Systemic Pathology. The Liver, Biliary System & Exocrine Pancreas. Blood supply Portal vein Hepatic arteries Portal Tracts (triad) Bile duct Hepatic artery Portal vein Hepatocyte function Liver cell enzymes AST; ALT; G-Gt. Histology Hepatocytes Acinar & lobules concepts zones
Systemic Pathology The Liver, Biliary System & Exocrine Pancreas
Blood supply Portal vein Hepatic arteries Portal Tracts (triad) Bile duct Hepatic artery Portal vein Hepatocyte function Liver cell enzymes AST; ALT; G-Gt Histology Hepatocytes Acinar & lobules concepts zones Vascular sinusoids Space of Disse Bile caniculi Perisinusoidal cells of Ito Changes with age Fetus α-fetoprotein Adult albumin Old brown atrophy (lipofuscin) Normal Structure & Function
Liver maintains metabolic homeostasis • Process dietary compounds • Synthesise serum proteins • Detoxification of blood • Excretion of endogenous waste bile • Liver vulnerable to many insults • Huge functional reserve advanced progression of disease before clinically apparent • Liver disease process can overlap with gall bladder & biliary tree
This is an in-situ photograph of the chest and abdominal contents. As can be seen, the liver is the largest parenchymal organ, lying just below the diaphragm. The right lobe (at the left in the photograph) is larger than the left lobe. The falciform ligament is the rough dividing line between the two lobes.
The cut surface of a normal liver has a brown color. Near the hilum here, note the portal vein carrying blood to the liver, which branches at center left, with accompanying hepatic artery and bile ducts. At the lower right is a branch of hepatic vein draining blood from the liver to the inferior vena cava.
Liver is divided histologically into lobules. The center of the lobule is the central vein. At the periphery of the lobule are portal triads. Functionally, the liver is divided into three zones, based upon oxygen supply. Zone 1 encircles the portal tracts (O2 blood from hepatic arteries enters). Zone 3 is located around central veins, where oxygenation is poor. Zone 2 is located in between.
Investigation of Liver Disease • Bilirubin • Enzymes • Albumin • Clotting factors • Immunology • Biopsy • Imaging
Infants(physiological neonatal jaundice) Structural Congenital Abnormalities: • Biliary atresia failure of bile duct development • Biliary hypoplasia • Autosomal dominant syndrome • Paucity of bile ducts dysmorphic facies, skeletal abnormalities & mental retardation • Congenital hepatic fibrosis • Autosomal recessive disorder • Hepatic fibrosis associated with cystic kidneys • Choledochal cysts Functional Abnormalities: • Congenital metabolic defects • Congenital hyperbilirubinaemias
Classification of Jaundice Pre-hepatic causes: • Haemolysis anaemia • Unconjugated hyperbilirubinaemia • Normal colour urine acholuric jaundice Intra-hepatic causes: • Hepatitis; decompensated cirrhosis; intr-hepatic bile duct loss; Pg; congenital hyperbilirubinaemia • Intra-hepatic cholestasis plugs of bile pigment descending canaliculi or bile ducts • Conjugated hyperbilirubinaemia variable urine darkening Post-hepatic causes: • Gallstones; biliary strictures; tumours; biliary atresia • Conjugated hyperbilirubinaemia urine darkening; pale faeces
Cholestasis Results from: • Hepatocellular dysfunction • Biliary obstruction Presentations: • Pruritis ( serum bile acids) • Hyperlipidaemia skin xanthomas (focal cholesterol accumulation) • Malabsorption EFA & fat soluble vitamins (A; D; K) • serum alkaline phosphatase Morphology: • Accumulation of bile pigment in hepatic parenchyma • Elongated green plugs of bile visible in dilated canaliculi rupture extravasion of bile into sinusoids phagocytosed by Kupffer cells) • Foamy degeneration fat droplet accumulation • Oedema & periductal neutrophilic infiltrates portal tract • Unrelieved obstruction portal tract fibrosis biliary cirrhosis
