A multicenter study on the application of artificial intelligence radiological characteristics to predict prognosis after percutaneous nephrolithotomy

Background

A model to predict preoperative outcomes after percutaneous nephrolithotomy (PCNL) with renal staghorn stones is developed to be an essential preoperative consultation tool.

Objective

In this study, we constructed a predictive model for one-time stone clearance after PCNL for renal staghorn calculi, so as to predict the stone clearance rate of patients in one operation, and provide a reference direction for patients and clinicians.

Methods

According to the 175 patients with renal staghorn stones undergoing PCNL at two centers, preoperative/postoperative variables were collected. After identifying characteristic variables using PCA analysis to avoid overfitting. A predictive model was developed for preoperative outcomes after PCNL in patients with renal staghorn stones. In addition, we repeatedly cross-validated their model's predictive efficacy and clinical application using data from two different centers.

Results

The study included 175 patients from two centers treated with PCNL. We used a training set and an external validation set. Radionics characteristics, deep migration learning, clinical characteristics, and DTL+Rad-signature were successfully constructed using machine learning based on patients' pre/postoperative imaging characteristics and clinical variables using minimum absolute shrinkage and selection operator algorithms. In this study, DTL-Rad signal was found to be the outstanding predictor of stone clearance in patients with renal deer antler-like stones treated by PCNL. The DTL+Rad signature showed good discriminatory ability in both the training and external validation groups with AUC values of 0.871 (95% CI, 0.800-0.942) and 0.744 (95% CI, 0.617-0.871). The decision curve demonstrated the radiographic model's clinical utility and illustrated specificities of 0.935 and 0.806, respectively.

Conclusion

We found a prediction model combining imaging characteristics, neural networks, and clinical characteristics can be used as an effective preoperative prediction method.

Ultrasound-guided percutaneous nephrolithotomy (PCNL) success rates in patients with elevated body mass index: a comparative study

Percutaneous nephrolithotomy (PCNL) is considered gold standard treatment of renal stones larger than 20 mm. Several studies have shown that ultrasound guidance during this procedure is more effective and safer than fluoroscopy. A higher body mass index (BMI) can make ultrasound-guided renal access more difficult and unsuccessful. We present a prospective analysis and comparison of ultrasound-guided PCNL in patients with normal and increased body mass index. We performed a prospective comparison of patients who underwent ultrasound-guided PCNL to remove renal stones by a single surgeon between 2020 and 2022. Patients with BMIs greater than 30 (mean 33.87-obese) were compared to those with BMIs less than 30 (mean 25.69-non-obese). Demographic, perioperative, and follow-up data were collected, analyzed, and included in this study. Total of 98 consecutive patients, with 49 patients in each group were analyzed. No statistically significant differences were observed in terms of stone volume (P = 0.085), stone density (P = 0.5590), location of renal access (P = 0.108), surgery duration (P = 0.38), blood loss (P = 0.54), or laboratory changes after surgery (P = 0.60). 87.76% of obese patients were stone free per CT scan at follow-up, compared to 73.47% of normal-weight patients (P = 0.1238). According to Clavien-Dindo classification, six patients in the non-obese group experienced grade II (10%) and grade III (2%) complications, as opposed to six patients in the obese group with grade I (2%), grade II (6%), and grade III (2%) complications. There was no significant correlation between body mass index and the success or safety of ultrasound-guided PCNL. Although more challenging, a higher BMI should not be an impediment to performing this approach. This method is safe, with no increased incidence of postoperative complications or compromise in stone-free status postoperatively and can diminish or avoid both patient's and medical team's exposure to ionizing radiation.

Dual-energy CT kidney stone characterization-can diagnostic accuracy be achieved at low radiation dose?

OBJECTIVES

To assess the accuracy of low-dose dual-energy computed tomography (DECT) to differentiate uric acid from non-uric acid kidney stones in two generations of dual-source DECT with stone composition analysis as the reference standard.

METHODS

Patients who received a low-dose unenhanced DECT for the detection or follow-up of urolithiasis and stone extraction with stone composition analysis between January 2020 and January 2022 were retrospectively included. Collected stones were characterized using X-ray diffraction. Size, volume, CT attenuation, and stone characterization were assessed using DECT post-processing software. Characterization as uric acid or non-uric acid stones was compared to stone composition analysis as the reference standard. Sensitivity, specificity, and accuracy of stone classification were computed. Dose length product (DLP) and effective dose served as radiation dose estimates.

RESULTS

A total of 227 stones in 203 patients were analyzed. Stone composition analysis identified 15 uric acid and 212 non-uric acid stones. Mean size and volume were 4.7 mm × 2.8 mm and 114 mm3, respectively. CT attenuation of uric acid stones was significantly lower as compared to non-uric acid stones (p < 0.001). Two hundred twenty-five of 227 kidney stones were correctly classified by DECT. Pooled sensitivity, specificity, and accuracy were 1.0 (95%CI: 0.97, 1.00), 0.93 (95%CI: 0.68, 1.00), and 0.99 (95%CI: 0.97, 1.00), respectively. Eighty-two of 84 stones with a diameter of  ≤ 3 mm were correctly classified. Mean DLP was 162 ± 57 mGy*cm and effective dose was 2.43 ± 0.86 mSv.

