INTRODUCTION

The histopathologic examination of the liver can provide otherwise unobtainable information regarding its structural integrity and the type and degree of injury and/or fibrosis that affect the liver [1]. It is also useful for monitoring the efficacy of treatment and permits the definitive diagnosis of tumors.

A liver biopsy is usually performed only after a thorough noninvasive clinical evaluation in patients with chronically (greater than six months) elevated liver biochemical tests. (See "Approach to the patient with abnormal liver function tests".) The pertinent clinical information should be made available to the pathologist so that the histopathological findings can be interpreted in the appropriate clinical context [2].

This topic review will focus on the interpretation of liver biopsy specimens. The examples presented represent the author's collection of specimens spanning four decades and have been used in training generations of gastroenterology and hepatology fellows. Thus, they may not always reflect contemporary diagnostic techniques or management approaches. Methods to obtain a liver biopsy are described elsewhere. (See "Percutaneous liver biopsy" and "Transjugular, laparoscopic and fine needle aspiration liver biopsy".) Scoring systems for grading the severity of liver biopsy specimens are presented elsewhere. (See "Histologic scoring systems for chronic liver disease".)

SEGMENTAL ANATOMY

The liver can be divided into the right and left hemiliver, each of which has its own blood supply. The right hemiliver comprises 50 to 70 percent of the liver mass (figure 1). The liver can be further subdivided into eight segments based upon the vascular or bile duct distribution.

LOBULE AND ACINAR MODELS

Two conceptual models have been proposed relating to the architecture of the hepatic parenchyma. Terminal portal veins and hepatic venules interdigitate between sinusoids. The "lobule" model considers the terminal hepatic venules to be the center of the hepatic microcirculation, while the "acinar" model (also known as the Rappaport classification) considers it to represent the periphery (figure 2) .