Hepatic Injury • Inflammation • Hepatitis • May be limited to portal veins or spill into parenchyma • Dead hepatocytes engulfed by macrophages • Degeneration • Ballooning irregular clumped cytoplasm & larger, clear spaces • Foamy retained biliary material diffuse foamy appearance • Steatosis accumulation of fat deposits in hepatocytes
Necrosis • Coagulative mummified hepatocytes remain (ischaemia) • Apoptosis toxic; immunologic • Lytic necrosis hepatocytes swell & rupture • Centrilobular equal distribution of necrosis around central vein (ischaemia; toxins; drugs) • Bridging severe inflammation or toxins • Portal-to-portal • Portal-to-central • Central-to-central • Fibrosis • Response to inflammation (irreversible) • Deposition of collagen effects on hepatic metabolism & blood flow • Begins around portal tracts or central veins spreads links other regions (bridging fibrosis) • Cirrhosis • Regenerating hepatocytes surrounded by scar tissue • Due to continued parenchymal injury & fibrosis • End stage of liver disease
Major Biochemical Consequences • Hepatocellular damage • serum aspartate aminotransferase (AST) • serum alanine aminotransferase (ALT) • Hepatocellular function • serum albumin • PT • serum ammonia • Biliary excretory function • serum & urine bilirubin • serum bile acids • serum alkaline phosphatase plasma membrane damage in bile canaliculi
Acute Liver Injury • The major causes of acute liver injury are: • viral infections • high alcohol consumption • adverse drug reactions • biliary obstruction, commonly due to gallstones. • Direct physical injury to the liver (e.g. laceration in a road traffic accident) • Recovery from acute liver injury, focal or diffuse, is attributable to the capacity of the organ for cellular regeneration. • However, in practice, the same agent may produce either an acute or a chronic illness, in the latter event not necessarily with any preceding clinically evident acute phase.
Histology • Histological evidence of: • liver cell degeneration or death • inflammatory reaction • Diagnostic changes specific to the causative agent. • Pattern of liver cell damage important: • Apoptosis • Death of individual liver cells • most frequent pattern in viral hepatitis • usually denotes certain recovery with no long-term sequelae. • Interface hepatitis (Piecemeal necrosis) • Death of periportal hepatocytes or entire acinar zones • usually zone 3 (bridging necrosis) • disturbs the hepatic architecture and leads to a risk of cirrhosis developing. • Panacinar Necrosis • Liver cell death substantially affecting the entire acinus • leads to liver failure and a significant risk of immediate death.
Clinico-Pathological Features • Most of the signs and symptoms of acute liver damage are predictable from the known functions of the liver. • malaise • jaundice • serum bilirubin and transaminases • Itching bile salt accumulation • severe cases evidence of liver failure. • Severe acute liver damage can lead to: • bruising and haemorrhage (clotting factor deficiency) • coma accumulation of toxic metabolites which mimic neurotransmitters ('false neurotransmitters').
Laboratory Investigations(Table 16.2 & 16.3) • elevated levels of serum enzymes & bilirubin • Liver cell damage • impairment of some bilirubin conjugation • failure to excrete conjugated bilirubin and any stercobilinogen absorbed from the gut (table 16.3) • urine is darkened by the presence of excess conjugated bilirubin and urobilin (derived by oxidation from urobilinogen) • As liver damage persists little or no bilirubin from liver urobilinogen disappears from urine • Jaundice due to bile duct obstruction-commonly by gallstones: • dark urine excess conjugated bilirubin • urobilinogen is usually absent, unless the obstruction is of very recent onset or intermittent, because no bilirubin reaches the intestine. • Examination of urine and faeces (for colour) can therefore assist in the differential diagnosis of jaundice (Table 16.2).