CONCLUSIONS

Low-dose dual-source DECT demonstrated high accuracy to discriminate uric acid from non-uric acid stones even at small stone sizes.

KEY POINTS

• Two hundred twenty-five of 227 stones were correctly classified as uric acid vs. non-uric acid stones by low-dose dual-energy CT with stone composition analysis as the reference standard. • Pooled sensitivity, specificity, and accuracy for stone characterization were 1.0, 0.93, and 0.99, respectively. • Low-dose dual-energy CT for stone characterization was feasible in the majority of small stones  < 3 mm.

[Mini-PCNL, micro-PCNL or RIRS: comparative efficacy and safety in renal stones up to 2 cm]

INTRODUCTION

One of the main trends in the evolution of endoscopic treatment of urolithiasis is the miniaturization of instruments. This is obvious in the development of minimally invasive percutaneous nephro-lithotomy (PCNL) and retrograde intrarenal surgery (RIRS). However, there are few studies comparing the efficiency and safety of these methods.

AIM

To evaluate and compare the efficiency and safety of mini-PCNL, micro-PCNL and RIRS in the treatment of kidney stones up to 2 cm in size.

MATERIALS AND METHODS

Between October 2020 and December 2022, a total 72 patients underwent minimally invasive endoscopic procedures in two centers, including RIRS (n=30), mini-PCNL (n=26) and micro-PCNL (n=16) using thulium fiber laser FiberLase U2. The efficiency of procedure (stone free rate [SFR]) was assessed using non-contrast-enhanced CT. SFR was considered as the absence of residual fragments > 4 mm. Complications (safety) were evaluated based on the Clavien-Dindo classification.

RESULTS

The mean age of all patients was 47.7 (22-84) years. There were no significant differences between three groups in stone characteristics according to CT (maximum diameter, density, volume and number of stones, the presence of pelvicalyceal dilation). SFR was significantly different between the groups (p=0.034). The overall SFR was 81.9% (n=59). After RIRS, mini-PCNL, and micro-PCNL the SFR was 93.3%, 80.8%, and 62.5%, respectively. A significant difference was found between the RIRS and micro-PNL groups, with 2 out of 30 and 6 out of 16 patients requiring repeat procedure, respectively (p=0.026). The overall rate of complication of grades I-II, IIIa and IIIb according to Clavien-Dindo was 6.9%, 9.7% and 6.9%, respectively. A significant difference was found between the RIRS and micro-PCNL (p=0.021) for grade I-II complications. A rate of grade III complications was not differed between the groups. The operation time was higher for mini-PNL (79.8 (30-145) min), and it was shorter for RIRS (55.7 (30-155) min). The length of stay was lower in RIRS group (4.5 (1-12) days).

CONCLUSION

The highest SFR was achieved in the RIRS group. In terms of the number of complications of I-II grades according to Clavien-Dindo, the duration of the procedure and the length of stay, RIRS also showed the advantage. There were no significant differences in efficiency and safety between the micro-PNL and mini-PNL. There are not enough studies comparing minimally invasive methods for treating kidney stones. It is necessary to continue research in this area in order to develop an optimal algorithm for choosing the method of endoscopic treatment.

Real-world Practice Stone-free Rates After Ureteroscopy: Variation and Outcomes in a Surgical Collaborative

BACKGROUND

Studies assessing the stone-free rate (SFR) after ureteroscopy are limited to expert centers with varied definitions of stone free. Real-world data including community practices related to surgeon characteristics and outcomes are lacking.

OBJECTIVE

To evaluate the SFR for ureteroscopy and its predictors across diverse surgeons in Michigan.

DESIGN, SETTING, AND PARTICIPANTS

We assessed the Michigan Urological Surgery Improvement Collaborative (MUSIC) clinical registry for patients with renal or ureteral stones treated with ureteroscopy between 2016 and 2021 who had postoperative imaging.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Stone free was defined as no fragments on imaging reports within 60 d entered by independent data abstractors. Factors associated with being stone free were examined using logistic regression, including annual surgeon volume. We then assessed variation in surgeon-level SFRs adjusted for risk factors.

RESULTS AND LIMITATIONS

We identified 6487 ureteroscopies from 164 surgeons who treated 2091 (32.2%) renal and 4396 (67.8%) ureteral stones. The overall SFRs were 49.6% (renal) and 72.7% (ureteral). Increasing stone size, lower pole, proximal ureteral location, and multiplicity were associated with not being stone free. Female gender, positive urine culture, use of ureteral access sheath, and postoperative stenting were associated with residual fragments when treating ureteral stones. Adjusted surgeon-level SFRs varied for renal (26.1-72.4%; p < 0.001) and ureteral stones (52.2-90.2%; p < 0.001). Surgeon volume was not a predictor of being stone free for renal stones. Limitations include the lack of imaging in all patients and use of different imaging modalities.

