Clinically insignificant residual fragments after flexible ureterorenoscopy: medium-term follow-up results

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.

The fate of clinically insignificant residual fragments following retrograde intrarenal surgery and factors affecting spontaneous passage

The remaining stone fragments after retrograde intrarenal surgery (RIRS) can lead to stone recurrence/regrowth, or stone-related events (SRE). We aimed to delineate the clinical circumstances that are decisive for spontaneous passage of clinical insignificant residual fragments (CIRF) (primary outcome) and define risk factors for stone recurrence/regrowth and their clinical manifestation (secondary outcome). A total of 115 patients who had CIRF following RIRS were included in this study. Demographic, clinical data, stone, and anatomic characteristics including infundibulopelvic angle (IPA), infundibular length (IL) and follow-up data of patients were analyzed. The mean follow-up time was 27.5 ± 6.9 months. 31 (26.9%) patients passed the CIRF spontaneously. Patients were divided into two groups as spontaneous fragment passage group and fragment remaining group and compared with respect to demographic, clinical, stone-related, and anatomic characteristics. 61.2% of patients had lower pole CIRF in fragment remaining group and 83.3% of patients in spontaneous fragment passage group (p = 0.031). In addition, IPA was wider in spontaneous fragment passage group (60.7° vs 51.4°, p = 0.001). A subanalysis was performed for fragment remaining group. In 84 patients, 44 (52.4%) patients were stable for their CIRF at their follow-up and included in stable group. 40 (47.6%) patients experienced stone re-growth (27 patients) or SRE (13 patients) at their follow up. Patients in re-growth/SRE group were older (49.1 vs 39.4 years, p = 0.047), had higher body mass index (28.2 vs 27 kg/m2, p = 0.03) and larger CIRF (2.8 vs 2.1 mm). CIRFs may be not expelled spontaneously and they may lead to additional morbidity and lithotripsy interventions.

Development of a novel mesh model to define a new index "amount of stone" to evaluate calculus and predicting the lithotripsy time

OBJECTIVE

Develop a mesh model to define a new "index amount of stone" to evaluate calculus and predict lithotripsy time.

METHODS

The stones were divided into target units with diameter of 5 mm by the mesh from x, y and z directions, and the cross-sectional areas between units were calculated as amount of stone as a new index to evaluate calculus. Design a prospective study with 112 cases of percutaneous nephrolithotomy to verify the reliability of this index, and to compare the accuracy of the quantity, volume and maximum diameter of stones in predicting the time of lithotripsy.

RESULTS

Amount of stone (Q) is reliable. The lithotripsy time was significantly correlated with the amount of stone, volume and maximum diameter of the stone (p < 0.01). The three regression equations were valid. The linear fit in the amount group was larger than that in the volume group, and further larger than that in the maximum diameter group, with R2 values of 0.716, 0.661 and 0.471, respectively.

CONCLUSIONS

It is more accurate and convenient to use amount of stone to evaluate calculus, which can be used to predict the lithotripsy time.

Comparative efficacy between retrograde intrarenal surgery with vacuum-assisted ureteral access sheath and minimally invasive percutaneous nephrolithotomy for 1-2 cm infectious upper ureteral stones: a prospective, randomized controlled study

Objective

To observe the efficacy and safety of retrograde intrarenal surgery combined with vacuum-assisted ureteral access sheath (V-UAS) and minimally invasive percutaneous nephrolithotomy (MPCNL) in patients with 1-2 cm infectious upper ureteral stone.

Patients and methods

A total of 173 patients with 1-2 cm infectious upper ureteral stone were prospectively randomized into two groups. Eighty-six in the V-UAS group and 87 cases as control in the MPCNL group. The SFRs at different times (Postoperative 1 day, 2nd week and 4th week) was considered as the primary outcome of the study. The secondary end points were operative time, postoperative hospital stay and operative complications.

