Open Access

ARTICLE

Urine kidney injury markers do not increase following gastric bypass: a multi-center cross-sectional study

Bryan D. Hinck¹, Ricardo Miyaoka¹, James E. Lingeman², Dean G. Assimos³, Brian R. Matlaga⁴, Rocky Pramanik⁵, John Asplin⁵, Benjamin Cohen¹, Manoj Monga¹

1 Glickman Urologic and Kidney Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
2 Indiana Clinic Urology, Indiana University, Indianapolis, Indiana, USA
3 Department of Urology, University of Alabama, Birmingham, Alabama, USA
4 James Buchanan Brady Urological Institute, Johns Hopkins University, Baltimore, Maryland, USA
5 Litholink Corporation, Laboratory Corporation of America Holdings Chicago, Illinois, USA
Address correspondence to Dr. Manoj Monga, Glickman Urologic and Kidney Institute, 9500 Euclid Avenue, Q10-1, Cleveland, OH 44195 USA

Canadian Journal of Urology 2018, 25(1), 9199-9204.

Abstract

Introduction: This study aims to determine whether markers of kidney injury correlate with urinary oxalate excretion. If such a relationship exists, these biomarkers could serve as early predictors of oxalate nephropathy. Gastric bypass surgery for obesity is known to be associated with postoperative hyperoxaluria, which can lead to urolithiasis and renal damage.
Materials and methods: Patients were recruited from four large academic medical centers at least six months after undergoing gastric bypass surgery. Participants provided a spot urine sample for analysis of three established biomarkers of kidney injury: 8-iso-Prostaglandin F_2α, N-acetyl-β-D-glucosaminidase, and neutrophil gelatinase-associated lipocalin. In addition, 24-hour urine samples were collected for stone risk analysis.
Results: A total of 46 patients participated in the study; the average age was 48.4 ± 11.3 years, with 40 women and 6 men. No significant differences were observed in any of the three kidney injury biomarkers when compared to reference ranges derived from healthy, non-hyperoxaluric subjects. Neither urinary oxalate excretion nor calcium oxalate supersaturation showed a correlation with any of the injury markers. Furthermore, no differences in biomarker levels were found between patients with hyperoxaluria (n = 17) and those with normoxaluria (n = 29).
Conclusions: Although hyperoxaluria is common following gastric bypass surgery, markers of kidney injury were not elevated in this cohort. Additionally, no correlation was found between urinary oxalate excretion and the evaluated biomarkers of renal injury.

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