How Accurate Are We in Estimating True Stone Volume? A Comparison of Water Displacement, Ellipsoid Formula, and a CT-Based Software Tool

Is Psoas Muscle Mass Associated with Failure of Ureteral Access Sheath Insertion and Complications from Retrograde Intrarenal Surgery? A Case-Control Study from RIRSearch group

Objective: To investigate the association between psoas muscle mass (PMM) and failure of ureteral access sheath (UAS) insertion and complications from retrograde intrarenal surgery (RIRS). Materials and Methods: A multicenter retrospective case-control study was conducted that included patients who underwent RIRS despite failure of UAS insertion (Cohort 1) and confounder-matched control patients who underwent RIRS after successful UAS insertion (Cohort 2). For morphometric analysis of PMM, ipsilateral psoas muscle areas (iPMAs) were measured using the coreslicer.com webkit. After comparing demographic, clinical, and complication rates and iPMAs between cohorts, gender-specific median iPMAs were also determined to further subdivide patients in each cohort as either low iPMAs or high iPMAs. Thereafter, patients were also compared in terms of RIRS complications. Results: Cohort 1 included 86 patients whereas Cohort 2 consisted of 124 matched cases. The median (interquartile range) iPMAs were similar between the cohorts: Cohort 1, 11.05 (6.82-14.44) cm2 versus 11.12 (6.97-13.69) cm2 for Cohort 2 (P ˃ .05). There was a significant inverse relationship between iPMAs with age (r = -0.222) and Charlson comorbidity index (r = -0.180) for all patients (P ˂ .05). Perioperative and postoperative complication rates were 8.1% and 16.3% for Cohort 1 and 6.5% and 21% for Cohort 2, respectively. The complication rates were not statistically different between patients with high iPMAs and those with low iPMAs, in male or female patients (P > .05). Conclusions: These results show that failure of UAS was not associated with PMM. Furthermore, since the complication rates were similar between patients with high PMM and low PMM, RIRS may be a reliable treatment choice for sarcopenic patients as well as in nonsarcopenic patients.

Safety and Efficacy of Retrograde Intrarenal Surgery in the Solitary Kidney: A Propensity Score-Matched Analysis of the RIRSearch Study Groups' Results

Background: The aim of this study was to evaluate the efficacy and safety of retrograde intrarenal surgery (RIRS) in patients with renal calculi with solitary kidneys (SKs). Materials and Methods: In this retrospective, multicenter study, a matched case-control study was carried out using the data from 522 RIRS patients treated between 2014 and 2021. Patients' demographic data, stone characteristics, operative outcomes, perioperative and postoperative complications, and surgical success were analyzed. All patients were evaluated with noncontrast-enhanced computed tomography (NCCT) preoperatively and 1 month after the surgery. Surgical success was defined as no evidence of remaining residual fragments of <3 mm in the first-month postoperative NCCT images. The case group of 29 patients with SKs (Group 1) treated with RIRS were matched with 76 control patients (Group 2) with bilateral kidneys, who underwent unilateral RIRS by propensity score-matched (PSM) analysis. Results: After PSM analysis, the demographic and clinical data did not differ significantly between the groups. The stone burden was similar between the groups: 733.6 mm3 (range: 50.4-7565.9) versus 991.1 mm3 (range: 201.2-4380.6) (P = .09), respectively. The perioperative complication rates were 13.8% (n = 4) in Group 1 and 11.8% (n = 9) in Group 2 (P = .78). There was no statistically significant difference between the groups for postoperative complication rates (minor complications, classified as Clavien 1 or 2), (6.9% [n = 2] versus 13.2% [n = 10; P = .34]), respectively. Surgical success was 82.8% (n = 24) in Group 1 and 83.6% in Group 2 (P = .92). There was no significant difference between preoperative and postoperative glomerular filtration rate and creatinine values (P = .005). Conclusions: Our results support that RIRS is a safe and effective treatment method in SK patients with similar complication and stone-free rates compared to patients who had bilateral functional kidneys and underwent unilateral RIRS.

