Multi-site microbiota alteration is a hallmark of kidney stone formation.

BACKGROUND: Inquiry of microbiota involvement in kidney stone disease (KSD) has largely focussed on potential oxalate handling abilities by gut bacteria and the increased association with antibiotic exposure. By systematically comparing the gut, urinary, and oral microbiota of 83 stone formers (SF) and 30 healthy controls (HC), we provide a unified assessment of the bacterial contribution to KSD. RESULTS: Amplicon and shotgun metagenomic sequencing approaches were consistent in identifying multi-site microbiota disturbances in SF relative to HC. Biomarker taxa, reduced taxonomic and functional diversity, functional replacement of core bioenergetic pathways with virulence-associated gene markers, and community network collapse defined SF, but differences between cohorts did not extend to oxalate metabolism. CONCLUSIONS: We conclude that multi-site microbiota alteration is a hallmark of SF, and KSD treatment should consider microbial functional restoration and the avoidance of aberrant modulators such as poor diet and antibiotics where applicable to prevent stone recurrence. Video Abstract.

Ureteral Stent Microbiota Is Associated with Patient Comorbidities but Not Antibiotic Exposure.

Ureteral stents are commonly used to prevent urinary obstruction but can become colonized by bacteria and encrusted, leading to clinical complications. Despite recent discovery and characterization of the healthy urinary microbiota, stent-associated bacteria and their impact on encrustation are largely underexplored. We profile the microbiota of patients with typical short-term stents, as well as over 30 atypical cases (all with paired mid-stream urine) from 241 patients. Indwelling time, age, and various patient comorbidities correlate with alterations to the stent microbiota composition, whereas antibiotic exposure, urinary tract infection (UTI), and stent placement method do not. The stent microbiota most likely originates from adhesion of resident urinary microbes but subsequently diverges to a distinct, reproducible population, thereby negating the urine as a biomarker for stent encrustation or microbiota. Urological practice should reconsider standalone prophylactic antibiotics in favor of tailored therapies based on patient comorbidities in efforts to minimize bacterial burden, encrustation, and complications of ureteral stents.

Outcomes of Conservative Management of Splenic Injury Incurred During Percutaneous Nephrolithotomy.

Purpose: Splenic injury is a rare complication after left-sided percutaneous nephrolithotomy (PCNL). Although initial observation is often espoused, the natural history of nonoperative conservative management is not well established and the implications of splenic injury are not fully defined in this context. We sought to describe outcomes of conservative management of splenic injury incurred at PCNL. Patients and Methods: We performed a multi-institutional retrospective review of individual patients who underwent PCNL complicated by trans-splenic nephrostomy access injury. Demographic info, intraoperative data, management strategies, and outcomes were reviewed. Results: Nine patients suffered splenic injury after left PCNL. All patients had supracostal upper pole access under fluoroscopic guidance. Splenic injury was identified by computed tomography (CT) in the eight of nine (89%) who had imaging on first postoperative day. All eight patients were managed conservatively with nephrostomy dwell time of 2-21 days, one of whom (11%) required blood transfusion. The remaining patient (11%)-who had tubeless PCNL without postoperative imaging presented 5 days postoperatively with a delayed bleed and underwent emergent splenectomy. Seven of the nine (78%) were managed nonoperatively and without need for transfusion or embolization. Conclusion: The majority of patients incurring splenic injury during PCNL can be managed conservatively with maintenance of nephrostomy tube for ≥2 days. Consequences of unrecognized splenic injury may include splenic bleed and may prompt transfusion and/or splenectomy, underscoring role of routine postoperative CT to allow timely diagnosis, particularly in those undergoing upper pole supracostal left-sided percutaneous renal access.

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

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

Celebrating 75 years.

