Natural History of Residual Fragments After Percutaneous Nephrolithotomy: Evaluation of Factors Related to Clinical Events and Intervention

Development and validation of a predictive model for post-percutaneous nephrolithotomy urinary sepsis: a multicenter retrospective study

BACKGROUND

The objective of this retrospective, multicenter study was to analyze the factors associated with the development of urogenital sepsis after percutaneous nephrolithotomy (PCNL) and to establish a nomogram prediction model of urogenital sepsis after PCNL.

METHODS

A total of 2066 postoperative PCNL patients were included from three medical institutions: Zunyi Medical University Hospital, Beijing Jishuitan Hospital Guizhou Hospital, and Fenggang County People's Hospital. Clinical data of 1623 patients from the Department of Urology of Zunyi Medical University Hospital were randomized into a training cohort (Zunyi training cohort, N.=1139) and an internal validation cohort (Zunyi internal validation cohort, N.=484) using computer generated random numbers in a 7:3 ratio. Univariate and multivariate logistic regression analyses were performed on the compliance training cohort to identify risk factors for urogenital sepsis after PCNL and to develop a column line graph prediction model based on these risk factors. Finally, Zunyi internal validation cohort and two external validation cohorts (Guiyang external cohort, N.=306; Fenggang external cohort, N.=137) were used to validate the prognostic accuracy of the nomogram prediction model. R4.2.2 statistical software was used for all statistical data analyses.

RESULTS

Multifactorial logistic regression analysis of the Zuiyi training cohort (N.=1139) identified five independent risk factors associated with urogenital sepsis after PCNL, including urine culture positivity (odds ratio [OR]=5.29, P<0.001), urine nitrite positivity (OR=5.97, P<0.001), operation time ≥60 min (OR=4.4, P=0.0037), residual stone (OR=5.18, P<0.001), and size ≥30 mm (OR=3.22, P=0.0086). Nomogram were constructed based on these independent risk factors. The area under the curve (AUC) of the nomogram model was 0.907 in the in-progress sample and 0.948 after internal validation. The AUC of the model was 0.855 and 0.804 after external validation of the Guiyang external validation cohort and the Fenggang validation cohort, respectively, indicating good discrimination ability. The calibration curves of the nomogram showed good agreement, and the decision curve analysis demonstrated high clinical utility.

CONCLUSIONS

Based on the clinical independent risk factors such as positive urine culture, positive urine nitrite, operation time ≥60min, stone residue, stone size ≥30mm, nomogram prediction model of urogenital sepsis after PCNL was established, which can provide reference for urologists to develop preoperative evaluation and treatment strategies for patients with percutaneous nephrolithotomy.

What is the definition of stone dust and how does it compare with clinically insignificant residual fragments? A comprehensive review

PURPOSE

During endoscopic stone surgery, Holmium:YAG (Ho:YAG) and Thulium Fiber Laser (TFL) technologies allow to pulverize urinary stones into fine particles, ie DUST. Yet, currently there is no consensus on the exact definition of DUST. This review aimed to define stone DUST and Clinically Insignificant Residual Fragments (CIRF).

METHODS

Embase, MEDLINE (PubMed) and Cochrane databases were searched for both in vitro and in vivo articles relating to DUST and CIRF definitions, in November 2023, using keyword combinations: "dust", "stones", "urinary calculi", "urolithiasis", "residual fragments", "dusting", "fragments", "lasers" and "clinical insignificant residual fragments".

RESULTS

DUST relates to the fine pulverization of urinary stones, defined in vitro as particles spontaneously floating with a sedimentation duration ≥ 2 sec and suited for aspiration through a 3.6Fr-working channel (WC) of a flexible ureteroscope (FURS). Generally, an upper size limit of 250 µm seems to agree with the definition of DUST. Ho:YAG with and without "Moses Technology", TFL and the recent pulsed-Thulium:YAG (pTm:YAG) can produce DUST, but no perioperative technology can currently measure DUST size. The TFL and pTm:YAG achieve better dusting compared to Ho:YAG. CIRF relates to residual fragments (RF) that are not associated with imminent stone-related events: loin pain, acute renal colic, medical or interventional retreatment. CIRF size definition has decreased from older studies based on Shock Wave Lithotripsy (SWL) (≤ 4 mm) to more recent studies based on FURS (≤ 2 mm) and Percutaneous Nephrolithotomy(PCNL) (≤ 4 mm). RF ≤ 2 mm are associated with lower stone recurrence, regrowth and clinical events rates. While CIRF should be evaluated postoperatively using Non-Contrast Computed Tomography(NCCT), there is no consensus on the best diagnostic modality to assess the presence and quantity of DUST.

