regression analysis was used for building a predictive nomogram with regression coefficients. An independent validation cohort consisted of 712 consecutive patients from September 2020 through April 2021. The performance of the predictive model was assessed in regard to discrimination, calibration, and clinical usefulness.

RESULTS

Predictors of stone-free failure included distal stone location (odds ratio = 1.540, P < 0.001), larger stone size (odds ratio = 1.722, P < 0.001), higher stone density (odds ratio = 1.722, P < 0.001), larger skin to stone distance (SSD) (odds ratio = 1.058, P < 0.001), and higher grade of hydronephrosis (odds ratio = 1.755, P = 0.010). For the validation cohort, the model showed good discrimination with an area under the receiver operating characteristic curve of 0.925 (95% confidence interval, 0.898, 0.953) and good calibration (unreliability test, P = 0.412). Decision curve analysis demonstrated that the model was also clinically useful.

CONCLUSIONS

This study demonstrated that stone location, stone size, stone density, SSD, and hydronephrosis grade were significant predictors of stone-free failure after SWL guided by ultrasound in patients with ureteral stones. This may guide clinical practice.

Ureteral wall thickness and distal ureteral density in patients with residual fragments after Ho:YAG laser semi-rigid ureterolithotripsy

Recent data suggest that greater ureteral density distal to ureteral stones or increased ureteral wall thickness (UWT) can predict impacted stones. The aim of our study was to evaluate if patients with residual fragments present with greater ureteral density and larger UWT when compared to stone-free patients. From January onward, a consecutive series of patients undergoing semi rigid Ho:YAG laser ureterolithotripsy (ULT) for ureteral stones were enrolled. A non-contrast enhanced computed tomography (CT) scan was performed before the procedure to evaluate distal ureteral density (DUD) and wall ureteral thickness (UWT) at the site of ureteral stones. Patients with residual fragments were compared to stone-free patients using a matched-pair analysis (1:1 scenario). Cases were matched sequentially using the following criteria: age, gender, body mass index (BMI), stone length, hydronephrosis, location of stones, and mean Hounsfield unit (HU) of the stone. Overall, 160 patients were enrolled, mean age was 57.9 ± 14 years, mean BMI was 25.8 ± 4 kg/m2, mean length of the stone was 10.6 ± 4.9 mm, and mean UWT was 1.4 ± 1.6 mm. A total of 150/160 (94%) patients presented hydronephrosis; mean HU stone was 868 ± 327; mean DUD was 54 ± 17.8 HU. Ureteral distal density (51.7 vs 56.6; p = 0.535) and ureteral distal thickness (1.39 vs 1.54; p = 0.078) were similar in both groups of patients. In our study, the evaluation of distal ureteral density does not predict stone-free rate. Further studies should evaluate the role for preoperative computer tomography in predicting surgery outcome.

Are the current nomograms sufficient to predict shockwave lithotripsy outcomes?

INTRODUCTION AND OBJECTIVES

To investigate factors affecting SWL outcomes, validate three current nomograms (Kim JK, Triple D and S3HoCKwave) and compare the predictive ability of the nomograms for SWL outcomes in upper urinary tract stones.

PATIENTS AND METHODS

Medical records of patients with renal and proximal ureteral stones treated with SWL between March 2013 and October 2020 were retrospectively reviewed. Factors affecting SWL success were analyzed with multivariate logistic regression analysis and the three predictive scoring systems compared with the area under the curve (AUC).

RESULTS

A total of 580 patients were included in our study. The overall stone free rate was 61% and 144/580 patients (24.8%) were stone free after one session. In multivariate logistic regression analysis, stone location at upper calyx (OR:2.988; 95%Cl: 1.350-6.612; p = 0.007), middle calyx (OR:3.036; 95%Cl: 1.472-6.258; p = 0.003), and lower calyx (OR:2.131; 95%Cl: 1.182-3.839; p = 0.012), as well as number of stones (OR:1.663; 95%Cl: 1.140-2.425; p = 0.008), maximum diameter of stone (OR:1.156; 95%Cl: 1.098-1.217; p < 0.001) and maximum Hounsfield Unit (OR:1.001; 95%Cl: 1.001-1.002; p < 0.001) were independent risk factors of SWL failure. The AUCs of the Kim JK, Triple D and S2HoCKwave scores for predicting SWL success were 0.678, 0.548, and 0.626 respectively.

CONCLUSIONS

Stone location, number, maximal diameter, and maximum HU were independent predictive factors for SWL outcome in the treatment of upper urinary tract stones. Current nomograms, "Kim JK nomogram", "Triple D score" and "S3HoCKwave score" can predict treatment success after SWL, but all of them have poor discrimination according to AUC analysis.

