Carly Kriedberg

Durability of the Next-generation Flexible Fiberoptic Ureteroscopes: A Randomized Prospective Multi-institutional Clinical Trial

OBJECTIVES To evaluate the durability of 4 next-generation flexible ureteroscopes in a randomized, multi-institutional, prospective study. METHODS Patients at 3 institutions were randomized to 1 of 4 flexible ureteroscopes: the Wolf Viper, Olympus URF-P5, Gyrus-ACMI DUR-8 Elite (DUR-8E), and Stryker FlexVision U-500. Each center used 1 scope from each manufacturer until it needed major repair (primary endpoint). Intraoperative data included total time of use, number of scope insertions through an access sheath, working time in the lower pole, number of insertions and total time for accessory instrumentation in the working channel, number of laser insertions through the working channel, and total laser energy used. RESULTS A total of 175 patients were randomized. The DUR-8E experienced early catastrophic failure (< or = 10 cases) at all 3 sites; however, this also occurred at 1 site each for the Stryker and Wolf scopes. The DUR-8E required major repair after the fewest average number of cases (5.3), the lowest average total time of usage (108 minutes), the fewest insertions through an access sheath (20.3), the shortest duration of laser firing (31.3 minutes), and the shortest instrument in the working channel time (224.7 minutes). As such, due to variation in durability within manufacturers, no differences could be demonstrated. Visibility ratings for the Wolf iper were significantly better than the DUR-8E (P = .034) and the Flexvision (P = .038). CONCLUSIONS The Wolf Viper, Olympus URF-P5, and Stryker Flexvision U-500 flexible ureteroscopes seem comparable with regard to durability. However, larger prospective registry-based studies are needed to document significant differences between them.

Roux-en-Y Gastric Bypass is Associated with Early Increased Risk Factors for Development of Calcium Oxalate Nephrolithiasis

BACKGROUND Patients treated for obesity with jejunoileal bypass (JIB) experienced a marked increased risk of hyperoxaluria, nephrolithiasis, and oxalate nephropathy developing. Jejunoileal bypass has been abandoned and replaced with other options, including Roux-en-Y gastric bypass (RYGB). Changes in urinary lithogenic risk factors after RYGB are currently unknown. Our purpose was to determine whether RYGB is associated with elevated risk of developing calcium oxalate stone formation through increased urinary oxalate excretion and relative supersaturation of calcium oxalate. STUDY DESIGN A prospective longitudinal cohort study of 24 morbidly obese adults (9 men and 15 women) recruited from a university-based bariatric surgery clinic scheduled to undergo RYGB between December 2005 and April 2007. Patients provided 24-hour urine collections for analysis 7 days before and 90 days after operation. Primary outcomes were changes in 24-hour urinary oxalate excretion and relative supersaturation of calcium oxalate from baseline to 3 months post-RYGB. RESULTS Compared with their baseline, patients undergoing RYGB had increased urinary oxalate excretion (31 +/- 10 mg/d versus 41 +/- 18 mg/d; p = 0.026) and relative supersaturation of calcium oxalate (1.73 +/- 0.81 versus 3.47 +/- 2.59; p = 0.030) 3 months post-RYGB in six patients (25%). De novo hyperoxaluria developed. There were no preoperative patient characteristics predictive of development of de novo hyperoxaluria or the magnitude of change of daily oxalate excretion. CONCLUSIONS This prospective study indicates that RYGB is associated with an earlier increase in urinary oxalate excretion and relative supersaturation of calcium oxalate than previously reported. Additional studies are needed to determine longterm post-RYGB changes in urinary oxalate excretion and identify patients that might be at risk for hyperoxaluria developing.