How to estimate stone volume and its use in stone surgery: a comprehensive review

OBJECTIVE

Current interventional guidelines refer to the cumulative stone diameter to choose the appropriate surgical modality (ureteroscopy [URS], extracorporeal shockwave lithotripsy [ESWL] and percutaneous nephrolithotomy [PCNL]). The stone volume (SV) has been introduced recently, to better estimate the stone burden. This review aimed to summarize the available methods to evaluate the SV and its use in urolithiasis treatment.

MATERIAL AND METHODS

A comprehensive review of the literature was performed in December 2022 by searching Embase, Cochrane and Pubmed databases. Articles were considered eligible if they described SV measurement or the stone free rate after different treatment modalities (SWL, URS, PCNL) or spontaneous passage, based on SV measurement. Two reviewers independently assessed the eligibility and the quality of the articles and performed the data extraction.

RESULTS

In total, 28 studies were included. All studies used different measurement techniques for stone volume. The automated volume measurement appeared to be more precise than the calculated volume. In vitro studies showed that the automated volume measurement was closer to actual stone volume, with a lower inter-observer variability. Regarding URS, stone volume was found to be more predictive of stone free rates as compared to maximum stone diameter or cumulative diameter for stones >20 mm. This was not the case for PCNL and SWL.

CONCLUSIONS

Stone volume estimation is feasible, manually or automatically and is likely a better representation of the actual stone burden. While for larger stones treated by retrograde intrarenal surgery, stone volume appears to be a better predictor of SFR, the superiority of stone volume throughout all stone burdens and for all stone treatments, remains to be proven. Automated volume acquisition is more precise and reproducible than calculated volume.

Multi-aspect analysis of ureteral access sheath usage in retrograde intrarenal surgery: A RIRSearch group study

Objective

To evaluate the effect of ureteral access sheath (UAS) use and calibration change on stone-free rate and complications of retrograde intrarenal surgery (RIRS).

Methods

Data from 568 patients undergoing RIRS for kidney or upper ureteral stones were retrospectively included. Firstly, patients were compared after 1:1 propensity score matching, according to UAS usage during RIRS (UAS used [+] 87 and UAS non-used [-] 87 patients). Then all UAS+ patients (n=481) were subdivided according to UAS calibration: 9.5-11.5 Fr, 10-12 Fr, 11-13 Fr, and 13-15 Fr. Primary outcomes of the study were the success and complications of RIRS.

Results

Stone-free rate of UAS+ patients (86.2%) was significantly higher than UAS- patients (70.1%) after propensity score matching (p=0.01). Stone-free rate increased with higher caliber UAS (9.5-11.5 Fr: 66.7%; 10-12 Fr: 87.0%; 11-13 Fr: 90.6%; 13-15 Fr: 100%; p<0.001). Postoperative complications of UAS+ patients (11.5%) were significantly lower than UAS- patients (27.6%) (p=0.01). Complications (8.7%) with 9.5-11.5 Fr UAS was lower than thicker UAS (17.2%) but was not statistically significant (p=0.09). UAS usage was an independent factor predicting stone-free status or peri- and post-operative complications (odds ratio [OR] 3.654, 95% confidence interval [CI] 1.314-10.162; OR 4.443, 95% CI 1.350-14.552; OR 4.107, 95% CI 1.366-12.344, respectively).

Conclusion

Use of UAS in RIRS may increase stone-free rates, which also increase with higher caliber UAS. UAS usage may reduce complications; however, complications seemingly increase with higher UAS calibration.

Effect of surface-partial-volume correction and adaptive threshold on segmentation of uroliths in computed tomography

Computed tomography (CT) is used to diagnose urolithiasis, a prevalent condition. In order to establish the strongest foundation for the quantifiability of urolithiasis, this study aims to develop semi-automated urolithiasis segmentation methods for CT images that differ in terms of surface-partial-volume correction and adaptive thresholding. It also examines the diagnostic accuracy of these methods in terms of volume and maximum stone diameter. One hundred and one uroliths were positioned in an anthropomorphic phantom and prospectively examined in CT. Four different segmentation methods were developed and used to segment the uroliths semi-automatically based on CT images. Volume and maximum diameter were calculated from the segmentations. Volume and maximum diameter of the uroliths were measured independently by three urologists by means of electronic calipers. The average value of the urologists´ measurements was used as a reference standard. Statistical analysis was performed with multivariate Bartlett's test. Volume and maximum diameter were in very good agreement with the reference measurements (r>0.99) and the diagnostic accuracy of all segmentation methods used was very high. Regarding the diagnostic accuracy no difference could be detected between the different segmentation methods tested (p>0.55). All four segmentation methods allow for accurate characterization of urolithiasis in CT with respect to volume and maximum diameter of uroliths. Thus, a simple thresholding approach with an absolute value may suffice for robust determination of volume and maximum diameter in urolithiasis.