CONCLUSION

DUST and CIRF refer to independent entities. DUST is defined in vitro by a stone particle size criteria of 250 µm, translating clinically as particles able to be fully aspirated through a 3.6Fr-WC without blockage. CIRF relates to ≤ 2 RF on postoperative NCCT.

Follow-up of urolithiasis patients after treatment: an algorithm from the EAU Urolithiasis Panel

OBJECTIVE

To develop a follow-up algorithm for urinary stone patients after definitive treatment.

MATERIALS AND METHODS

The panel performed a systematic review on follow-up of urinary stone patients after treatment (PROSPERO: CRD42020205739). Given the lack of comparative studies we critically evaluated the literature and reached a consensus on the follow-up scheme.

RESULTS

A total of 76 studies were included in the analysis, including 17 RCTs. In the stone-free general population group, 71-100% of patients are stone-free at 12 months while 29-94% remain stone-free at 36 months. We propose counselling these patients on imaging versus discharge after the first year. The stone-free rate in high-risk patients not receiving targeted medical therapy is < 40% at 36 months, a fact that supports imaging, metabolic, and treatment monitoring follow-up once a year. Patients with residual fragments ≤ 4 mm have a spontaneous expulsion rate of 18-47% and a growth rate of 10-41% at 12 months, supporting annual imaging follow-up. Patients with residual fragments > 4 mm should be considered for surgical re-intervention based on the low spontaneous expulsion rate (13% at 1 year) and high risk of recurrence. Plain film KUB and/or kidney ultrasonography based on clinicians' preference and stone characteristics is the preferred imaging follow-up. Computed tomography should be considered if patient is symptomatic or intervention is planned.

CONCLUSIONS

Based on evidence from the systematic review we propose, for the first time, a follow-up algorithm for patients after surgical stone treatment balancing the risks of stone recurrence against the burden of radiation from imaging studies.

International Alliance of Urolithiasis (IAU) guideline on staghorn calculi management

BACKGROUND

The stone burden based management strategy reported in the guidelines published by different associations is well known for a long time. Staghorn calculi, representing the largest burden and most complex stones, is one of the most challenging cases to practicing urologists in clinical practice. The International Alliance of Urolithiasis (IAU) has released a series of guidelines on the management of urolithiasis.

PURPOSE

To develop a series of recommendations for the contemporary management management of staghorn calculi and to provide a clinical framework for urologists treating patients with these complex stones.

METHODS

A comprehensive literature search for articles published in English between 01/01/1976 and 31/12/2022 in the PubMed, OVID, Embase and Medline database is performed. A series of recommendations are developed and individually graded following the review of literature and panel discussion.

RESULTS

The definition, pathogenesis, pathophysiology, preoperative evaluation, intraoperative treatment strategies and procedural advice, early postoperative management, follow up and prevention of stone recurrence are summarized in the present document.

CONCLUSION

A series of recommendations regarding the management of staghorn calculi, along with related commentary and supporting documentation offered in the present guideline is intended to provide a clinical framework for the practicing urologists in the management of staghorn calculi.

The significance of clinically insignificant residual fragments after percutaneous nephrolithotomy: an analysis into the relevance of complete stone clearance

PURPOSE

After treatment for kidney stones, residual fragments with a diameter of ≤ 4 mm are traditionally referred to as 'clinically insignificant residual fragments'. We hypothesize that patients with these fragments are at an increased risk for stone-related morbidity, such as complaints, hydronephrosis, and stone regrowth, when compared to stone-free patients. This study aimed to investigate the relevance of complete stone clearance in surgical treatment of urolithiasis.

METHODS

We conducted a single-center retrospective cohort study. Patients who underwent percutaneous nephrolithotomy between 2015 and 2020 were included if a CT-scan was available within 6 months after the procedure, and the follow-up duration was at least 1 year. The stone-free status at the end of the first stone episode during the study period was categorized as fully stone-free, not stone-free with small residual fragments (≤ 4 mm) and not stone-free with large residual fragments (> 4 mm). Follow-up data were collected, including stone-related events and re-intervention rates.

RESULTS

A total of 103 subjects were included with a median follow-up of 21.4 months. Stone-related events occurred in 10 (29.4%) of the fully stone-free subjects, 20 (58.8%) of the subjects with small residual fragments and 25 (71.4%) of the subjects with large residual fragments. The stone-related event-free survival per subgroup resulted in a significantly different survival distribution in a log rank test (p = 0.008).

CONCLUSION

A complete stone-free status seems to be of fundamental importance for decreasing stone-related morbidity. Further developments and research should focus on optimizing the full clearance of stone material during PCNL.

