Alcohol-Induced Liver Disease

Blood Tests

Routine laboratory tests are typically normal or only slightly deranged during the early stages of ALD. Abnormal liver tests include slight increases in the levels of serum transaminases and sometimes alkaline phosphatase. The levels of serum aspartate aminotransferase (AST) tend to rise more than those of alanine aminotransferase (ALT) and a high ASL/ALT ratio (typically >2) may be a useful pointer to an alcoholic rather than a nonalcoholic etiology. Elevations in serum gamma glutamyl transpeptidase (GGT) levels and mean corpuscular volume (MCV) of erythrocytes are both helpful markers of excess alcohol consumption, particularly in the early stages of liver disease.

There is increasing interest in the use of serum markers as noninvasive tests to estimate the severity of fibrosis. These are widely used in patients with NAFLD, typically in combination with assessments of liver stiffness with methods such as transient elastography (discussed further later). A number of serum biomarkers have been shown to have good predictive value for the presence of advanced fibrosis and cirrhosis in patients with ALD. These include: FibroTest, which combines alpha-2-macroglobulin, haptoglobin, GGT, ApoA1, bilirubin, age, and sex; FibrometerA, which combines prothrombin time, alpha-2-macroglobulin, hyaluronic acid, and age; and Hepascore, which combines bilirubin, GGT, alpha-2-macroglobulin, hyaluronic acid, age, and gender.

Imaging Studies

Radiologic assessments are useful in confirming the presence and severity of steatosis. Although ultrasound has been widely used to detect steatosis, it is relatively insensitive when steatosis is mild in severity and also has limited value for quantifying fat content. Other imaging techniques such as magnetic resonance imaging and magnetic resonance spectroscopy have improved sensitivity for the detection and quantification of hepatic steatosis.

Imaging studies are unable to make a distinction between simple steatosis and steatohepatitis, and this therefore represents a potentially important indication for liver biopsy. In recent years, there has been considerable interest in noninvasive methods for assessing liver fibrosis. The most widely used is transient elastography (FibroScan), which provides a measure of liver stiffness. Transient elastography (TE) is generally most reliable in identifying people who have minimal or advanced fibrosis and is less helpful in the assessment of intermediate stages of fibrosis, where liver biopsy may still be indicated. A number of studies have suggested that TE accurately identifies advanced fibrosis (defined as Metavir stage F3) and cirrhosis (F4) in patients with ALD. The accuracy of transient elastography is reduced in the presence of severe steatosis or active inflammation, particularly lobular inflammation, which may limit its utility in the assessment of patients with alcoholic steatohepatitis. There is also some evidence to suggest that active alcohol consumption itself may result in increased liver stiffness, which resolves after periods of abstinence ranging from 1 week to a few months of abstinence.

In patients who have progressed to cirrhosis, radiologic studies play an important role in detecting and monitoring abnormal nodules (see Chapter 31 ) that may herald the development of hepatocellular carcinoma (HCC). Histologic features of HCC and other focal liver lesions arising in the setting of ALD are discussed later.

Alcoholic Fatty Liver

Steatosis is the earliest and most common histologic manifestation of alcohol-induced liver injury. The fat that accumulates is mainly triglyceride and can be attributed to the effects of alcohol metabolism on hepatic fatty acid synthesis. Steatosis thus occurs predominantly in perivenular hepatocytes, which have the highest concentration of enzymes involved with alcohol metabolism ( Fig. 24.3 ). In more severe cases, steatosis may involve the entire lobule.

Three main patterns of steatosis have been described in ALD: macrovesicular, microvesicular, and a mixed pattern (macrovesicular and microvesicular) ( Fig. 24.4 ). Macrovesicular steatosis is usually the predominant form and is characterized by the presence of single, large, cytoplasmic fat droplets, which lead to hepatocyte enlargement and peripheral displacement of the nucleus. Macrovesicular steatosis typically predominates, but droplets of smaller size are also frequently present. These are likely to represent different phases in the evolution of fat accumulation within hepatocytes. Fat initially appears in a membrane-bound form localized within the endoplasmic reticulum. As droplets become larger, they fuse and form non–membrane-bound droplets. Although these smaller fat droplets have in the past been referred to as microvesicular steatosis, there is an increasing acceptance that they should be regarded as a variant of macrovesicular steatosis for which the term “mediovesicular steatosis” has been proposed. Instead “true” microvesicular steatosis refers to the presence of multiple tiny cytoplasmic fat droplets, which are too numerous to count and result in hepatocytes having a foamy or clear cytoplasm. This pattern of injury typically occurs in conditions associated with disorders of mitochondrial beta-oxidation, such as Reye syndrome or acute fatty liver of pregnancy, but may also occur rarely as a manifestation of ALD (“alcoholic foamy degeneration,” discussed further later).

