Prevalence of Liver Steatosis and Fibrosis and the Diagnostic Accuracy of Ultrasound in Bariatric Surgery Patients

Liver steatosis can progress to fibrosis, cirrhosis, and eventually to end-stage liver disease and hepatocellular carcinoma. We thus determined the prevalence of liver steatosis and fibrosis in patients undergoing bariatric surgery using liver biopsy. We also determined the suitability of ultrasound for diagnosis of liver steatosis with and without simultaneously considering patient characteristics. We reviewed preoperative liver ultrasound and intraoperative liver biopsy results in 451 bariatric surgery patients along with their clinical characteristics between 2005 and 2009. Among 435 patients with conclusive biopsy results, estimated prevalence of liver steatosis was 71.5% (95% confidence interval 67%, 76%) and that of fibrosis was 27% (23%, 31%). Sensitivity of ultrasound for liver steatosis was 86% (82%, 90%); its specificity was 68% (59%, 76%). Positive predictive value of ultrasound for liver steatosis was 87% (82%, 91%), and its negative predictive value was 67% (58%, 75%). Overall diagnostic accuracy was 81% (77% 85%). Sensitivity was improved in patients with higher nonalcoholic fatty liver disease activity scores (NAS) [odds ratio (OR) 1.4 (1.1, 1.9) for a one unit increase in NAS] and prolonged duration of obesity [OR 1.3 (1.1, 1.6) for a 5-year increase in duration] but was worsen by higher body mass index. About three quarters of bariatric surgery patients have liver steatosis, and about a quarter have fibrosis. One third of patients with liver steatosis develop fibrosis without significant clinical manifestations. Ultrasound was only moderately diagnostic for liver steatosis but was sufficient for clinical use in patients with a NAS score a parts per thousand yen2 and when the duration of obesity was > 30 years.