Visceral adipose tissue loss and 24-hour urinary profile changes post-bariatric surgery

Abstract

Introduction: The relationship between obesity and nephrolithiasis is a well-documented phenomenon. Visceral adipose tissue (VAT) has been proposed to be an accurate indicator of metabolic derangement. We present a study that investigates the relationship between computed tomography (CT) delineated VAT measurements and 24-hour urine (24 HU) profiles in the context of profound weight loss.

Materials and methods: A total of 86 patients with a history of nephrolithiasis who underwent bariatric surgery were reviewed. All patients had pre and postoperative 24 HU analysis and CT kidney and urinary bladder performed. CT-based fat delineation program, AnalyzePro, was used to measure VAT at levels L4-L5 (VAT 1) and L1-L2 (VAT2). Univariate and multivariate analysis was utilized to examine associations between VAT measurements and comorbidities, 24 HU values, and postoperative urinary changes.

Results: Preoperative VAT2 was correlated with preoperative serum creatinine and all 24 HU (R2: 0.23-0.43, p = < 0.001-0.030). Only VAT1 and VAT2 had relationships with hypertension, dyslipidemia, and metabolic syndrome (R2: 0.25-0.30, p = 0.004-0.015). The percent change in VAT1 and VAT2 was a significant predictor of change in 24 HU uric acid (respectively, R2: 0.14, beta: -0.03, p = 0.002 and R2: 0.13, beta: -0.03, p = 0.003).

Conclusions: This study found VAT to have strong correlations with urinary outcomes in obese patients, especially in the excretion of uric acid. These findings support a potential use of CT delineated measurements of fat as a surrogate measure for urinary metabolites, and may be used as a marker for patient counseling in stone prevention.

Keywords: 24-hour-urine; bariatric surgery; nephrolithiasis; uric acid; visceral adipose tissue.