Simple steatosis is generally regarded as a “benign” condition, which has a low risk of progression to cirrhosis and is readily reversible following abstention from alcohol. However, the presence of fat within hepatocytes is likely to be a substrate for the more severe forms of liver injury associated with inflammation and fibrosis. In support of this suggestion, it has been shown that the severity of steatosis in an index biopsy is predictive for progression to cirrhosis. Patients with “pure” fatty and a mixed droplet pattern of steatosis have also been found to have a higher risk of progressing to cirrhosis than those with pure macrovesicular steatosis (28% versus 3% during a median interval of 10.5 years). These differences may reflect a variation in metabolic responses to alcohol, with susceptible individuals having a tendency to develop more severe oxidative stress-induced injury to mitochondria, which in turn predisposes to the development of (true) microvesicular steatosis. The resulting effects on mitochondrial membrane permeability may lead to the formation of giant mitochondria, which have also been suggested as an adverse prognostic feature in cases that otherwise have simple steatosis.

As discussed earlier, severe steatosis rarely results in sudden death. Postmortem histology shows a predominantly microvesicular or mixed pattern of steatosis without typical features of steatohepatitis. Other changes seen include megamitochondria and bilirubinostasis.

The term alcoholic foamy degeneration has been used to describe rare cases presenting with a predominantly microvesicular pattern of steatosis associated with clinical features of jaundice and hepatomegaly ( Fig. 24.5 ). Other changes seen in affected cases included bile stasis and mild perisinusoidal fibrosis without significant inflammatory infiltration. Rapid recovery typically occurs on abstention from alcohol.

Lipogranulomas are localized collections of inflammatory cells associated with fat droplets and are thought to represent a response to extravasated lipid. They occur mainly in liver lobules but can also be present in portal tracts. Small aggregates composed only of macrophages are best referred to as microgranulomas. Larger aggregates may also contain other inflammatory cells, including lymphocytes, neutrophils, and eosinophils ( Fig. 24.6A ). Rarely, well-formed epithelioid granulomas without readily identified fat droplets may be seen, causing diagnostic problems in the distinction from other causes of granulomatous liver disease. Serial sections usually reveal a fat vacuole in such cases. Multinucleated cells may also have a foamy cytoplasm reflecting ingested lipid. Larger lipogranulomas may be associated with small foci of fibrous scarring (see Fig. 24.6B ), but these are not thought to be important in the pathogenesis of progressive fibrosis.

Alcoholic Steatohepatitis

Classical morphologic descriptions have used the term alcoholic hepatitis to describe changes seen in the intermediate phase between simple steatosis and progressive fibrosis leading to cirrhosis. However, steatosis is usually still present; therefore, the term alcoholic steatohepatitis is perhaps more appropriate and in line with the terminology used to define different stages in the evolution of NAFLD. The term alcoholic steatonecrosis , used in early descriptions of ALD, also refers to the same histologic features. As discussed earlier, the clinical manifestations of alcoholic steatohepatitis range from mild asymptomatic disease to acute presentation with jaundice, fever, and signs of hepatic decompensation.

Three main features that characterize steatohepatitis are fatty change, hepatocyte ballooning (typically associated with formation of Mallory-Denk bodies), and lobular inflammation ( Fig. 24.7 ) ( eSlide 24.1, eSlide 24.2 ). These changes predominate in centrilobular regions of the liver parenchyma. Although steatosis is present in the majority of cases, it may be mild or absent in people who have been recently abstinent, whereas other features of steatohepatitis still persist. Likewise, steatosis is rarely conspicuous in cases presenting with florid features of severe alcoholic hepatitis; this may again reflect a period of alcohol abstinence as a result of severe symptomatic liver disease.