Viral Hepatitis • The main hepatitis viruses are HAV; HBV; HCV; HEV (Table 16.3) • These hepatitis viruses are immunologically distinct infection usually confers life-long immunity to the infecting virus but not to the others. • The clinical features range: • Asymptomatic • trivial illness without jaundice (anicteric hepatitis) • significant illness with jaundice and other clinical evidence of disturbed liver function. • Yellow fever (group B arbovirus) • shares many clinical and histological features with typical ‘viral’ hepatitis • not included geographical distribution is very restricted • Ab detection: IgM killer acute disease; IgG memory • Other viruses that may cause hepatitis: • EBV infectious mononucleosis • HSV-1 • CMV • Rubella; adenovirus; enterovirus
Clinical Consequences • Carrier State • Harbours virus (can transmit) • No apparent disease; sub-clinical symptoms (non-progressive) • Normal serum transaminase • Asymptomatic Infection • Incidental identification • Increased serum transaminase & presence of anti-viral Ab • Acute Viral Hepatitis • Incubation non-specific pre-icteric phase specific icteric phase convalescence • Chronic Viral Hepatitis • Asymptomatic, biochemical or serological evidence of continuing or relapsing hepatic disease (> 6 months) • Viruses major cause (others? e.g. RHO; drugs; …) • Variable clinical features with persistent increased aminotranferase
Hepatitis A Virus • Small, non-enveloped, single stranded RNA piconovirus • Benign self-limiting disease • Mostly epidemic poor hygiene & sanitation • Faecal-oral trasmission • contaminated food & drink • Virus shed in stool 2-3 weeks before & 1 week after onset of jaundice • Relatively short incubation period (2-6 weeks) • Mild or asymptomatic benign & self-limiting • Virus not directly cytotoxic to hepatocytes • Liver injury d.t. immunologically mediated damage of infected cells • no chronic hepatitis or carrier state • Diagnosis • IgM-anti-HAV-Ab acute illness; viral shedding • IgG-anti-HAV-Ab life-time immunity; previous exposure
Hepatitis B Virus • Double-stranded DNA containing hepadnaviradae: • HBcAg (core-Ag) nucleocapsid ‘core’ protein • HBeAg nucleocaspid protein secreted into blood • HBsAg (suface-Ag ) envelope glycoprotein immunogenic in blood • DNA polymerase joins DNA together • HBV-x-protein transcription activator of host genes incorporated into host genome cancer? • Results in: • Acute hepatitis with recovery & virus clearence • Non-progressive chronic hepatitis • Progressive chronic disease cirrhosis • Fulminant hepatitis with massive liver cell necrosis • Asymptomatic carrier state with or without progressive sub-clinical disease
Transmission • Blood & bodily fluids sexual contact • Body secretion contact (e.g. semen; saliva; tears; etc) • Contaminated needles or blood products • Relatively long incubation period 4-26 weeks • Remains in blood during active episodes of acute & chronic hepatitis present in all physiological & pathological body fluids (except stool) 2-phases of HBV infection • Proliferative phase • HBV DNA in episomal form • Formation of complete virons & all associated antigens • Activation of cytotoxic CD8+ T-lymphocytes • Integrative phase • Viral DNA incorporated into host genome
HBV Pathology • Infection causes viral antigens to appear on the cell surface HBsAg • HBsAg recognised by the body's immune system infected liver cells that bear them are destroyed • Impaired immunity or tolerance to the antigen virus can survive in the liver cells without causing damage asymptomatic carriers body fluids are a risk to other individuals. • Liver biopsies of HBV-infected carriers show that the liver cells have a ground-glass texture to their cytoplasm due to the abundance of virus particles.
Serum markers follow natural disease course: • HBs-Ag • Before onset of symptoms peaks during overt disease • Declines over 3 – 6 months • HBe-Ag • Appear soon after HBs-Ag active viral replication • Shows continued replication or infectivity progression chronic hepatitis • HBV-DNA; DNA-polymerase • Appear soon after HBs-Ag active viral replication Body response during acute disease: • IgM-anti-HBc-Ab • Detectable before symptom onset • Concurrent with aminotransferase • Replaced by IgG-anti-HBc (months) • Anti-HBe-Ab • Acute infection peaked wane period begins • IgG-anti-HBs-Ag • Rises after acute disease • Detectable weeks to months after HBs-Ag
The A virus appears to be directly cytopathic. The B virus evokes liver cell injury by causing viral antigens to be expressed on the liver cell surface infected cells are eliminated immunologically. An asymptomatic carrier state can ensue in the absence of specific immunity. The pathogenesis of other hepatitis viral infections is uncertain.
HBV Clinical Features • HBV infection more serious than HAV • Infection is more likely to produce a clinical illness jaundice • More likely to result in long-term sequelae • chronic hepatitis • Cirrhosis • fulminating acute infection extensive hepatic necrosis death • Hepatitis B virus is also implicated in the pathogenesis of liver cell carcinoma. • Specific diagnosis: • hepatitis B surface antigen (HBsAg) • HBeAg indicate the presence of active liver disease.
