Upper-tract Stone Research Articles

PD51-05 THE BURDEN OF KIDNEY STONES IN PRIMARY CARE

You have accessJournal of UrologyStone Disease: Evaluation III1 Apr 2015PD51-05 THE BURDEN OF KIDNEY STONES IN PRIMARY CARE Melissa Mendez, Michael Lipkin, Glenn Preminger, and Charles Scales Melissa MendezMelissa Mendez More articles by this author , Michael LipkinMichael Lipkin More articles by this author , Glenn PremingerGlenn Preminger More articles by this author , and Charles ScalesCharles Scales More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.1765AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Urinary lithiasis is a highly prevalent condition in the United States, affecting nearly 1 in 11 persons in their lifetime. Many stones pass without requiring surgical intervention, and uneven workforce distribution reduces access to urologic care in many areas. Patients may be initially evaluated or managed by primary care physicians. Given this context, we sought to characterize the utilization of primary care visits for patients with urinary stones in the United States. METHODS We performed a cross-sectional analysis of ambulatory visits for patients with upper tract stones between 2008 and 2010 using the National Ambulatory Care Survey (NAMCS). NAMCS is a multistage probability survey of non-hospital-based outpatient visits in the United States. It is specifically designed to provide nationally representative estimates of healthcare utilization. The survey includes information regarding patient demographics, health conditions, services and physician specialty. Visits were identified using ICD-9-CM diagnostic codes. National estimates were compared using the Rao-Scott chi square test or univariate linear regression, as appropriate. All analyses accounted for the complex sampling structure of the NAMCS. RESULTS During the study period, an estimated 10.6 million ambulatory visits for patients with upper tract stones occurred. Urologists provided care at just more than half of these visits (56%), and primary care physicians provided care during 33% of visits. Patients seen in primary care were younger (46.4 vs. 53.0 years, p = 0.01) and more likely to be of non-white ethnicity (26% vs 11%, p = 0.007) than those seen by a urologist. There were no differences in visits to primary care versus urology by patient sex or metropolitan location. Most visits (61%) to primary care were for a new presentation of a stone, with a smaller proportion for a recurrence of chronic stone disease (16%). In contrast, only about one-third of visit to urologists represented new presentation of a stone (p<0.001 vs primary care). CONCLUSIONS A substantial portion of ambulatory visits for patients with kidney stones occurs in the primary care setting. Many of these visits are for new onset of a symptomatic stone. Further research is required to gain a better understanding of utilization, variation, and outcomes of care for these patients. For patients not requiring surgical intervention, treatment in a primary care setting may provide a lever to reduce the overall cost of care for kidney stones in the United States. © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e1110 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information Melissa Mendez More articles by this author Michael Lipkin More articles by this author Glenn Preminger More articles by this author Charles Scales More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

