CHAPTER 9 Chronic Hepatitis

Definition and causes

Chronic hepatitis is a common reason for persistently abnormal liver function tests ¹ and forms the background for the development of much cirrhosis² and hepatocellular carcinoma. It is defined as persistence of liver injury with raised aminotransferase levels or viral markers for more than 6 months.³ This definition, though artificial, helps to establish a borderline in studies of acute and chronic hepatitis. In practice, however, this borderline is not always easy to draw, because acute self-limiting hepatitis is sometimes prolonged beyond 6 months and chronic hepatitis may have an acute or indefinable onset. Many chronic liver diseases have an inflammatory component, but the term chronic hepatitis is often restricted to a limited number of causes (Table 9.1). Some of the histological features of this group, such as interface hepatitis and lymphocytic infiltration, are also found in other conditions (Table 9.2) not included in this chapter. For the sake of clarity, a diagnosis of chronic hepatitis should therefore include the probable cause whenever possible.

Table 9.1 Classic causes of chronic hepatitis

Hepatitis B, with or without HDV infection

Hepatitis C

Autoimmune hepatitis

Drug-induced hepatitis

Chronic hepatitis of unknown cause

Table 9.2 Conditions sharing pathological features with classic forms of chronic hepatitis

Wilson’s disease

α₁-Antitrypsin deficiency

Primary biliary cirrhosis

Primary sclerosing cholangitis

Classification and nomenclature

In 1994, two international working parties recommended the replacement of the old histological classification into chronic active, chronic persistent and chronic lobular hepatitis by a predominantly aetiological classification supplemented by semi-quantitative scoring.⁴^,⁵ This reflected the fact that the cause of a chronic hepatitis could, by 1994, be determined in most patients and appropriate treatment given. Also, it had become apparent that the future course of a chronic hepatitis could not after all be accurately predicted from the histological appearances. The several systems available for semi-quantitative scoring are discussed in detail at the end of the chapter.

Use of liver biopsy in chronic hepatitis

Opinion is divided on the need for biopsy in the diagnosis and management of patients with chronic hepatitis.⁶^,⁷ Histology continues to play a central role in the assessment of new treatment regimes, however, and is used by many physicians to establish a diagnosis and to guide management.⁸^,⁹ Criteria used by physicians for the latter include the severity of the hepatitis (grading), the extent of progression towards cirrhosis (staging) and individual features such as steatosis and iron deposition. In the case of autoimmune hepatitis, liver biopsy plays an important part in the decision to stop treatment.¹⁰ In patients with multiple aetiological agents, biopsy may help to establish their relative importance; an example of this is the patient with thalassaemia and viral hepatitis. Large-cell and small-cell change (dysplasia), possible predictors of hepatocellular carcinoma, are sometimes found before cirrhosis develops but will be discussed with the latter, in Chapter 10.

Table 9.3 lists the possible reasons for liver biopsy in chronic hepatitis.

Table 9.3 Uses of liver biopsy in chronic hepatitis

Histological features of chronic hepatitis

Portal changes

Most small portal tracts are infiltrated to a variable extent by lymphocytes together with smaller numbers of plasma cells and occasional segmented leucocytes. A few eosinophils are often present. Lymphoid aggregates and lymphoid follicles with germinal centres are common in, but not exclusive to, hepatitis C. Larger conducting tracts are less affected than small terminal tracts and this has to be taken into account in assessing the severity of a hepatitis.

In the mildest forms of chronic hepatitis, the infiltrate is confined to portal tracts (Fig. 9.1) and the margins of the tracts remain regular. In the more severe forms, infiltration extends into the adjacent parenchyma, as described below. In mild chronic hepatitis, the tracts are often enlarged and short fibrous spurs may be seen extending from them (Fig. 9.2). These and other structural changes are most easily evaluated in reticulin or collagen stains. Interlobular bile ducts may be damaged, as shown by irregularity of the epithelial wall, vacuolation and infiltration by lymphocytes.

Figure 9.1 Chronic hepatitis B, mild.