CONCLUSIONS

The real-world complete SFR after ureteroscopy is suboptimal with substantial surgeon-level variation. Interventions focused on surgical technique refinement are needed to improve outcomes for patients undergoing ureteroscopy and stone intervention.

PATIENT SUMMARY

Results from a diverse group of community practicing and academic center urologists show that for a large number of patients, it is not possible to be completely stone free after ureteroscopy. There is substantial variation in surgeon outcomes. Quality improvement efforts are needed to address this.

Combined semirigid and flexible ureterorenoscopy for the treatment of large renal stones

Ureteroscopy is recognized as a minimally invasive and readily accessible method with low morbidity, favorable outcomes, and rapid post-interventional recovery. Recent advancements in rigid and flexible ureteroscopes have enhanced their efficiency, durability, and capability to accommodate accessory instruments. In this retrospective analysis, we evaluated 75 consecutive patients with large renal stones (stone burden between 2 and 4 cm) treated using a combination of semirigid and flexible ureteroscopy between January 1, 2020, and December 31, 2021. Stone properties and anatomical information were collected from the image archives derived from computed tomography (CT) and/or KUD radiography. Multiple ureteroscopy sessions were required for bigger stones. The length of the hospital stay, operation time, stone-free rate, preoperative and postoperative complications, and complication rates were examined. The average age of the patients was 52.7 years, with a mean stone burden of 31.45 mm. Most stones were in the renal pelvis, followed by the upper calyx. The average operative time was 56.2 minutes. After the initial ureteroscopy session, the stone clearance rate was 76%, which increased to 92% after two ureteroscopy sessions. Complication rates were evaluated using the Clavien-Dindo modified system, with an overall complication rate of 18.4%. Most of the complications were Clavien Grades I and II, with no grade V complication encountered. Large renal stones can be treated by combining semirigid and flexible ureteroscopy to reduce the operative time and protect the flexible ureteroscope.

A Novel Computed Tomography-Ultrasound Image Fusion Technique for Guiding the Percutaneous Kidney Access

PURPOSE

To describe the feasibility of computed tomography (CT)-ultrasound image fusion technique on guiding percutaneous kidney access in vitro and vivo.

MATERIALS AND METHODS

we compare CT-ultrasound image fusion technique and ultrasound for percutaneous kidney puncture guidance by using an in vitro pig kidney model. The fusion method, fusion time, ultrasound screening time, and success rate of puncture were compared between the groups. Next, patients with kidney stones in our hospital were randomized in the study of simulated puncture guidance. The general condition of patients, fusion method, fusion time, and ultrasound screening time were compared between the groups.

RESULTS

A total of 45 pig models were established, including 23 in the CT-ultrasound group and 22 in the ultrasound group. The ultrasound screening time in the CT-ultrasound group was significantly shorter than that in the ultrasound group (P < .001). In addition, the success rate of puncture in the CT-ultrasound group was significantly higher than that in the ultrasound group (P =.015). Furthermore, in the simulated PCNL puncture study, baseline data including age, BMI, and S.T.O.N.E score between the two groups showed no statistical difference. The ultrasound screening time of the two groups was (2.60 ± 0.33) min and (3.37 ± 0.51) min respectively, and the difference was statistically significant (P < .001).

CONCLUSION

Our research revealed that the CT-ultrasound image fusion technique was a feasible and safe method to guide PCNL puncture. Compared with traditional ultrasound guidance, the CT-ultrasound image fusion technique can shorten the learning curve of PCNL puncture, improve the success rate of puncture, and shorten the ultrasound screening time.

Retrograde intrarenal surgery for stones associated with renal anomalies: caliceal diverticulum, horseshoe kidney, medullary sponge kidney, megacalycosis, pelvic kidney, uretero-pelvic junction obstruction

PURPOSE OF REVIEW

Nowadays, due to the increase of imaging diagnosis, we identify easily renal anomalies, and we can choose between a wide range of armamentarium to treat symptomatic stones in those challenging cases. However, there is a lack of evidence and consensus on its use. The aim of this narrative review is to collect all the available data about safety and efficacity of retrograde intrarenal surgery (RIRS) in the treatment of kidney stones associated to a renal anomaly.

RECENT FINDINGS

Renal anomalies are uncommon findings and even more if it has to be associated with renal stones. After a literature review of the past 2 years, there are a small number of studies that compare the outcomes in patients who have been treated with minimally invasive modalities and they are mainly focus on RIRS.

SUMMARY

It is of extreme importance to know the advances on the stone treatment in anomalous kidneys. With the development of new laser technologies, RIRS is becoming a more interesting technique with high success rate and safety. Further studies are needed to make an accurate statement about the adequate surgical technique for each renal anomaly and also, clinical trials using new laser technologies.

Percutaneous management of caliceal diverticula: a narrative review

PURPOSE OF REVIEW

Caliceal diverticula are relatively uncommon within urologic practice and may be difficult to diagnose and treat. We aim to highlight contemporary studies examining surgical interventions for patients with caliceal diverticula, with a focus on percutaneous intervention, and provide updated practical recommendations for the management of these patients.