2022 recommendations of the AFU Lithiasis Committee: Objectives, results, residual stones and fragments

The main objectives of interventional stone treatment are stone removal, symptom elimination, and kidney function preservation. After treatment of kidney stones (extracorporeal shock wave lithotripsy [ESWL], or endoscopy), fragments may remain in the kidney, either deliberately left in place or due to treatment failure (i.e. residual stone [RS], resistant to ESWL, left or inaccessible by endoscopy), or due to failure to eliminate the obtained fragments (i.e. residual fragments [RF]). Their management may differ. The most commonly used definition of RF in the literature is based on a size cut-off (≤4mm) and on three criteria: spontaneous clearance rate, secondary intervention rate, and disease progression rate. RF may be spontaneously eliminated (42%), persist and increase in size (32%), or become complicated and require a secondary urological procedure (36%). Like for the initial treatment, it is important to consider the stone composition for the treatment decision-making concerning RS/RF. METHODOLOGY: These recommendations were developed using two methods: the Clinical Practice Recommendation (CPR) method and the ADAPTE method, depending on whether the question was considered in the European Association of Urology (EAU) recommendations (https://uroweb.org/guidelines/urolithiasis) (EAU, 2022) and their adaptability to the French context.

Nomogram to predict the risk of adverse outcomes in patients with residual stones following percutaneous nephrolithotomy

PURPOSE

To investigate the risk factors associated with adverse outcomes in patients with residual stones after percutaneous nephrolithotomy (PCNL) and to establish a nomogram to predict the probability of adverse outcomes based on these risk factors.

METHODS

We conducted a retrospective review of 233 patients who underwent PCNL for upper urinary tract calculi and had postoperative residual stones. The patients were divided into two groups according to whether adverse outcomes occurred, and the risk factors for adverse outcomes were explored by univariate and multivariate analyses. Finally, we created a nomogram for predicting the risk of adverse outcomes in patients with residual stones after PCNL.

RESULTS

In this study, adverse outcomes occurred in 125 (53.6%) patients. Multivariate logistic regression analysis indicated that the independent risk factors for adverse outcomes were the diameter of the postoperative residual stones (P < 0.001), a positive urine culture (P = 0.022), and previous stone surgery (P = 0.004). The above independent risk factors were used as variables to construct the nomogram. The nomogram model was internally validated. The calculated concordance index was 0.772. The Hosmer-Lemeshow goodness-of-fit test was performed (P > 0.05). The area under the ROC curve of this model was 0.772.

CONCLUSIONS

Larger diameter of residual stones, positive urine culture, and previous stone surgery were significant predictors associated with adverse outcomes in patients with residual stones after PCNL. Our nomogram could help to assess the risk of adverse outcomes quickly and effectively in patients with residual stones after PCNL.

The Fate of Residual Fragments After Percutaneous Nephrolithotomy: Results from the Endourologic Disease Group for Excellence Research Consortium

Background: Residual fragments (RFs) after percutaneous nephrolithotomy (PCNL) have a significant impact on patients' quality of life and clinical course. There is a paucity of studies that evaluate the natural history of RFs after PCNL. The objective of this study is to compare rates of reintervention, complications, stone growth, and passage in patients with RFs >4, ≤4, and ≤2 mm after PCNL. Methods: Sites from the Endourologic Disease Group for Excellence (EDGE) research consortium examined data of PCNL patients from 2015 to 2019 with at least 1-year follow-up. RF passage, regrowth, reintervention, and complications were recorded and RFs were stratified into >4 and ≤4 mm groups, as well as >2 and ≤2 mm groups. Potential predictors for stone-related events after PCNL were determined using multivariable logistic regression analysis. It was hypothesized that larger RF thresholds would result in lower passage rates, faster regrowth, and greater clinically significant events (complications and reinterventions) than smaller RF thresholds. Results: A total of 439 patients with RFs >1 mm on CT postoperative day 1 were included in this study. For RFs >4 mm, rates of reintervention were found to be significantly higher and Kaplan-Meier curve analysis showed significantly higher rates of stone-related events. Passage and RF regrowth were not found to be significantly different compared with RFs ≤4 mm. However, RFs ≤2 mm had significantly higher rates of passage, and significantly lower rates of fragment regrowth (>1 mm), complications, and reintervention compared with RFs >2 mm. On multivariable analysis, older age, body mass index, and RF size were found to be predictive of stone-related events. Conclusions: With the largest cohort to date, this study by the EDGE research consortium further confirms that clinically insignificant residual fragment is problematic for patients after PCNL, particularly in older more obese patients with larger RFs. Our study underscores the importance of complete stone clearance post-PCNL and challenges the use of Clinically insignificant residual fragment (CIFR).

