Liver; Infections and Infestations

Question 1

Cholangitis

Answer 1

Cholangitis is the term used to describe inflammation of the extrahepatic or intrahepatic bile ducts, or both.

There are two main types of cholangitis— pyogenic and primary sclerosing

Question 2

Pyogenic Cholangitis

Answer 2

Cholangitis occurring secondary to obstruction of a major extrahepatic duct causes pyogenic cholangitis.

Most commonly, the obstruction is from impacted gallstone; other causes are carcinoma arising in the extrahepatic ducts, carcinoma head of pancreas, acute pancreatitis and inflammatory strictures in the bile duct. Bacteria gain entry to the obstructed duct and proliferate in the bile.

Question 3

Pyogenic Cholangitis; morphology

Answer 3

The affected ducts show small beaded abscesses accompanied by bile stasis along their course and larger abscesses within the liver.

The abscesses are composed of acute inflammatory cells which in time are replaced by chronic inflammatory cells and enclosed by fibrous capsule.

Question 4

Pyogenic Liver Abscesses classified on the basis of the mode of entry.

Answer 4

1. Ascending cholangitis: is inflammation of the bile duct (cholangitis), usually caused by bacteria ascending from its junction with the duodenum (first part of the small intestine).
2. Portal pyaemia by means of spread of pelvic or gastrointestinal infection.
3. Septicaemia through spread by hepatic artery.
4. Direct infection resulting in solitary liver abscess.
5. Iatrogenic causes include liver biopsy, percutaneous biliary drainage and accidental surgical trauma.
6. Cryptogenic from unknown causes, especially in the elderly.

Question 5

Pyogenic Liver Abscesses; Gross Anatomy.

Answer 5

• They occur as single or multiple yellow abscesses,1 cm or more in diameter, in an enlarged liver.
• A single abscess generally has a thick fibrous capsule.
• The abscesses are particularly common in right lobe of the liver.

Question 6

Pyogenic Liver Abscesses; Morphology

Answer 6

Typical features of abscess are seen. There are multiple small neutrophilic abscesses with areas of extensive necrosis of the affected liver parenchyma. The adjacent viable area shows pus and blood clots in the portal vein, inflammation, congestion and proliferating fibroblasts.

Question 7

Amoebic liver abscesses

Answer 7

• They are caused by the spread of Entamoeba histolytica from intestinal lesions.
• The trophozoite form of amoebae in the colon invade the colonic mucosa forming flask-shaped ulcers from where they are carried to the liver in the portal venous system.
• The patients, generally from tropical and subtropical countries, may give history of amoebic dysentery in the past.
• Cysts of E. histolytica in stools are present in only 15% of patients of hepatic amoebiasis.

Question 8

Amoebic liver abscesses; Gross anatomy

Answer 8

• Amoebic liver abscesses are usually solitary and more often located in the right lobe in the posterosuperior portion.
• Amoebic liver abscess may vary greatly in size but is generally of the size of an orange.
• The centre of the abscess contains large necrotic area having reddish-brown, thick pus resembling anchovy or chocolate sauce.

Question 9

Amoebic liver abscesses; Morphology

Answer 9

The necrotic area consists of degenerated liver cells, leucocytes, red blood cells, strands of connective tissue and debris.

Amoebae are most easily found in the liver tissue at the margin of abscess.

PAS-staining is employed to confirm the trophozoites of E. histolytica.

Question 10

Heptic tuberclosis & its morphlogy

Answer 10

• Tuberculosis of the liver occurs as a result of miliary dissemination from primary complex or from chronic adult pulmonary tuberculosis.
• The patients may have unexplained fever, jaundice, hepatomegaly or hepatosplenomegaly. There may be elevated serum alkaline phosphatase levels and hyperglobulinaemia.

Morphology:

The basic lesion is the epithelioid cell granuloma characterised by central caseation necrosis with destruction of the reticulin framework and peripheral cuff of lymphocytes.

Question 11

Hydatid Disease (Echinococcosis)

Answer 11

Hydatid disease occurs as a result of infection by the larval cyst stage of the tapeworm, Echinococcus granulosus.

About 70% of hydatid cysts develop in the liver which acts as the first filter for ova. However, ova which pass through the liver enter the right side of the heart and are caught in the pulmonary capillary bed and form pulmonary hydatid cysts. Some ova which enter the systemic circulation give rise to hydatid cysts in the brain, spleen, bone and muscles.

Complications of hydatid cyst include its rupture (e.g. into the peritoneal cavity, bile ducts and lungs), secondary infection and hydatid allergy due to sensitisation of the host with cyst fluid.

The diagnosis is made by peripheral blood eosinophilia, radiologic examination and serologic tests such as indirect haemagglutination test and Casoni skin test.

Question 12

Hydatid Disease; Morphology

Answer 12

The cyst wall is composed of 3 distinguishable zones-

1. Pericyst is the outer host inflammatory reaction consisting of fibroblastic proliferation, mononuclear cells, eosinophils and giant cells, eventually developing into dense fibrous capsule which may even calcify.
2. Ectocyst is the intermediate layer composed of characteristic acellular, chitinous, laminated hyaline material.
3. Endocyst is the inner germinal layer bearing daughter cysts (brood-capsules) and scolices projecting into the lumen.

Question 13

Hydatid Sand

Answer 13

Hydatid sand is the grain-like material composed of numerous scolices present in the hydatid fluid. Hydatid fluid, in addition, contains antigenic proteins so that its liberation into circulation gives rise to pronounced eosinophilia or may cause anaphylaxis.