Results

There was no obvious difference between two groups in patients' demographics and preoperative clinical characteristics (all P > 0.05). Postoperative data showed that the SFR at postoperative 1 day in the V-UAS group was significantly lower than that in the MPCNL group (73.2% vs. 86.2%, P = 0.034). However, there was no statistical significance between two groups in SFRs during postoperative 2 weeks and 4 weeks (All P > 0.05). The levels of WBC, CRP and PCT were all significant lower in the V-UAS group than those in the MPCNL group at the postoperative 24 h and 48 h (all P < 0.05). Postoperative complications included fever (≥38.5°C), bleeding, pain and urosepsis. In terms of the rates of fever, pain and urosepsis, MPCNL group were all significantly higher than those in the V-UAS group (10.3 vs. 2.4%, P = 0.031; 14.9 vs. 2.4%, P = 0.003; 4.6 vs. 0.0%, P = 0.044; respectively). No significant difference was found between two groups in bleeding. Meanwhile, postoperative hospital stay in the V-UAS group was more shorten than that in the MPCNL group (3.7 vs. 5.9 days, P < 0.001).

Conclusions

Our study showed that RIRS with V-UAS, a new partnership to treat 1-2 cm infectious upper ureteral stones, was satisfying as it achieved a high SFR rate and a low rate of infectious complications. This method was safe and reproducible in clinical practice.

Calcium Oxalate Crystallization: Influence of pH, Energy Input, and Supersaturation Ratio on the Synthesis of Artificial Kidney Stones

The removal of kidney stones can lead to small residual fragments remaining in the human body. Residual stone fragments can act as seeds for kidney stone crystallization and may necessitate another intervention. Therefore, it is important to create a consistent model with a particle size comparable to the range of kidney stone fragments. Thus, the size-determining parameters such as supersaturation ratio, energy input, and pH value are examined. The batch crystallizations were performed with supersaturation ratios between 5.07 and 6.12. The compositions of the dried samples were analyzed with Raman spectroscopy, infrared spectroscopy, and X-ray diffraction (XRD). The samples were identified as calcium oxalate monohydrate with spectroscopic analysis, while calcium oxalate dihydrate being the most prominent crystalline species at all supersaturation ratios for the investigated conditions. The aggregate size, obtained with analytical centrifugation, varied between 2.9 and 4.3 μm, while the crystallite domain size, obtained from XRD, varied from 40 to 61 nm. Our results indicate that particle sizes increase with increasing supersaturation, energy input, and pH. All syntheses yield a high particle heterogeneity and represent an ideal basis for reference materials of small kidney stone fragments. These results will help better understand and control the crystallization of calcium oxalate and the aggregation of such pseudopolymorphs.

European Association of Urology Section of Urolithiasis and International Alliance of Urolithiasis Joint Consensus on Percutaneous Nephrolithotomy

CONTEXT

Although percutaneous nephrolithotomy (PCNL) has been performed for decades and has gone through many refinements, there are still concerns regarding its more widespread utilization because of the long learning curve and the potential risk of severe complications. Many technical details are not included in the guidelines because of their nature and research protocol.

OBJECTIVE

To achieve an expert consensus viewpoint on PCNL indications, preoperative patient preparation, surgical strategy, management and prevention of severe complications, postoperative management, and follow-up.

EVIDENCE ACQUISITION

An international panel of experts from the Urolithiasis Section of the European Association of Urology, International Alliance of Urolithiasis, and other urology associations was enrolled, and a prospectively conducted study, incorporating literature review, discussion on research gaps (RGs), and questionnaires and following data analysis, was performed to reach a consensus on PCNL.

EVIDENCE SYNTHESIS

The expert panel consisted of 36 specialists in PCNL from 20 countries all around the world. A consensus on PCNL was developed. The expert panel was not as large as expected, and the discussion on RGs did not bring in more supportive evidence in the present consensus.

CONCLUSIONS

Adequate preoperative preparation, especially elimination of urinary tract infection prior to PCNL, accurate puncture with guidance of fluoroscopy and/or ultrasonography or a combination, keeping a low intrarenal pressure, and shortening of operation time during PCNL are important technical requirements to ensure safety and efficiency in PCNL.

PATIENT SUMMARY

Percutaneous nephrolithotomy (PCNL) has been a well-established procedure for the management of upper urinary tract stones. However, according to an expert panel consensus, core technical aspects, as well as the urologist's experience, are critical to the safety and effectiveness of PCNL.

Retrograde intrarenal surgery of renal stones: a critical multi-aspect evaluation of the outcomes by the Turkish Academy of Urology Prospective Study Group (ACUP Study)

AIMS

To outline and evaluate the incidence, management and follow-up of the residual fragments (RFs) following retrograde intrarenal surgery (RIRS) of renal stones by the Turkish Academy of Urology Prospective Study Group (ACUP Study).

