Abstract

Pengqiu Min
West China Hospital, Sichuan University, China

The intrahepatic bile duct abscess (IBDA) includes the infection of bile duct itself and the surrounding liver parenchyma abscess [1,2]. It is one of the most severe and important complications of the biliary tract inflammatory diseases. The IBDA is rather popular in China and in some area of Asia as well.

Usually, the IBDA is secondary to the acute obstructive suppurative cholangitis (AOSC) resulting from some obstructive factors and retrograde infection of the bile duct due to different pathogenicity. The causes of the stricture and obstruction of the bile duct may be the cholelith or ascaris within the lumen of biliary duct; the malignancy and inflammatory process originating in the wall of bile duct; the masses adjacent to the biliary tract, especially at the level of the portal hepatis, such as the hepatocellular carcinoma, the cholangiocarcinoma, the mass formation of alveolar type echinococcus, and the enlargement of lymph nodes, etc., compressing and invading the lumen of the biliary tract.

The main pathological processes and the changes of IBDA are as follows: at beginning, the pyogenic cholangitis and pericholangitis occur, consequently the fluid collection with high pressure within the bile duct presents and results in cholangiectasis, and then, the wall of bile duct can be destroyed and penetrated, and the liver parenchyma adjoining the lesion can be invaded and result in liver abscess formation. This kind of liver abscess is usually located at the peripheral area of the liver and preferentially distributes along the biliary tree, which is why it is nominated as IBDA.

The patients with IBDA usually had a history of repeated recurrence of biliary tract disorders or underwent biliary tract surgery. The clinical findings of IBDA mainly include fever, upper right quadrant pain, jaundice, neutrophilia and other findings of primary diseases.

According to a study on the CT manifestations of 31 cases with IBDA identified by surgery or puncture drainage (n=26) and clinical antibiotic therapy with follow up (n=5), the CT features of IBDA can be concluded as follows:
Signs of Liver Abscess (n=31)
Location: preferentially occurred in the peripheral region of the liver, 28 cases (90%)
Size: ranged from 0.2 to 10 cm in diameter
Gas within abscess: 11 cases (35.5%)
Enhancement of the abscess wall: with (9 cases, 29%) and without (22 cases, 71%) surrounded with circular low density shadow Signs of obstructive site of bile duct (N=15)
Cholelithiasis: 8 cases, nodular shape with moderate high attenuation located within the dilated bile duct
Hepatic common bile duct adjacent to the porta hepatis invaded by hepatocellular carcinoma: 2 cases, the lesion of HCC invading the porta hepatis and resulting in dilatation of the intrahepatic bile duct
Hepatic common bile duct adjacent to the porta hepatis invaded by cholangiocarcinoma: 2 cases, contrast enhanced mass occurring in the porta hepatis area, irregular thickening of the bile duct wall, bile duct stricture, and invaded adjacent fat tissue
Alveolar type of echinococcus adjacent to the porta hepatis: 1 case, heterogeneous density with obscure border, irregular calcified spots, no obvious enhancement, and compression of adjacent bile duct with dilatation of intrahepatic bile duct
Ascaris located within left hepatic duct: 1 case, “the sign of double track” showing in the dilated left bile duct, representing the body of ascaris
Post-operative stricture of bile duct: 1 case, gradually tapered stricture of bile duct

SIGNS OF DILATED BILE DUCT (N=29)
Dilatation of bile ducts relevant to obstructive site: 15cases
Extensive dilatation of bile ducts: 14 cases
Communication between dilated bile duct and liver abscesses: 5 cases
Dilated bile ducts located adjacent to liver abscesses: 8 cases

SIGNS OF COMMUNICATION BETWEEN BILE DUCT AND GI TRACT (N=13)
Post-choledochoenterostomy: 11 cases, of which 7 cases with visualization of the anastomosis site Choledochoenteric fistula: 2 cases, gas within gall bladder with obscure border, and hard to separate from adjacent duodenum Gas within intrahepatic bile ducts; 10 cases

In conclusion, CT manifestations of IBDA with different pathogenicity include signs of liver abscess and biliary tract abnormalities. CT features of IBDA are not only helpful for diagnosing the liver abscess, but also can specify the cholangiogenic pathogenicity.