Hepatocyte ballooning probably reflects alcohol-induced damage to the cytoskeleton of hepatocytes and is thought to represent a critical step in the pathogenesis of progressive liver injury. Affected hepatocytes are typically, but not always, larger than normal and become rounded rather than polygonal in shape. The cytoplasm undergoes clarification, largely because of the intracellular accumulation of fluid. In contrast with hepatocytes showing macrovesicular steatosis, where a single large fat droplet completely displaces the normal cytoplasm, ballooned hepatocytes have a reticulated appearance and contain delicate strands of residual cytoplasmic material. In some cases, the latter form larger ropelike aggregates characteristic of Mallory hyaline (Mallory-Denk bodies) (see Fig. 24.7 ). Although hepatocyte ballooning represents a key feature in the distinction between simple steatosis and steatohepatitis, it is often difficult to assess and prone to subjective interpretation. Furthermore, other conditions may lead to hepatocyte swelling and clarification resembling that seen in ALD. These include conditions associated with glycogen accumulation (eg, glycogen storage disease or type 1 diabetes with poor glycemic control) and diseases associated with acute or chronic cholestasis.

Features supporting a diagnosis of hepatocyte ballooning related to fatty liver disease (alcoholic or nonalcoholic) include a perivenular distribution, coexistent steatosis, and the presence of Mallory-Denk bodies. Immunohistochemistry is helpful in demonstrating Mallory hyaline, particularly in cases where this is poorly formed or present in small amounts and difficult to visualize in sections stained with routine hematoxylin and eosin ( Fig. 24.8A ). Proteins associated with Mallory hyaline that can be demonstrated immunohistochemically include keratins 8 and 18 (K8 and K18), p62, and ubiquitin. Loss of membranous expression of K8 and K18 may be helpful in distinguishing the hepatocyte ballooning occurring in fatty liver disease and other diseases associated with Mallory-Denk body formation (eg, chronic cholestatic syndromes) from other conditions associated with pale swollen hepatocytes, such as microvesicular steatosis or ischemic hepatocyte ballooning (see Fig. 24.8B ). In cases of NAFLD, costaining with K8/18 as well as ubiquitin has been found to improve the detection of subtle hepatocellular injury arising from cytoskeletal injury; in particular identifying damaged normal-sized hepatocytes not readily appreciated as “ballooned” in conventional hematoxylin and eosin stained sections. This in turn improved the categorization of cases previously classified as having suspicious/borderline NASH. Immunostaining for K8/18 has likewise been shown to improve observer agreement for identifying ballooned hepatocytes and for grading disease severity in patients presenting with acute alcoholic steatohepatitis complicating alcoholic cirrhosis.

Giant mitochondria may also be found in ballooned hepatocytes ( eSlide 24.3 ). They are typically present as globular eosinophilic inclusions of a size similar to hepatocyte nuclei ( Fig. 24.9 ). Needle-shaped forms of giant mitochondria are also recognized. Giant mitochondria are mostly centrilobular in distribution and frequently coexist with Mallory-Denk bodies. They stain red with chromotrope aniline blue (see Fig. 24.9 ), contrasting with Mallory-Denk bodies, which stain blue with this method. Although they typically occur as part of the morphologic spectrum of alcoholic steatohepatitis, giant mitochondria can also be seen in cases with pure fatty liver, where their presence has been associated with an increased risk of progression to fibrosis or cirrhosis. The presence of giant mitochondria appears to correlate with recent heavy alcohol consumption and with more advanced liver disease. Although giant mitochondria are most typically seen in ALD, they have also been described in NAFLD and in a number of other chronic liver diseases, and in the latter they tend to be fewer in number and lack a zonal distribution.

Lobular inflammation typically involves a mixed population of cells, including a prominent component of neutrophils (see Fig. 24.7 ). The latter have a tendency to aggregate around ballooned hepatocytes containing Mallory-Denk bodies, a phenomenon sometimes referred to as satellitosis ( Fig. 24.10 ). Cases with prominent hepatic infiltration with neutrophils may also be associated with peripheral blood neutrophilia. Neutrophil binding to hepatocytes mediates cell death by oxidative stress and release of lysosomal enzymes. Other cell types seen in perivenular regions include T lymphocytes and enlarged Kupffer cells, some of which may contain fat vacuoles. More diffuse lobular mononuclear inflammation occurs in some cases.