INTRODUCTION: Following the introduction of shock wave lithotripsy (SWL), ureteroscopy (URS), and percutaneous nephrolithotomy (PCNL), the subspecialty of endourology was born in the late 1970s. The purpose of this study was to report milestones in Canadian endourology, highlighting Canada's contributions to the field. METHODS: A review of the literature was performed from the late 1970s to the present. The literature review included bibliographic and digital resources. Additionally, records and recollections by various individuals were used, including some who were directly involved. RESULTS: Endourology was born in Canada when SWL, URS, and PCNL emerged as minimally invasive treatment options for stones in the early to mid-1980s. According to our research, the first PCNL was performed at the University of Toronto in 1981. Dr. Joachim Burhenne, a Harvard-trained radiologist from Germany, first used extracorporeal SWL in Canada at the University of British Columbia (UBC) for the treatment of biliary stones. Treatment for urinary tract stones followed at UBC and Dalhousie University. The first worldwide use of the holmium laser for lithotripsy of urinary tract calculi took place at the University of Western Ontario. Other endourology milestones in Canada include the formation of the Canadian Endourology Group and the emergence of the Endourological Society-accredited fellowship programs at the University of Toronto and Western University in the 1990s. Canada hosted the 21st and 35th World Congress of Endourology and Shock Wave Lithotripsy annual meeting in Montreal and Vancouver, respectively. CONCLUSIONS: Canadian urologists have led many advances in SWL, URS, and PCNL over the past four decades and, for a relatively small community, have made significant contributions to the field. Through the training of the next generation of endourologists at Canadian institutions, the future of endourology in Canada is bright.

The evolution of percutaneous nephrolithotomy: Analysis of a single institution experience over 25 years.

INTRODUCTION: Over time, the incidence of nephrolithiasis has risen significantly, and patient populations have become increasingly complex. Our study aimed to determine the impact of changes in patient demographics on percutaneous nephrolithotomy (PCNL) outcomes. METHODS: A retrospective analysis of a prospectively collected database was carried out from 1990-2015. Patient demographics, comorbidities, stone and procedure characteristics were analyzed. Multivariate logistic regression was used to evaluate differences in operative duration, complications, stone-free rate, and length of stay. RESULTS: A total of 2486 patients with a mean age of 54±15 years, body mass index (BMI) of 31±8, and stone surface area of 895±602 mm2 were analyzed; 47% of patients had comorbidities, including hypertension (22%), diabetes mellitus (14%), and cardiac disease (13%). Complication rate was 19%, including a 2% rate of major complications (Clavien grade III-V). There was a statistically significant increase in patient age, BMI, and comorbidities over time, which was correlated with an increased complication rate (odds ratio [OR] 1.15; p=0.010). The overall transfusion rate was 1.0% and remained stable (p=0.131). With time, both OR duration (mean Δ 16 minutes; p<0.001) and hospital length of stay (mean Δ 2.4 days; p<0.001) decreased significantly. Stone-free rate of 1873 patients with available three-month followup was 87% and decreased significantly over time (OR 1.09; p<0.001), but was correlated with an increased use of computed tomography (CT) scans for followup imaging. CONCLUSIONS: Despite an increasingly complex patient population, PCNL remains a safe and effective procedure with a high stone-free rate and low risk of complications.

Randomized Controlled Trial Comparing Three Different Modalities of Lithotrites for Intracorporeal Lithotripsy in Percutaneous Nephrolithotomy.

PURPOSE: To compare the efficiency (stone fragmentation and removal time) and complications of three models of intracorporeal lithotripters in percutaneous nephrolithotomy (PCNL). MATERIALS AND METHODS: Prospective, randomized controlled trial at nine centers in North America from 2009 to 2016. Patients were randomized to one of three lithotripter devices: the Cyberwand, a dual-probe ultrasonic device; the Swiss Lithoclast Select, a combination pneumatic and ultrasonic device; and the StoneBreaker, a portable pneumatic device powered by CO2 cartridges. Since the StoneBreaker lacks an ultrasonic component, it was used with the LUS-II ultrasonic lithotripter to allow fair comparison with combination devices. RESULTS: Two hundred seventy patients were enrolled, 69 were excluded after randomization. Two hundred one patients completed the study: 71 in the Cyberwand group, 66 in the Lithoclast Select group, and 64 in the StoneBreaker group. The baseline patient characteristics of the three groups were similar. Mean stone surface area was smaller in the StoneBreaker group at 407.8 mm2 vs 577.5 mm2 (Lithoclast Select) and 627.9 mm2 (Cyberwand). The stone clearance rate was slowest in the StoneBreaker group at 24.0 mm2/min vs 28.9 mm2/min and 32.3 mm2/min in the Lithoclast Select and Cyberwand groups, respectively. After statistically adjusting for the smaller mean stone in the StoneBreaker group, there was no difference in the stone clearance rate among the three groups (p = 0.249). Secondary outcomes, including complications and stone-free rates, were similar between the groups. CONCLUSIONS: The Cyberwand, Lithoclast Select, and the StoneBreaker lithotripters have similar adjusted stone clearance rates in PCNL for stones >2 cm. The safety and efficacy of these devices are comparable.