Hyperoxaluria Is a Long-Term Consequence of Roux-en-Y Gastric Bypass: A 2-Year Prospective Longitudinal Study

BACKGROUND Recent studies suggest that patients undergoing Roux-en-Y gastric bypass (RYGB) for morbid obesity are at risk for hyperoxaluria, nephrolithiasis, and oxalate nephropathy. Our objective was to conduct a long-term prospective longitudinal study to establish the incidence, clinical progression, and severity of hyperoxaluria after RYGB. STUDY DESIGN Patients undergoing RYGB between December 2005 and April 2007 provided 24-hour urine collections for comprehensive stone risk analysis 1 week before and 3 months and 1 and 2 years after surgery. Primary outcomes were changes in 24-hour urinary oxalate excretion and relative supersaturation of calcium oxalate from baseline to 2 years post-RYGB. RESULTS The cohort consisted of 21 patients, including 5 (24%) men and 16 (76%) women. Mean preoperative age and body mass index (calculated as kg/m(2)) were 48.2 +/- 10.5 years (range 25 to 64 years) and 50.5 +/- 9.1 (range 39.7 to 66.6), respectively. Urinary oxalate excretion increased significantly after RYGB (33 +/- 9 mg/day versus 63 +/- 29 mg/day; p <or= 0.001). De novo hyperoxaluria developed in 11 (52%) patients. Increasing age at the time of surgery was predictive of de novo hyperoxaluria developing (odds ratio = 1.162; 95% CI, 1.002-1.347; p = 0.046). The percentage of patients with hypocitraturia increased from 10% at baseline to 48% at 2 years. The relative supersaturation of calcium oxalate was unchanged (1.73 +/- 0.67 versus 2.20 +/- 2.07; p = 0.27). CONCLUSIONS RYGB is associated with a long-term increase in urinary oxalate excretion and decrease in urinary citrate excretion. Although calcium oxalate relative supersaturation increases early in the postoperative period, this returns to baseline with long-term follow-up. These data suggest that patients who have undergone RYGB are at risk for oxalate nephropathy developing.

Lithogenic Risk Factors in the Morbidly Obese Population

PURPOSE To our knowledge baseline lithogenic risk factors in the morbidly obese population are currently unknown. Prior studies evaluated known stone formers and correlated risk with increasing body mass index. We describe risk factors for urinary stone formation in a group of unselected morbidly obese patients. MATERIALS AND METHODS Patients scheduled for gastric bypass provided a 24-hour urine collection before surgery. Patient demographics, medications and supplement consumption were recorded. A dietary intake diary was converted into daily kcal, Ca, Na and protein consumption. Differences between groups based on gender, history of diabetes or nephrolithiasis, diuretic use and Ca supplementation were evaluated. Correlation of stone risk parameters with body mass index was evaluated. RESULTS A total of 45 patients provided samples for analysis. Mean +/- SD body mass index was 49.5 +/- 9.1 kg/m(2) and mean age was 47.0 +/- 10.5 years. Overall 97.8% of patients had at least 1 lithogenic risk factor identified. Low urinary volume was the most common abnormality, affecting 71.1% of patients. Male patients excreted significantly more Ox (p = 0.0014), Na (p = 0.020), PO(4) (p = 0.0083) and SO(4) (p = 0.0014) than females. Patients with a history of nephrolithiasis excreted significantly more oxalate (p = 0.018) and had higher relative Na urate supersaturation (p = 0.00093) than nonstone formers. Hydrochlorothiazide use was associated with significantly increased Na urate relative supersaturation (p = 0.0097). Increasing body mass index was inversely associated with Mg (r = -0.38, p = 0.01) and brushite (r = -0.30, p = 0.04). CONCLUSIONS Of our cohort of morbidly obese patients 98% had at least 1 lithogenic risk factor identified on 24-hour urine collection. This study identified a high urinary stone risk in the morbidly obese and suggests possible avenues for dietary and/or pharmacological preventive measures. Future studies will determine how bariatric surgery alters these risk factors.