MP28-09 BALLOON DILATION OF THE URETER: A CONTEMPORARY REVIEW OF OUTCOMES AND COMPLICATIONS

You have accessJournal of UrologyStone Disease: Surgical Therapy II1 Apr 2015MP28-09 BALLOON DILATION OF THE URETER: A CONTEMPORARY REVIEW OF OUTCOMES AND COMPLICATIONS Nicholas Kuntz, Andreas Neisius, Matvey Tsivian Tsivian, Momin Ghaffar, Fernando Cabrera, Ramy Youssef, Michael Ferrandino, Nishant Patel, Roger Sur, Glenn Preminger, and Michael Lipkin Nicholas KuntzNicholas Kuntz More articles by this author , Andreas NeisiusAndreas Neisius More articles by this author , Matvey Tsivian TsivianMatvey Tsivian Tsivian More articles by this author , Momin GhaffarMomin Ghaffar More articles by this author , Fernando CabreraFernando Cabrera More articles by this author , Ramy YoussefRamy Youssef More articles by this author , Michael FerrandinoMichael Ferrandino More articles by this author , Nishant PatelNishant Patel More articles by this author , Roger SurRoger Sur More articles by this author , Glenn PremingerGlenn Preminger More articles by this author , and Michael LipkinMichael Lipkin More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.1232AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Ureteroscopy is a well-established treatment for symptomatic ureteral and renal stones. Ureteral balloon dilation may be necessary to allow passage of endoscopic instruments or ureteral access sheaths (UAS). Herein, we assessed the outcomes and complications associated with ureteral balloon dilation during ureteroscopic procedures. METHODS A retrospective review (2000-2012) was performed on patients who received balloon dilation of the ureter prior to endoscopic treatment of upper tract stones. An 18 Fr UromaxTM balloon dilator was used in all cases. Prior ureteral strictures, radiation therapy or urothelial cancer were excluded. The primary outcomes were: stone-free rates, complications, treatment failures and stricture rates. Stone-free was defined as no residual stones at follow-up imaging. Complications were divided into intraoperative and post-operative (Satava and Clavien-Dindo classification). Treatment failure was defined as inability to access the stone despite dilation, requiring a second procedure. Ureteral stricture diagnosis required new onset hydronephrosis on follow-up imaging without evidence of obstructing stone and a confirmatory functional study or endoscopic finding. RESULTS Overall, 151 patients fulfilled study criteria, with a median follow-up of 12 months. The median age was 51, and 65% were male. Multiple stones were seen in 36%, and median maximum stone diameter was 7mm. UAS were employed in almost 80% of cases, and JJ stents were left in 96%. Approximately 50% of balloon dilations were employed secondary to the inability to pass a UAS. There were 8 (5%) intra-operative ureteral perforations. Of these, 7 were managed with a ureteral stent, 1 with a PCN tube, and 4 patients required endoscopic re-treatment (Satava 2b). The overall post-operative complication rate was 7% (11). Notably, of these 11 complications, there are only 4 that are a direct result from balloon dilation. A single ureteral stricture attributed to balloon dilation was identified. The treatment failure rate was 5%, and stone-free rate was 72%, with a predominant utilization of IVP and CT scan at post-op imaging. CONCLUSIONS In this contemporary review, balloon dilation of the ureter prior to endoscopic treatment of stone disease was associated with a high success rate and few complications. The use of ureteral balloon dilation may reduce the need for secondary procedures for patients undergoing ureteroscopy for the treatment of proximal ureteral and intra-renal stones. © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e314 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information Nicholas Kuntz More articles by this author Andreas Neisius More articles by this author Matvey Tsivian Tsivian More articles by this author Momin Ghaffar More articles by this author Fernando Cabrera More articles by this author Ramy Youssef More articles by this author Michael Ferrandino More articles by this author Nishant Patel More articles by this author Roger Sur More articles by this author Glenn Preminger More articles by this author Michael Lipkin More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Balloon Dilation of the Ureter: A Contemporary Review of Outcomes and Complications

During ureteroscopy ureteral balloon dilation may be necessary to allow for passage of endoscopic instruments or access sheaths. We assessed the efficacy and complications associated with ureteral balloon dilation. We retrospectively reviewed the records at 2 institutions from 2000 to 2012 to identify patients who underwent ureteral balloon dilation during ureteroscopic treatment of upper tract stones. An 18Fr balloon dilator was used in all cases. Patients with documented ureteral stricture, radiation therapy or urothelial cancer were excluded from analysis. Primary outcomes were the stone-free rate, operative complications, balloon dilation failure and the postoperative ureteral stricture rate. Complications were divided into intraoperative and postoperative groups according to the Satava and Clavien-Dindo classifications, respectively. A total of 151 patients fulfilled study criteria. Median followup was 12 months. The stone-free rate was 72% and median time to first postoperative imaging was 2.8 months. Balloon dilation failed in only 8 patients (5%). Eight intraoperative ureteral perforations (5%) were identified, which were managed by a ureteral stent in 7 patients and a percutaneous tube in 1. Endoscopic re-treatment was required in 4 patients with Satava 2b postoperative complications. The postoperative complication rate was 8% (11 cases). A single ureteral stricture was attributable to balloon dilation. In this contemporary review balloon dilation of the ureter before endoscopic treatment of stone disease was associated with a high success rate and few complications. Ureteral balloon dilation may decrease the need for a secondary procedure in patients undergoing ureteroscopy to manage proximal ureteral and intrarenal stones.

What is the incidence of kidney stones after chemotherapy in patients with lymphoproliferative or myeloproliferative disorders?

