National Imaging Trends after Ureteroscopic or Shock Wave Lithotripsy for Nephrolithiasis

Surgeon, and Institution Characteristics Associated Surgical Preferences in the Pediatric KIDney Stone Care Improvement Network

OBJECTIVE

To reveal barriers and opportunities to implement evidence for the management of pediatric kidney stone disease, we determined surgeon and institutional factors associated with preferences for the type of surgical intervention for kidney and ureteral stones.

METHODS

We conducted a cross-sectional study of urologists participating in the Pediatric KIDney Stone Care Improvement Network (PKIDS) trial. Questionnaires ascertained strengths of urologists' preferences for types of surgery as well as characteristics of participating urologists and institutions. The outcome was the strength of preferences for ureteroscopy, shockwave lithotripsy, and percutaneous nephrolithotomy for four scenarios for which two alternative procedures are recommended by the AUA guidelines: (1) 2 cm kidney stone, (2) 9 mm proximal ureteral stone, (3) 1.5 cm lower pole kidney stone, (4) 1 cm nonlower pole kidney stone. Principal component analysis was performed to identify unique clusters of factors that explain surgical preferences.

RESULTS

One hundred forty-eight urologists at 29 sites completed surveys. Stated preferences were highly skewed except for the choice between ureteroscopy and percutaneous nephrolithotomy for a 1.5 cm kidney stone. Shockwave lithotripsy ownership and local practice patterns most frequently associated with the strength of surgeons' preferences for the type of surgery. Principal component analysis revealed that three clusters of stone, patient, and heterogenous characteristics explained 30% of the variance in preferences.

CONCLUSION

There is wide variation in the strengths of preferences for surgical interventions supported by current guidelines that are partially explained by surgeon and institutional characteristics. These results reveal opportunities to develop strategies for guidelines that consider real-world drivers of care.

Ureterorenoscopic stone procedures have low success rates and poor post-operative follow-up: results from an Australian tertiary health service

BACKGROUND

To assess the results of ureterorenoscopy (URS) for upper tract urolithiasis in a contemporary Australian tertiary healthcare setting.

METHODS

Hospital records of all URS stone procedures performed between January 2017 and December 2018 in a metropolitan service were retrospectively reviewed. Outcome measures including stone free rates, adherence to postoperative follow-up and complications rates were recorded.

RESULTS

385 patients (387 renal units) with mean age 53.8 (range 18-89) underwent URS for stones measuring between 2 and 27 mm (median 8 mm). 465 URS were performed with 1029 total procedures performed. 48.6% of operations were performed as day cases. Complications were recorded in 9% of the 465 URS cases with 42.9% of these Clavien II or more. The representation rate to our Emergency Departments was 15.4%. Only 49.1% (201) of patients had a follow-up review with imaging to assess stone free rates. Of the 201 patients who underwent imaging, only 38.3% were stone free. Stone analysis was performed in 34.5%.

CONCLUSION

Less than half of all patients were reviewed despite undergoing expensive, time consuming surgery for a condition with a high recurrence rate. In agreement with recent publications stone-free rates were low, with significant complications and representation rates. Stone surgery should be given the attention and resources equivalent to cancer surgery to improve results.

LEVEL OF EVIDENCE

2b.

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.

Feasibility of stone recurrence risk stratification using the recurrence of kidney stone (ROKS) nomogram

This study seeks to evaluate the recurrence of kidney stones (ROKS) nomogram for risk stratification of recurrence in a retrospective study. To do this, we analyzed the performance of the 2018 ROKS nomogram in a case-control study of 200 patients (100 with and 100 without subsequent recurrence). All patients underwent kidney stone surgery between 2013 and 2015 and had at least 5 years of follow-up. We evaluated ROKS performance for prediction of recurrence at 2- and 5-year via area under the receiver operating curve (ROC-AUC). Specifically, we assessed the nomogram's potential for stratifying patients based on low or high risk of recurrence at: a) an optimized cutoff threshold (i.e., optimized for both sensitivity and specificity), and b) a sensitive cutoff threshold (i.e., high sensitivity (0.80) and low specificity). We found fair performance of the nomogram for recurrence prediction at 2 and 5 years (ROC-AUC of 0.67 and 0.63, respectively). At the optimized cutoff threshold, recurrence rates for the low and high-risk groups were 20 and 45% at 2 years, and 50 and 70% at 5 years, respectively. At the sensitive cutoff threshold, the corresponding recurrence rates for the low and high-risk groups were of 16 and 38% at 2 years, and 42 and 66% at 5 years, respectively. Kaplan-Meier analysis revealed a recurrence-free advantage between the groups for both cutoff thresholds (p < 0.01, Fig. 2). Therefore, we believe that the ROKS nomogram could facilitate risk stratification for stone recurrence and adherence to risk-based surveillance protocols.

