Risk Factors For Urinary Stone Formation In The Morbidly Obese

Main Category: Urology / Nephrology
Also Included In: Obesity / Weight Loss / Fitness;  Public Health
Article Date: 10 Sep 2007 - 0:00 PDT

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UroToday.com - Presented Monday, 03 September 2007 at the 29th Congress of the Societe International d'Urologie - SIU 2007 - Optimizing Clinical Outcomes in Prostate and Renal Cell Carcinomas - The Second Annual Symposium on Advanced GU Malignancy - Palais des Congres de Paris, France

Introduction: Objective: To prospectively analyze urinary parameters that predispose to stone formation in the morbidly obese.

Methods: Thirty-two females and thirteen males scheduled to undergo bariatric surgery submitted a 24-hour urine collection for metabolic stone risk analysis (Mission Pharmacal) along with a 24-hour dietary intake diary. Body mass index (BMI) and medical history were recorded. A registered dietician converted dietary intake diaries from the raw food intake amounts to their corresponding metabolic equivalent.

Results: The mean age was 46.9 ± 10.5 years and mean BMI (kg/m2) was 46.4 ±10.1. All patients met the NIH classification of morbid obesity (BMI ≥ 40). All subjects had at least 1 abnormality identified in their urine profile that placed them at high risk for stone formation. The mean total volume was 1.5 ± 0.7 L/day, with 71.1% of patients demonstrating low urine volumes (<2L). Elevated relative supersaturation was identified for sodium urate in 53.3% of patients, uric acid in 57.7%, calcium oxalate in 28.8% and brushite in 15.5%. The following abnormalities were also identified: hypocitraturia (13.3%, min 46 mg/d), hypernatriuria (35.5%, max 436 meq/d), hyperuricosuria (22.2%, max 1303 mg/d), hyperoxaluria (11.1%, max 52 mg/d), and hypercalciuria (33.3%, max 544 mg/d). Low urinary pH (≤5.5) was identified in 31.1%.

Conclusions: In this study, 100% of morbidly obese patients had at least one abnormality in their urine profiles that predispose them to urinary stone formation. Longitudinal studies will evaluate the impact of bariatric surgery on these underlying risks.

Authors: Monga M, Duffey B, Pedro R, Weiland D, Melquist J, Kriedberg C, Ikramuddin S, Kellogg T, Slusarek B, Stessman M

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