The portal tract is heavily infiltrated with lymphocytes. These do not extend beyond the margins of the tract, the limiting plate of hepatocytes is intact and interface hepatitis is absent. Some hepatocytes have a ground-glass appearance. (Needle biopsy, H&E.)

Figure 9.2 Chronic hepatitis.

Short septa extend from the slightly enlarged portal tract (P) but normal architectural relationships are preserved. (Needle biopsy, reticulin.)

Parenchymal changes

The periportal lesion: interface hepatitis

In all but the mildest forms of chronic hepatitis, the inflammatory infiltrate extends from the portal tracts into the adjacent parenchyma and there is destruction of hepatocytes (Figs 9.3, 9.4). This process of interface hepatitis or piecemeal necrosis is most easily identified by the irregularity of the limiting plates of hepatocytes around the portal tracts. The term ‘interface hepatitis’ is now often preferred to the older term ‘piecemeal necrosis’ because there is evidence to suggest that apoptosis rather than necrosis may be involved.¹¹^,¹² However, the relative roles played by apoptosis and necrosis in viral hepatitis are not yet entirely clear, because the two processes share several characteristics.¹³

Figure 9.3 Interface hepatitis.

In contrast to the upper margin of this portal tract, the edges of the lower margin are blurred by inflammatory infiltration and hepatocyte loss. (Needle biopsy, H&E.)

Figure 9.4 Interface hepatitis.

At a higher magnification than Fig. 9.3, lymphocytes are seen infiltrating between surviving hepatocytes. The interface between inflamed portal tract and parenchyma is irregular. (Needle biopsy, H&E.)

Interface hepatitis at its mildest is recognised by lymphocytes in the periportal parenchyma, in association with hepatocellular damage. In more severe examples, trapped surviving hepatocytes may be seen within the inflammatory infiltrate (Fig. 9.5) and fibrous septa extend from the portal tract (Fig. 9.6). In cirrhotic livers the process is seen at the edges of nodules and septa rather than immediately around portal tracts (see Fig. 10.19); in either case, however, the hepatitic process involves the interface between connective tissue and parenchyma.

Figure 9.5 Chronic hepatitis, mild to moderate.

The lower edge of the portal tract shows interface hepatitis, with trapping of hepatocytes in the infiltrate (arrows). (Needle biopsy, H&E.)

Figure 9.6 Chronic hepatitis with fibrosis.

Fibrosis extends from the portal tract above into the parenchyma. (Needle biopsy, reticulin.)

Interface hepatitis varies not only in severity, but also in the extent of involvement of the interface, whatever its exact location. This is taken into consideration in some grading systems. With more severe interface hepatitis and liver-cell damage, periportal progenitor cells may become activated to produce a ductular reaction (proliferated bile ductules).¹⁴ The blurring of the margins of the portal tracts in such instances then results from the combination of periportal chronic inflammatory cells and the ductular structures (Fig. 9.7). The presence of scattered neutrophils near the ductules should not be confused with biliary obstruction, cholangitis or a presumed drug reaction; they are normal constituents of the ductular reaction, mediated by cytokines expressed by the ductular cells.¹⁵

Figure 9.7 Ductular reaction in chronic hepatitis with marked activity.

The margins of the portal tract (P) above and below are expanded and effaced by marked interface hepatitis. The white arrow marks the native bile duct. Within the irregular border of interface hepatitis at bottom are bile ductular structures (ductular reaction), one of which (arrow) is enlarged in the inset. Inset: Scattered neutrophils surround and partially infiltrate the flattened ductule (arrow) in this area of lymphoplasmacytic interface hepatitis. (Needle biopsy, H&E.)

