Page 620 - Textbook of Pathology, 6th Edition

604 remaining cases various causes associated with increased The effects of portal venous obstruction depend upon
thrombotic tendencies are attributed to polycythaemia vera, the site of obstruction. The most important effect, irrespective
paroxysmal nocturnal haemoglobinuria, oral contraceptives, of the site of occlusion or cause, is portal hypertension and
pregnancy, postpartum state, intra-abdominal cancers (e.g. its manifestations (page 630). If the obstruction is in the
hepatocellular carcinoma), chemotherapy, radiation and extrahepatic portal vein along with extension of occlusion
myeloproliferative diseases. Formation of membranous into splenic vein, it may result in venous infarction of the
webs, probably congenital or as a consequence of organised bowel. Pylephlebitis may be followed by multiple pyaemic
thrombosis, in the suprahepatic portion of inferior vena cava liver abscesses.
is another important cause.
Peliosis Hepatis
MORPHOLOGIC FEATURES. Grossly, the liver is enlar- Although sinusoidal dilatation can occur secondary to many
ged, swollen, red-purple and has a tense capsule. liver diseases, peliosis hepatis is an uncommon condition of
Histologically, the changes in sudden hepatic vein primary sinusoidal dilatation that results in blockage of blood
occlusion are those of centrilobular congestion, necrosis outflow and may result in massive intraperitoneal
and rupture of sinusoids into the space of Disse. In slowly haemorrhage. Although exact etiology is not known, peliosis
developing thrombosis, the changes are more chronic and hepatis and another related condition, bacillary angiomatosis
include fibrosing reaction in the centrilobular zone that (page 413), have been found to occur in HIV-infected patients
may progress to cardiac cirrhosis.
whose CD4+ T cell counts fall below 100/μl. Opportunistic
infection with Bartonella henselae in poor hygienic conditions
CLINICAL FEATURES. Budd-Chiari syndrome is clinically in these cases results in blood-filled cysts in liver partly lined
characterised by either an acute form or chronic form by endothelial cells and having mixed inflammatory cells in
depending upon the speed of occlusion. a fibromyxoid background.
In the acute form, the features are abdominal pain, Etiologic association of peliosis hepatis with consumption
vomiting, enlarged liver, ascites and mild icterus. of anabolic steroids and oral contraceptives has also been
In the more usual chronic form, the patients present with suggested and is self-limiting with withdrawal of the
pain over enlarged tender liver, ascites and other features of offending agent.
portal hypertension.
The acute form of illness leads to acute hepatic failure III. HEPATIC ARTERIAL OBSTRUCTION
SECTION III
and death, whereas in chronic form the patient may live for Diseases from obstruction of the hepatic artery are
months to a few years.
uncommon. Rarely, accidental ligation of the main hepatic
Hepatic Veno-occlusive Disease artery or its branch to right lobe may be followed by fatal
infarction. Obstruction of the small intrahepatic arterial
Hepatic veno-occlusive disease consists of intimal thickening, branches usually does not produce any effects because of
stenosis and obliteration of the terminal central veins and good collateral circulation.
medium-sized hepatic veins. The venous occlusion results
in pathologic changes similar to those of Budd-Chiari
syndrome and can be distinguished from the latter by LIVER CELL NECROSIS
demonstration of absence of thrombosis in the major hepatic All forms of injury to the liver such as microbiologic, toxic,
veins. circulatory or traumatic, result in necrosis of liver cells. The
Systemic Pathology
The cause and stimulus for hepatic veno-occlusive extent of involvement of hepatic lobule in necrosis varies.
disease are obscure. The condition is more widespread in Accordingly, liver cell necrosis is divided into 3 types: diffuse
countries such as Africa, India and certain other tropical (submassive to massive), zonal and focal.
countries where ‘bush tea’ (medicinal tea) is consumed that
contains hepatotoxic alkaloids. The disease has also been 1. DIFFUSE (SUBMASSIVE TO MASSIVE) NECROSIS.
found in association with administration of antineoplastic When there is extensive and diffuse necrosis of the liver
drugs and immunosuppressive therapy. involving all the cells in groups of lobules, it is termed
diffuse, or submassive to massive necrosis. It is most
II. PORTAL VENOUS OBSTRUCTION commonly caused by viral hepatitis or drug toxicity.
Obstruction of the portal vein may occur within the 2. ZONAL NECROSIS. Zonal necrosis is necrosis of
intrahepatic course or in extrahepatic site. hepatocytes in 3 different zones of the hepatic lobule (page
Intrahepatic cause of portal venous occlusion is hepatic 592). Accordingly, it is of 3 types; each type affecting
cirrhosis as the commonest and most important, followed in respective zone is caused by different etiologic factors:
decreasing frequency by tumour invasion, congenital hepatic i) Centrilobular necrosis is the commonest type involving
fibrosis and schistosomiasis. hepatocytes in zone 3 (i.e. located around the central vein).
Extrahepatic causes of portal vein obstruction are intra- Centrilobular necrosis is characteristic feature of ischaemic
abdominal cancers, intra-abdominal sepsis, direct invasion injury such as in shock and CHF since zone 3 is farthest from
by tumour, myeloproliferative disorders and upper the blood supply. Besides, it also occurs in poisoning with
abdominal surgical procedure followed by thrombosis. chloroform, carbon tetrachloride and certain drugs.