METHODS

Following the ethical committee approval, 15 centers providing data regarding the incidence, management, and follow-up of RFs after RIRS were included and all relevant information was recorded into the same electronic database program ( https://acup.uroturk.org.tr/ ) created by Turkish Urology Academy for Residual Stone Study.

RESULTS

A total of 1112 cases underwent RIRS for renal calculi and RFs were observed in 276 cases (24.8%). Of all the parameters evaluated, our results demonstrated no statistically significant relation between preoperative DJ stenting and the presence of RFs (χ2 (1) = 158.418; p = 0.099). RFs were significantly higher in patients treated with UAS (82 patients, 29.3%) during the procedure compared to the cases who did not receive UAS (194 patients, 23.3%) (χ2 (1) = 3.999; p = 0.046). The mean period for a secondary intervention after RIRS was 28.39 (± 12.52) days. Regarding the procedures applied for RF removal, re-RIRS was the most commonly performed approach (56%).

CONCLUSIONS

Despite the reported safe and successful outcomes, the incidence of RFs is higher, after the RIRS procedure particularly in cases with relatively larger calculi. Such cases need to be followed in a close manner and although a second flexible ureteroscopy is the treatment of choice for fragment removal in the majority of these patients, shock wave lithotripsy and percutaneous nephrolithotomy may also be preferred in selected cases.

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.

External physical vibration lithecbole facilitating the expulsion of upper ureteric stones 1.0-2.0 cm after extracorporeal shock wave lithotripsy: a prospective randomized trial

To observe the efficacy and safety of External Physical Vibration Lithecbole (EPVL) in patients with upper ureteric stones 1.0–2.0 cm after extracorporeal shock wave lithotripsy (ESWL). A total of 271 patients with upper ureteric stones 1.0–2.0 cm were prospectively randomized into two groups. One hundred and twenty-seven cases in the treatment group accepted EPVL therapy and 144 cases as control after ESWL. The stone expulsion status and stone-free rates (SFRs) between two groups were compared at the 1st, 2nd and 4th weekends by imaging examinations. All of 271 patients were randomly assigned to two groups, of which 127 patients were included in the treatment group and 144 in the control group. EPVL was successful in assisting the discharge of stone fragments. The rate of stone expulsion at day 1 in the treatment group was significantly higher than in the control group (79.5% vs. 64.6%, P = 0.006). The SFRs of the 1st weekend (76.3% vs. 61.8%, P = 0.010), the 2nd weekend (88.2% vs. 77.1%, P = 0.017) and the 4th weekend (92.1% vs. 84.0%, P = 0.042) in the treatment group were all significantly higher than that in the control group. However, no statistical significance was found in complications between the two groups (P > 0.05). Furthermore, in the treatment group the patients were treated a mean 4.3 sessions of EPVL. EPVL and ESWL are ideal complementary partners in the treatment of upper ureteric stones 1.0–2.0 cm, satisfying both high SFR and low complication. This method is safe and reproducible in clinical practice, and it also needs large-scale multicenter prospective studies further to prove the above conclusions.

Does Previous Failed Shockwave Lithotripsy Treatment Have an Influence on Retrograde Intrarenal Surgery Outcome?

Background: The prevalence of urolithiasis is nearly 20% and patients with urolithiasis constitute an essential part of the patients referred to the urology clinic. Many parameters should be considered for the management of renal stones and authors recommend extracorporeal shockwave lithotripsy (SWL), retrograde intrarenal surgery (RIRS), and percutaneous nephrolithotripsy (PNL), as treatment options. Among these techniques, SWL does not require general anesthesia, has 89% success rate for renal pelvic stones: 83% for upper caliceal stones, 84% for middle caliceal stones, and 68% for lower caliceal stones. In this study, we aimed to investigate whether the previously failed SWL treatment affects RIRS outcome. Methods: Patients who underwent RIRS for kidney stones between January 2012 and December 2017 in Diskapi Yildirim Beyazit Training and Research Hospital were reviewed retrospectively. Patients treated with primary RIRS (186 patients) were classified as Group 1. The outcomes of these patients were compared with those of 186 patients who underwent RIRS after failed SWL treatment using matched-pair analysis, and these patients were classified as Group 2. Results: The procedure success was defined as the sum of the stone-free and clinically insignificant residual fragments (CIRFs); final success rates were 90.3% and 91.9%, respectively. If we compare the final success rates, there was no statistically significant difference between both groups (P = .584). Conclusions: As a result, there is no negative effect of the previous unsuccessful SWL treatment on the RIRS success. Patients with CIRF should be followed up more carefully in terms of becoming symptomatic.

