Korean Society of Endourology and Robotics (KSER) recommendation on the diagnosis, treatment, and prevention of urolithiasis

Effect of long-term postoperative OM-89 administration on bacteriuria from suspected infectious stones

PURPOSE

We aimed to evaluate the effect of long-term oral OM-89 therapy on the urinary microflora in patients with urolithiasis.

MATERIALS AND METHODS

Patients underwent surgical removal of urinary stones followed by no OM-89 treatment for six months or daily OM-89 administration. Urine culture and urinary polymerase chain reaction (PCR) were performed at the baseline visit (V1) and at 2 months (V2) and 6 months (V3) after the operation.

RESULTS

A total of 113 patients completed the study. The rate of urinary bacteria detection by urine culture at V3 did not differ between OM-89 treated and untreated groups (p>0.999); however, the PCR detection rate tended to be higher in OM-89 untreated group than in OM-89 treated group (p=0.052). Escherichia coli and Enterococcus spp. were the bacteria most commonly detected via both urine culture and PCR at all timepoints. Risk factors for the detection of bacteria by urine culture at V3 were positive culture at V1 (p=0.048) and female sex (p=0.048), whereas positive PCR at V3 was associated with female sex (p=0.023), positive PCR at V2 (p<0.001), and no OM-89 treatment (p=0.038). The use of OM-89 was associated with decreased rates of bacterial detection by PCR at V2 and a further decrease at V3.

CONCLUSIONS

Long-term immunization with OM-89 could further decrease the frequency of urinary bacterial colonization after surgical removal of urinary stones. OM-89 could be used as a complementary therapy if a retrieved stone is suspected to be related to infection.

Rise in intraluminal temperature during ureteroscopy: Is this a concern?

The global increase in urolithiasis prevalence has led to a shift towards minimally invasive procedures, such as retrograde intrarenal surgery, supported by advancements in laser technologies for lithotripsy. Pulsed lasers, particularly the holmium YAG and the newer thulium fiber laser, have significantly transformed the management of upper urinary tract stones. However, the use of high-power lasers in these procedures introduces risks of heat-related injury. Laser lithotripsy works through photothermal and photomechanical effects to fragment stones, but up to 96% of the laser energy is converted into heat, increasing the risk of thermal damage to the surrounding urothelial mucosa. Studies show that even at low-power settings, intrarenal temperatures can exceed the threshold for cellular injury, particularly in confined spaces like the ureter. This narrative review explores strategies to mitigate thermal injury, including optimizing laser settings, improving irrigation flow rates, and incorporating novel methods such as cold irrigation, controlling outflow resistance, and using suction. Understanding these approaches is crucial to enhancing patient safety during high-power laser lithotripsy procedures.

Investigation and quantification of composition variability in urinary stone analysis

PURPOSE

To investigate the variability in urinary stone composition analysis due to sampling and suggest potential solutions.

MATERIALS AND METHODS

We collected 1,135 stone fragments from 149 instances that had undergone a stone removal at Hanoi Medical University Hospital from January 2022 to August 2022. Each fragment was ground into fine powder and divided into separate specimens if the amount was abundant. For composition analyzing every specimen, Fourier transform infrared spectroscopy was performed. The composition of a given fragment was the average of its belonging specimens. The variability in composition was assessed on the fragment level (i.e., between fragments of an instance). We defined an instance as "significantly variable" if the maximum difference in any composition across its belonging fragments was equal to or greater than a given threshold.

RESULTS

On average, there were 7.6±3.3 stone fragments per instance and 2.3±0.5 specimens per fragment. We found that the variability could be substantial on the fragment level. Eighty-nine (69.5%) and 70 (54.7%) out of 128 multiple-component instances were significantly variable if the threshold was set at 20% and 30%, respectively. The variability of an instance on the fragment level was correlated with the size of fragment and the number of components.

CONCLUSIONS

Our study demonstrated the significant variability in urinary stone composition and showed that it correlated with the size and the impurity of samples. Mapping denotation while sampling and analyzing as well as reporting the composition of individual fragments could be valuable to reduce potential variability.