This study describes the incidence and risk factors of de novo nephrolithiasis among patients with lymphoproliferative or myeloproliferative diseases who have undergone chemotherapy. From 2001 to 2011, patients with lymphoproliferative or myeloproliferative disorders treated with chemotherapy were retrospectively identified. The incidence of image proven nephrolithiasis after chemotherapy was determined. Demographic and clinical variables were recorded. Patients with a history of nephrolithiasis prior to chemotherapy were excluded. The primary outcome was incidence of nephrolithiasis, and secondary outcomes were risk factors predictive of de novo stone. Comparative statistics were used to compare demographic and disease specific variables for patients who developed de novo stones versus those who did not. A total of 1,316 patients were identified and the incidence of de novo nephrolithiasis was 5.5% (72/1316; symptomatic stones 1.8% 24/1316). Among patients with nephrolithiasis, 72.2% had lymphoproliferative disorders, 27.8% had myeloproliferative disorders, and 25% utilized allopurinol. The median urinary pH was 5.5, and the mean serum uric acid, calcium, potassium and phosphorus levels were 7.5, 9.6, 4.3, and 3.8 mg/dL, respectively. In univariate analysis, mean uric acid (p=0.013), calcium (p<0.001)), and potassium (p=0.039) levels were higher in stone formers. Diabetes mellitus (p<0.001), hypertension (p=0.003), and hyperlipidemia (p<0.001) were more common in stone formers. In multivariate analysis, diabetes mellitus, hyperuricemia, and hypercalcemia predicted stone. We report the incidence of de novo nephrolithiasis in patients who have undergone chemotherapy. Diabetes mellitus, hyperuricemia, and hypercalcemia are patient-specific risk factors that increase the odds of developing an upper tract stone following chemotherapy.

Estimating the Nationwide, Hospital Based Economic Impact of Pediatric Urolithiasis

The incidence of urolithiasis is increasing in children and adolescents but the economic impact of this problem is unclear. We examined 2 large databases to estimate the nationwide economic impact of pediatric urolithiasis. We analyzed the 2009 NEDS and KID, used ICD-9-CM codes to identify children 18 years or younger diagnosed with urolithiasis and abstracted demographic and charge data from each database. We identified 7,348 weighted inpatient discharges in KID and 33,038 emergency department weighted encounters in NEDS. Of the patients 32% and 36% were male, respectively. Inpatients were younger than those who presented to the ED (mean age 13.9 vs 15.7 years). Most patients had private insurance (52.9% to 57.2%) and the South was the most common geographic region (39.5% to 44.4%). The most common procedures were ureteral stent placement in 20.4% to 24.1% of cases, followed by ureteroscopy in 3.8% to 4.4%. Median charges per admission were $13,922 for a weighted total of $229 million per year. Median emergency department charges were $3,991 per encounter for a weighted total of $146 million per year. Each day in 2009 in the United States an estimated 20 children were hospitalized and 91 were treated in the emergency department for upper tract stones. A conservative estimate of 2009 annual charges related to pediatric urolithiasis in the United States is at least $375 million. This is likely a significant underestimate of the true economic burden of pediatric urolithiasis because it accounts for neither outpatient management nor indirect costs such as caregiver time away from work.

Contemporary Surgical Trends in the Management of Upper Tract Calculi

Upper tract nephrolithiasis is a common surgical condition that is treated with multiple surgical techniques, including shock wave lithotripsy, ureteroscopy and percutaneous nephrolithotomy. We analyzed case logs submitted to the ABU by candidates for initial certification and recertification to help elucidate the trends in management of upper tract urinary calculi. Annualized case logs from 2003 to 2012 were analyzed. We used logistic regression models to assess how surgeon specific attributes affected the way that upper tract stones were treated. Cases were identified by the CPT code of the corresponding procedure. A total of 6,620 urologists in 3 certification groups recorded case logs, including 2,275 for initial certification, 2,381 for first recertification and 1,964 for second recertification. A total of 441,162 procedures were logged, of which 54.2% were ureteroscopy, 41.3% were shock wave lithotripsy and 4.5% were percutaneous nephrolithotomy. From 2003 to 2013 there was an increase in ureteroscopy from 40.9% to 59.6% and a corresponding decrease in shock wave lithotripsy from 54% to 36.3%. For new urologists ureteroscopy increased from 47.6% to 70.9% of all stones cases logged and for senior clinicians ureteroscopy increased from 40% to 55%. Endourologists performed a significantly higher proportion of percutaneous nephrolithotomies than nonendourologists (10.6% vs 3.69%, p <0.0001) and a significantly smaller proportion of shock wave lithotripsies (34.2% vs 42.2%, p = 0.001). Junior and senior clinicians showed a dramatic adoption of endoscopic techniques. Treatment of upper tract calculi is an evolving field and provider specific attributes affect how these stones are treated.