Burden of Urolithiasis: Trends in Prevalence, Treatments, and Costs.

CONTEXT: The recent evolution of management options for urolithiasis has presented a unique dilemma for the modern urologist. A comprehensive understanding of epidemiological trends along with current provider preferences in treating urinary stones would be beneficial. OBJECTIVE: To review trends in the prevalence, treatments, and costs of urolithiasis worldwide. EVIDENCE ACQUISITION: A literature review was performed using the MEDLINE database, the Cochrane Library Central search facility, Web of Science, and Google Scholar between 1986 and 2016. Keywords used for the search were "urolithiasis" and "prevalence; treatment; and cost". EVIDENCE SYNTHESIS: The incidence and prevalence of urinary stones are rising around the world, including regions that have historically had low rates of urolithiasis. Common theories explaining this trend involve climate warming, dietary changes, and obesity. Shockwave lithotripsy (SWL) has been the preferred mode of treatment since its introduction in the 1980s. However, ureteroscopy (URS) has become increasingly popular for small stones regardless of location because of lower recurrence rates and costs. Developing countries have been slower to adopt URS technology and continue to use percutaneous nephrolithotomy at a steady rate. CONCLUSIONS: URS has recently challenged SWL as the treatment modality preferred for small upper urinary tract stones. In some cases it is less expensive but still highly effective. As the burden of stone disease increases worldwide, appropriate selection of stone removal therapies will continue to play an important role and will thus require further investigation. PATIENT SUMMARY: Urinary stones are becoming more prevalent. Recent advances in technology have improved the management of this disease and have decreased costs.

KIM-1 Is a Potential Urinary Biomarker of Obstruction: Results from a Prospective Cohort Study.

INTRODUCTION: Partial or complete obstruction of the urinary tract is a common and challenging urological condition that may occur in patients of any age. Serum creatinine is the most commonly used method to evaluate global renal function, although it has low sensitivity for early changes in the glomerular filtration rate or unilateral renal pathology. Hence, finding another measurable parameter that reflects the adaptation of the renal physiology to these circumstances is important. Several recent studies have assessed the use of new biomarkers of acute kidney injury (AKI), but the information among patients with stone disease and those with obstructive uropathy is limited. MATERIAL AND METHODS: A prospective cohort study was conducted to determine the urinary levels of kidney injury molecule-1 (KIM-1), Total and Monomeric neutrophil gelatinase-associated lipocalin (NGAL) in patients with hydronephrosis secondary to renal stone disease, congenital ureteropelvic junction obstruction or ureteral stricture. Comparison between patients with hydronephrosis and no hydronephrosis was carried out along with correlation analysis to detect factors associated with biomarker expression. RESULTS: Urinary levels of KIM-1 significantly decreased after hydronephrosis treatment in patients with unilateral obstruction (1.19 ng/mL vs 0.76 ng/mL creatinine, p = 0.002), additionally KIM-1 was significantly higher in patients with hydronephrosis compared to stone disease patients without radiological evidence of obstruction (1.19 vs 0.64, p = 0.006). Total and Monomeric NGAL showed a moderate correlation with the presence of leukocyturia. We found that a KIM-1 value of 0.735 ng/mg creatinine had a sensitivity of 75% and specificity of 67% to predict the presence of hydronephrosis in preoperative studies (95% CI 0.58-0.87, p = 0.006). CONCLUSION: Our results show that KIM-1 is a promising biomarker of subclinical AKI associated with hydronephrosis in urological patients. NGAL values were influenced by the presence of leukocyturia, limiting its usefulness in this population.

Perioperative characteristics of dogs undergoing open versus laparoscopic-assisted cystotomy for treatment of cystic calculi: 89 cases (2011-2015).