Comparison of Superpulse Thulium Fiber Laser vs Holmium Laser for Ablation of Renal Calculi in an In Vivo Porcine Model

Introduction and Objectives: We sought to compare the effectiveness and efficiency of the superpulse thulium fiber laser (sTFL to the holmium: yttrium-aluminum-garnet [Ho:YAG] laser for ureteroscopic "dusting" of implanted renal stones in an in vivo porcine model. Methods: Twenty-four porcine kidneys (12 juvenile female Yorkshire pigs) were randomized to Ho:YAG or sTFL treatment groups. Canine calcium oxalate stones were scanned with computed tomography to calculate stone volume and stone density; the stones were randomized and implanted into each renal pelvis via an open pyelotomy. In all trials, a 14F, 35 cm ureteral access sheath was placed. With a 9.9F dual lumen flexible ureteroscope, laser lithotripsy was performed using dusting settings: Ho:YAG 200 μm laser fiber at 16 W (0.4 J, 40 Hz) or sTFL 200 μm laser fiber at 16 W (0.2 J, 80 Hz). Lithotripsy continued until no fragments over 1 mm were observed. No stone basketing was performed. Throughout the procedures, intrarenal and renal pelvis temperatures were measured using two percutaneously positioned K-type thermocouples, one in the upper pole calyx and one in the renal pelvis. After the lithotripsy, the ureteropelvic junction was occluded, the kidneys were bivalved, and all residual fragments were collected, dried, weighed, and then measured with an optical laser particle sizer. Results: Implanted stones were similar in volume and density in both groups. Intraoperative collecting system temperatures were similar for both groups (all <44°C). Compared to Ho:YAG, sTFL ablated stones faster (9 vs 27 minutes, p < 0.001) with less energy expenditure (8 vs 26 kJ, p < 0.001), and a greater stone clearance rate (73% vs 45%, p = 0.001). After sTFL lithotripsy, 77% of the remaining fragments were ≤1 mm vs 17% of fragments ≤1 mm after Ho:YAG treatment (p < 0.001). Conclusions: In an in vivo porcine kidney, using dusting settings, sTFL lithotripsy resulted in shorter ablation times, higher stone clearance rates, and markedly smaller stone fragments than Ho:YAG lithotripsy.

[Evaluation of the results and feasibility of vibration, diuresis and inversion therapy in the treatment of upper urinary tract stones]

OBJECTIVES

To evaluate the feasibility, efficiency, and predictive factors of therapeutic success of Vibration, Diuresis and Inversion (VDI) therapy for the removal of upper urinary tract stones.

METHODS

It is a retrospective, single-center study at the CHU - La Conception, Marseille, France including all patients treated with VDI from 2013 to 2018. VDI was indicated for stones <6mm in first-line treatment or for residual fragments <6mm after ureteroscopy, PCNL, microPCNL. The protocol included 4 sessions in outpatient care from 2013 to 2015 then 6 sessions from 2015 to 2018 and a final radiological evaluation.

RESULTS

In total, 109 patients or 489 sessions are reported: median age was 55 years [14-84], median BMI 25kg/m² [15-37], average cumulative size of kidney stones 3mm ±4. VDI was performed after flexible ureteroscopy (62%), SWL (20%), percutaneous treatment (9%) or as a first-line treatment (9%). Compliance was 87 %. The median VAS during the session was 0[0-8]. The incidence of post-session renal colic was 4% (all Clavien I). The postoperative fragment-free and microfragment rates were respectively 39% and 21%, i.e. an overall success of 60% for kidney stones, and 43% and 21%, i.e. an overall success of 64% for lower pole kidney stones.

CONCLUSION

VDI is a simple, non invasive and well tolerated technique for the elimination of small renal lithiasis after SWL, ureteroscopy, PCNL or as a first-line treatment.

Duration of Follow-up and Timing of Discharge from Imaging Follow-up, in Adult Patients with Urolithiasis After Surgical or Medical Intervention: A Systematic Review and Meta-analysis from the European Association of Urology Guideline Panel on Urolithiasis

CONTEXT

No algorithm exists for structured follow-up of urolithiasis patients.

OBJECTIVE

To provide a discharge time point during follow-up of urolithiasis patients after treatment.

EVIDENCE ACQUISITION

We performed a systematic review of PubMed/Medline, EMBASE, Cochrane Library, clinicaltrials.gov, and reference lists according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. Fifty studies were eligible.