Verification of surgical factors affecting the efficiency of stone extraction with one-surgeon basketing technique using a f-URSL simulation model

PURPOSE

Stone extraction is an important treatment option when performing flexible ureteroscopic lithotripsy (f-URSL) for upper urinary stones. We used a f-URSL simulator model to investigate surgical factors affecting the efficacy of stone extraction with the one-surgeon basketing technique.

MATERIALS AND METHODS

This simulator-based study involved eight urologists and eight residents. These participants each performed two tasks, with Flexor (Cook Medical) and Navigator (Boston Scientific) ureteral access sheaths, with and without the M-arm (MC Medical) single-use basket holder, and with models representing both left and right kidneys. The two tasks were to touch each renal calix with the ureteroscope, and to extract stones. As outcomes, we recorded the number of times that the ureteroscope became stuck during insertion, the number of times a stone was dropped during removal, the number of times the basket forceps were opened and closed, and the time required to accomplish each task.

RESULTS

The ureteroscope became stuck significantly more often when Navigator was used compared with Flexor overall, and for both urologists and residents (all p<0.01). Stones were dropped significantly more often on the ipsilateral side (kidney on the same side as the operator's hand) than on the contralateral side overall (p=0.01), and the basket forceps were opened and closed significantly more often on the ipsilateral side than on the contralateral side both overall and by residents (all p<0.01).

CONCLUSIONS

The efficiency of stone extraction during f-URSL with the one-surgeon basketing technique was affected by differences in ureteral access sheath and the kidney side.

Percutaneous Nephrostomy versus Ureteral Stent for Severe Urinary Tract Infection with Obstructive Urolithiasis: A Systematic Review and Meta-Analysis

Background and Objectives: The European Association of Urology guidelines on urolithiasis highlight the limited evidence supporting the superiority of percutaneous nephrostomy (PCN) over retrograde ureteral stent placement for the primary treatment of infected hydronephrosis secondary to urolithiasis. We, therefore, conducted a systematic review and meta-analysis comparing the effects of PCN and retrograde ureteral stent in patients with severe urinary tract infections secondary to obstructive urolithiasis. Materials and Methods: Meta-analyses were performed to compare four outcomes: time for the temperature to return to normal; time for the white blood cell (WBC) count to return to normal; hospital length of stay; and procedure success rate. After a full-text review, eight studies were identified as relevant and included in our systematic review and meta-analysis. Results: No significant difference was detected between PCN and retrograde ureteral stenting for the time for the temperature to return to normal (p = 0.13; mean difference [MD] = -0.74; 95% confidence interval [CI] = -1.69, 0.21; I2 = 96%) or the time for the WBC count to return to normal (p = 0.24; MD = 0.46; 95% CI = -0.30, 1.21; I2 = 85%). There was also no significant difference between methods for hospital length of stay (p = 0.78; MD = 0.45; 95% CI = -2.78, 3.68; I2 = 96%) or procedure success rate (p = 0.76; odds ratio = 0.86; 95% CI = 0.34, 2.20; I2 = 47%). Conclusions: The clinical outcomes related to efficacy did not differ between PCN and retrograde ureteral stenting for severe urinary tract infection with obstructive urolithiasis. Thus, the choice between procedures depends mainly on the urologist's or patient's preferences.