Hepatitis C Virus • Single stranded RNA virus Flaviviridae • Multiple types & sub-types • Transmission: • Close personnel contact • Inoculations & blood transfusions • Incubation period 2-26 weeks • Clinical course milder than HBV 75% asymptomatic • HCV RNA detectable in blood • 1-3 weeks • With episodic increase of aminotransferase levels • Even in absence of clinical symptoms • Neutralizing anti-HCV-Ab’s weeks to months • Tendency to chronicity 20% cirrhosis
Histology • HAV & HBV : • cytoplasmic swelling of liver cells • apoptotic death of individual liver cells formation of eosinophilic Councilman bodies (first described in yellow fever) • infiltration of portal tracts by mixed inflammatory cells and expansion by oedema • hyperplasia of Kupffer cells recovery cellular debris (ceroid) accumulates in their cytoplasm • accumulation of bile in liver cells, which are often swollen, and within the intercellular canaliculi cholestasis • HCV: • presence of lymphocytes within the vascular sinusoids • fatty change in the hepatocytes • sometimes with relatively little evidence of active liver cell death. • this combination of features is unusual in HAV or HBV infection.
Hepatitis D Virus • Double straded coat • HBs-Ag coat N.B. co-infection • HDV-Ag RNA • Transmission parental • Incubation 4 – 7 weeks • Rarely cause fulmnant or chronic hepatitis • 2 settings • Acute co-infection HBV & HDV in serum • Supra-infection in chronic HBV carier state • IgM-anti-HDV-Ag indicator of recent infection • Co-infection IgM-anti-HBc-Ag • Chronic HBV from HDV supra-infection • IgM-HBc-Ag • Continued HDV-Ab (IgM & IgG)
Hepatitis E Virus • Non-enveloped, single stranded RNA virus • Water-borne agent enterically transmitted viron detected in stool • Endemic to India; Sporadic outbreaks uncommon • Incubation period 2 – 8 weeks • Usually self-limiting full recovery is usual • Not associated with chronic liver disease or persistent viraemia • High mortality rate amongst pregnant woman • HEV-Ag cytoplasm of hepatocytes acute phase • Serum anti-HEV-Ag & HEV-RNA
Hepatitis G Virus • Flavivirus (similar to HCV) • Transmission • Replication in mononuclear cells no increased transaminases • No pathological effects • Blood supply does not require screening • Positive effects on patients infected with HIV
Grossly, there are areas of necrosis and collapse of liver lobules seen here as ill-defined areas that are pale yellow. Such necrosis occurs with hepatitis.
The necrosis and lobular collapse is seen here as areas of haemorrhage and irregular furrows and granularity on the cut surface of the liver.
Viral hepatitis leads to liver cell destruction. A mononuclear inflammatory cell infiltrate extends from portal areas and disrupts the limiting plate of hepatocytes which are undergoing necrosis, the so-called "piecemeal" necrosis of chronic active hepatitis. In this case, the hepatitis B surface antigen (HbsAg) and hepatitis B core antibody (HbcAb) were positive.
Individual hepatocytes are affected by viral hepatitis. Viral hepatitis A rarely leads to significant necrosis, but hepatitis B can result in a fulminant hepatitis with extensive necrosis. A large pink cell undergoing "ballooning degeneration" is seen below the right arrow. At a later stage, a dying hepatocyte is seen shrinking down to form an eosinophilic "councilman body" below the arrow on the left.
This is a case of viral hepatitis C, which in half of cases leads to chronic liver disease. The extent of chronic hepatitis can be graded by the degree of activity (necrosis and inflammation) and staged by the degree of fibrosis. In this case, necrosis and inflammation are prominent, and there is some steatosis as well. Regardless of the grade or stage, the etiology of the hepatitis must be sought, for the treatment may depend upon knowing the cause, and chronic liver diseases of different etiologies may appear microscopically and grossly similar.
This is a case of viral hepatitis C which is at a high stage with extensive fibrosis and progression to macronodular cirrhosis, as evidenced by the large regenerative nodule at the center right. The screening laboratory test for this form of viral hepatitis is the hepatitis C antibody test.