The lobular lesion

Deeper within the parenchyma there are varying degrees of hepatocellular damage and inflammation, sometimes called the lobular component or lobular hepatitis. Most commonly, this takes the form of focal necrosis, but confluent and bridging necrosis may also be seen. Panlobular necrosis is rare in chronic hepatitis. Also uncommon is the finding of severe lobular hepatitis in the absence of substantial portal and periportal inflammation.¹⁶ The severity of lobular hepatitis correlates with the accumulation of progenitor cells.¹⁷

Focal (spotty) necrosis is seen as areas of hepatocyte loss with infiltration by lymphocytes, macrophages and other cells. Each area covers the space normally occupied by up to about four or five hepatocytes (Fig. 9.8). Larger areas of hepatocyte loss are referred to as confluent necrosis (see Ch. 4). As in acute hepatitis, bridging necrosis refers to confluent necrosis and collapse linking vascular structures and is usually restricted to bridges linking portal tracts to terminal hepatic venules.

Figure 9.8 Chronic hepatitis with lobular activity.

Clumps of inflammatory cells, some of them associated with hepatocyte loss, extend through the parenchyma. The portal tract above is inflamed. (Needle biopsy, H&E.)

Severe lobular hepatitis is often accompanied by the formation of small rounded or ovoid gland-like clusters of surviving hepatocytes, so-called hepatitic rosettes (Fig. 9.9). Unlike cholestatic rosettes (Ch. 4), these are embedded in connective tissue and probably form as a result of hyperplasia of hepatocytes trapped in a collapsed and inflamed area of parenchyma.

Figure 9.9 Chronic hepatitis, severe, with rosette formation.

Parenchymal architecture has been completely disrupted. Surviving hepatocytes have formed gland-like rosettes, which are separated by bridges of collapse and inflammation. (Needle biopsy, H&E.)

In a minority of patients with chronic hepatitis some of the hepatocytes fuse to form multinucleated giant cells like those of neonatal hepatitis (Fig. 9.10). In adults this is termed postinfantile giant-cell transformation; it is an occasional feature of autoimmune hepatitis and of chronic hepatitis C (with or without human immunodeficiency virus (HIV) co-infection),¹⁸^,¹⁹ typically present only in perivenular regions.

Figure 9.10 Post-infantile giant-cell transformation in chronic hepatitis.

The affected perivenular hepatocytes are enlarged and pale with multiple nuclei (arrows). In adults this may be seen in autoimmune hepatitis or in chronic hepatitis C with or without HIV co-infection. (Needle biopsy, H&E.)

Other hepatocyte changes seen in chronic hepatitis include steatosis, iron deposition and oncocytic change. Steatosis is commonest in chronic hepatitis C and is further discussed under that heading below, as is siderosis. Iron deposits are sometimes focal.²⁰ Substantial hepatocellular siderosis should always lead to consideration of possible hereditary haemochromatosis, but siderosis is not necessarily related to an HFE gene mutation.²¹ Oncocytic change results from the accumulation of large numbers of closely packed mitochondria in hepatocytes, giving them a granular, densely eosinophilic appearance²²^,²³ (Fig. 9.11). These cells are most common within hepatitic rosettes. Mitochondrial hyperplasia in these cells appears to be a compensatory response to mitochondrial DNA dysfunction.²⁴ Finally, the appearance of bile thrombi in dilated canaliculi is most unusual in chronic hepatitis. While this type of cholestasis could result from an acute exacerbation of chronic disease, alternative explanations such as drug hepatotoxicity should be considered.

Figure 9.11 Oncocyte formation in chronic hepatitis.

Some of the hepatocytes in this severe chronic hepatitis have intensely eosinophilic granular cytoplasm. Others have a ground-glass appearance. (Needle biopsy, H&E.)

In some patients with chronic viral or autoimmune hepatitis, distinctive eosinophilic and diastase periodic acid–Schiff (PAS)-positive inclusions are seen in sinusoidal endothelial cells ²⁵ (Fig. 9.12). The inclusions have been shown to contain immunoglobulins.²⁶

Figure 9.12 Sinusoidal inclusion-containing endothelial cells.

In this example of chronic hepatitis C, multiple small granular inclusions are seen in the endothelium. (Needle biopsy, diastase–PAS.)