Retrograde Cystonephroscopy for Complex Renal Calculi Using Novel Dual Action Aspiration, Irrigation Cystoscope: Initial Case Series

Introduction Percutaneous nephrolithotomy (PCNL) is the gold standard treatment for kidney stones ≥ 2 cm; however, it remains an invasive procedure with significant risks especially in individuals with severe medical co-morbidities. In contrast, while ureteroscopy is far less morbid, a major impediment to its use for larger calculi is the inability to evacuate the many fragments created during laser lithotripsy. Herein, we describe two patients with large volume calculi and a third high risk patient with a smaller stone that were treated with cystonephroscopy using a recently released, 16Fr flexible cystoscope equipped with dual aspiration and irrigation capabilities. Materials and Methods Three consecutive female patients underwent retrograde cystonephroscopy from June 2021 to July 2021 with a novel 16Fr aspiration enabled flexible cystoscope. Demographic data were collected. Pre-operative and post-operative CT-scan images were reviewed to determine linear stone dimensions and scalene ellipsoid volume. Results The three female patients had an average age of 72.3 years and an American Society of Anesthesiologists (ASA) physical status score of 3. The mean preoperative stone volume was 4950 mm³. The average post-cystonephroscopy stone volume was 217 mm³ resulting in a total stone clearance rate of 97%. No major complications occurred. Average procedure time was 176 minutes. Conclusions Among three high risk female patients, two with large volume calculi, retrograde cystonephroscopy with a novel aspiration-enabled cystoscope allowed for the procedure to be successfully completed solely via a retrograde approach.

FACTORS AFFECTING PATIENT RADIATION EXPOSURE DURING PRONE AND SUPINE PERCUTANEOUS NEPHROLITHOTOMY

Purpose Radiation exposure from fluoroscopy poses risks to patients and surgeons. Percutaneous Nephrolithotomy (PCNL) has traditionally required fluoroscopy, however the use of ultrasound (US) has decreased radiation exposure. US-guidance in supine PCNL may further reduce radiation exposure. In this study we investigate patient and operative factors affecting fluoroscopy time (s), total radiation dose (mGy) and effective radiation dose (ERD) (mSv) in patients undergoing US-guided supine or prone PCNL. Methods: We performed a retrospective study of patients undergoing US-guided PCNL in prone position and supine position. Patients with multiple access tracts, pre-existing renal access or fluoroscopic renal access were excluded. Patient demographic, radiologic and operative data were collected, and compared between the two groups. Results: 99 patients were included: 45 prone (P-PCNL) and 54 supine (S-PCNL). There were no significant demographic differences between the two groups. Operative time, access location, tract length and total radiation dose (mGy) also did not differ. S-PCNL was associated with lower ERD (2.92mSv ± 0.32 vs 5.3mSv ± 0.7, p=0.0014) despite increased fluoroscopy time (86.32s ± 7.7 vs. 51.00s ± 5.1, p=0.004), and was more likely a mini-PCNL (35.2‰ vs 15.9‰, p=0.032). In multivariate analysis, supine PCNL remained associated with reduced ERD compared to prone (p=0.002), whereas BMI (p<0.001) and staghorn calculi (p<0.001) were independently associated with increased ERD.

Influence of the laser pulse shape in the treatment of stones in the upper urinary tract

PURPOSE

Urinary stones can be successfully treated using a Holmium: Yttrium-Aluminum-Garnet (Ho: YAG) laser. Regarding success rates, laser pulse energy, frequency, and pulse width are well-known contributing factors. Whether the pulse shape might be a further factor influencing the laser efficiency is unclear. This study aimed to evaluate different modes of laser pulse shapes in a real-world setting.