RECENT FINDINGS

Studies within the last 3 years examining surgical treatment options for caliceal diverticular calculi are limited. When flexible ureteroscopy (f-URS) and percutaneous nephrolithotomy (PCNL) are examined within the same observational cohorts, PCNL is associated with improved stone-free rates (SFRs), lower requirement for re-intervention, and longer lengths of stay (LOS). Retrograde f-URS for the treatment of caliceal diverticula and diverticular calculi is associated with satisfactory safety and efficacy outcomes. There are no studies in the last 3 years that provide supporting evidence to use shock wave lithotripsy to treat caliceal diverticular calculi.

SUMMARY

Recent studies examining surgical interventions for patients with caliceal diverticula are limited to small observational studies. Heterogeneity in LOS and follow-up protocol limits comparisons between series. Despite technological advancements in f-URS, PCNL appears to be associated with more favorable and definitive outcomes. PCNL continues to be the preferred treatment strategy for patients with symptomatic caliceal diverticula when deemed technically feasible.

Identification of Clinically Insignificant Renal Calculi on Sonography

OBJECTIVE

To determine factors predicting if a radiologists... report of a .. stone... on ultrasound (US) was not actually a clinically significant stone, based on subsequent computed tomogram (CT). US often overestimates stone size and various pathologic entities are also hyperechoic;.ßthus, a subsequent CT without a clinically significant stone may represent unnecessary radiation exposure. A decision-tree and nomogram were developed to predict when stones are unlikely on subsequent CT.

METHODS

Retrospective analysis of patients, of any age, receiving CT within 24.ßhours of a sonographic report documenting a single renal stone, during 2019...2020, in any phase of care, at one institution. Novel stone-likelihood-systems for US and CT (US-SLS, CT-SLS) were devised and validated to classify stones as clinically significant or insignificant, with CT as the gold standard. Binomial logistic regression predicting clinically significant stones was performed with sonographic and patient characteristics.

RESULTS

Eight hundred twenty patients had US followed by CT, 228 (27.8%) reported documented stones, 140 (17.1%) reported a single stone. Clinically significant stones were associated with larger stone size (P: .002), location (P: .002), hydronephrosis (P: .04), shadowing-artifact (P: .02) depth.ßto.ßstone (P: .008), and Body mass Index (BMI) (P: .01). US-SLS had higher sensitivity (95.4%) and negative-predictive-value (81.8%) compared to a multivariate model of significant variables.

CONCLUSION

US-SLS appears to exclude clinically irrelevant .. stones... better than established criteria including twinkle or shadow in this retrospective analysis. A diagnostic algorithm and nomogram are presented. US-SLS and the associated decision tree can assist providers in avoiding unnecessary radiation when clinically significant stones are unlikely.

Ultrasound-Only Percutaneous Nephrolithotomy Is Safe and Effective Compared to Fluoroscopy-Directed Percutaneous Nephrolithotomy

Introduction: Outcomes after ultrasound-only percutaneous nephrolithotomy (PCNL), in which no fluoroscopy is used, are not well known. The goal of this study was to compare outcomes of ultrasound-only and fluoroscopy-directed PCNL. Materials and Methods: Prospectively collected data from the Registry for Stones of the Kidney and Ureter database were reviewed for all patients who underwent PCNL at one academic center from 2015 to 2021. Primary outcomes were complications and stone-free rates (no residual fragments ≥3 mm). Results: Of the 141 patients who underwent ultrasound-only PCNL and 147 who underwent fluoroscopy-directed PCNL, there was no difference in complication rates (15% vs 16%, p = 0.87) or stone-free status (71% vs 65%, p = 0.72), respectively. After adjusting for body mass index, American Society of Anesthesiologists (ASA), stone size, and stone complexity by Guy score, ultrasound-only PCNL was not associated with any increased odds of complications (odds ratio [OR] 0.7, 95% confidence interval [CI] 0.3-1.6, p = 0.41) or residual stone fragments ≥3 mm (OR 1.0, 95% CI 0.5-1.9, p = 0.972) compared with fluoroscopy-directed PCNL. Ultrasound-only PCNL was associated with shorter operative time (median 99.5 vs 126 minutes, p < 0.001), and the use of ultrasound remained a significant predictor of short operative time (<100 minutes) after controlling for supine positioning, stone size, and stone complexity by Guy score (OR 2.31, 95% CI 1.01-5.29, p = 0.048). Patients in the ultrasound-only group were spared a mean radiation exposure dose of 10 mGy per procedure. Conclusions: Ultrasound-only PCNL is safe and achieves similar stone-free rates compared with fluoroscopy-directed PCNL with the added benefit of avoidance of radiation.