Individual causes of chronic hepatitis

Chronic hepatitis B and D

Chronic hepatitis B infection in both adults and children ²⁷^,²⁸ goes through a series of phases marked by different serological, histological and immunocytochemical findings.²⁹ It begins with a period of immune tolerance, in which there are high levels of hepatitis B virus (HBV)-DNA in serum. Hepatitis B e antigen (HbeAg) is positive and anti-HBe negative. Histological activity varies, and both interface hepatitis and lobular hepatitis may be seen on liver biopsy. However, low levels of activity are more common. The surface antigen, HbsAg, is most abundant in the characteristic ground-glass hepatocytes (Fig. 9.13). The ground-glass cells are typically scattered singly throughout the parenchyma at this stage of infection. Their name derives from the finely granular appearance of the central part of the cytoplasm, which is rich in endoplasmic reticulum and hepatitis B surface material. Other organelles are located at the cell periphery and often appear to be separated from the ground-glass area by a pale halo. HBsAg can be demonstrated immunohistochemically (Fig. 9.14) and with orcein or Victoria blue methods. It is most abundant in the ground-glass hepatocytes, but can also be seen in a membranous or submembranous location in hepatocytes without a ground-glass pattern. The differential diagnosis of ground-glass hepatocytes is from the oncocytic cells described in the previous section, from drug-induced hypertrophy of the endoplasmic reticulum (Fig. 8.1) and from inclusion-containing hepatocytes in cyanamide toxicity (Ch. 8), Lafora’s disease, immunosuppressed transplant patients (Ch. 16) and fibrinogen storage disease.³⁰ Clinical circumstances together with immunostaining for HBsAg make confusion unlikely.

Figure 9.13 Chronic hepatitis B with ground-glass hepatocytes.

In many hepatocytes the central part of the cytoplasm has a homogeneous ground-glass appearance. A paler-staining halo is seen around the ground-glass areas in some cells. (Needle biopsy, H&E.)

Figure 9.14 Hepatitis B surface and core antigens with immunohistochemistry.

A: Characteristic cytoplasmic inclusions of HBsAg are present. Inset: HBsAg staining is sometimes membranous or submembranous. B: Nuclear as well as cytoplasmic staining of HBcAg is present in this case, consistent with active viral replication. (Explant liver, specific immunoperoxidase stains.)

The core antigen, HBcAg, is also demonstrable by immunostaining (Fig. 9.14). It is mainly located in hepatocyte nuclei, but also in cytoplasm when necroinflammatory activity is high. Positive nuclear staining correlates with viral load.³¹ Nuclei which contain large amounts of core protein sometimes have a pale, homogeneous appearance on haematoxylin and eosin (H&E)-stained sections and have been described as ‘sanded’³² (Fig. 9.15).

Figure 9.15 ’Sanded’ nuclei with hepatitis B core antigen.

In this case of chronic hepatitis B the pale homogeneous appearance of the affected hepatocyte nuclei (long arrows) reflects the presence of many intra-nuclear core particles. Several normal-appearing nuclei are in the field (short arrows). Many hepatocytes have ground-glass inclusions. (Needle biopsy, H&E.)

The immunotolerant phase of chronic HBV infection is followed by immune clearance and seroconversion to a non-replicative phase in which HBeAg disappears from serum to be replaced by anti-HBe. During the phase of immune clearance, of very variable length, histological activity is typically high.

In the third, non-replicative phase, histological activity is usually considered to be low, as are markers of viral replication. However, in a large study of liver biopsies from patients in this phase, about one-third showed varying degrees of interface hepatitis, sometimes in the presence of normal aminotransferase levels.³³ Lobular activity was not necessarily accompanied by portal and periportal inflammation. Ground-glass hepatocytes may be aggregated in focal accumulations in the non-replicative phase.

Reactivation of virus replication and histological activity are common and are sometimes associated with the emergence of viral mutants. In some of these mutants, expression of HBeAg is defective and histological activity is unexpectedly high, in spite of the negative HBeAg and presence of anti-HBe.

Finally, in a minority of patients with chronic HBV infection, HBsAg becomes negative and anti-HBs appears in the serum. HBV-DNA may still be detectable in small amounts in serum and liver.