MATERIALS AND METHODS

The Dornier Medilas® H Solvo (Weßling, Germany) was used in the treatment of ureter and kidney stones. Patients were randomized into standard pulse shape (SPS) and new pulse shape groups (NPS1; ureter) and (NPS2; kidney pelvis), depending on the stone localization. The primary endpoint was laser efficiency defined as mm³ stone destruction per overall operating time. Secondary endpoints encompassed number of stone recoveries and stone-free rate.

RESULTS

Altogether 145 patients (24 SPS vs. 32 NPS1; 51 SPS vs. 38 NPS2) were included. No differences in sex, age, body mass index, stone localization and stone composition were found, except for preoperative stone size (133±95 [SPS] vs. 197±139 [NPS1] mm³; p=0.023) and (348±298 [SPS] vs. 525±429 [NPS2] mm³; p=0.042). Regarding the primary endpoint, a significant increase in laser efficiency could be detected for the NPS1 and NPS2 groups compared to the SPS groups (39.9±44.9 vs. 28.8±30.2 and 51.7±61.3 vs. 22.4±24.2 mm³/min [mean±standard deviation]). No statistically significant differences were found for secondary endpoints and perioperative complication rates.

CONCLUSIONS

Efficiency of the Ho: YAG laser can be positively influenced by different pulse shapes. This adds the variable of individualized intraoperative decision making.

Utility of stone volume estimated by software algorithm in predicting success of medical expulsive therapy

INTRODUCTION

We sought to assess the accuracy of using stone volume (SV) estimated with a software algorithm as a predictor for stone passage in a trial of medical expulsive therapy (MET).

METHODS

We identified patients with ureteral stones discharged from the emergency department on MET. Patients with infection, non-ureteral stones, or needing immediate surgical intervention were excluded. For each stone, longest dimension (LD) was recorded, and SV was estimated by a computed tomography (CT)-based region-growing (RG) algorithm and standard ellipsoid formula (EF). Stone passage within 30 days was assessed via electronic chart and followup phone call.

RESULTS

Fifty-one patients were included for analysis (53±16.7 years, 24% female). The mean LD was 4.85±2.02 mm. The mean SV was similar by EF and RG (0.051±0.057cm³ vs. 0.049±0.052 cm³, p=0.28). Thirty-three (65%) patients passed their stone, while 18 (35%) did not. The mean LD for passed stones vs. failed passage was 4.1±1.7 mm vs. 6.2±1.8 mm (p=0.0002); the mean EF volume was 0.028±0.035 cm³ vs. 0.093±0.066 cm³ (p=0.00007); and the mean volume by RG was 0.028±0.027 cm³ vs. 0.088±0.063 cm³ (p=0.00005).

CONCLUSIONS

The clinical utility of SV estimated by software algorithm as a predictor for success of MET has not previously been examined. We demonstrated that spontaneously passed stones had a significantly smaller volume than those requiring intervention. Further prospective studies are needed to validate these findings and establish volume thresholds for probability of stone passage.

Morphometry scores: Clinical implications in the management of staghorn calculi

Due to their large size, rapid growth, and attendant morbidity, staghorn calculi are complex clinical entities that impose significant treatment-related challenges. Moreover, their relative heterogeneity-in terms of both total stone burden and anatomic distribution-limits the ability to standardize their characterization and the reporting of surgical outcomes. Several morphometry systems currently exist to define the volumetric distribution of renal stones, in general, and to predict the outcomes of percutaneous nephrolithotomy; however, they fall short in their applicability to staghorn stones. In this review, we aim to discuss the clinical utility of morphometry systems and the influence of pelvicalyceal anatomy on the management of these complex calculi.

Modern imaging techniques in urinary stone disease

PURPOSE OF REVIEW

Radiological imaging techniques are a fast developing field in medicine. Therefore, the purpose of this review was to identify and discuss the latest changes of modern imaging techniques in the management of urinary stone disease.