Urolithiasis in Kidney Transplant Patients: A Multicenter KSER Research Series

Background and Objectives: Urolithiasis occurrence is uncommon in kidney transplantation patients, though it has serious implications, including acute kidney injury in the transplanted kidney. This study investigates the leading causes of urolithiasis in kidney transplantation patients, the diagnostic process, and the outcomes of multimodal management. Materials and Methods: Data collection spanned from January 1997 to December 2021, involving kidney transplantation patients with urolithiasis from the database of the Korean Society of Endourology and Robotics (KSER) research committee. Analysis encompassed factors triggering urolithiasis, the diagnostic process, stone attributes, treatment methods, and outcomes. Results: Our analysis included 58 kidney transplantation patients with urolithiasis from eight medical centers. Of these patients, 37 were male and 4 had previous urolithiasis diagnoses. The mean age was 59.09 ± 10.70 years, with a mean duration from kidney transplantation to diagnosis of 76.26 ± 183.14 months. The most frequent method of stone detection was through asymptomatic routine check-ups (54.7%). Among the 58 patients, 51 underwent stone treatment. Notably, 95.3% of patients with ureter stones received treatment, a significantly higher rate than the 66.7% of patients with renal stones (p = 0.010). Success rates showed no significant differences between renal (70%) and ureter stone (78.0%) groups (p = 0.881). Conclusions: Urolithiasis in transplanted kidneys constitutes an acute condition requiring emergency intervention. Endo-urological interventions are effective for kidney transplantation patients with urolithiasis. To ensure prevention and early detection, diligent follow-up and routine imaging tests are necessary.

A comparison of S.T.O.N.E nephrolithometry scoring system, Guy's stone score, and Seoul National University Renal Stone Complexity (S-ReSC) in predicting mini-PCNL stone-free rate

The main goal of the study is to evaluate the three stone scoring systems (S.T.O.N.E nephrolithometry scoring system (STONE), Guy's stone score (GSS) and Seoul National University Renal Stone Complexity (S-ReSC)) for the stone-free rate (SFR) of mini-PCNL. We retrospectively analyzed 72 patients who received mini-PCNL from February 2018 to October 2020. The SFR, complication rates, hospitalization days and recurrence rates were analyzed using three stone scoring systems. The result showed statistical significance in the association between scoring system and stone-free (STONE: OR 95%CI 0.409 (0.221-0.759), p = 0.0045; S-ReSC OR 95%CI 0.633 (0.401-0.999), p = 0.0497), but not GSS (OR 95%CI 0.776 (0.397-1.516), p = 0.4581). After adjusting the potential confounding factors, the area under curve (AUC) of STONE, GSS, and S-ReSC was 0.86, 0.78, and 0.81, respectively, and Akaike information criterion (AIC) of STONE, GSS, and S-ReSC was 64.65, 74.89, and 69.92, respectively. The accuracy rate of STONE, GSS, and S-ReSC was 0.81, 0.75, and 0.79, respectively. There was no statistically difference of predicting stone recurrence (p = 0.46, 0.53, 0.86), complications (p = 0.74, 0.51, 0.16) and hospitalization days (p = 0.77, 0.86, 0.87) in STONE, GSS, and S-ReSC, respectively. In conclusion, both the STONE and S-ReSC stone scoring systems are viable for predicting the SFR following mini-PCNL, especially after variable adjustment with the STONE system demonstrating superiority over S-ReSC.

Training ultrasound-guided percutaneous nephrostomy technique with porcine model

PURPOSE

There is increasing interest in the use of ultrasound for endoscopic and percutaneous procedures. Access can be achieved without radiation exposure under ultrasound guidance. Our aim was to develop a porcine-based training model for ultrasound-guided percutaneous renal access that could also be personalized to a specific patient.

MATERIALS AND METHODS

The Institutional Animal Care and Use Committee of Severance Hospital approved the study protocol. An anesthetized pig was placed in the dorsal lithotomy position. For the nephrostomy puncture, a Chiba biopsy needle with an echo tip was used under ultrasound guidance. Eight residents and three consultants in urology participated. Puncture time was defined as the nephrostomy time to confirm the flow of irrigation via the needle. After training, satisfaction survey results for clinical usability and procedural difficulty were evaluated.

RESULTS

The 5-point Likert scale satisfaction survey for clinical usability and procedural difficulty found mean results of 4.64 and 4.09 points, respectively. There were no differences between residents and consultants for either variable. For all participants combined, there was a significant difference for nephrostomy time between the first and second trials (278.8±70.6 s vs. 244.5±47.0 s; p=0.007). The between-trial difference was greater for residents (291.5±71.2 s vs. 259.1±41.9 s; p=0.039). The difference for the consultant was not significant (245.0±69.4 s vs. 205.7±42.5 s; p=0.250).