This complex evolution, not always as orderly as the above simplified description might suggest, is marked by a very variable degree of fibrosis, depending on the severity and timing of the hepatitic process. Cirrhosis may develop at any stage, especially in patients whose HBV infection is complicated by infection with other viruses such as HCV and HDV.³⁴

Apart from the presence of ground-glass hepatocytes and HBV antigens, there are other features which characterise chronic hepatitis B. Marked variation in the size and appearance of hepatocyte nuclei has been described,³⁵ as has close contact between hepatocytes and lymphocytes,³⁶ in keeping with the immunological nature of the hepatitis. The lymphocytes are usually of CD8+ type, in contrast to the portal infiltrate, which is rich in CD4+ lymphocytes, B lymphocytes and dendritic cells.³⁷ Lymphoid follicles are occasionally found in portal tracts but are less common and less prominent than in hepatitis C.³⁸

Infection with the delta virus (HDV) modifies infection with HBV, as already noted in Chapter 6. Its presence is associated with relatively high histological activity except after liver transplantation. Inflammation is rarely restricted to portal tracts, and there is likely to be substantial inflammation in periportal areas as well as deeper within the lobules. Positive immunostaining for HDV (see Fig. 6.16) denotes active infection. A ‘sanded’ appearance similar to that produced by hepatitis core protein may be seen when there is abundant HDV in hepatocyte nuclei.³⁹ In the presence of HDV infection there is a greater risk of chronicity than with HBV alone, and liver-associated mortality is increased.⁴⁰ Once cirrhosis has developed in patients with hepatitis B, HDV infection confers a greater risk of developing hepatocellular carcinoma and a higher mortality.⁴¹ The prevalence of HDV infection has declined since the 1970s and 1980s as a result of measures to eradicate HBV infection.⁴²

Chronic hepatitis C

Chronic hepatitis C affects more than 170 million persons worldwide.⁴³ It is not usually life-threatening until cirrhosis develops, typically several decades after onset of the hepatitis. Factors associated with faster progression to cirrhosis include older age,⁴⁴ male sex, fibrosis on initial biopsy,⁴⁵ high necroinflammatory activity on initial biopsy,⁴⁶ iron deposition (see Pathological features, below), alcohol consumption, previous HBV infection⁴⁷ and HIV infection.⁴⁸ There are six different genotypes of the virus⁴⁹ affecting disease severity and response to specific treatment;⁵⁰ patients with genotypes 2 and 3 respond best to specific therapy.

The use of liver biopsy in the management of patients with HCV infection has been the subject of extensive discussion. There are serious efforts to replace biopsy to some extent with formulae based on biochemical findings,⁵¹^,⁵² but these fail to predict histological findings accurately.⁸^,⁹ Repeatedly normal or near-normal serum aminotransferases suggest mild histological changes,⁵³ yet a substantial proportion of such patients has been found to have serious liver damage and even cirrhosis.⁵⁴^,⁵⁵ The consensus view appears to be that liver biopsy currently continues to provide useful information not obtainable in other ways.^7,^56,⁵⁷

Pathological features

The histological features of chronic hepatitis C, although not completely diagnostic in themselves, are very characteristic ³⁸^,⁵⁸ (Table 9.4). The portal infiltrate is rich in lymphocytes which often form aggregates or follicles, some of them with prominent germinal centres (Fig. 9.16). These follicles are easily identified in reticulin preparations (Fig. 9.17). Follicles are not restricted to hepatitis C and can also be found in hepatitis B, autoimmune hepatitis and primary biliary cirrhosis, but in hepatitis C they are particularly common and prominent. Within, or to one side of the lymphoid infiltrates, damaged interlobular bile ducts may be seen, as in acute hepatitis. The damage takes the form of vacuolation, stratification and crowding of epithelial cells, and infiltration by lymphocytes.⁵⁹ The virus has been demonstrated in bile-duct epithelium and in bile.⁶⁰ Bile-duct damage is occasionally, but by no means always, associated with a clinically cholestatic course, and rare ductopenia has been reported.⁶¹^,⁶²