EVIDENCE SYNTHESIS

From a pooled analysis of 5467 stone-free patients, we estimated that for a safety margin of 80% for remaining stone free, patients should be followed up using imaging, for at least 2 yr (radiopaque stones) or 3 yr (radiolucent stones) before being discharged. Patients should be discharged after 5 yr of no recurrence with a safety margin of 90%. Regarding residual disease, patients with fragments ≤4 mm could be offered surveillance up to 4 yr since intervention rates range between 17% and 29%, disease progression between 9% and 34%, and spontaneous passage between 21% and 34% at 49 mo. Patients with larger residual fragments should be offered further definitive intervention since intervention rates are high (24-100%). Insufficient data exist for high-risk patients, but the current literature dictates that patients who are adherent to targeted medical treatment seem to experience less stone growth or regrowth of residual fragments, and may be discharged after 36-48 mo of nonprogressive disease on imaging.

CONCLUSIONS

This systematic review and meta-analysis indicates that stone-free patients with radiopaque or radiolucent stones should be followed up to 2 or 3 yr, respectively. In patients with residual fragments ≤4 mm, surveillance or intervention can be advised according to patient preferences and characteristics, while for those with larger residual fragments, reintervention should be scheduled.

PATIENT SUMMARY

Here, we review the literature regarding follow-up of urolithiasis patients. Patients who have no stones after treatment should be seen up to 2-3 yr, those with large fragments should be reoperated, and those with small fragments could be offered surveillance with imaging.

International Alliance of Urolithiasis (IAU) Guideline on percutaneous nephrolithotomy

The International Alliance of Urolithiasis (IAU) would like to release the latest guideline on percutaneous nephrolithotomy (PCNL) and to provide a clinical framework for surgeons performing PCNLs. These recommendations were collected and appraised from a systematic review and assessment of the literature covering all aspects of PCNLs from the PubMed database between January 1, 1976, and July 31, 2021. Each generated recommendation was graded using a modified GRADE methodology. The quality of the evidence was graded using a classification system modified from the Oxford Center for Evidence-Based Medicine Levels of Evidence. Forty-seven recommendations were summarized and graded, which covered the following issues, indications and contraindications, stone complexity evaluation, preoperative imaging, antibiotic strategy, management of antithrombotic therapy, anesthesia, position, puncture, tracts, dilation, lithotripsy, intraoperative evaluation of residual stones, exit strategy, postoperative imaging and stone-free status evaluation, complications. The present guideline on PCNL was the first in the IAU series of urolithiasis management guidelines. The recommendations, tips and tricks across the PCNL procedures would provide adequate guidance for urologists performing PCNLs to ensure safety and efficiency in PCNLs.

Fluoroscopy-free RIRS on the second session after ureteral stent placement

Aim:

Fluoroscopy is used in some stages of the conventional Retrograde Intrarenal Surgery (RIRS) procedure and is beneficial. On the other hand, radiation exposure is its most obvious disadvantage. As a subgroup, we aimed to show that fluoroscopy-free technique is safe and effective in patients who underwent RIRS after passive dilatation.

Materials and methods:

Between October 2018 and April 2020, 54 cases of second session RIRS of renal stones performed by a single surgeon were retrospectively evaluated. Patients’ demographic characteristics (age, gender), stone features (laterality, size, number, volume, and location), mean operative time, and, perioperative and postoperative complications, as well as the stone-free rate (SFR), were all retrospectively evaluated. The results were classified as stone free, clinical insignificant residual fragments (CIRF), and presence of residual stones. Complications were graded using the Clavien–Dindo classification system. We used a modified surgical technique.

Results:

All of complications were minor. There were no major complications (Clavien grade III–IV). The stone-free rate was 70.3% (38/54) on the first day after surgery and 83.3% (45/54) 1 month afterward, respectively. If we accept the absence of residual stone as success, we can say that it is about 91% successful in the first month.

Conclusion:

This technique has a high stone-free success rate and a low complication rate without the use of radiation. For surgeons experienced in endourology, we can say that the fluoroscopy-free technique is safe and effective in secondary-session RIRS cases which passive dilatation was performed by inserting a ureteral catheter before.

Robot-Assisted Mini-Endoscopic Combined Intrarenal Surgery for Complex and Multiple Calculi: What Are the Real Advantages?

