1Department of Pathology, University of California, San Francisco, 505 Parnassus Avenue, M590, Box 0102, San Francisco, CA 94143-0102, USA. Electronic address: email@example.com.
2Department of Pathology, University of California, San Francisco, 505 Parnassus Avenue, M590, Box 0102, San Francisco, CA 94143-0102, USA.
This article reviews diagnostic criteria for nonalcoholic steatohepatitis (NASH), current grading and staging methodology, and diagnostic challenges and pitfalls in routine practice. Current practice guidelines and prognostic and treatment considerations are discussed. The clinical diagnosis of nonalcoholic fatty liver disease may represent stable disease without progressive liver damage, in the form of nonalcoholic fatty liver (NAFL), or aggressive disease that will progress to advanced fibrosis, in the form of NASH. NASH is diagnosed from a liver biopsy after assessment by a pathologist to distinguish NASH from NAFL (and other histologic mimics of NASH); this distinction is critical for patient management.