Underuse of 24-Hour Urine Collection Among Children With Incident Urinary Stones: A Quality-of-care Concern?

To determine the prevalence of 24-hour urine collection among first-time pediatric stone formers and investigate factors associated with its use. Using data from the MarketScan Commercial Claims and Encounters Database (2002-2006), children presenting to the emergency department with an incident episode of upper urinary tract stone disease were identified through a diagnosis code-based algorithm. The number of patients performing a 24-hour urine collection within 6months of this encounter was calculated. Temporal trends in the prevalence of use were assessed. We fitted multivariate logistic regression models to examine factors associated with testing. In total, 1848 children presented with an incident upper tract stone, of which 12.0% submitted a 24-hour urine collection. This percentage remained stable over the study period. Testing was more common among younger patients (P<.001) and those who visited urologists (P<.001) or nephrologists (P<.001). The odds of testing were nearly 4-fold or 7-fold higher if the patient saw a urologist (odds ratio, 3.99; 95% confidence interval, 2.83-5.62) or a nephrologist (odds ratio, 7.00; 95% confidence interval, 3.95-12.41), respectively. Despite rates of stone recurrence, 24-hour urine collection appears to be underused among children. Efforts to increase its use are therefore likely to benefit pediatric patients with urinary stone disease.

MP73-16 CHARACTERIZING UROLITHIASIS IN PATIENTS WITH URINARY DIVERSION

You have accessJournal of UrologyStone Disease: Evaluation III1 Apr 2014MP73-16 CHARACTERIZING UROLITHIASIS IN PATIENTS WITH URINARY DIVERSION Evan Carlos, Humberto Martinez-Suarez, Adam Kadlec, and Thomas Turk Evan CarlosEvan Carlos More articles by this author , Humberto Martinez-SuarezHumberto Martinez-Suarez More articles by this author , Adam KadlecAdam Kadlec More articles by this author , and Thomas TurkThomas Turk More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2014.02.2369AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Urinary diversion itself is a risk factor for urolithiasis. This study describes a cohort of patients with urinary diversion and upper tract urolithiasis and secondarily compares that cohort to a group of patients with urinary diversion without stones. METHODS A database of 620 patients undergoing urinary diversion over an 11-year period (2003-2013) at a single institution was reviewed for stone formers. The subjects were divided into three diversion groups: ileal conduit (IC), neobladder (NB) and continent cutaneous pouch (CCP). Those with stones prior to diversion were excluded. The stone formers were matched 2:1 for age at diversion and gender to yield a control group. Date of stone formation was determined by the first postoperative imaging study indicating stone presence. Key outcomes were time to stone formation and stone composition. RESULTS At a median follow up period of 3.1 years, 28 patients (4.5% of total) had formed a stone; 20 (3.2% of total) had upper tract stones alone. Median follow up for all stone formers was 5.3 years and 1.4 years for controls. NBs had the time to stone formation at 1.31 years (p=0.021) when compared to IC’s 5.51 and CCP’s 8.10 years. A negative correlation was found between time to stone formation and pre-op serum glucose >140 mg/dl (R=-0.557, p=0.003). A positive correlation was noted between patients’ BUN >20 mg/dl and time to stone formation (R=0.395, p=0.041). Age at diversion had a negative correlation with time to stone formation, (R= -0.579; p=0.001). Stone analysis demonstrated no significant difference in primary stone composition among the three diversion groups, although calcium phosphate carbonate stones occurred more in CCPs. CONCLUSIONS A sizeable number of patients form stones after urinary diversion in relatively short-term follow-up. This study suggests that patients with neobladder diversion may form stones sooner than other diversion types. The distribution of stone compositions is similar across diversion types. Pre-operative BUN<20, serum glucose >140, and advanced patient age at time of diversion may be risk factors for upper tract stone formation. © 2014FiguresReferencesRelatedDetails Volume 191Issue 4SApril 2014Page: e871 Advertisement Copyright & Permissions© 2014MetricsAuthor Information Evan Carlos More articles by this author Humberto Martinez-Suarez More articles by this author Adam Kadlec More articles by this author Thomas Turk More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...

