Healed hepatic cystic echinococcosis with chronic hydatid cysto-hepato-bronchial fistula

Clinical History

The patient with a severe aortic valve stenosis underwent radiologic workup for a procedure of transcatheter aortic valve implantation. History was non-contributory.

Imaging Findings

Plain chest film showed a cardiomegaly; subtle calcification below the right diaphragm were appreciable (Fig. 1). Contrast-enhanced computed tomography (CT) showed a hypoattenuating nodule measuring 2.5 cm in diameter in the hepatic segment VII. The nodule exhibited an irregular calcified rim and contained a small bubble gas; a direct communication with a bronchus of the anterior segment of RLL was detected (Fig. 2).

Discussion

Intrathoracic rupture accounts for 0.6-16% of complications of a hepatic hydatid cyst, with a mortality rate ranging from 5 to 43% [1, 2]. Intrathoracic migration of a hepatic hydatid cyst occurs almost exclusively through the bare area of the liver, a well-known anatomic pathway for a potential dissemination of a hepatic abscess into the mediastinum [3]. A growing hepatic hydatid cyst can act as a pressure-eroding factor on the bare area of the liver, a weak point with a decreased resistance due to the lack of a peritoneal layer; rupture of the diaphragm may be also caused by a superimposed infection or necrotizing effect of bile or trauma [3–5].

Involvement of the diaphragm varies from simple adherence, sometimes not requiring surgical repair of the diaphragm, perforation of the diaphragm, intrathoracic growth, rupture into the pleural cavity, spreading into lung parenchyma without or with involvement of bronchial branches, chronic bronchial fistula [1]. Classifications of thoracic involvement and cysto-bronchial fistulization were proposed for surgical purpose [1, 4].

Symptoms of an intrapulmonary rupture of a hepatic hydatid cyst clinically are biliptysis, hydatidemesis, haemoptysis, chest pain, cough with expectoration, fever, weight loss and fatigue; allergic reactions and abdominal symptoms (pain, hepatomegaly, jaundice) are less frequent [4–6]. Spontaneous healing is possible when the cystic content is completely cleared through the bronchial tree [6].

Plain chest film can show an elevation of the diaphragm, a pleural effusion sometimes loculated, lung consolidation, laminated atelectasis, a pulmonary mass with an air-fluid level [3, 7].

US remains a keystone in diagnosing cystic echinococcosis of the liver [6, 8] and can show a pleural effusion, but can scarcely demonstrate the diaphragmatic rupture [3].

Conversely CT can reliably detect trans-diaphragmatic spreading of hepatic hydatid cyst, which hinges on a combination of such findings:
a) structural deformity of the hepatic hydatid cyst, with discontinuity and deformity of the calcified or non-calcified cyst wall, signs of contained rupture (waterlilly or snake sign) with gas bubbles into the cyst itself;
b) a round inhomogeneous lesion in the right thoracic cavity with areas of low attenuation and calcifications;
c) ipsilateral pleural effusion [2].

Moreover the cysto-hepato-bronchial fistula can be directly demonstrated with reformations obtained by multislice CT imaging.

MR imaging, highly reliable in staging hepatic hydatid cyst [9], can show the intrathoracic involvement thanks to the possibility of multiplanar acquisitions and thus can be useful in the surgical work up [1].

Differential Diagnosis List

Final Diagnosis

Chronic hydatid cysto-hepato-bronchial fistula

URL:	https://www.eurorad.org/case/13540
DOI:	10.1594/EURORAD/CASE.13540
ISSN:	1563-4086