Retrograde Intrarenal Surgery Versus Miniaturized Percutaneous Nephrolithotomy for Kidney Stones >1cm: A Systematic Review and Meta-analysis of Randomized Trials

CONTEXT

Although miniaturized percutaneous nephrolithotomy (mPCNL) and retrograde intrarenal surgery (RIRS) are both options for treating >1cm kidney stones, controversies exist on whether one is more effective and safer than the other.

OBJECTIVE

To systematically appraise randomized trials comparing the effectiveness and safety of mPCNL and RIRS for treating >1cm kidney stones.

EVIDENCE ACQUISITION

A systematic search on PubMed/Medline, Web of Science, Embase, and ClinicalTrials.gov was conducted in August 2020 following the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA). Randomized trials comparing mPCNL and RIRS for >1cm kidney stones, and reporting stone-free rate (SFR), hemoglobin drop, transfusion rate, length of hospital stay (LOS), and/or complications, were included.

EVIDENCE SYNTHESIS

Eight studies compared mPCNL and RIRS, but one was not included due to its high risk of bias. SFR was higher for mPCNL (RR: 1.06 [95% coefficient interval {CI}, 1.01-1.10], p=0.008). Hemoglobin drop was higher for mPCNL (mean difference [MD]: 0.35 [95% CI, 0.05-0.65] g/dl, p=0.02); however, transfusion rates were similar (p=0.44). Complication rate was similar between mPCNL and RIRS (p=0.39), and the LOS was higher for mPCNL (MD: 1.11 [95% CI, 0.06-2.16] d, p=0.04). A subgroup analysis of lower pole stones showed that SFR was higher for mPCNL (RR: 1.09 [95% CI, 1.00-1.19], p=0.05).

CONCLUSIONS

Both approaches are effective and safe. Among these approaches, mPCNL has a higher SFR than RIRS for overall >1cm renal and lower pole stones, but longer LOS, and a higher hemoglobin drop that does not translate into higher transfusion rates. Complications are comparable.

PATIENT SUMMARY

Randomized trials have evaluated whether miniaturized percutaneous nephrolithotomy (mPCNL) or retrograde intrarenal surgery is more effective and safer for treating >1cm stones. After comparing the stone-free rate, hemoglobin drop, transfusion rate, length of hospital stay, and complications between both the approaches, mPCNL was found to be slightly more effective, but both were equally safe.

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

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.

[Flexible ureterorenoscopy and laser lithotripsy for upper urinary tract stones in neurologic patients with severe motor disability]

OBJECTIVE

The study's objective was to evaluate the effectiveness and morbidity of flexible ureterorenoscopy and laser lithotripsy for upper urinary tract stones in patients with a nervous system pathology including severe motor disability.

METHODS

Between 2006 and 2013, we retrospectively analyzed 83 flexible ureterorenoscopy to treat 63 kidneys in 42 patients. Stone free (SF) kidneys defined as an absence of stones on computerized tomography, renal ultrasound, X-ray or direct ureterorenoscopy, were considered a surgical success. Complications were classified according to the Clavien-Dindo system.

RESULTS

Success rates were 49.2 %, 57.1 % and 58.7 %, respectively after first, second and third flexible ureterorenoscopy procedure. Clearance after one procedure was achieved in 64.3 % of cases involving less than 20mm stones. No major complication (Clavien-Dindo>2) was described (0 %). Complication rates were 44.7 %, with 31.6 % Clavien-Dindo 2. The main complication was urosepsis, which occurred in 27.6 % of cases.

CONCLUSION

Flexible ureteroscopy and laser lithotripsies for upper urinary tract stones in neurologic patients with severe motor disability are associated with a lower success rate and some frequent low grade complications compared to overall population. In clinical practice, the indications of flexible ureterorenoscopy for these patients seem restricted.

LEVEL OF EVIDENCE

5.

History of Ureteral Stenting Negatively Affects the Outcomes of Extracorporeal Shockwave Lithotripsy. Results of a Matched-pair Analysis

To evaluate the impact of ureteral stenting history to the outcomes of extracorporeal shockwave lithotripsy, we retrospectively analysed patients who underwent shockwave lithotripsy with Dornier Gemini lithotripter between September 2010 and August 2012. Forty seven patients (group A) who had a double J stent which was removed just before the procedure were matched-paired with another 47 patients (group B) who underwent shockwave lithotripsy having no stent history. The correlation between ureteral stenting history and stone-free rates was assessed. Stone-free rates were 68.1% and 87.2% for patients of group A and B, respectively (p=0.026). Postoperative complications were not different between groups. Multivariate analysis revealed that stone size (p=0.007), stone location (p=0.044) and history of ureteral stenting (p=0.046) were independent predictors for stone clearance after shockwave lithotripsy. Ureteral stents adversely affect shockwave lithotripsy outcome, even if they are removed before the procedure. Stenting history should divert treatment plan towards intracorporeal lithotripsy.