Liver cell death is also thought to be an important component of the progressive liver injury that occurs in alcoholic steatohepatitis. Ballooning degeneration is generally regarded as a precursor lesion for lytic necrosis and is likely to be mediated by alcohol-induced oxidative stress resulting in the formation of reactive oxygen species, which damage cytoplasmic and nuclear proteins, mitochondria and other organelles and DNA. However, in contrast with severe forms of acute hepatitis (eg, viral, drug-induced, or autoimmune) lytic necrosis is rarely conspicuous histologically. In some cases of severe alcoholic hepatitis, florid neutrophilic infiltration in perivenular regions may be associated with foci of confluent hepatocyte loss and fibrous obliteration of perivenular sinusoids ( Fig. 24.11 ). The term central sclerosing hyaline necrosis has been used to describe this constellation of changes. There is increasing evidence to suggest that apoptosis is an important mechanism of cell death in alcoholic fatty liver disease. However, in contrast with the lobular inflammation seen in acute hepatitis associated with viral agents, drugs, or autoimmune hepatitis, apoptotic bodies are rarely prominent histologically in alcoholic steatohepatitis ( Fig. 24.12 ). Studies using the in situ transferase–mediated dUTP nick-end labeling index as a marker of apoptosis in ALD have shown that the apoptosis index may be as high as 30% and that the apoptotic index correlates with clinical evidence of disease severity as measured by the Maddrey score.

In cases of severe alcoholic hepatitis presenting clinically with jaundice and signs of liver failure, bilirubinostasis is frequently a prominent feature histologically. Most of these cases have features of acute-on-chronic liver disease with extensive fibrosis often amounting to cirrhosis. Bile pigment in this setting has been observed in the cytoplasm of hepatocytes, biliary canaliculi, or bile ductules. As observed in earlier studies of patients developing severe systemic illness with jaundice and sepsis, the presence of ductular cholestasis (“cholangitis lenta”) is associated with the development of infections in patients hospitalized with severe alcoholic hepatitis.

The most important consequence of the centrilobular hepatocellular injury and inflammation that characterize alcoholic hepatitis is the development of fibrosis, which in turn has the potential to progress to cirrhosis. The presence of any degree of fibrosis indicates progressive liver injury and is predictive of the development of more severe fibrosis. Lipid release from hepatocytes may also be important in the pathogenesis of centrilobular fibrosis by causing mechanical obstruction of small hepatic veins and surrounding sinusoids.

Several overlapping patterns of fibrosis in centrilobular regions have been described ( eSlide 24-1B, eSlide 24-3B ). The earliest manifestation is the presence of activated hepatic stellate cells (myofibroblasts) in centrilobular sinusoids; these can be demonstrated by immunohistochemical staining for smooth muscle actin. This leads to the deposition of collagen fibers within perisinusoidal spaces (perisinusoidal fibrosis), a pattern of fibrosis also seen in conditions where there is impaired sinusoidal blood flow (eg, portal or hepatic venous insufficiency). The most distinctive pattern of fibrosis (pericellular fibrosis) involves collagen fibers completely surrounding individual hepatocytes in a “chicken-wire”–like fashion ( Fig. 24.13 ). Pericellular fibrosis is closely related to ballooned hepatocytes and is rarely seen in conditions other than fatty liver disease. In some cases, bands of collagen develop around the outer walls of hepatic veins, resulting in apparent thickening of vein walls; this pattern is termed perivenular fibrosis and has been defined as an area of fibrous thickening measuring at least 4 μm in thickness and involving at least two-thirds of the perimeter of the terminal hepatic venule. It may result in varying degrees of narrowing of the hepatic vein lumen, sometimes referred to as phlebosclerosis ( eSlide 24.1B, eSlide 24.4 ), and is sometimes also associated with inflammatory infiltration of the vein wall (lymphocytic phlebitis). Foci of perivenular fibrosis can sometimes be seen in a liver biopsy otherwise showing simple steatosis and may precede the development of alcoholic hepatitis. Care should be taken to avoid mistaking normal variation in the thickness of hepatic vein walls or tangentially sectioned vessels as evidence of pathologic fibrosis. The presence of relatively immature collagen (staining positively with a trichrome stain but lacking elastic fibers) as a distinct band surrounding the elastic wall of a hepatic vein branch provides clear evidence of a pathologic process. The term perivenular fibrosis is potentially ambiguous, as the other patterns of fibrosis occurring in centrilobular regions could also be classified as perivenular on the basis of their anatomic location.

Fibrosis can also develop within the intima of hepatic venules leading to progressive luminal obliteration ( Fig. 24.14 ; see Fig. 24.11B ). Hepatic venoocclusive lesions are thought to occur as a consequence of reduced blood flow into the hepatic vein and are also seen in cases of cirrhosis occurring as a complication of other chronic liver diseases.

The various patterns of fibrosis occurring in centrilobular regions in ALD contribute to the development of precirrhotic portal hypertension. They are also important precursor lesions in the development of progressive fibrosis, which ultimately results in cirrhosis.