Background: To determine the stone-free rates (SFR) with robot-assisted mini-endoscopic combined intrarenal surgery (mini-ECIRS) and evaluate the impact of intraoperative assessment of stone-free status compared to postoperative non-contrast computed tomography (NCCT) scan findings. Methods: A total of 42 consecutive patients (44 renal units) diagnosed with complex/multiple renal stones were enrolled and reviewed in a retrospective manner. While retrograde access with the flexible scope was performed by using Avicenna Roboflex, mini-percutaneous nephrolithotomy was performed through a 16.5F sheath. Demographic, clinical characteristics of the cases along with perioperative complications were recorded, analyzed, and compared to the reported data in the literature. Results: Forty-two renal units (95.5%) were endoscopically confirmed to be stone-free at the end of the procedure, of which all were confirmed to be stone-free in postoperative NCCT examination. Complications were observed in 3 of the 42 (7.1%) patients, which were classified as Clavien grade I. The mean operation and fluoroscopy time were 103.7 ± 20.6 minutes and 71 ± 13.7 seconds, respectively. Conclusion: Our results demonstrate that robot-assisted mini-ECIRS could reveal high SFR in complex and multiple stones. In addition, endoscopic flexible ureteroscopic evaluation of the collecting system at the end of the procedure could let the surgeon predict stone-free status more reliably and successfully.

[Follow-up after urolithiasis management]

BACKGROUND

Urinary stones often affect younger people. Because the risk of recurrence is high, regular follow-up is important for individuals at risk.

OBJECTIVE

To summarize the extent of urinary stones and the health and economic impact in the population; to provide recommendations for general and stone-specific follow-up.

MATERIALS AND METHODS

Analysis and discussion of publications and guideline recommendations.

RESULTS

The risk of recurrence after a stone attack can be high depending on the risk profile. An initial metabolic workup should be performed promptly after stone therapy. General dietary management should be intensified by stone-specific dietary management depending on the risk profile. Nutritional counseling may be helpful. Imaging after stone therapy is used to monitor the success of treatment and detect recurrences early. Since the risk of recurrence can vary greatly depending on the stone composition, not only the type of imaging but also its frequency should be adjusted accordingly. The same applies to the various stone therapies, which help determine the frequency and type of imaging follow-up. Exact guidelines and cost-effectiveness analyses of follow-up examinations after stone therapy are unfortunately missing.

CONCLUSIONS

Acute urolithiasis represents an excruciating experience for patients. Accordingly, their willingness to undergo metaphylaxis and follow-up shortly after the event is strong. Since the risk of recurrence after a stone attack can be very high, regular follow-up after stone therapy is essential. The frequency of follow-up should be adapted to the probability of stone recurrence.

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.

Comparison of percutaneous nephrolithotomy and retrograde intrarenal surgery outcomes for kidney stones larger than 2 cm from Guy's stone scoring system perspective

OBJECTIVE

To compare surgical outcomes of percutaneous nephrolithotomy (PNL) and retrograde intrarenal surgeries (RIRS) as a result of kidney stones larger than 2 cm, together with Guy's stone scores (GSS).

MATERIALS AND METHODS

The data of 811 patients with stone sizes 2-6 cm were operated using PNL (n = 361) and RIRS (n = 450) reviewed retrospectively. GSS were graded 1, 2, 3 or 4 according to the computed tomography findings. Stone-free rate (SFR), operation times, length of hospital stay (LOHS) and Clavien complications (CC) were recorded.

RESULTS

Although mean operative times were significantly longer in the RIRS group than the PNL group in GSS grades 1, 2 and 3 (P < .001), it was similar between the two groups in GSS grade 4 (P = .186). SFRs in the PNL and RIRS group were 90.3% and 58.4% on post-operative 10th day (P < .001), and it raised up to 95.3% and 81.6% after secondary interventions (P < .001). Significantly higher SFRs observed in the PNL group in GSS grades 1, 2 and 3 categories. On postoperative 10th day, the SFRs were similar in both GSS grade 4 categories (P = .06). LOHS was longer in the PNL group (P < .001). Although LOHS was significantly longer only in GSS grade 3 (P = .043) and GSS grade 4 (P < .001) in the PNL group, it was similar in GSS grade 1 and 2 between groups. Clavien complications increased in line with GSS in the PNL group (P < .001), but the difference did not differ between GSS grade 3 and 4.

CONCLUSION

SF of PNL in a single session and short operation time seems to be significant especially in GSS grades 1, 2 and 3 category stones. Although the number of patients in the GSS 4 group is very small to claim this, RIRS might be considered as an alternative to PNL in a special group of patients such as GSS grade 4 because of its lower complication rates and shorter LOHS.

