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Calcium oxalate supersaturation increases early after Roux-en-Y gastric bypass.
MedLine Citation:
PMID:  23953730     Owner:  NLM     Status:  Publisher    
BACKGROUND: Calcium oxalate (CaOx) nephrolithiasis is an adverse effect of Roux-en-Y gastric bypass surgery (RYGB). It is unknown when the increased risk for CaOx stone formation occurs after surgery.
METHODS: We studied 13 morbidly obese adults undergoing RYGB with 24-hour urine collections at 4 weeks before and 1, 2, 4, and 6 months after surgery and computed CaOx relative saturation ratio (RSR) by EQUIL2.
RESULTS: Eleven patients were female, mean±standard deviation age was 41.1±7.2 years, and none had diabetes or chronic kidney disease. Median (interquartile range) urinary oxalate excretion increased linearly from 12.6 (10.9-37.9) mg/24 hr at baseline to 28.4 (14.4-44.0) mg/24 hr at 6 months (slope = .188; P = .005). CaOx RSR increased significantly at 2 months after RYGB (1.4 [1.2-2.4] to 4.9 [1.7-10.0]; P = .017) and rose throughout the study to 5.7 (3.7-12.2) at 6 months (P = .001) with a positive linear slope (.255; P = .001). One patient had critical CaOx supersaturation (RSR = 34.7) and severe hyperoxaluria (101.7 mg/24 hr) at 6 months after RYGB. Significant decreases over time were seen in urine volume and sodium and potassium excretion, but no changes were noted in urinary pH, calcium, magnesium, or citrate.
CONCLUSIONS: Our data suggest that CaOx RSR, and thus risk for nephrolithiasis, rises as early as 2 months after RYGB and increases gradually in the first 6 months, largely because of reduced urine volume and increased urinary oxalate excretion. Interventions to reduce CaOx RSR, such as adequate fluid intake and agents to bind enteric oxalate, need to be evaluated in patients at risk for nephrolithiasis after RYGB.
Varun Agrawal; Xiao J Liu; Thomas Campfield; John Romanelli; J Enrique Silva; Gregory L Braden
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-4-26
Journal Detail:
Title:  Surgery for obesity and related diseases : official journal of the American Society for Bariatric Surgery     Volume:  -     ISSN:  1878-7533     ISO Abbreviation:  Surg Obes Relat Dis     Publication Date:  2013 Apr 
Date Detail:
Created Date:  2013-8-19     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101233161     Medline TA:  Surg Obes Relat Dis     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2013 American Society for Metabolic and Bariatric Surgery. Published by Elsevier Inc. All rights reserved.
Division of Nephrology and Hypertension, Fletcher Allen Health Care, Burlington, Vermont. Electronic address:
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