Efficacy analysis of self-help position therapy after holmium laser lithotripsy via flexible ureteroscopy

BACKGROUND

To observe the efficacy of self-help position therapy (SHPT) after holmium laser lithotripsy via flexible ureteroscopy (FURS).

METHODS

From January 2010 to November 2015, 736 nephrolithiasis patients who had received FURS lithotripsy were analyzed retrospectively. In position group, 220 cases accepted SHPT after lithotripsies, and 428 cases as control, coming from another independent inpatient area in the same center. The stone-free status (SFS) between two groups were compared at the 2nd, 4th and 12th week ends by X-ray examinations.

RESULTS

The preoperative incidence of hydronephrosis (25.9% vs. 18.0%, p = 0.018) or lower calyceal seeper (33.6% vs. 24.3%, p = 0.012) and the proportion of patients with > 2.0 cm stones (33.6% vs. 24.3%, p = 0.003) were all significantly higher in position group than in control group. There were no substantial difference between two groups in age, BMI, gender and medical histories. In postoperative followup, the incidence of hydronephrosis in position group was significantly lower than in control group (9.5% vs. 15.7%, p = 0.032) after removing double-J stents. In position group, the SFS of the 2nd week end (60.9% vs. 47.2%, p = 0.001), the 4th week end (74.1% vs. 62.8%, p = 0.004) and the 12th week end (86.9% vs. 79.4%, p = 0.021) were all significantly higher than those in control group.

CONCLUSIONS

SHPT after holmium laser lithotripsy via FURS may increase postoperative SFS, accelerate stone fragment clearance, and decrease the incidence of hydronephrosis after removal of double-J stents. The therapy does not require professional assistance and is economical, simple, and effective.

The Clinical Efficacy of Dual-Lumen Catheter Technique in Retrograde Intrarenal Surgery for the Management of Nephrolithiasis: A Propensity Score Analysis

OBJECTIVE

To assess the clinical efficacy of dual-lumen catheter technique in retrograde intrarenal surgery (RIRS) in terms of stone-free rate.

METHODS

The data of 172 patients who underwent RIRS for renal stones between 2010 and 2017 were retrospectively reviewed. Patients were classified into two groups depending on whether the dual-lumen catheter technique was used (group 1, n = 25) or not (group 2, n = 147) during RIRS. In turn, all patients of group 1 were compared with those of group 2 using propensity score analysis methods. Clinical variables, including post-RIRS residual fragments (RFs) (≥2 mm) and dusts (sandy stones) (≤1 mm), were compared between both groups. Logistic regression analyses were conducted to identify the predictors of postoperative RFs and dusts.

RESULTS

According to propensity score analysis, no other clinical variables were significantly different between the two groups, except the dust-free rate was significantly higher in group 1 than in group 2 (92% vs 40%, p < 0.001). In multivariate analysis, the performance of dual-lumen catheter technique was an independent predictor of the absence of dusts after RIRS (odds ratio [OR], 0.040; 95% confidence interval [CI], 0.070-0.220). In addition, on performing multivariate analyses in another matched population, it was found that although the technique adversely affected the removal of RFs (OR, 4.711; 95% CI, 1.203-18.447), it showed an excellent effect on the evacuation of dusts (OR, 0.049; 95% CI, 0.007-0.347).

CONCLUSION

Our analyses suggest that the use of dual-lumen catheter during RIRS can facilitate the evacuation of sandy stones. However, further prospective randomized trials are required to verify the usefulness of this technique in real clinical practice.

New for Old-Coagulum Lithotomy vs a Novel Bioadhesive for Complete Removal of Stone Fragments in a Comparative Study in an Ex Vivo Porcine Model

OBJECTIVES

To evaluate a recently reported new bioadhesive system for the retrieval of small residual fragments (RFs) after intracorporeal lithotripsy, we systematically compared this system with coagulum lithotomy in retrograde intrarenal surgery.