Enhancing sizing accuracy in ultrasound images with an alternative ADMIRE model and dynamic range considerations

Ultrasound imaging can struggle with sizing accuracy, especially when the targets have a significantly different amplitude compared to the surrounding background. In this work, we consider the challenging task of accurately sizing hyperechoic structures, and specifically kidney stones, where accurate sizing is critical for determining medical intervention. AD-Ex, an extended alternative model of our aperture domain model image reconstruction (ADMIRE) pre-processing method, is introduced and is designed to improve clutter removal and improve sizing accuracy. We compare this method against other resolution enhancing methods such as minimum variance (MV) and generalized coherence factor (GCF), and against those methods using AD-Ex as a pre-processing tool. These methods are evaluated among patients with kidney stone disease, with the task of accurately sizing the stones against the gold standard, computed tomography (CT). Stone ROI's were selected using contour maps as reference from which the lateral stone size was estimated. Among the in vivo kidney stone cases we processed, AD-Ex+MV had the overall lowest sizing error among the methods, with an average error of 10.8% compared to the next best method AD-Ex which had an average error of 23.4%. For reference, DAS had an average error of 82.4%. Though dynamic range was evaluated to determine optimal thresholding for sizing applications, variability between stone cases was too high for any conclusions to be drawn at this time.

[Not Available]

Kidney stone disease is rapidly increasing with a strong relationship to metabolic syndrome. This review gives a brief overview of the current state and current treatment modalities. Increasing use of CT and ultrasound scans leads to increased diagnosis of asymptomatic kidney stones, which rarely require treatment. The trend in stone treatment goes towards endoscopic lithotripsy which together with ESWL enables a personalised approach. Obstructive stones with infection require urgent intervention to reduce mortality. Increased fluid intake, dietary changes as well as potassium citrate supplements are the most important elements in stone prevention in the common idiopathic stone disease.

In Vivo Prediction of Kidney Stone Fragility Using Radiomics-Based Regression Models

Introduction: The surgical technique for urinary stone removal is partly influenced by its fragility, as prognosticated by the clinician. This feasibility study aims to develop a linear regression model from CT-based radiomic markers to predict kidney stone comminution time in vivo with two ultrasonic lithotrites. Materials and Methods: Patients identified by urologists at our institution as eligible candidates for percutaneous nephrolithotomy were prospectively enrolled. The active engagement time of the lithotrite in breaking the stone during surgery denoted the comminution time of each stone. The comminution rate was computed as the stone volume disintegrated per minute. Stones were grouped into three fragility classes (fragile, moderate, hard), based on inverse of the comminution rates with respect to the mean. Multivariable linear regression models were trained with radiomic features extracted from clinical CT images to predict comminution times in vivo. The model with the least root mean squared error (RMSE) on comminution times and the fewest misclassification of fragility was finally selected. Results: Twenty-eight patients with 31 stones in total were included in this study. Stones in the cohort averaged 1557 (±2472) mm3 in volume and 5.3 (±7.4) minutes in comminution time. Ten stones had nonmoderate fragility. Linear regression of stone volume alone predicted comminution time with an RMSE of 6.8 minutes and missed all 10 stones with nonmoderate fragility. A fragility model that included stone volume, internal morphology, shape-based radiomics, and device type improved RMSE to below 3.3 minutes and correctly classified 20/21 moderate and 6/10 nonmoderate stones. Conclusions: CT metrics-based fragility models may provide information to surgeons regarding kidney stone fragility and facilitate the selection of stone removal procedures.

Role of Hounsfield Unit in Predicting Outcomes of Shock Wave Lithotripsy for Renal Calculi: Outcomes of a Systematic Review

PURPOSE OF REVIEW

Extracorporeal shock wave lithotripsy success rates depend on several stone and patient-related factors, one of which is stone density which is calculated on computed tomography scan in Hounsfield Units. Studies have shown inverse correlation between SWL success and HU; however, there remains considerable variation between studies. We performed a systematic review regarding the use of HU in SWL for renal calculi to consolidate the current evidence and address current knowledge gaps.

RECENT FINDINGS

Database including MEDLINE, EMBASE, and Scopus were searched from inception through August 2022. Studies in English language analysing stone density/attenuation in adult patients undergoing SWL for renal calculi were included for assessment of Shockwave lithotripsy outcomes, use of stone attenuation to predict success, use of mean and peak stone density and Hounsfield unit density, determination of optimum cut-off values, nomograms/scoring systems, and assessment of stone heterogeneity. 28 studies with a total of 4,206 patients were included in this systematic review with sample size ranging from 30 to 385 patients. Male to female ratio was 1.8, with an average age of 46.3 years. Mean overall ESWL success was 66.5%. Stone size ranged from 4 to 30 mm in diameter. Mean stone density was used by two-third of the studies to predict the appropriate cut-off for SWL success, ranging from 750 to 1000 HU. Additional factors such as peak HU and stone heterogeneity index were also evaluated with variable results. Stone heterogeneity index was considered a better indicator for success in larger stones (cut-off value of 213) and predicting SWL stone clearance in one session. Prediction scores had been attempted, with researchers looking into combining stone density with other factors such as skin to stone distance, stone volume, and differing heterogeneity indices with variable results. Numerous studies demonstrate a link between shockwave lithotripsy outcomes and stone density. Hounsfield unit < 750 has been found to be associated with shockwave lithotripsy success, with likelihood of failure strongly associated with values over 1000. Prospective standardisation of Hounsfield unit measurement and predictive algorithm for shockwave lithotripsy outcome should be considered to strengthen future evidence and help clinicians in the decision making.