Kids with stones—data on causes and treatment safety

Two retrospective studies published recently in The Journal of Urology add to the body of evidence on paediatric upper-tract stone disease. The first study shows that obesity is not a significant risk factor for urolithiasis in children, whereas the second confirms the use of percutaneous nephrolithotomy (PCNL) as a safe and effective treatment modality.

High Recurrence Rate at 5-Year Followup in Children after Upper Urinary Tract Stone Surgery

Pediatric urolithiasis has been treated with shock wave lithotripsy, ureteroscopy and percutaneous nephrolithotomy with high success rates during short-term followup. We studied our success rate and modifiable risk factors in patients with at least 5 years of followup postoperatively. Retrospective chart review was performed for patients younger than 18 years who underwent upper tract stone surgery between 1999 and 2007, were stone-free afterward and had at least 5 years of followup. Recurrence rate, and anatomical and metabolic abnormalities were assessed. Of 60 eligible children 30 (33 kidneys) had at least 5 years of followup. Average patient age at surgery was 10 years, 17 patients were female and 20 kidneys had anatomical abnormalities. Overall recurrence rate at 5 years was 55% (95% CI 38%-70%). Ureteral stones had a lower recurrence rate than renal stones (5 of 19 and 13 of 14, respectively, p <0.001). Patients with abnormal anatomy had a 65% (95% CI 43%-82%) chance of recurrence within 5 years vs 38% (95% CI 18%-65%) in those with normal anatomy (p = 0.17). Of the 18 recurrences 10 required a second operation, 7 demonstrated abnormal anatomy and 14 involved calcium based stones. A 24-hour urine test in 13 children revealed 10 with hypercalciuria and 11 with hypocitraturia, with 9 patients exhibiting both conditions. We found a high recurrence rate in children with stones requiring surgical intervention, particularly those with abnormal anatomy. This finding should be confirmed in a larger multicenter study of recurrence rates. In the meantime our results suggest a need for aggressive diagnosis and treatment of metabolic abnormalities.

Outcomes of intracorporeal lithotripsy of upper tract stones is not affected by BMI and skin-to-stone distance (SSD) in obese and morbid patients

The purpose of this study is to determine if body mass index (BMI) and stone skin distance (SSD) affect stone free rate (SFR) in obese and morbid obese patients who underwent flexible URS for proximal ureteral or renal stones < 20 mm. A retrospective chart review was performed of consecutive patients that underwent flexible URS. Inclusion criteria were: proximal ureteral stones and renal stones less than 20 mm in the preoperative computed tomography (CT). SFR were then compared according to SSD and BMI. A total of 153 patients were eligible for this analysis, 49 (32.02%) with SSD < 10 cm and 104 (67.97%) with SSD ≥ 10 cm. The mean stone size was 10.5 ± 6.4 mm. The overall SFR in our study was 82.4%. The SFR for the SSD < 10 and ≥ 10 were 79.6% and 83.7% respectively (p = 0.698) and for BMI < 30, ≥ 30 and < 40 and ≥ 40 were 82.9%, 81.7% and 90.9% respectively. Regression analysis showed no affect between BMI or SSD regarding SFR. Ureteroscopy should be considered as a first-line of treatment for renal/proximal stones in obese and morbid obese patients. URS may be preferable to SWL in obese patients independently of the SSD, BMI or the location of proximal stones.

Development of upper tract stones in patients with congenital neurogenic bladder

ObjectivePatients with neurogenic bladder are at increased risk of developing upper tract stones. We hypothesized that patients with lower urinary tract stone disease are at greater risk of developing upper tract stones. MethodsWe performed a 10-year retrospective case–control study of patients with neurogenic bladder to determine the association between bladder and upper tract stones. Independent risk factors for upper tract stones were assessed. Cases and controls were matched 1:1. Univariable analysis was performed by Fisher's exact test and the Mann–Whitney U test. Multivariable logistic regression was performed. Results52 cases and controls were identified. Cases were significantly more likely to be non-ambulatory, have bowel–urinary tract interposition, thoracic level dysraphism, and history of bladder stones. On multivariable analysis, independent predictors of stone formation were male sex (OR 2.82; p = 0.02), dysraphism involving the thoracic spine (OR 3.37; p = 0.014) bowel–urinary tract interposition (OR 2.611; p = 0.038), and a history of bladder stones (OR 3.57; p = 0.015). ConclusionPatients with neurogenic bladder are at increased risk for upper tract stones. The presence of bladder stones may herald the development of upper tract stones. The predictors of stone disease identified should guide prospective studies to better understand the natural history of upper tract stone development in this population.