CONCLUSIONS

We developed a porcine-based ultrasound-guided nephrostomy puncture training model. Satisfaction survey results indicated high clinical usability and procedural difficulty. For nephrostomy time, the model was more effective for urology residents than for consultants.

The Consecutive 200 Cases of Endoscopic-Combined Intrarenal Surgery: Comparison between Standard and Miniature Surgeries

Background and Objectives: Percutaneous nephrolithotomy (PCNL) is still the gold-standard treatment for large and/or complex renal stones. Endoscopic combined intrarenal surgery (ECIRS) was developed with the goal of minimizing the number of access tracts of PCNL while simultaneously improving the one-step stone-free rate (SFR). The aim of this study was to share the experience of the consecutive 200 cases of ECIRS in one institute and analyze surgical outcomes of mini-ECIRS and standard ECIRS. Materials and Methods: We performed ECIRS for 200 adult patients between July 2017 and January 2020. An ECIRS was performed with the patient under general anesthesia in the intermediate-supine position. Surgeries were finished using a tubeless technique with a simple ureteral stent insertion. Results: There were significant differences in the mean maximal stone length (MSL), the variation coefficient of stone density (VCSD), the linear calculus density (LCD), the Seoul National University Renal Stone Complexity (S-ReSC), and the modified S-ReSC scores in stone characteristics, and estimated blood loss (EBL) and operation time in peri-operative outcomes between conventional and mini-ECIRS. After propensity-score matching, there was only a difference in EBL between the two groups. In logistic regression models, MSL [odds ratio (OR) 0.953; 95% confidence interval (CI) 0.926-0.979; p < 0.001], LCD (OR 4.702; 95% CI 1.613-18.655; p = 0.013) were significant factors for the success rate after ECIRS. Conclusions: In patients who underwent a mini-ECIRS, the stones were relatively smaller and less complex, and the operation time was shorter. However, if the size of stones was similar, there was no difference in the success rate, but EBL was lower in mini-ECIRS than in standard surgery.

A Prospective Study on the Impact of Clinical Factors and Adjusted Triple D System for Success Rate of ESWL

Objective: Our study aimed to evaluate the success rate of ESWL and identify relevant treatment-specific factors affecting treatment outcomes, as well as to assess the accuracy of the updated Triple D scoring system and compare it with older systems. Material and Methods: A prospective study of 71 patients who received ESWL treatment for renal stones that were 5-15 mm in size was completed. The patient having no residual stones or residual stones lesser than 4 mm after ESWL was identified as a treatment success. Univariate and multivariate logistic regression and ROC curves were used to identify important factors for treatment outcomes. Results: Successful treatment was achieved for 66.2% of patients. The stone volume (SV), mean stone density (MD), and delivered power to the stone volume unit ratio (SMLI/SV) were defined as the most critical factors influencing ESWL success. An updated Triple D score system with a, SMLI/SV ratio could be an alternative to older systems and reach an even higher accuracy. A limitation of this study is the limited sample size due to the COVID-19 pandemic. Conclusions: Our results show that the three factors that most influence the success of ESWL are the stone size, mean stone density, and SMLI/SV ratio. Based on this, we present a simple updated triple D score system to predict ESWL success, which could be implemented in future clinical practice.

Clinical Course and Mutational Analysis of Patients with Cystine Stone: A Single-Center Experience

Cystinuria is a known genetic disorder. To date, two genes, SLC3A1 and SLC7A9, have been identified as causes of cystinuria. In this study of 10 patients with cystinuria, which is the largest Korean cohort ever studied, we examined the patients' phenotypes, clinical courses, and genetic analyses. A total of 10 patients with cystinuria diagnosed with cystine stones in a single tertiary medical center (Severance Hospital, Seoul, Republic of Korea) from April 2000 to July 2023 were included in the study. All of the patients participated in mutational studies, and the clinical presentation and consecutive laboratory findings of the patients were analyzed retrospectively. After the initial stone-related surgery or procedure at our hospital, 6 of the 10 patients underwent additional surgery at least once for recurrent stones. Genetic analyses identified six new mutations, of which only two patients had type B mutations. The most common genotype was compound heterozygous type A. We investigated the genotypes and clinical courses of 10 Korean patients with cystinuria who had not been previously reported. More data are needed to statistically analyze the genotype and phenotype of cystinuria.

