Histologic variation of grade and stage of nonalcoholic fatty liver disease in liver biopsies

Background: Sampling error regarding disease grade and stage has been ascribed to needle liver biopsies in patients with chronic liver disease. Although several studies evaluating sampling error in liver biopsies exist, none have investigated this phenomenon in patients with non-alcoholic fatty liver disease (NAFLD). This study alms to determine the rate and extent of sampling error in liver biopsies obtained from patients undergoing Roux-en-Y gastric bypass (RYGBP) surgery for morbid obesity. Methods: 10 morbidly obese patients underwent simultaneous liver biopsies from the right and left hepatic lobes during an open examination preceding the RYGBP procedure. The biopsies were subsequently randomly evaluated and then blindly re-evaluated by a liver pathologist. Degrees of inflammatory activity and fibrosis were determined and scored for each sample using a semi-quantitative system with 3 grades and 4 stages. Results: No grading differences were observed, and 3 patients (30%) had a difference of at least 1 stage between the right and left lobes. One patient had a 2-stage difference in paired samples, with significantly different biopsy sizes and number of portal tracts. Blinded histologic re-evaluation did not result in grading or staging scores that differed from the original evaluation. Conclusions: Liver biopsy samples taken from the right and left hepatic lobes showed similar grades of disease activity, but differed in histopathologic staging in 30% of the NAFLD patients. Obtaining an adequately sized biopsy (> 1.0 cm in length with > 10 portal tracts) greatly reduces sampling error.