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.

The 2023 Stone-Free CT Mandate: Addressing the Two Sides of the Debate

To the editors of the Journal of Endourology, we write to express our reservations in the recent announcement that starting in 2023 all reporting of stone-free rates be based on CT.

Variation and Correlation in Postoperative Imaging After Shockwave Lithotripsy and Ureteroscopy by Treatment Modality: Results of a Statewide Clinical Registry

OBJECTIVE

To understand how patient, practice/urologist-level factors impact imaging after ureteroscopy (URS) and shockwave lithotripsy (SWL).

METHODS

Using the Reducing Operative Complications from Kidney Stones (ROCKS) clinical registry from the Michigan Urological Surgery Improvement Collaborative (MUSIC), we identified patients undergoing URS and SWL between 2016-2019. Frequency and modality of 60-day postoperative imaging was assessed. We made bivariate comparisons across demographic/clinical data and assessed provider/practice-level imaging rate variation. We assessed correlation between imaging use within practices by treatment modality. Multivariable logistic regression controlling for practice/urologist variation was used to adjust for group differences.

RESULTS

14,894 cases were identified (9621 URS, 5273 SWL) from 33 practices and 205 urologists. Overall postoperative imaging rate was 49.1% and was significantly different following URS and SWL (36.3% vs 72.4%,p<0.01). Substantial practice variation was seen in rates following URS (range 0-93.1%) and SWL (range 36-95.2%). Odds of postoperative imaging by practice varied significantly (range 0.02-1.96). Moderate postoperative imaging correlation for URS and SWL (0.7,p<0.001) was seen. No practice had significantly higher odds of post-URS imaging. There was increased odds of postoperative imaging for SWL modality, larger stones and renal stones.

CONCLUSION

Imaging rates after URS are almost half the rate for SWL with wide variation, underscoring uncertainty with how postoperative imaging is approached. However, practices who have higher post-URS imaging rates also image highly after SWL. Increased patient complexity and renal stone location drive imaging following URS.

When the sheath hits the fan: an argument against the routine use of ureteral access sheaths

n/a.

Clinician Versus Nomogram Predicted Estimates of Kidney Stone Recurrence Risk

Purpose: Kidney stone recurrence rates vary between patients. A patient's risk informs the frequency and intensity of preventative interventions. Clinicians routinely use clinical experience to estimate risk. We sought to compare clinician estimated recurrence risk with the recurrence of kidney stones (ROKS) nomogram. Materials and Methods: We surveyed members of the Endourological Society with clinical expertise in kidney stones. Respondents estimated the risk of recurrence for patients in three clinical vignettes corresponding to low, intermediate, and high recurrence risk from the nomogram. Clinician estimates were compared with ROKS estimates. Results: The majority of the 318 respondents were from North America (n = 127, 40%). The most commonly estimated recurrence was 50% at 5 years. The respondents' estimates were significantly different from the ROKS predicted recurrence rate for all cases (Case 1, 50% vs 93% p < 0.0001; Case 2, 50% vs 60% p < 0.0001; Case 3, 60% vs 22% p < 0.0001). The ROKS predicted estimates ranged from 22% to 93%, whereas the median urologist-derived 5-year risk estimates for each case ranged from 50% to 60%. The median range of estimates by respondents across cases was 20%, narrower than the 71% for the ROKS nomogram. The majority of respondents (95%) do not use nomograms in practice, mostly because of lack of awareness of useful nomograms (59%). Conclusions: This study suggests that clinicians may not be able to distinguish those with high and low recurrence risk when compared with peers and when compared with a nomogram. Clinical decision support tools are needed to enable clinicians to better estimate stone recurrence risk.