TRIAL REGISTRATION

International Prospective Register of Systematic Reviews (PROSPERO) database: CRD42020224647.

Hydrochlorothiazide and Prevention of Kidney-Stone Recurrence

BACKGROUND

Nephrolithiasis is one of the most common conditions affecting the kidney and is characterized by a high risk of recurrence. Thiazide diuretic agents are widely used for prevention of the recurrence of kidney stones, but data regarding the efficacy of such agents as compared with placebo are limited. Furthermore, dose-response data are also limited.

METHODS

In this double-blind trial, we randomly assigned patients with recurrent calcium-containing kidney stones to receive hydrochlorothiazide at a dose of 12.5 mg, 25 mg, or 50 mg once daily or placebo once daily. The main objective was to investigate the dose-response effect for the primary end point, a composite of symptomatic or radiologic recurrence of kidney stones. Radiologic recurrence was defined as the appearance of new stones on imaging or the enlargement of preexisting stones that had been observed on the baseline image. Safety was also assessed.

RESULTS

In all, 416 patients underwent randomization and were followed for a median of 2.9 years. A primary end-point event occurred in 60 of 102 patients (59%) in the placebo group, in 62 of 105 patients (59%) in the 12.5-mg hydrochlorothiazide group (rate ratio vs. placebo, 1.33; 95% confidence interval [CI], 0.92 to 1.93), in 61 of 108 patients (56%) in the 25-mg group (rate ratio, 1.24; 95% CI, 0.86 to 1.79), and in 49 of 101 patients (49%) in the 50-mg group (rate ratio, 0.92; 95% CI, 0.63 to 1.36). There was no relation between the hydrochlorothiazide dose and the occurrence of a primary end-point event (P = 0.66). Hypokalemia, gout, new-onset diabetes mellitus, skin allergy, and a plasma creatinine level exceeding 150% of the baseline level were more common among patients who received hydrochlorothiazide than among those who received placebo.

CONCLUSIONS

Among patients with recurrent kidney stones, the incidence of recurrence did not appear to differ substantially among patients receiving hydrochlorothiazide once daily at a dose of 12.5 mg, 25 mg, or 50 mg or placebo once daily. (Funded by the Swiss National Science Foundation and Inselspital; NOSTONE ClinicalTrials.gov number, NCT03057431.).

Is the Supine Position Suitable for Ultrasound-Guided Percutaneous Nephrolithotomy in Patients with Complex Renal Stones?

INTRODUCTION

The aim of the study was to assess the safety and efficacy of ultrasound (US)-guided percutaneous nephrolithotomy (PCNL) for complex renal stones when performed in a modified supine position.

METHODS

We retrospectively reviewed the charts of patients who underwent PCNL for complex renal stones at our institution between August 2018 and December 2021. During this time, 188 consecutive patients underwent US-guided PCNL in the prone position (P group, n = 129) or in the flank-free modified supine position (S group, n = 59). Patient demographics and intraoperative and postoperative data were analyzed.

RESULTS

Successful renal access was achieved in all patients. The baseline demographics were comparable between the two groups. The numbers of renal access were significantly higher (2.1 ± 0.4 vs. 1.2 ± 0.2, p = 0.002), and the operation time was comparable (79.1 ± 14.6 min vs. 96.2 ± 19.6 min, p = 0.06) between the two groups. The postoperative hospital stay was also shorter in the P group (6.2 ± 1.5 d vs. 10.2 ± 1.7 d, p = 0.008). The postoperative hemoglobin loss was similar between the P and S groups (1.7 ± 0.4 g/dL vs. 1.8 ± 0.3 g/dL, p = 0.12). The stone-free rate was significantly lower in the S group (57.5% vs. 82.7%, p < 0.001). There were no embolization or septic complications. Twelve patients (20.3%) in the S group underwent simultaneous or staged retrograde flexible ureteroscopy to remove residual stones.

CONCLUSION

US-guided PCNL in the modified supine position was a safe treatment for complex renal stones. However, the single-session stone clearance rate was not ideal. The supine flank-free position may be unsuitable for US-guided PCNL in patients with complex renal stones according to our preliminary findings.

Single-center experience of micro-perc in the treatment of children with 1.0-2.0 cm sized kidney stones in the Galdakao-modified supine Valdivia position

OBJECTIVE

We aimed to explore the applicability and safety of micro-percutaneous nephrolithotomy (micro-perc) in the treatment of children with kidney stones in the Galdakao-modified supine Valdivia (GMSV) position under the guidance of whole-course ultrasound.

MATERIALS AND METHODS

Patients were aged < 18 years in the GMSV position who underwent micro-perc for kidney stones under ultrasound guidance between August 2020 and May 2022 at our institution were reviewed retrospectively.