Hepatitis C accounts for most (but not all) cases formerly called "non-A, non-B hepatitis". In addition to this serologic test PCR and genotyping can be performed. Nucleic acid sequencing identifies of six common HCV types (1a,b-5) which have different clinical courses and responsiveness to alpha interferon therapy. Infection with HCV type 1b or 4 leads to more severe liver disease, faster progression to chronic hepatitis, and less responsiveness to interferon therapy. Type 1a, 2, 3, and 5 infections have a more favorable prognosis. Type 2 and 3 infections may be treated with shorter therapeutic regimens.
This trichrome stain demonstrates the collapse of the liver parenchyma with viral hepatitis. The blue-staining areas are the connective tissue of many portal tracts that have collapsed together.
Autoimmune Hepatitissyndrome of chronic hepatitis with heterogenous set of immunologic abnormalities • Histology indistinguishable from chronic viral hepatitis • Endolent or severe course responds to immuno-suppression • Salient features • Female predominance (70%) • Absence of serological markers of viral aetiology • serum IgG levels • High titres of auto-Ab (80%) • frequency HLA-B8 or HLA-DRw3 • Other forms of autoimmune disease e.g. RA; SLE; Sjogrens; etc • Sub-types • Circulating anti-nuclear and/or anti-smooth muscle-Ab (80%) • Liver/kidney microsomal type 1 Ab’s (5%) • Presence of Ab to soluble liver Ag • Symptomatic patients present with severe liver damage • 5% cirrhosis death
Liver Abscess • Developing countries • Parasitic liver abscesses more common • E.g. amaobia; helmithic • Developed (Western) Countries • Bacterial or fungal origin more common • Complication of infections elswhere • Organisms reach liver via • Ascending infection in biliary tract (ascending cholangitis) • Vascular seeding portal or arterial • Direct liver invasion from nearby source • Penetrating injury
Risk factors debilitating dx with immunodeficiency: • Immunocomprimised • Chemotherpy • Old age • Marrow failure • Pyrogenic bacteria hepatic abscesses • Solitary or multiple lesions • Small to masssive in size • Clinical features • Fever • RUQ pain • Tender hepatomegaly • Jaundice (biliary obstruction) • Antibiotic treatment may contain smaller lesions • Surgical drainage often necessary • Diagnosis often delayed 30 – 90% mortality rate
Drug & Toxin Induced Liver Dx • Injury due to • Direct toxicity • Conversion of drug/non-endogenous substance to active toxin • Immune mechanisms drug/toxin acting as a hapten • Classification • Predictable (intrinsic) sufficient amount accumulated • Unpredictable (isiosyncratic) immune response • May take the form of • Hepatic necrosis • Cholestasis • Insidious onset of liver dysfunction • Injury may be immediate or take weeks or months to develop • Clinically & histologically indistinguishable from chronic viral hepatitis or autoimmune hepatitis
Alcoholic Liver Disease • Excessive alcohol consumption • 80g ethonol per day short term mild, reversible hepatic changes (e.g. fatty liver) • 160g ethonol per day 10-20 yrs severe liver injury • Chronic intake 80 -160g ethonol per day bordorline risc • Females more susceptible than males ( gastric metabolism of ethonol) • 10-15% alcoholics cirrhosis individual genetic susceptibility • No ‘safe’ upper limit for alcohol consumption
R-OH major coloric source: • Malnutrtion • Vitamin deficiencies • Clinical Features • Hepatic failure • Massive GIT haemorrhage • Intercurrent infection • Hepatorenal syndrome • Hepatocellular Ca • Compounded by • Impaired digestion (mucosal damage) • pancreatitis • 3 distinct forms • Hepatic steatosis 80% • Alcoholic hepatitis 10-35% • Cirrhosis 10%
Hepatic Steatosis • R-OH intake microvascular lipid droplets accumulate in hepaocytes • Chronic R-OH intake macrovascular globules accumulte displaces & compresses nuclei to the periphery • Macroscopically large, soft, yellow & greasy liver • Fatty change reversible until appearance of fibrosis • Little or no fibrosis at onset fibrosis develops around central vein extends to adjacent sinusoids • Clinical features • Hepatomegally • Mild serum bilirubin & ALP • May be no clnical or biochemical evidence