Consultation on kidney stones, Copenhagen 2019: aspects of intracorporeal lithotripsy in flexible ureterorenoscopy

Purpose

To summarize current knowledge on intracorporeal laser lithotripsy in flexible ureterorenoscopy (fURS), regarding basics of laser lithotripsy, technical aspects, stone clearance, lithotripsy strategies, laser technologies, endoscopes, and safety.

Methods

A scoping review approach was applied to search literature in PubMed, EMBASE, and Web of Science. Consensus was reached through discussions at the Consultation on Kidney Stones held in September 2019 in Copenhagen, Denmark.

Results and conclusions

Lasers are widely used for lithotripsy during fURS. The Holmium laser is still the predominant technology, and specific settings for dusting and fragmenting have evolved, which has expanded the role of fURS in stone management. Pulse modulation can increase stone ablation efficacy, possibly by minimizing stone retropulsion. Thulium fibre laser was recently introduced, and this technology may improve laser lithotripsy efficiency. Small fibres give better irrigation, accessibility, and efficiency. To achieve optimal results, laser settings should be adjusted for the individual stone. There is no consensus whether the fragmentation and basketing strategy is preferable to the dusting strategy for increasing stone-free rate. On the contrary, different stone scenarios call for different lithotripsy approaches. Furthermore, for large stone burdens, all laser settings and lithotripsy strategies must be applied to achieve optimal results. Technology for removing dust from the kidney should be in focus in future research and development. Safety concerns about fURS laser lithotripsy include high intrarenal pressures and temperatures, and measures to reduce both those aspects must be taken to avoid complications. Technology to control these parameters should be targeted in further studies.

Endourology survey on radiation exposure and post-ureteroscopy US and CT reveals a need for clear guidelines

BACKGROUND

Nephrolithiasis patients undergo repeated imaging increasing their radiation risk. Guidelines recommend imaging following ureteroscopic lithotripsy (URSL), but not the modality or frequency of imaging. As such, we sought to elucidate common imaging practices following URSL and current knowledge of radiation exposure among endourologists.

METHODS

A web-based survey of Endourological Society members was used to evaluate knowledge and clinical practices regarding radiation exposure in post-URSL imaging. Respondents were grouped by years of experience (< 10, >= 10 years) and geographic location (USA or non-USA). An interaction term was included in the models to allow response rate to vary across experience level with geographic location and P values were derived from model main effects.

RESULTS

A total of 309 respondents answered the survey out of the 1800 active members of the Endourological Society that received the survey (17.2% total response rate). 204 of the respondents were included in our analysis as fellowship trained endourologists that perform URSL with a mean of 13.3 years in practice (IQR 6.75, 20 years). Overall, routine postoperative imaging is performed by 92% of respondents: 97% in the USA and 88% outside the US (P = 0.143). 39% of respondents correctly estimated standard dose CT scan (SCT) dose, while 36% correctly estimated that of a low-dose CT scan (LCT). American urologists correctly identified the SCT radiation dose more often than non-US respondents (54% vs 32%, respectively) (P value = 0.004). Respondents with < 10 years of experience more frequently identified the correct SCT dose (52% vs. 34%, respectively), though not significantly so (P value = 0.171). 79% of respondents consider LCT quality to be similar to SCT and 50% would use LCT on obese patients. However, only 26% of respondents identified that image quality deteriorates with BMI > 30 kg/m².

CONCLUSIONS

We demonstrate a knowledge gap regarding radiation exposure during CT scans and the limitations of low-dose CT imaging. This gap is wider in non-US-based urologists and in those with over 10 years of experience. However, all urologists would benefit from improved education and clear guidelines regarding radiation exposure in nephrolithiasis patients.

Shockwave Lithotripsy Use in the State of Michigan: American Urological Association Guideline Adherence and Clinical Implications

OBJECTIVE

To understand how treatment of patients with urinary stones by shockwave lithotripsy (SWL) aligns with current published practice guidelines.