Urolithiasis in adult spina bifida patients: study in 260 patients and discussion of the literature

To describe incidence and risk factors of urinary tract stones in adult spina bifida (SB) patients. Although spina bifida patients have an allegedly higher risk of urinary tract stones, only two small non-English case series are available and do not provide adequate epidemiological data and analyses on risk factors. A total of 260 adult SB patients followed in our centre for 10 years were retrospectively analysed for stone disease. Both a univariate analysis (Fisher's exact, two-sided Student's t test) and a binary logistic regression analysis were performed to identify independent risk factors for stone disease. Of the 260 patients, 24 (9.2 %) were identified with a history of urolithiasis. Fourteen patients (5.4 %) had bladder stones in 26 episodes. Sixteen patients (6.2 %) had upper urinary tract stones: 14 kidney stones and two ureteral stones. Lifetime incidence of both bladder stones and upper tract stones was 2.25 per 1,000 patient-years. Recurrent urinary tract infections (OR 4.34, p = 0.013) and incorporation of bowel tissue into a continent reservoir (including enterocystoplasty) (OR 4.80, p = 0.012) were independent risk factors for bladder stone disease in a multivariate model. An indwelling catheter was an independent predictor for upper tract stones (OR 5.89, p = 0.02). Urolithiasis, especially in the bladder, is a frequent finding in patients with SB. Bladder stones occur about 10 times more often in SB patients than in the population. In patients without risk factors, frequent ultrasound of the urinary tract is not necessary for the sole detection of stones.

The surgical management of upper tract stone disease among spinal cord-injured patients

Retrospective cohort study, using linked, population-based health-care data. To describe the incidence, management and outcomes of surgically treated kidney stones after spinal cord injury (SCI). To evaluate the impact of a past history of kidney stones on the occurrence of kidney stones. Ontario, Canada. A total of 5121 patients were followed a median of 4 years after an incident SCI (occurring between 2002 and 2011). The primary outcome was surgical intervention for upper tract kidney stones. In follow-up, 66 patients (1.3%) had 89 episodes of surgically treated kidney stones. Treatments included: ureteroscopic lithotripsy (34%), ureteral stent/percutaneous nephrostomy (30%), shockwave lithotripsy (19%) or percutaneous nephrolithotripsy (17%). Following stone treatment, the 30-day mortality rate was low, and the 30-day admission rate to an intensive care unit was 12%. A history of surgically treated kidney stones before SCI (compared with no such history) was associated with a higher risk of kidney stones after SCI (27 vs 3 per 1000 person-years; adjusted hazard ratio 14.74, 95% confidence interval 5.69-38.22). During intermediate follow-up after SCI, surgically treated upper tract kidney stones occur in 1.3% of patients. Ureteroscopy with lithotripsy is the most common treatment. A history of surgically managed kidney stones before SCI portends a higher risk of stones after SCI.

Evaluation of acute renal colic: a comparison of non-contrast CT versus 3-T non-contrast HASTE MR urography

With the introduction of a 3-T scanner, magnetic resonance urography (MRU) may be an alternative imaging modality for evaluation of acute renal colic. We performed a prospective study to compare the performance of computed tomography (CT) with half-Fourier single shot turbo spin-echo (HASTE) MRU in the evaluation of patients with suspected renal colic. Patients presenting to the emergency department with acute renal colic were eligible for inclusion. Following a standard CT stone evaluation, patients underwent a non-contrast HASTE MRU study with a 3-T scanner. The presence of perinephric fluid, hydronephrosis, ureteral obstruction, and calculus was assessed. A total of 22 patients completed the study. Twenty (91%) were diagnosed with an upper tract stone by radiographic findings. MRU detected a discrete stone in 50% of the patients with stones detected by CT. Perinephric fluid was noted in 12 MRUs, compared to 7 CTs. Using CT as the reference standard, the combination of stone or perinephric fluid and ureteral dilation gave MRU a sensitivity of 84%, specificity of 100%, and accuracy of 86% (95% CI 0.72-1.0). HASTE MRU with a 3-T MR scanner can reliably detect the presence of upper urinary tract obstruction. Although CT imaging remains the superior modality with which to detect calculi, MRU detects a greater number of secondary signs of upper tract obstruction. For situations in which the use of ionizing radiation is undesirable, MRU is a reasonable imaging alternative.