Intraoperative cone beam computed tomography for detecting residual stones in percutaneous nephrolithotomy: a feasibility study

Cone beam computed tomography (CBCT) provides multiplanar cross-sectional imaging and three-dimensional reconstructions and can be used intraoperatively in a hybrid operating room. In this study, we investigated the feasibility of using a CBCT-scanner for detecting residual stones during percutaneous nephrolithotomy (PCNL). Intraoperative CBCT-scans were made during PCNL procedures from November 2018 until March 2019 in a university hospital. At the point where the urologist would have otherwise ended the procedure, a CBCT-scan was made to image any residual fragments that could not be detected by either nephroscopy or conventional C-arm fluoroscopy. Residual fragments that were visualized on the CBCT-scan were attempted to be extracted additionally. To evaluate the effect of this additional extraction, each CBCT-scan was compared with a regular follow-up CT-scan that was made 4 weeks postoperatively. A total of 19 procedures were analyzed in this study. The mean duration of performing the CBCT-scan, including preparation and interpretation, was 8 min. Additional stone extraction, if applicable, had a mean duration of 11 min. The mean effective dose per CBCT-scan was 7.25 mSv. Additional extraction of residual fragments as imaged on the CBCT-scan occurred in nine procedures (47%). Of the follow-up CT-scans, 63% showed a stone-free status as compared to 47% of the intraoperative CBCT-scans. We conclude that the use of CBCT for the detection of residual stones in PCNL is meaningful, safe, and feasible.

Development and validation of a simple stone score to estimate the probability of residual stones prior to percutaneous nephrolithotomy

BACKGROUND

The aim of the present study was to develop and internally validate a simple stone score (SSS) to estimate the probability of clinically significant residual fragments (CSRF) prior to percutaneous nephrolithotomy (PNL).

METHODS

The files of 1170 PNL procedures between January and December 2015 were evaluated. CT-derived stone characteristics were examined. Caliceal stone distribution (CSD) was assigned three grades based on the number of calices involved regardless of the renal pelvis (I = no or single calix; II = more than one calix; and III = more than 2 calices or complete staghorn stones). CSRF was defined as any residuals >4 mm in postoperative CT. A logistic regression model to predict the CSRF was fitted, and coefficients were used to develop the SSS. The SSS was validated by discrimination, calibration, and decision curve analysis (DCA).

RESULTS

Patients' data were split into training (936, 80%) and validating (234, 20%) datasets. In the training partition, independent predictors of CSRF were CSD-grade II (OR: 4.2; 95%CI: 2.5-7; P<0.001), grade III (OR: 7.8; 95%CI: 4.2-14.4; P<0.001) and largest stone diameter (LSD) (OR:1.3; 95%CI: 1.1-1.6; P<0.001). Score points 0, 1, 2, and 0, 3, 9 were given to LSD<30, 30-40, >40 mm, and CSD grades I, II, III, respectively. Discrimination of the SSS was 0.79 and after 10-fold cross-validation and internal validation was 0.86. The calibration plot and DCA highlighted the validity and clinical significance of the SSS.

CONCLUSIONS

The novel SSS could be used to describe the risk of CSRF prior to PNL. Further studies are invited for external validation.

Impact of Stone Size, Location, and Stone Composition on the Efficacy of Extracorporeal Shock Wave Lithotripsy for Residual Stone after Percutaneous Nephrolithotomy

This study aimed to determine the impact of stone size, location and stone composition the efficacy of extracorporeal shock wave lithotripsy (ESWL) in the management of residual stone after percutaneous nephrolithotomy (PCNL). The design of this study was a retrospective that conducted between January 2012 until December 2016. The population in this study were all patients with residual stones post PCNL. Exclusion criteria were patients with multiple stones and patients with a history of previous treatment for residual stones such as nephroscopy, flexible ureterorenoscopy, ESWL or medical therapy). The variables studied in this study were stone size, stone location, and stone composition. Before ESWL was carried out, all patients underwent Kidney Ureter Bladder (KUB). After ESWL, all patients underwent ultrasonography (USG) and KUB to determine the stone clearance status. The sample of this study was 125 patients. The overall stone-free rate (SFR) of ESWL in managing post-PCNL residual stones is 72%. SFR based on stone size variable are 73.7% and 71.3% respectively for stones with a size = 5 mm and >5 mm (p = 0.78). SFR based on stone location variable was 67.1%, 75.8%, and 81.8% respectively for the residual stone located at the upper pole, middle pole and lower pole. There are no significant differences in the entire variable. This study concludes that ESWL can be used as effective additional management to treat post-PCNL residual stones with satisfactory SFR.