OBJECTIVE To compare perioperative characteristics of dogs with cystic calculi treated via open versus laparoscopic-assisted cystotomy (LAC). DESIGN Retrospective case series. ANIMALS 89 client-owned dogs that underwent open cystotomy (n = 39) or LAC (50). PROCEDURES Medical records of dogs that underwent cystotomy between 2011 and 2015 were reviewed. History, signalment, surgery date, results of physical examination, results of preoperative diagnostic testing, details of surgical treatment, duration of surgery, perioperative complications, treatment costs, and duration of hospitalization were recorded. RESULTS 5 of 50 (10%) dogs required conversion from LAC to open cystotomy (OC). There was no significant difference between the LAC (1/50) and OC (2/39) groups with regard to percentage of patients with incomplete removal of calculi. Duration of surgery was not significantly different between the LAC (median, 80 min; range, 35 to 145 min) and OC (median, 70 min; range, 45 to 120 min) groups. Postoperative duration of hospitalization was significantly shorter for dogs that underwent LAC (median, 24 hours; range, 12 to 48 hours) versus OC (median, 26 hours; range, 12 to 63 hours). Surgical and total procedural costs were significantly higher for patients undergoing LAC. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that LAC may be an acceptable minimally invasive technique for treatment of cystic calculi in dogs. Surgery times were similar to those for dogs undergoing OC; however, surgical and total procedural costs were higher. Further investigation is suggested to determine which patients may benefit from LAC versus traditional OC.

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

OBJECTIVE: To determine the natural history of residual fragments (RF) after percutaneous nephrolithotomy in long-term patient follow-up and to identify possible predictive factors for future intervention. MATERIALS AND METHODS: We assessed all patients from 2006 to 2013 with postoperative computed tomography scan revealing RF, who did not undergo second-look nephroscopy or immediate ancillary procedures, and with at least 12 months of clinical follow-up. We evaluated factors associated with clinical, radiological, and surgical outcomes. Kaplan-Meier curves were used to calculate the proportion of asymptomatic and treatment-free patients during follow-up. RESULTS: From 781 percutaneous nephrolithotomies performed, 202 patients underwent postoperative computed tomography scan and 44 patients with residual stones were included in the analysis. Mean follow-up was 57.9 months. A total of 24 patients (54.5%) developed at least 1 clinical outcome, and 32 (72.7%) patients had a surgical intervention. Only 4 patients had radiological evidence of stone passage. Multivariate analysis found that RF >4 mm and struvite or apatite stones were significant predictors for surgical intervention. The 5-year estimated probability to remain intervention free was 29%. CONCLUSION: Despite the size of the RF, the vast majority of patients required an intervention during long-term follow-up. We identified that RFs of diameter >4 mm associate with the need for a surgical therapy, but the rate of clinical events was not affected by the size or location of the stones. Struvite or apatite composition stones had an increased risk of intervention during follow-up. Spontaneous passage was an uncommon event in this cohort.

The Impact of Distraction on Laparoscopic Skills in Veterinary Medical Students.

OBJECTIVE: To investigate the impact of distraction on the performance of a simulator-based laparoscopic task in veterinary students. STUDY DESIGN: Prospective, randomized trial. SAMPLE POPULATION: Years 1-4 veterinary students (n=41). METHODS: Participants repeated a simulated laparoscopic peg transfer task to eliminate any learning effects and were subsequently randomized to receive either a cognitive (double-digit addition questions, n=21) or sensory distraction (dogs barking and anesthesia monitor alerts, n=20). The laparoscopic task scores were compared between baseline and in the presence and absence of each distraction. The number of addition questions attempted, and the number of questions answered correctly in 1 minute were compared between baseline and during a concurrent laparoscopic task. RESULTS: Baseline laparoscopic task scores were not significantly different between groups (P=.09). Laparoscopic task scores were significantly lower than baseline when performed with the cognitive distraction (P<.001) and significantly higher than baseline when performed with the sensory distraction (P=.005). Participants undergoing cognitive distraction attempted significantly fewer addition questions (P<.001) and answered significantly fewer addition questions correctly (P<.001) when a concurrent laparoscopic task was performed. CONCLUSION: Cognitive distraction had a negative impact on the performance of a laparoscopic task in this cohort of veterinary students, whereas sensory distraction had a positive effect.

Assessing the Magnitude of Effect of Bone Structures on Shockwave Lithotripsy Fragmentation: Results from an In Vitro Study.