Residual Fragments Following Ureteroscopic Lithotripsy: Incidence and Predictors on Postoperative Computerized Tomography

Residual fragments following ureteroscopy for calculi may contribute to stone growth, symptoms or additional interventions. We reviewed our experience with ureteroscopy for calculus disease to define the incidence and establish factors predictive of residual fragments. Records associated with 667 consecutive ureteroscopic lithotripsy procedures for upper urinary calculi were reviewed. In 265 procedures (40%) computerized tomography was done between 30 and 90 days postoperatively. They comprised the study group. Residual fragments were defined as any residual ipsilateral stone greater than 2 mm. Included in the study were 121 men and 127 women with a mean age of 47 years. Mean target stone diameter was 7.6 mm. The stone location was the kidney in 30% of cases, ureter in 50%, and kidney and ureter in 20%. Residual fragments were detected on computerized tomography after 101 of 265 procedures (38%). Pretreatment stone size was associated with residual fragments at a rate of 24%, 40% and 58% for stones 5 or less, 6 to 10 and greater than 10 mm, respectively (p <0.001). Additionally, stone location in the kidney (p <0.001) or the kidney and ureter (p = 0.044), multiple calculi (p = 0.003), longer operative time (p = 0.008) and exclusive use of flexible ureteroscopy (p = 0.029) were associated with residual fragments. In a multivariate model only pretreatment stone diameter greater than 5 mm was independently associated with residual fragments after ureteroscopy (diameter 6 to 10 and greater than 10 mm OR 2.03, p = 0.03 and OR 3.74, p = 0.003, respectively). Of patients who underwent ureteroscopic lithotripsy for calculi 38% had residual fragments by computerized tomography criteria, including more than 50% with stones 1 cm or greater. Such data may guide expectations regarding the success of ureteroscopy in attaining stone-free status.

Bladder Neck Closure in Conjunction with Enterocystoplasty and Mitrofanoff Diversion for Complex Incontinence: Closing the Door for Good

Bladder neck closure is an irreversible procedure requiring compliance with catheterization of a cutaneous stoma and historically has been reserved for the definitive treatment of intractable incontinence after prior failed procedures. We assessed long-term outcomes of our patients undergoing bladder neck closure including continence status, additional surgical interventions, postoperative complications, conception and sexual function, and satisfaction with bladder neck closure. We performed a retrospective review of all patients who underwent bladder neck closure between 1990 and 2010 at our institution. A total of 28 consecutive patients (exstrophy 15 and neurogenic bladder 13 [myelomeningocele 4, cloacal anomaly 4, spinal cord injury 2, VACTERL (Vertebral Anorectal Cardiac Tracheo-Esophageal Radial Renal Limb) 1, sacral agenesis 1 and urogenital sinus 1]) were identified. Of these patients 19 (68%) had undergone 20 unsuccessful bladder neck procedures before bladder neck closure. Bladder neck closure was initially successful in 27 of the 28 (96.4%) patients. One patient required subsequent closure of a postoperative vesicovaginal fistula. Median time from bladder neck closure was 69 months (range 16 to 250). In 11 patients 16 additional procedures were required, including stomal injection of bulking agents (2), stomal revision for stenosis (2) or prolapse (1), percutaneous nephrolithotripsy for stone (1), open cystolithotomy (2), extracorporeal shock wave lithotripsy for upper tract stones (4), repair of augment rupture (3) and open retrograde ureteral stenting for stone (1). The total surgical re-intervention rate was 39.3% (11 of 28). There were no observed cases of progressive or de novo hydronephrosis. Bladder neck closure in conjunction with enterocystoplasty and Mitrofanoff diversion is an effective means of achieving continence in complex cases as a primary or secondary therapy. Long-term urological followup into adulthood is essential.