Definition, treatment and outcome of residual fragments in staghorn stones

Technological advances in minimally invasive treatment of stone disease and its integration with concomitant clinical practice are amongst the most important achievements in urology. Despite the wealth of information accumulated over the years and the richness of existing literature, the knowledge about the definition, treatment and outcomes of residual stone fragments after percutaneous nephrolithotomy (PNL) is still insufficient. Due to the high stone load a lot of patients with staghorn stones have residual fragments (RFs) after treatment with PNL, which depends on the size of tract, definition of stone free rate (SFR), timing of evaluation and the imaging used. No consensus exists on the imaging modality or their timing in the evaluation of possible RFs. The treatment of residual stones is apparently different depending on the facilities of the department and the preference of the surgeon, which includes active surveillance, shock wave lithotripsy (SWL), retrograde intrarenal surgery (RIRS) or a second look PNL.

Stone residual fragments: A thorny problem

Urolithiasis represents a widespread and common disorder among the world population, with a predicted increase in affected patients in the coming years. Treatment of renal and ureteral stones varies widely, and achieving true stone-free status in all patients is still difficult. Moreover, imaging used to assess residual fragments following procedure impacts the diagnosed stone-free rate percentage considerably. In particular, the use of computed tomography scans has led to a better evaluation of residual fragments as well as so-called clinically insignificant residual fragments, which in a considerable number of cases are, despite their definition, causes of adverse urological events, thus creating a thorny problem for both patients and urologists. Currently, there is no gold standard or validated protocol regarding the management, clearance and prevention of residual fragments. In this article, we review the current literature regarding residual fragments, clinically insignificant residual fragments and their natural history, reporting on diagnostic methods, incidence, complications and outcome with the use of less invasive procedures, taking into consideration viable treatment and management of patients affected.

Shock Wave Lithotripsy is More Effective for Residual Fragments after Percutaneous Nephrolithotomy than for Primary Stones of the Same Size: A Matched Pair Cohort Study

Aims

To compare the outcome of shock wave lithotripsy (SWL) on post-percutaneous nephrolithotomy (PCNL) residual fragments (RFs) versus primary stones of the same size through a matched pair study.

Methods

Patients with a single 5-15 mm fragment 3 months after PCNL were enrolled (study group n = 59). The control group (n = 67) consisted of all adult patients with a single 5-15 mm renal stone.

Results

The success rate of SWL was significantly higher in the study group (81.4 vs. 59.7%; p = 0.008; OR: 2.95). With a cutoff point of Hounsfield units (HU) 750: the success rate was significantly lower in patients with a stone HU ≥ 750 (OR: 3.488). This HU cutoff value had no effect on the outcome of SWL in patients with post-PCNL RF (p = 0.14). On the other hand, the outcome of SWL was significantly more favorable in control group when HU < 750 (p = 0.02).

Conclusion

The success rate of SWL was 2.95-fold higher for post-PCNL RFs than in a stone burden-matched control group. The likelihood of stone clearance after SWL was 3.488-fold greater when HU was less than 750. This effect of HU was more prominent in patients receiving SWL for their primary stones while SWL was evenly effective on post PCNL RFs with different HUs.

Complications, Re-Intervention Rates, and Natural History of Residual Stone Fragments After Percutaneous Nephrolithotomy

INTRODUCTION

The management of residual fragments (RFs) that persist after percutaneous nephrolithotomy (PCNL) has been poorly studied. Fragments have the potential to grow or cause symptoms. The aim of this study was to follow patients with fragments after PCNL to identify predictors of stone-related events (re-interventions and complications) after PCNL.

PATIENTS AND METHODS

Data were retrospectively collected from patients who underwent surgery from 2008 to 2013 at our hospital. Patients with fragments of any size on postoperative day 1 computed tomography of the kidney, ureter, and bladder radiograph (CT-KUB) were included, and patients with planned secondary interventions were excluded. Subgroup analysis was performed on subjects with CT-plain X-ray to determine fragment growth or passage.

RESULTS

Of the 658 patients who received a postoperative CT-KUB on day 1, 299 patients (45%) had fragments that were 1 mm or larger. From this, 263 patients met the study criteria and were included. The size of fragments, using a 4 mm cutoff, did not predict the passage of fragments (p = 0.173) or growth (p = 0.572). On multivariable logistic regression analysis, previous history of renal stones and size of fragment were found to be predictive for stone-related events (p = 0.002 and 0.027, respectively). Kaplan-Meier analysis identified patients with fragments >4 mm having a shorter survival time before the occurrence of stone-related events (p = 0.044).

CONCLUSIONS

The true stone-free rate was 55% after PCNL. However, 82.5% were stone free or had RFs 4 mm or less, which correlates with previous studies. Larger RFs had higher rates of stone-related events and shorter time to occurrence of stone-related events. The growth and spontaneous passage of RFs was independent of RF size, emphasizing the importance of obtaining a stone-free status after PCNL.