Complications of Cystic Hydatid Disease (continued)

Direct Rupture

Direct rupture, which can have disastrous consequences, occurs when both endocyst and pericyst are torn. This usually happens to lesions near the edge of the liver, where the protective pericyst may be deficient and where there is little host tissue to offer support. In the lungs, the thin pericyst and compliant pulmonary parenchyma around cysts offer relatively poor protection to the endocyst. Fluid and infectious scolices spill into the peritoneal or pleural cavity causing seeding (Fig. 3.30) and often anaphylaxis, which is much more frequent after direct rupture than after communicating rupture, apparently a result of antigenic hydatid fluid contacting a serosal surface.

Direct rupture into many sites has been reported, including the liver, bile ducts (Fig. 3.29), pleura, lung, gastrointestinal tract, and great vessels. Direct rupture into soft tissues almost certainly explains the development of small satellite lesions around a cyst. This type of rupture probably accounts for most reports of recurrence after surgery. Other causes of "recurrence" are small lesions that were not detected preoperatively, and growth of new lesions resulting from spillage of scolices during surgery. More complex explanations of recurrence such as exophytic growth do not seem tenable on biological grounds because there is no germinal layer on the outside of the endocyst. Bulging of part of the wall of the mother cyst, sometimes seen when cysts are near the edge of the liver or when they abut a fissure, must not be confused with exophytic budding. Biliary obstruction is usually not a feature of direct rupture because the cyst is quickly decompressed and solid elements are not forced into downstream ducts. Direct rupture usually leads to premature death of the cyst and theoretically can result in bacterial infection of the pericyst cavity.

Hydatid cysts in any site which result from rupture are termed secondary cysts (Figs. 3.30 & 3.31). Most pleural cysts result from direct rupture of lung hydatids into the pleural space or from rupture of liver cysts through the diaphragm. Biliary-bronchial fistulae are a consequence of direct rupture of a liver cyst through the diaphragm and pleural membranes into the lung. The inflammatory reaction elicited by bile in the lung facilitates the biliary-bronchial connection. Cyst rupture is shown diagramatically in (Fig. 3.26).

Fig. 3.29 ERCP showing connection between the biliary tree and a Type II cyst. During prolonged medical treatment before intended elective surgery the cyst ruptured and this Saudi Arabian patient developed biliary obstruction. Urgent surgery was performed to avoid the development of cholangitis. C collapsed pericyst. Arrow communicating bile duct. (Courtesy of Dr. Lewall.)

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