INTRODUCTION: Several anatomic and clinical factors have been implicated in the failure rates of shock wave lithotripsy (SWL), including the attenuating effects of bony structures. We designed an in vitro model that incorporates the lumbar spine, including vertebral bodies and transverse processes along the pathway of shockwaves, to mimic the clinical scenario during SWL of upper ureteral stones. We hypothesized that the presence of bone structures in the SWL pathway significantly affects the fragmentation rate. MATERIALS AND METHODS: An ordnance gelatin (OG) model was conceptualized and created to allow a pig's lumbar spine to be embedded within it. Artificial urinary calculi weighing 2 ± 0.1 g (1.2-cm diameter) were prepared using BegoStone plaster. The trial was divided into two arms: group 1 models had OG only and served as the control and group 2 models had the bone embedded in the gelatin with stone wells placed above the transverse processes. Twenty-four stones per group were subjected to SWL using the STORZ MODULITH SLX-F2 lithotripter, using the same treatment parameters. Fragments were sieved through 2- and 4-mm filters, and the fragmentation coefficients (FC) were calculated. The Mann-Whitney test was used to compare FC between the two groups. RESULTS: The mean fragmentation rate of group 1 was statistically significantly higher compared with group 2 using a 4-mm sieve (43% vs 0.62%, p < 0.001) and the 2-mm filter (18% vs 0.52%, p < 0.001). CONCLUSIONS: The presence of bone structures dramatically reduces the fragmentation rate of phantom stones using an OG in vitro model. The OG model is inexpensive and simple to use to simulate clinical situations during SWL.

Multicenter External Validation and Comparison of Stone Scoring Systems in Predicting Outcomes After Percutaneous Nephrolithotomy.

BACKGROUND AND PURPOSE: Several scoring systems have recently emerged to predict stone-free rate (SFR) and complications after percutaneous nephrolithotomy (PCNL). We aimed to compare the most commonly used scoring systems (Guy's stone score, S.T.O.N.E. nephrolithometry, and CROES nomogram), assess their predictive accuracy for SFR and other postoperative variables, and develop a risk group stratification based on these scoring systems. MATERIALS AND METHODS: We performed a retrospective review of patients who have had a PCNL at four academic institutions between 2006 and 2013. Primary outcome was SFR within 3 weeks of the surgery and secondary outcomes were operative time (OT), complications, and length of stay (LOS). We performed chi-squared, t-test, logistic, linear, and Poisson regressions, as well as receiver operating characteristics curve with area under the curve (AUC) calculation. RESULTS: We identified 586 patients eligible for analysis. Of these, 67.4% were stone free. Guy's, S.T.O.N.E., and CROES score were predictive of SFR on multivariable logistic regression (odds ratio [OR]: 1.398, 95% confidence interval [CI]: 1.056, 1.852, p = 0.019; OR: 1.417, 85% CI: 1.231, 1.631, p < 0.001; OR: 0.993, 95% CI: 0.988, 0.998, p = 0.004) and have similar predictive accuracy with AUCs of 0.629, 0.671, and 0.646, respectively. On multivariable linear regression, only S.T.O.N.E. was an independent predictor of longer OT (ß = 14.556, 95% CI: 12.453, 16.660, p < 0.001). None of the scores were independent predictors of postoperative complications or a longer LOS. Poisson regression allowed for risk group stratification and showed the S.T.O.N.E. score and CROES nomogram to have the most distinct risk groups. CONCLUSIONS: The three evaluated scoring systems have similar predictive accuracy of SFR. S.T.O.N.E. has additional value in predicting OT. Risk group stratification can be used for patient counseling. Further research is needed to identify whether or not any is superior to the others with regard to clinical usefulness and predictive accuracy.

The Effect of Renal Cysts on the Fragmentation of Renal Stones During Shockwave Lithotripsy: A Comparative In Vitro Study.

PURPOSE: To assess the potential effect of simple renal cysts (SRC) on stone fragmentation during shockwave lithotripsy (SWL) in an in vitro model. MATERIALS AND METHODS: The in vitro model was constructed using 10% ordnance gelatin (OG). Models were created to mimic four scenarios: Model A-with an air-filled cavity (suboptimal for stone fragmentation); model B-without a cavity (normal anatomy); model C-with a 3-cm serum filled cavity (to represent a small SRC); model D-with a 4-cm serum filled cavity (to represent a larger SRC). SWL was applied to 24 standardized phantom stones (weight of 2±0.1 g) in each model using a standardized protocol. Stone fragments were retrieved, then dried overnight at room air temperature. Fragmentation coefficient (FC) was calculated for each stone, for fragments<4 mm and <2 mm. RESULTS: The OG in vitro model was robust enough for the proposed research. There was no fragmentation evident in model A as expected. The mean FC was 29.7 (±20.5) and 39.7 (±23.7) for <4 mm fragments (P=0.069) and 7.6 (±4.1) and 10.6 (±6.7) for <2 mm fragments (P=0.047), for noncystic and cystic models, respectively. The mean FC was 29.7 (±20.5), 38.8 (±26.2) and 40.7 (±21.3) for <4 mm fragments (P=0.213) and 7.6 (±4.1), 11.1 (±8) and 10.2 (±5.3) for <2 mm fragments (P=0.138), for models B, C, and D, respectively. CONCLUSION: Our in vitro experiment confirms better stone fragmentation associated with SWL in the presence of adjacent SRC.