Pyridoxine and Dietary Counseling for the Management of Idiopathic Hyperoxaluria in Stone-forming Patients

OBJECTIVES To examine the effects of dietary manipulation and pyridoxine medical management for idiopathic hyperoxaluria in patients with nephrolithiasis. METHODS A retrospective longitudinal study of the patients treated in our stone clinics from July 2007 to February 2009 was performed. All patients were evaluated with pre- and postintervention 24-hour urine collection and met a registered dietician. Recommendations to keep urine volume above 2 L per day, sodium restriction, protein moderation, increased calcium intake with meals and low oxalate diet combined with oral pyridoxine were given. Initial dosage ranged from 50 to 100 mg per day depending on the baseline oxalate level, and was titrated to a maximum of 200 mg daily. Subjects with at least two 24-hour urine collections were included in the study. RESULTS Of 314 patients with complete metabolic and urinary profile evaluation, 95 subjects were identified with idiopathic hyperoxaluria. Mean follow-up was 18.4 ± 14.8 months and mean age was 50.3 ± 12.8 years. In patients treated with the combination of dietary counseling and pyridoxine, there was a significant change in urinary parameters in 75% of patients with a significant decrease in urinary oxalate excretion (58.26 ± 27.05 to 40.61 ± 15.04, P < .0001). In all, 39% of the patients had a decrease from a high urine oxalate levels (>40 mg/d) to a normal range urine oxalate (55.30 ± 22.04 to 33.45 ± 3.93, P = .0004). No peripheral neuropathy was reported. CONCLUSIONS Dietary management and medical treatment using pyridoxine may be an effective first-line therapy to decrease hyperoxaluria in patients who form stones.

Celecoxib in the Management of Acute Renal Colic: A Randomized Controlled Clinical Trial

OBJECTIVES To evaluate the efficacy of celecoxib as an analgesic and medical expulsive agent in acute renal colic. METHODS A prospective randomized double-blind study was conducted on patients presenting with an obstructing ureteral calculus < 10 mm in largest diameter. Patients were randomized to 400 mg of celecoxib, followed by 200 mg every 12 hours for 10 days, or to placebo. Patients with a solitary kidney, renal insufficiency (CR > 1.8), urinary tract infection, or significant cardiovascular disease were excluded. RESULTS A total of 57 patients provided consent of which 53 completed the study. Four patients were excluded from the analysis because of stone passage or withdrawal of consent before the first dose of study medication. No significant difference was noted in the spontaneous stone passage rate (celecoxib 55.2%, placebo 54.2%) and between celecoxib and placebo with regard to days to stone passage (7.0 vs 9.0, P = .6) or size of stone passed (3.9 vs 4.6 mm, P = .18). No significant difference was noted in pain analog scores (2.6 vs 3.5, P = .71) or narcotic doses (13.2 vs 13.6, P = .74). Furthermore, a 25% decrease in narcotic use (or 19 mg based on placebo mean) was outside the 80% one-sided confidence interval for the change in mean narcotic use between the 2 groups. Thus, it is unlikely (< 20%) that we missed a clinically significant beneficial effect of celecoxib on narcotic consumption because of sample size. CONCLUSIONS Celecoxib does not facilitate stone passage or decrease narcotic requirements in patients with acute renal colic.

Correlation between stress and kidney stone disease.

BACKGROUND AND PURPOSE Prevalence of kidney stone disease is increasing worldwide, and several factors may be involved. We aimed to establish a correlation between stress and kidney stones. PATIENTS AND METHODS We prospectively evaluated 200 patients with a diagnosis of kidney stone disease having them self-respond to a validated questionnaire to measure stress (Perceived Stress Scale-10 [PSS-10]). Stone-related characteristics and potential stressing factors were assessed. Variables that were significant on the univariate analysis were used to construct a model that was able to explain the variability in PSS-10 score in our patients. RESULTS Mean PSS-10 score was 15.3 ± 1.1. Female sex (P=0.014), occurrence of death or serious illness of a family member or close friend within the last 6 months of the interview (P=0.044), occurrence of other psychological trauma (P<0.0001) all proved to be significant factors. Stone-related aspects associated with stress were presence of symptoms at the time of the interview (P=0.012) and passage of two or more stones per year (P=0.022). We were able to construct a model that explains 34% of the variability of the PSS-10 between subjects. Employment status was the only significant variable, but sex, age, and presence of symptoms at the time of questionnaire administration had to be kept in to achieve a model that explains the largest variability. CONCLUSIONS Passage of two or more stones per year and presence of symptoms proved to be factors related to elevated stress in patients with a diagnosis of kidney stone disease. Female sex, age, and unemployment may also contribute to a stressed state in this population.