METHODS

We used the Michigan Urologic Surgery Improvement Collaborative Reducing Operative Complications for Kidney Stones registry to understand SWL use in the state of Michigan. This prospectively maintained clinical registry includes data from community and academic urology practices and contains clinical and operative data for patients undergoing SWL and ureteroscopy (URS). We identified patients undergoing SWL from 2016 to 2019. In accordance with AUA guidelines, we evaluated practice patterns in relation to recommendations for treatment selection for SWL as well as clinical implications of guideline nonadherence.

RESULTS

Four thousand, two hundred and nine SWL procedures performed across 34 practices were analyzed. Perioperative antibiotics were administered to 61.3% of patients undergoing SWL. A ureteral stent was placed at the time of SWL in 2.7% of patients. For lower pole renal stones >1 cm or large (>2 cm) renal stones in the registry, 32.2% and 58.9% of patients, respectively, underwent SWL, while the remainder were treated with URS. In these instances, SWL was associated with inferior stone-free rate (SFR) relative to URS. In patients with residual stones after SWL, 34.6% were treated with repeat SWL with lower SFR than those treated with subsequent URS. Postoperatively, 42.1% of patients were prescribed alpha-blockers with no benefit seen in terms of SFR.

CONCLUSION

Substantial variation exists among urology practices with regard to SWL use. These data serve to inform quality improvement efforts regarding appropriateness criteria for SWL in Michigan.

Assessment of Residual Stone Fragments After Retrograde Intrarenal Surgery

OBJECTIVES

To define the most suitable approach to assess residual stone fragments after retrograde intrarenal surgery (RIRS).

METHODS

Ninety-two patients (115 renal units) submitted to RIRS for symptomatic kidney stones >5 mm and <20 mm or <15 mm in the lower Calyx diagnosed by noncontrast CT (NCCT) were prospectively studied. Residual fragments were assessed by endoscopic evaluation (END) at the end of the procedure and by NCCT, ultrasonography (US), and kidney, ureter, and bladder radiograph (KUB) on the 90th postoperative day (POD). NCCT was considered the gold standard for the evaluation of residual fragments after RIRS.

RESULTS

The 90th POD NCCT resulted in stone-free status in 74.8% (86/115), 0-2 mm in 8.7% (10/115), and >2 mm residual fragments in 16.5% (19/115) renal units. Stone-free status by END at the end of RIRS was coincident with NCCT in 93.0% of the cases (40/43). There were no cases of residual fragments >2 mm on NCCT if END resulted in stone-free status. In all cases where END resulted in residual fragments >2 mm, US proved to be correct according to NCCT. Neither US nor KUB was able to identify residual fragments between 0 and 2 mm. KUB had only 31.6% (6/19) sensitivity to detect residual fragments >2 mm and did not add sensitivity or specificity to US.

CONCLUSIONS

In the follow-up imaging after RIRS, we suggest that if END resulted in residual fragments <2 mm, a 90th POD NCCT should be performed. US may be used if END showed fragments >2 mm.

National Trends in CT Utilization and Estimated CT-related Radiation Exposure in the Evaluation and Follow-up of Stone Patients

OBJECTIVE

To describe trends in computed tomography (CT) use and estimate the radiation exposure among stone formers using a national insurance claims database.

METHODS

Within MarketScan, adult stone patients from 2007 to 2013 were identified using International Classification of Diseases-Revision 9, International Classification of Diseases-Revision 10, and Current Procedural Terminology codes. Patients were classified as "active" (≥2 diagnosis codes for nephrolithiasis, or receipt of stone surgery) or "inactive" (1 stone diagnosis) and compared to age- and gender-matched controls. CT utilization was tracked over 3 years for each group. Annual CT-related radiation exposure was estimated using previously published dose values and compared using Kruskal-Wallis and χ² tests. Demographic factors associated with greater CT exposure were identified on multivariate logistic regression.

