FC012: Urinary Lithogenic Profile in Patients with Non-Alcoholic Fatty Liver Disease

Abstract

Abstract BACKGROUND AND AIMS Several epidemiological studies have observed an increased risk for nephrolithiasis in patients affected by non-alcoholic fatty liver disease (NAFLD). However, the urinary lithogenic risk profile for patients with NAFLD is currently unknown. METHOD We systematically analysed the urinary metabolic profile of patients affected by NAFLD and liver cirrhosis (LC), followed at the hepatology outpatient clinic of our institution, compared to healthy individuals. A complete metabolic work-up for kidney stone disease was performed in all subjects. Multivariable linear regression models adjusted for age, sex, body mass index, eGFR and diabetes, were applied to assess differences in urinary lithogenic risk factors between healthy individuals and patients affected by NAFLD and LC. RESULTS A total of 42 patients and 12 healthy individuals were included in the analysis. No differences in age, sex and BMI were found among patients affected by NAFLD and LC, whereas the latter were more diabetic (71.4% versus 14.3%). After adjusting for multiple confounders, patients with NAFLD and LC had lower urinary magnesium (−55 mg/24 h; 95% CI −104, −6; P = 0.03 and −63 mg/24 h; 95% CI −121, −6; P = 0.03, respectively) and borderline oxalate (−1.21 mg/24 h; 95% CI −2.42, −0.01; P = 0.05 and −1.42 mg/24 h; 95% CI −2.79, −0.04; P = 0.04, respectively) excretions, compared with healthy controls. Compared with LC patients, NAFLD patients showed higher urinary ammonia (539 mEq/24 h; 95% CI 245, 833; P < 0.01), ammonia/net acid excretion ratio (0.40; 95% CI 0.18, 0.62; P < 0.01), urine pH (1.16; 95% CI 0.44, 1.88; P = 0.05) and lower urinary uric acid excretion (−210 mg/24 h; 95% CI −419, −0.29; P < 0.01) and titratable acidity (−9.7 mEq/24 h; 95% CI −19.0, −0.4; P = 0.04). CONCLUSION Altered urinary ammonia and magnesium excretions seems to be involved in the higher risk for stone formation found in patients with NAFLD. More studies are needed to investigate stone phenotypes and renal handling of ammonia in this setting.