MATERIALS AND METHODS

We extracted 30 human stone fragments (≤1 mm) in an ex vivo porcine kidney model using a flexible ureteroscope for three groups: (1) the novel bioadhesive, (2) autologous blood as a natural adhesive, and (3) (control group) a conventional retrieval basket. Each group consisted of 15 test runs. Outcomes were evaluated regarding the macroscopic stone-free rate (SFR), retrieval time, and number of ureteral passages.

RESULTS

For groups 1 and 2, a significant advantage in stone clearance, mean retrieval time, and number of retrievals was detected compared to the control group (p = 0.001). The time and number of retrievals were significantly lower in group 1 (10:36 minutes, p = 0.001) than in group 2 (26:12 minutes, p = 0.001), with shorter clotting time and better visibility.

CONCLUSIONS

These data show the general feasibility of intrarenal RF embedding to improve the SFR. Our data furthermore suggest the superiority of the artificial bioadhesive embedding agent over the application of native blood. Further in vivo studies and other research are necessary to confirm the adhesive's effect in patients.

Residual stones after percutaneous nephrolithotomy: comparison of intraoperative assessment and postoperative non-contrast computerized tomography

OBJECTIVES

To compare the intraoperative surgeon perspective for detection of residual fragments (RFs) after percutaneous nephrolithotomy (PNL) with postoperative NCCT.

METHODS

A prospective study of adult patients who underwent PNL between March and September 2014 was conducted. Stone complexity was evaluated using the Guy's stone score (GSS). All patients were evaluated by pre- and postoperative NCCT. After the procedure, the surgeon had been asked whether there were residual stones or not. The sensitivity, specificity and predictive values were tested against postoperative NCCT. Predictors of accurate intraoperative assessment were determined using univariate and multivariate statistical analyses.

RESULTS

The study included 306 consecutive patients. The surgeons reported no residual stones in 236 procedures; of whom 170 (72%) were reported stone-free by NCCT. On the other hand, 65 out of 70 procedures (93%) reported with residual stones by the surgeons were true by NCCT. The sensitivity was 50% and the NPV was 72%, while the specificity was 97% and the PPV was 93%. On multivariate analysis, only lower GSS (p < 0.001) was independently associated with true negative surgeon opinion.

CONCLUSIONS

Although there was a high surgeon ability to detect post-PNL residual stones, postoperative imaging is mandatory because of the high false negative rates and low NPV. The surgeon opinions can be judged only in stones with lower GSS. The NPV could be enhanced if a consistent definition of clinically significant RFs is introduced.

Novel Biocompatible Adhesive for Intrarenal Embedding and Endoscopic Removal of Small Residual Fragments after Minimally Invasive Stone Treatment in an Ex Vivo Porcine Kidney Model: Initial Evaluation of a Prototype

PURPOSE

Residual fragments related to endoscopic intracorporeal lithotripsy are a challenging problem. The impact of residual fragments remains a subject of discussion and growing evidence highlights that they have a central role in recurrent stone formation. Therefore, we developed a novel bioadhesive system for intrarenal embedding and retrieval of residual fragments after endoscopic lithotripsy in an ex vivo porcine kidney model.

MATERIALS AND METHODS

In a standardized setting 30 human stone fragments 1 mm or less were inserted in the lower pole of an ex vivo porcine kidney model. We assessed the extraction efficacy of flexible ureteroscopy using the bioadhesive system in 15 preparations and a conventional retrieval basket in 15. Outcomes were compared regarding the endoscopic and macroscopic stone-free rate, and overall time of retrieval.

RESULTS

Embedding and retrieving the residual fragment-bioadhesive complex were feasible in all trial runs. We observed no adverse effects such as adhesions between the adhesive and the renal collecting system or the instruments used. The stone-free rate was 100% and 60% in the bioadhesive and conventional retrieval groups, respectively (p = 0.017). Mean retrieval time was significantly shorter at 10 minutes 33 seconds vs 36 minutes 56 seconds in the bioadhesive group vs the conventional group (p = 0.001).

CONCLUSIONS

This novel method involving adhesive based complete removal of residual fragments from the collecting system has proved to be feasible. Our evaluation in a porcine kidney model revealed that this technology performed well. Further tests, including inpatient studies, are required to thoroughly evaluate the benefit and potential drawbacks of bioadhesive based extraction of residual fragments after intracorporeal lithotripsy.