Dose Optimization Using a Deep Learning Tool in Various CT Protocols for Urolithiasis: A Physical Human Phantom Study

Background and Objectives: We attempted to determine the optimal radiation dose to maintain image quality using a deep learning application in a physical human phantom. Materials and Methods: Three 5 × 5 × 5 mm3 uric acid stones were placed in a physical human phantom in various locations. Three tube voltages (120, 100, and 80 kV) and four current-time products (100, 70, 30, and 15 mAs) were implemented in 12 scans. Each scan was reconstructed with filtered back projection (FBP), statistical iterative reconstruction (IR, iDose), and knowledge-based iterative model reconstruction (IMR). By applying deep learning to each image, we took 12 more scans. Objective image assessments were calculated using the standard deviation of the Hounsfield unit (HU). Subjective image assessments were performed by one radiologist and one urologist. Two radiologists assessed the subjective assessment and found the stone under the absence of information. We used this data to calculate the diagnostic accuracy. Results: Objective image noise was decreased after applying a deep learning tool in all images of FBP, iDose, and IMR. There was no statistical difference between iDose and deep learning-applied FBP images (10.1 ± 11.9, 9.5 ± 18.5 HU, p = 0.583, respectively). At a 100 kV-30 mAs setting, deep learning-applied FBP obtained a similar objective noise in approximately one third of the radiation doses compared to FBP. In radiation doses with settings lower than 100 kV-30 mAs, the subject image assessment (image quality, confidence level, and noise) showed deteriorated scores. Diagnostic accuracy was increased when the deep learning setting was lower than 100 kV-30 mAs, except for at 80 kV-15 mAs. Conclusions: At the setting of 100 kV-30 mAs or higher, deep learning-applied FBP did not differ in image quality compared to IR. At the setting of 100 kV-30 mAs, the radiation dose can decrease by about one third while maintaining objective noise.

Comparative Analysis of Surgical Outcomes of Flexible Ureteroscopy and Da Vinci Robotic Surgery in Community Patients with Renal Pelvic Stones Larger than 2 cm

Background and Objectives: This study evaluated and compared the surgical outcomes of retrograde intrarenal surgery (RIRS) lithotripsy versus robot-assisted laparoscopic pyelolithotomy (RAPL) in community patients with renal pelvic stones larger than 2 cm. Materials and Methods: A total of 77 patients who underwent RIRS (RIRS group, n = 50) or RAPL (RAPL group, n = 27) at our institution between December 2016 and July 2022 were recruited. A single surgeon performed all surgical operations. Preoperative, operative, and postoperative data were recorded. The study evaluated various clinical outcomes, namely, urinary tract infections, analgesic use, emergency room readmissions, stone clearance rates, surgical complications, and medical expenditures associated with the treatment courses, and compared them between the groups. Results: The RAPL group had a larger mean stone diameter and higher degree of hydronephrosis than the RIRS group did. The RIRS group had superior outcomes regarding operative time, length of postoperative hospital stay, surgical wound pain, and medical expenditures. Regarding postoperative outcomes, comparable rates of postoperative urinary tract infection, prolonged analgesic use, and emergency room readmissions were observed between the groups. However, the RAPL group had a higher stone clearance rate than the RIRS group did (81.5% vs. 52.0%, p = 0.014). Conclusions: For the surgical treatment of renal pelvis stones larger than 2 cm, RAPL has a superior stone clearance rate than RIRS; however, RIRS achieves superior outcomes in terms of medical expenditures, length of hospital stay, and surgical wound pain. Both procedures were equally safe.