RESULTS

A total of 23 patients, 15 males and 8 females, received micro-perc. The average stone size was 1.6 cm (range 1.1-2.0 cm). Among them, 12 patients had left kidney stones, 10 patients had right kidney stones, and 1 patient had bilateral kidney stones. The mean operative time was 55.3 min (range 35-86 min). The mean hospital stay was 2.9 days (range 2-4 days). The mean hemoglobin decrease was 1.7 g/L (range 0.9-3.2 g/L). A total of 17 patients had complete stone clearance at 48 h postoperatively. A total of 22 patients had complete stone clearance at 2 weeks postoperatively.

CONCLUSION

Our results demonstrate that micro-perc under ultrasound guidance is a safe and effective method for the treatment of children with kidney stones in the GMSV position. Further research is warranted to confirm these results.

Nephrocolocutaneous fistula from a staghorn calculus

Fistula formation between the kidney, colon and the skin is an extremely rare complication arising from renal infections secondary to renal stone formation. During the 1980s, reports of nephrocolic fistulas, with or without involvement of the skin, were commonly caused by genitourinary tuberculosis. Due to improvements in diagnosis and specifically the development of anti-Koch's therapy, the incidence of nephrocolic or nephrocolocutaneous fistulas has become uncommon especially in developed countries.We report a case of a patient residing in a developing country, presenting with a 20-year history of a left flank lesion extruding minimal purulent output daily. He was seen at the emergency department due to weakness and was managed as a case of urosepsis. Contrast-enhanced CT scan and fistulogram showed a staghorn calculus in the left kidney with connections to the descending colon and skin. The patient eventually underwent a left hemicolectomy with en bloc excision of the kidney and fistula tract.

Can additional variables be used to predict stone-free rates following retrograde intrarenal surgery? Anticoagulants and parenchyma thickness: a detailed examination

The purpose of this article is to identify the factors that predict the success of retrograde intrarenal surgery (RIRS), with a focus on the effect of renal parenchymal thickness and anticoagulant use on stone-free rates. From February 2014 to April 2022, cases of kidney stones treated with RIRS at our clinic were retrospectively screened. The study included 642 cases meeting all inclusion and exclusion criteria. The patients who were observed to be stone free after a single session of RIRS were assigned to Group F, while those with residual fragments were assigned to Group R. Group F comprised 472 patients, while Group R included 170 patients. The two groups have compared certain preoperative and postoperative laboratory and radiological parameters. The infundibulopelvic angle was significantly more acute in Group R (45.63 ± 16.25 vs. 49.28 ± 15.36, p = 0.011) while patients in Group F tended to have thicker parenchyma (27.39 ± 8.38 vs. 22.88 ± 5.56, p < 0.001). In our analysis of multivariate logistic regression, stone size (OR: 1.074, 1.037-1.113; p < 0.001), lower calyceal location (OR: 0.550, 95% CI 0.364-0.831; p = 0.005), multiple numbers of stones (OR 0.254, 95% CI 0.166-0.389; p =  < 0.001), the value of parenchymal thickness (OR 0.911, 95% CI 0.882-0.941; p =  < 0.001) and more importantly use of anticoagulants/antiplatelets (OR 0.557, 95% CI 0.333-0.933; p = 0.026) appeared to be independent predictors of stone-free status after RIRS. Further evaluation of the data revealed that the cut-off value of the renal parenchymal thickness for an effective stone-free status in a ROC curve analysis was 24.5 with 62.9% sensitivity and 56.8% specificity (area under curve value: 0.654 [95% CI 0.608-0.699, p < 0.001]). The endourologist may be able to make more informed decisions by evaluating renal parenchymal thickness in addition to patient-related factors like anticoagulant use, which we find significantly affects outcomes, along with the stone and renal anatomy-related factors.

Imaging After Ureteroscopy: Practice Patterns, Patient Adherence and Impact on Subsequent Management in an Urban Academic Hospital System

OBJECTIVE

To evaluate practice patterns of post-ureteroscopy (URS) imaging, to assess predictors of imaging order, type and completion, and to analyze impact on patient management.

METHODS

We conducted a retrospective review of patients who underwent URS for nephrolithiasis at a single institution between May, 2020 to May, 2021. Patient demographic, clinical and operative characteristics were reviewed, and surgeons' years in practice. Post-URS imaging studies less than 6 months post-operative were reviewed. Changes in patient management were defined as additional imaging tests ordered or subsequent unplanned surgery. Patient, provider and surgical variables were compared between those who had imaging ordered and those who did not.

RESULTS

A total of 289 patients underwent URS. About 234 (81.0%) had post-operative imaging ordered; 147 (62.8%) completed them. Baseline demographics, stone and surgical variables were similar among those who did and did not have imaging ordered and among patients who completed imaging and did not. Pre-operative hydronephrosis was associated with ordering of post-operative imaging (OR = 4.08, P = .01). Urologists in practice less than 5 years were more likely to order post-operative imaging compared to those in practice for more than 5 years (<5: 90.6%, 15+: 53.7%; P <.001). Management changed for 52 of 147 (35.4%) patients who completed imaging; additional imaging was ordered for 38 patients (25.9%) and a second, unplanned surgery was performed for 14 (9.5%).