Endoscopically Determined Stone Clearance Predicts Disease Recurrence Within 5 Years After Retrograde Intrarenal Surgery

OBJECTIVE

To assess stone-related events (SREs) requiring retreatment in a series of 100 consecutive patients treated by retrograde intrarenal surgery (RIRS) for renal stones and to evaluate potential risk factors thereof.

PATIENTS AND METHODS

The primary outcome was incidence of SRE (medical or surgical treatment). Secondary outcomes included side of SRE, time to SRE, and late complications. Analysis of potential risk factors included high-risk stone formers (HRSFs), obesity, high stone burden, and lower pole stones. In addition, we evaluated endoscopically determined small residual fragments (SRF) of <1 mm (i.e., fragments too small for retrieval) as an independent risk factor.

RESULTS

Eighty-five of the 99 patients were followed up for a mean of 59 months (31-69), among whom 26 (30.1%) had SRE. Thirty-four of the 85 (40%) patients were HRSFs, 22 of whom experienced SRE (both sides) during follow-up (64.7%, p < 0.001). Eight of the 17 patients (47.1%) with SRF experienced ipsilateral side SRE compared with 13 (19.1%) of the 68 without SRF (p = 0.022, hazard ratio 2.823, 95% confidence interval [95% CI] 1.16, 6.85). Risk for ipsilateral SRE was unaffected by the presence of SRF among HRSFs (p = 0.561). Of low-risk patients with SRF, 33.3% experienced ipsilateral SRE, while those without SRF experienced no ipsilateral SRE (p < 0.001).

CONCLUSION

Endoscopically determined stone clearance predicts disease recurrence within 5 years after RIRS. Even SRF are an important risk factor for future stone-related (ipsilateral) events; therefore, patients with residual fragments of any size should not be labeled "stone free" and endoscopic stone treatment should aim at complete stone clearance.

Kidney stones

Kidney stones are mineral deposits in the renal calyces and pelvis that are found free or attached to the renal papillae. They contain crystalline and organic components and are formed when the urine becomes supersaturated with respect to a mineral. Calcium oxalate is the main constituent of most stones, many of which form on a foundation of calcium phosphate called Randall's plaques, which are present on the renal papillary surface. Stone formation is highly prevalent, with rates of up to 14.8% and increasing, and a recurrence rate of up to 50% within the first 5 years of the initial stone episode. Obesity, diabetes, hypertension and metabolic syndrome are considered risk factors for stone formation, which, in turn, can lead to hypertension, chronic kidney disease and end-stage renal disease. Management of symptomatic kidney stones has evolved from open surgical lithotomy to minimally invasive endourological treatments leading to a reduction in patient morbidity, improved stone-free rates and better quality of life. Prevention of recurrence requires behavioural and nutritional interventions, as well as pharmacological treatments that are specific for the type of stone. There is a great need for recurrence prevention that requires a better understanding of the mechanisms involved in stone formation to facilitate the development of more-effective drugs.

Clinical significance of residual fragments in 2015: impact, detection, and how to avoid them

PURPOSE

Residual fragments are common after stone treatment. Little is known about clinical outcomes relevant to the patient. This comprehensive review of the literature highlights the impact of residual fragments, modes of detection, and treatment strategies to avoid residual fragments in shock wave therapy, ureteroscopy, and percutaneous nephrolithotomy.

METHODS

A comprehensive review of current literature was performed using PubMed(®), MEDLINE(®), Embase™, Ovid(®), Google Scholar™, and the Cochrane Library. Publications relevant to the subject were retrieved and critically appraised.

RESULTS

Residual fragments after treatment for urinary stones have a significant impact on a patient's well-being and future course. (Ultra-) low-dose non-contrast computed tomography detects small residuals most reliably. In shock wave lithotripsy, adherence to basic principles helps to improve results. Various techniques and devices facilitate complete stone clearance in conventional and miniaturized percutaneous nephrolithotomy and (flexible) ureteroscopy. Promising new technologies in shock waves, lasers, and robotics (and potentially microrobotics) are on the horizon.

CONCLUSIONS

Residual fragments are relevant to patients. Contemporary treatment of urolithiasis should aim at complete stone clearance.