RECENT FINDINGS

The introduction of iterative image reconstruction enables low-dose and ultra-low-dose (ULD) protocols. Although current guidelines recommend their utilization in nonobese patients recent studies indicate that low-dose imaging may be feasible in obese (<30 kg/m) but not in bariatric patients. Use of dual energy computed tomography (CT) technologies should balance between additional information and radiation dose aspects. If available on a dose neutral basis, dual energy imaging and analysis should be performed. Current guidelines recommend measuring the largest diameter for clinical decision making; however, recent studies suggest a benefit from measuring the volume based on multiplanar reformation. Quantitative imaging is still an experimental approach.

SUMMARY

The use of low-dose and even ULD CT protocols should be diagnostic standard, even in obese patients. If dual energy imaging is available, it should be limited to specific clinical questions. The stone volume should be reported in addition to the largest diameter for treatment decision and a more valid comparability of upcoming studies.

Stone Burden Measurement by 3D Reconstruction on Noncontrast Computed Tomography Is Not a More Accurate Predictor of Stone-Free Rate After Percutaneous Nephrolithotomy Than 2D Stone Burden Measurements

Purpose: Stone burden has been reported as an independent predictor of stone-free rate after percutaneous nephrolithotomy (PCNL); however no consensus exists on a standardized method for measuring stone burden. Recently, stone volume has been advocated as the most accurate means of measuring stone burden. We aimed to compare different measuring methods of stone burden and to identify the predictive value of each for outcomes after PCNL. Materials and Methods: We performed a retrospective review of a prospective database of patients who underwent PCNL between 2006 and 2013. A preoperative CT and postoperative imaging at discharge were necessary for eligibility. Stone burden was assessed through four different ways on CT images: (1) cumulative stone diameter; (2) estimated SA (surface area) calculated as longest × orthogonal diameter × π/4; (3) manual outline of stone and computer SA calculation; and (4) automated 3D volume calculation using specific software. Primary outcome was stone-free status (SFS) at discharge. Secondary outcomes included operative time and the need for an ancillary procedure. Regression analysis and receiver operating characteristic curve analysis were used to evaluate the predictive value of each method. Results: Of 313 included patients, 69.6% were stone free at discharge. All measures of stone burden were independent predictors of SFS [OR and 95% CI of 1.027 (1.014, 1.040), 1.481 (1.180, 1.858), 1.736 (1.266, 2.380), and 1.311 (1.127, 1.526), respectively] and demonstrated similar predictive accuracy (area under the curve = 0.630, 0.630, 0.627, and 0.638, respectively). Stone burden by any measure was an independent predictor of operative time and secondary procedure. Conclusions: We demonstrated that measuring stone burden by manual outline or automated 3D volume on reformatted CT images had no added value compared with orthogonal measurement for predicting outcomes after PCNL.

Materialise's interactive medical image control system (MIMICS) is feasible for volumetric measurement of urinary calculus

In this study, we aimed to investigate the feasibility of using Materialise's interactive medical image control system (MIMICS) to measure urinary calculi volume. We used a cylinder measuring to measure the same polymer clay volume in different groups. Polymer clay was made into an oval shape, an antler type, and a multiple irregular shapes by hand. They are divided into three groups, that is, A, B, and C, each of which has seven polymer clays. The computer tomography (CT) 3D images of each sample were obtained by 256iCT scanning. The CT 3D image was imported into MIMICS to measure the theoretical volume and average CT value of polymer clay. The differences between the volume and CT values measured by MIMICS and 256iCT were evaluated. The volume of each polymer clay that was measured by a measuring cylinder was 34.7 ml. The average CT values of groups A, B, and C measured by 256iCT were 1121.3 ± 35.8, 1071.3 ± 22.2, and 1083.9 ± 6.3 Hu, respectively. The theoretical volume and CT values of the ceramics measured by MIMICS were as follows: the averaged volume of group A was 35.1 ± 0.4 ml, and the average CT value was 1065.7 ± 5.3 Hu. The average volume of group B was 34.5 ± 0.2 ml, and the average CT value was 1008.9 ± 7.7 Hu. The average volume of group C was 34.4 ± 0.5 ml, and the average CT value was 980.9 ± 6.1 Hu. MIMICS was reliable in measuring urinary stone volume. The difference between the CT values measured by MIMICS and 256iCT was statistically significant. MIMICS had a slightly lower CT value than that of 256iCT. However, from the data point of view, the difference between the two methods was small.