CONCLUSION

The main predictive factor of ordering post-URS imaging was surgeons' time in practice and pre-operative hydronephrosis. Post-operative imaging changed management in 35.4% of patients. We recommend the development of guidelines encouraging routine imaging for patients following ureteroscopy.

[Diagnostic values of urinary citrate for kidney stones in patients with primary gout]

OBJECTIVE

To evaluate the relationship between 24 h urinary ion content and kidney stones, and to explore the diagnostic values of kidney stone in primary gout patients.

METHODS

Patients diagnosed with primary gout had ultrasound scanning of both feet and kidneys in Peking University First Hospital from Jan. 2020 to May 2021. Their clinical characteristics were compared between the positive and negative kidney stone groups, and the relationship between kidney stone and urinary ion composition were analyzed. Risk factors of kidney stone were analyzed. The explored diagnostic values were evaluated for urinary oxalate and citrate according with uric acid kidney stones by dual-energy computed tomography (DECT).

RESULTS

Among the 100 gouty patients, 80 patients had uric acid crystal deposition in lower joints of extremity by ultrasonography, 61 patients had kidney stone, and 34 had kidney uric acid stones by DECT. All the multiple kidney stones were proved as uric acid kidney stones by DECT. Compared with patients without kidney stone group proved by ultrasonography, patients with kidney stone had longer gouty duration [(48.7±26.6) months vs. (84.0±30.6) months, P=0.01], higher 24 h urinary oxalate [(20.1±9.6) mg vs. (28.6±20.7) mg, P=0.001] and lower 24 h urinary citrate [(506.3±315.4) mg vs. (355.7±219.6) mg, P=0.001]. Compared with the patients without kidney stone by DECT, the patients with uric acid kidney stone also had longer disease duration [(49.1±28.4) months vs. (108.3±72.2) months, P=0.001], higher 24 h urinary oxalate [(23.6±16.9) mg vs. (28.5±18.8) mg, P < 0.05], lower 24 h urinary citrate [(556.0±316.3) mg vs. (391.7±261.2) mg, P < 0.05], higher serum uric acid [(466.2±134.5) μmol/L vs. (517.2±18.1) μmol/L, P < 0.05] and higher 24 h urinary uric acid [(1 518.1±893.4) mg vs. (1 684.2±812.1) mg, P < 0.05]. Logistic regression analysis showed long gout disease duration (OR=1.229, 95%CI: 1.062-1.522, P < 0.05), high serum uric acid level (OR=1.137, 95%CI: 1.001-1.213, P=0.01), low 24 h urinary citrate (OR=0.821, 95%CI: 0.659-0.952, P=0.01) were all risk factors of kidney stones by ultrasonography. Also, long gout disease duration (OR=1.201, 95%CI: 1.101-1.437, P=0.005), high serum creatine uric level (OR=1.145, 95%CI: 1.001-1.182, P=0.04), low 24 h urinary citrate (OR=0.837, 95%CI: 0.739-0.931, P=0.02) were all risk factors of kidney uric acid stones by DECT.

CONCLUSION

Long disease duration and low 24 h urinary citrate were risk factors for kidney stones.

Percutaneous nephrostomy for complex renal stones: Percutaneous renal access behind the stone versus renal calyx dilation

OBJECTIVE

To evaluate the technical success rate and complications associated with percutaneous nephrostomy (PCN) via percutaneous renal access behind the stone and renal calyx dilation in patients with complex renal stones.

MATERIALS AND METHODS

From January 2010 to February 2021, we identified 69 patients with 70 complex renal stones who underwent PCN. Complex renal stones were classified as simple (renal pelvis only) (27.1%, 19/70), borderline staghorn (8.6%, 6/70), partial staghorn (51.4%, 36/70), or complete staghorn (12.9%, 9/70). All PCNs were performed under ultrasound and fluoroscopic guidance using one of two renal-entry techniques: puncture behind the stone (56%, 39/70) or renal calyx dilation (44%, 31/70). Then, we retrospectively evaluated the technical success rates and complications associated with each renal entry access technique.

RESULTS

The overall technical success rate was 100%, and the complication rate was 20.0% (14/70). For those who underwent renal access behind the stone, the complication rate was 15.4% (6/39), and six patients (six PCNs) had transient gross hematuria. For those who underwent dilated renal calyx entry, the complication rate was 25.8% (8/31), and one patient had significant bleeding complications requiring transfusion. Furthermore, seven patients (seven PCNs) had transient gross hematuria. Overall, the complication rates did not differ between the technique groups (p = 0.279).

CONCLUSION

PCN for complex renal stones has a high technical success rate and an acceptable complication rate regardless of the specific technique. Renal entry behind the stone is as safe and feasible as approaching via a dilated renal calyx.