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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, METHODS, RESULTS. Meshes: Adult, Calcium Oxalate, Female, Gastric Bypass, Humans, Hyperoxaluria, Kidney Calculi, Male, Middle Aged, Obesity, Morbid, Prospective Studies.
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Does calcium oxalate supersaturation increase early after Roux-en-Y gastric bypass? Context: 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. 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. 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.
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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. Final Decision: yes