Determining a Performance Envelope for Capture of Kidney Stones Functionalized with Superparamagnetic Microparticles

Complete stone removal is important in upper tract stone surgery. Unfortunately, even with the latest technologic advances, current methods only achieve 50% to 80% complete clearance of upper tract stones at the time of primary treatment. Our group has explored the novel use of peptide-coated iron oxide superparamagnetic microparticles that bind to calcium stones, allowing for extraction of these stones with magnetic tools. We present analytic and numeric models that characterize stone attraction performance for feasible magnetic tool sizes and stone magnetization levels. Magnetostatics equations are applied to a simplified, one-dimensional scenario of a spherical target coated with a variable amount of superparamagnetic particles, placed under the influence of a magnetic field aimed at vertical attraction (capture) of the target. Equations are parameterized in terms of (a) target size, ranging from 0.5 mm to 3 mm to represent stone sizes of interest, (b) effective magnetization per surface area delivered by the particle binding chemistry, and (c) distance to the field source. Target capture is predicted to be effective in the low, single-digit millimeter distance range, favoring smaller stones and then up to a practical upper limit of 3 mm diameter. Higher iron loading chemistries have a direct improvement in magnetic force and therefore increase the viability of the technique, albeit along an asymptotic trendline. We are able to characterize the potential for kidney stone capture via magnetic attraction. Computer-developed models show good correlation with experimental results using actual magnetized stone samples. Future research efforts can use the proposed techniques to estimate the performance impact of advanced magnetic tools and surface chemistries.

In Vitro Comparison of Prototype Magnetic Tool with Conventional Nitinol Basket for Ureteroscopic Retrieval of Stone Fragments Rendered Paramagnetic with Iron Oxide Microparticles

We developed a prototype magnetic tool for ureteroscopic extraction of magnetized stone particles. We compared its efficiency for retrieving magnetized calcium oxalate monohydrate stone particles with that of a conventional nitinol basket from the pelvi-collecting system of a bench top ureteroscopic simulator. Iron oxide microparticles were successfully bound to 1 to 1.5, 1.5 to 2 and 2 to 2.5 mm human calcium oxalate monohydrate stones. Several coated fragments of each size were implanted in the collecting system of a bench top ureteroscopic simulator. Five-minute timed stone extraction trials were performed for each fragment size using a back loaded 8Fr magnetic tool mounted on a 0.038-inch guidewire or a conventional basket. The median number of fragments retrieved per timed trial was compared for the magnetic tool vs the basket using the Mann-Whitney U test. For 1 to 1.5 mm fragments the median number retrieved within 5 minutes was significantly higher for the prototype magnetic tool than for the nitinol basket (9.5 vs 3.5, p = 0.03). For 1.5 to 2 mm fragments the magnetic tool was more efficient but the difference in the number of fragments retrieved was not statistically significant (9.5 vs 4.5, p = 0.19). For 2 to 2.5 mm fragments there was no difference between the instruments in the number retrieved (6 per group, p = 1.0). The prototype magnetic tool improved the efficiency of retrieving stone particles rendered paramagnetic that were less than 2 mm but showed no advantage for larger fragments. This system has the potential to decrease the number of small retained fragments after ureteroscopic lithotripsy.

Renal Stone Disease in Spinal-Cord–Injured Patients

Renal stone disease is common among patients with spinal cord injury (SCI). They frequently have recurrent stones, staghorn calculi, and bilateral stone disease. The potential risk factors for stones in the SCI population are lesion level, bladder management strategy, specific metabolic changes, and frequent urinary tract infections. There has been a reduction in struvite stones among these patients, likely as a result of advances in their urologic care. The clinical presentation of stone disease in patients with SCI may involve frequent urinary infections or urosepsis, and at the time of presentation patients may need emergency renal drainage. The proportion of patients who have their stones treated with different modalities is largely unknown. Shockwave lithotripsy (SWL) is commonly used to manage stones in patients with SCI, and there have been reports of stone-free rates of 50% to 70%. The literature suggests that the morbidity associated with percutaneous nephrolithotomy in these patients is considerable. Ureteroscopy is a common modality used in the general population to treat patients with upper tract stone disease. Traditional limitations of this procedure in patients with SCI have likely been overcome with new flexible scopes; however, the medical literature has not specifically reported on its use among patients with SCI.