RESULTS

Of active stone patients, 112,140 underwent surgery and 215,376 were managed nonoperatively. There were 175,228 inactive stone patients and 502,744 controls. On average, active stone patients received nearly 10 times as many CTs as controls at 3 years (P <.001), and more acute imaging (P <.001). About 25% and 15% of operative and nonoperative patients, respectively, received ≥3 CTs in 3 years. This was associated with female gender. For nonoperative patients, this was also associated with age, residence in the North-Central or South regions, and inversely associated with metropolitan residence (all P <.01). Over 10% of active stone patients are estimated to receive >20 mSv in the first year alone.

CONCLUSION

CT use and nonsurgical radiation exposure for active stone patients is significant. Over 10% are estimated to exceed occupational limits in the first year. Judicious CT imaging and low-dose protocols are critical for stone patients.

Computed Tomography Radiation Exposure Among Referred Kidney Stone Patients: Results from the Registry for Stones of the Kidney and Ureter

Purpose: Kidney stone patients routinely have CT scans during diagnostic work-up before being referred to a tertiary center. How often these patients exceed the recommended dose limits for occupational radiation exposure of >100 mSv for 5 years and >50 mSv in a single year from CT alone remains unknown. This study aimed to quantify radiation doses from CTs received by stone patients before their evaluation at a tertiary care stone clinic. Methods: From November 2015 to March 2017, consecutive new patients enrolled into the Registry for Stones of the Kidney and Ureter (ReSKU™) had the dose-length product of every available CT abdomen/pelvis within 5 years of their initial visit recorded, allowing for an effective dose (EDose) calculation. Multivariate logistic regression analysis identified factors associated with exceeding recommended dose limits. Models were created to test radiation reducing effects of low-dose and phase-reduction CT protocols. Results: Of 343 noncontrast CTs performed, only 29 (8%) were low-dose CTs (calculated EDose <4 mSv). Among 389 total patients, 101 (26%) and 25 (6%) had an EDose >20 mSv and >50 mSv/year, respectively. Increased body mass index, number of scans, and multiphase scans were associated with exceeding exposure thresholds (p < 0.01). The implementation of a low-dose CT protocol decreased the estimated number of scans contributing to overexposure by >50%. Conclusions: Stone patients referred to a tertiary stone center may receive excessive radiation from CT scans alone. Unnecessary phases and underutilization of low-dose CT protocols continue to take place. Enacting new approaches to CT protocols may spare stone patients from exceeding recommended dose limits.

National Imaging Trends after Percutaneous Nephrolithotomy

PURPOSE

Followup imaging after percutaneous nephrolithotomy serves to detect postoperative complications, residual fragments and silent hydronephrosis. However, the timing and optimal imaging modality remain poorly defined. We describe imaging use patterns after percutaneous nephrolithotomy.

MATERIALS AND METHODS

In the MarketScan® database we identified patients 17 to 64 years old who underwent percutaneous nephrolithotomy between 2007 and 2014. Imaging modalities were identified by CPT, and ICD-9 and 10 codes, and tracked for 1 year after percutaneous nephrolithotomy. The modalities included computerized tomography, renal ultrasound, abdominal x-ray and intravenous pyelogram. Cumulative longitudinal use patterns were characterized and the association with demographic factors was assessed by the chi-square test.

RESULTS

Of the 6,495 patients included in analysis 29% and 15% had undergone no postoperative imaging by 3 and 12 months, respectively. While abdominal x-ray was the most common modality at 3, 6 and 12 months, performed in 46%, 53% and 62% patients, respectively, nearly 50% underwent computerized tomography by 1 year. Of these patients 34% underwent computerized tomography within 3 months, which was done within the first 3 days in 69%. During the study period renal ultrasound use increased by 13% while computerized tomography and abdominal x-ray use remained relatively stable. Female gender, residence in the Northeast, no health maintenance organization status and treatment in a metropolitan statistical area were independently associated with higher rates of renal ultrasound on multivariate analyses (p <0.05).

CONCLUSIONS

Among insured adults national imaging patterns vary following percutaneous nephrolithotomy. Many patients do not receive any followup imaging while approximately half undergo computerized tomography within a year. Imaging patterns may be evolving with the increased use of ultrasound.