Identifying risk factors for development of nephrolithiasis in end-stage renal disease patients.

INTRODUCTION: We sought to assess the incidence and risk factors for stone development in patients with end-stage renal disease (ESRD) on hemodialysis (HD). METHODS: Medical records of patients receiving HD between 2007 and 2017 were retrospectively reviewed. Patients who had been on HD for at least three months and had imaging studies (computed tomography [CT] scans or ultrasound [US]) pre- and post-initiation of HD were included. Exclusion criterion was presence of stones pre-HD. De novo stones were defined as renal stones found on followup imaging. Demographics, laboratory data, comorbidities, and dialysis characteristics were compared between non-stone-formers and stone-formers using propensity score matching. RESULTS: A total of 133 patients met the inclusion criteria. Their median age was 68.5 years, median body mass index 28.7 kg/m2, and median dialysis duration 59.5 months. After HD, 14 (10.5%) patients developed de novo stones and their median dialysis-to-stone duration was 23.5 months. When compared with non-stone-formers, stone-formers had significantly lower incidence of hypertension (48.2% vs. 14.3%; p=0.03), lower serum ionized calcium (1.16 vs. 1.07 mmol/L; p=0.01) and magnesium (0.95 vs. 0.81 mmol/L; p=0.01), and significantly higher serum uric acid (281.5 vs. 319.0 µmol/L; p=0.03). Multivariate analysis demonstrated that lower serum ionized calcium (adjusted odds ratio [OR] 0.00001; 95% confidence interval [CI] 0-0.18) and magnesium (adjusted OR 0.0003; 95% CI 0-0.59) were significantly associated with stone-formation. CONCLUSIONS: The incidence of de novo nephrolithiasis in ESRD patients on HD was 10.5%. Increased serum uric acid, decreased serum magnesium and ionized calcium, and absence of hypertension were associated with increased stone-formation in ESRD patients on HD.

Prevalence and metabolic abnormalities of vitamin D-inadequate patients presenting with urolithiasis to a tertiary stone clinic.

OBJECTIVE: To assess the prevalence and metabolic abnormalities of patients with inadequate vitamin D (VD) presenting with urolithiasis to a tertiary stone clinic in North America. MATERIAL AND METHODS: A retrospective review of consecutive patients presenting from August 2009 to January 2010 was performed. Demographic and clinical data were collected together with metabolic stone workup, including 2 24-hour urine collections and serum 25-hydroxy VD [25(OH)D]. VD inadequacy (VDI) included VD deficiency and VD insufficiency defined as 25-(OH) VD levels <20 ng/mL and 21-29 ng/mL, respectively. RESULTS: Of 101 patients, 81 (80.2%) were found to have VDI: 34 (33.7%) were deficient and 47 (46.5%) had insufficient VD. Mean age was 50.4 ± 15.8 years and the mean body mass index was 28.7 ± 5.8 kg/m(2). Forty-two percent were smokers, 51% were recurrent stone formers, and 54% had positive family history of urolithiasis. Hyperparathyroidism was detected in 25.9% of patients, of which 91% of them were secondary to VDI. Hypocalcemia and hyperuricemia were found in 36% and 11% of patients, respectively. Of 81 VDI patients, 69 (85.2%) had complete 24-hour urine collections, of which 92.7% had at least one abnormality. However, only 40% of patients with normal VD had metabolic abnormalities (P <.0001). The most prevalent pattern of urinary abnormalities in VDI patients were suboptimal volume (45%), hypocitaturia (24%), hypocalciuria (33%), hypercalciuria (20%), hyperuricosuria (16%), cystinuria (5%), and hyperoxaluria (7.2%). CONCLUSION: In this preliminary study, patients presenting with urolithiasis were found to have a high prevalence of inadequate VD associated with abnormalities on metabolic stone work-up.

Targeting individual hemodynamics to maintain renal perfusion during pneumoperitoneum in a porcine model.

BACKGROUND: Although aggressive fluid hydration prevents a decrease in renal cortical perfusion (RCP) during laparoscopic donor nephrectomy, excess fluid is deleterious. We assessed whether goal-directed fluid administration, based on hemodynamic measures, would maintain RCP during pneumoperitoneum with less fluid loading. METHODS: In a pilot study of 7 pigs, goal-directed fluid administration was guided by monitoring of stroke volume (SV) by esophageal Doppler measurement. During 15 mmHg CO(2) pneumoperitoneum, a bolus of 5 mL/kg 0.9% NaCl was given when SV decreased to 90% of baseline. Next, 18 pigs were randomized into 3 groups: low fluid (5 mL/kg per hour), high fluid (25 mL/kg per hour) and goal directed. Urine output, heart rate, mean arterial pressure, cardiac output, SV, and RCP were recorded every 15 minutes. RESULTS: Pilot data revealed mean RCP (mL/min per 100 g) was maintained (40 vs 39) during pneumoperitoneum using goal-directed therapy. In the randomized study, RCP was decreased in the low fluid group (43 vs 29; P= .02), but maintained in the high (46 vs 40) and goal-directed (42 vs 39) groups. Mean fluid administered in the goal-directed group during pneumoperitoneum was 10 mL/kg and only 3 of 6 of pigs required boluses. Urine output was decreased in all 3 groups. CONCLUSION: A goal-directed strategy during pneumoperitoneum allows for tailored fluid administration and maintains RCP with lower volumes of intravenous fluid.