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	Complications of Cystic Hydatid Disease *Rupture* The causes of rupture include trauma, medical treatment, and degeneration of the endocyst. Three types of rupture are possible: contained, communicating and direct. *Contained Rupture* This occurs when the endocyst ruptures in a lesion in which patent biliary radicals (or bronchi in the case of pulmonary lesions) do not penetrate the pericyst (Fig. 3.27 ). The actual incidence of contained rupture is unknown since it is asymptomatic and is diagnosed fortuitously when sectional imaging shows floating membranes within the hydatid lesion. Lung hydatids are often not imaged by CT or MRI and virtually never by ultrasound so contained rupture of lung lesions is probably underdiagnosed. Contained rupture does not invariably cause premature death of the cyst and does not predispose to secondary bacterial infection. Fig. 3.27 Transverse CT scan through the liver showing ruptured Type I hydatid cysts in a Saudi Arabian child who was treated medically with an oral antihelminthic which killed the cysts and caused spontaneous rupture. Because the cysts did not become smaller and there was no evidence of biliary obstruction, the rupture was assumed to be contained. Purely medical treatment is generally avoided in such cases because of the danger of provoking communicating or direct rupture. This patient was lost to follow-up. (Courtesy of Dr. Lewall and Clinical Radiology, 1998). *Communicating Rupture* Communicating rupture is possible when biliary radicals or bronchi perforate the pericyst in the liver or lung, allowing fluid and formed elements to escape into the biliary or bronchial tree (Fig. 3.28). Communicating rupture in the lung leads to expectoration of salty fluid and sometimes of fragments of endocyst, which the patient describes as "grape skins". If air enters the partially evacuated pericyst cavity, the "floating water lily sign" is seen on upright chest radiographs. Communicating rupture is apparently more common in lung than liver, presumably because of a higher incidence of bronchial than biliary patency through the pericyst. This is probably because bronchi are more robust than bile ducts and are less likely to be obliterated by the developing pericyst. Communicating rupture of lung cysts does not always kill the parasite. Because of the propensity of lung cysts to rupture, surgeons usually operate on lung lesions before they attend to those in the liver if the patient has both. Scolices probably do not survive in the hostile environment of the biliary tree, but scolices that were accidentally spilled into the tracheobronchial tree during resection of pulmonary hydatids were estimated to be the cause of secondary lung lesions in 0.61 % of 650 patients. Thus, it is likely that spontaneous communicating rupture of lung cysts can lead to transbronchial spread of hydatid disease. The distinction between contained and communicating rupture is not always possible. .... Fig. 3.28 (A) Longitudinal ultrasound scan of liver showing type I cyst prior to treatment. (B) Transverse US scan after treatment with an oral antihelminthic which caused the cyst to rupture. The fact that the cyst became smaller and less spherical proves that this is a communicating rupture even though dilated bile ducts are not demonstrable. Note the detached endocyst membranes on this transverse scan. A few days after this examination this Saudi Arabian patient developed biliary obstruction and required surgery. (Courtesy of Dr. Lewall and Clinical Radiology, 1998). Next Page Previous Page