Risk Factors for Postoperative Complications of Percutaneous Nephrolithotomy at a Tertiary Referral Center.

PURPOSE: We sought to describe and evaluate the complications related to percutaneous nephrolithotomy and identify risk factors of morbidity according to the modified Clavien scoring system. We also sought to specify which perioperative factors are associated with minor and major complications. MATERIALS AND METHODS: We retrospectively analyzed data on patients who underwent percutaneous nephrolithotomy from 1990 to 2013. Descriptive statistics were used to analyze patient characteristics, medical comorbidities and perioperative features. Complications were categorized according to the Clavien score for percutaneous nephrolithotomy. The Mann-Whitney and Fisher exact tests were used as appropriate. Logistic regression analysis was performed to look for prognostic factors associated with major complications. RESULTS: A total of 2,318 surgeries were evaluated. Mean age of the population was 53.7 years. The stone-free rate at hospital discharge was 81.6%. The overall complication rate was 18.3%. Two deaths occurred. Patients with any postoperative complications were older, had more comorbidities, were more likely to have staghorn calculi and had longer operative time and hospital stay on univariate analysis (p<0.05). Age 55 years or older and upper pole access were independent predictors of major complications on multivariate analysis. Other factors such as a history of urinary tract infections, body mass index, stone composition, previous percutaneous nephrolithotomy and multiple tracts were not associated with a major complication. CONCLUSIONS: At our center percutaneous nephrolithotomy is an excellent option for complex kidney stone management with a low overall complication rate. Older patient age and upper pole access are significantly associated with an increased risk of a major complication.

A comparison of outcomes after percutaneous nephrolithotomy in children and adults: a matched cohort study.

INTRODUCTION: Percutaneous nephrolithotomy (PCNL) has surpassed open stone surgery as the operation of choice for large and complex stone burdens (figure). Although the procedure was developed in adults, its principles have been extrapolated to children. There is a paucity of literature comparing outcomes of PCNL in adults and children for similar stone burdens. OBJECTIVE: The purpose of this study was to evaluate outcomes following PCNL among children and adults with similar stone burdens. PATIENTS AND METHODS: Data on patient characteristics and outcomes for 2196 consecutive patients undergoing PCNL at a single institution were collected prospectively from January 1992 to July 2013. Thirty-one pediatric patients undergoing 39 PCNLs were identified. Each pediatric PCNL was matched in a ratio of 1:4 to adult PCNLs by year of surgery and stone burden characteristics (staghorn, partial staghorn, number of stones). All PCNLs were performed by two fellowship-trained endourologists who operate on both adult and pediatric patients. Ultrasonic lithotripsy was used primarily. The primary outcome measure was stone-free rate (SFR) at hospital discharge. Secondary outcomes included the need for second-look nephroscopy, length of hospital stay, complication rate, and blood transfusion rate. The Student t test was used for continuous variables and the Fisher exact for categorical variables. RESULTS: The median age for the pediatric group was 13.9 ± 4.30 years and for the adult group was 55.4 ± 15.1 years. Pediatric patients tended to present with metabolic stones, with no difference in rates of infection stones. No difference was found in SFR at time of hospital discharge (86.1% vs. 86.4%, p = 0.2). More pediatric patients required a second access tract than adult patients (15.4% vs. 4.52%, p = 0.02). There was no significant difference in the need for second-look nephroscopy, length of stay, or complication rates (overall and by Clavien classification subgroup) between both groups. The rates of blood transfusion were low in both groups (0% vs. 0.6%, p = 0.80). DISCUSSION: There was no difference in primary and secondary outcomes among children compared with adults undergoing PCNL in our study. The outcomes reported in this study were similar to published literature. A limitation of this study is the low number of pediatric patients. However, it is unique to have a single-center study that compares PCNL outcomes in both adult and pediatric patient and accounts for stone burden characteristics. CONCLUSIONS: Although principles of PCNL were developed in adults, this study affirms the safety and efficacy of PCNL in both pediatric and adult patients.