Pericardial Hydatid Cyst

A 69-year-old male was admitted to our hospital with chest pain, fatigue and dry cough lasting for one month prior to admission. His medical history yielded no important clinical feature. Physical examination revealed normal respiratory and heart function. Chest X-ray demonstrated widening of the mediastinum with lobulated contours.

Axial contrast-enhanced CT images (Fig 1 a,b) demonstrate a low-attenuated mass with multicystic appearance located in the left pericardial space. Axial chest CT image (Fig 2 a) reveals a low attenuated mass adjacent to ascending aorta. Axial chest CT image (Fig 2 b) at lower level shows a pseudoaneurysm arising from right lateral wall of the ascending aorta protruding into the neighbouring low attenuated cystic mass.

Hydatid cyst is a parasitic disease which occurs secondary to the development of the larval form of E. Granulosus. Cardiac involvement in hydatid disease is very uncommon and accounts for 0.5%-2% of all hydatisosis cases. Most frequently involved site in the heart is myocardium while pericardial involvement occurs in 2%-10% of cardiac echinococcosis [1, 2].    Pericardial involvement of hydatid cyst may be caused by systemic circulation which results from fissuring of hydatid cyst from liver or lung, transdiaphragmatic dissemination or via lymphatic circulation [3].

       Patients with pericardial hydatid cyst may remain asymptomatic until echinococcal cyst causes pressure effect on surrounding structures. Presenting symptoms of uncomplicated pericardial hydatid cyst include chest pain due to the stretch of pericardium and/or compression of coronary vessels, dyspnea, and palpitations [4].

Although pericardial hydatid cyst can be depicted by transthoracic echocardiography cross-sectional imaging studies like CT and/or MRI are usually necessary which demonstrate preoperative cardiac anatomy, the location and size, calcification of the cyst, and its adhesions and relationship to adjacent structures. CT is a better imaging technique in revealing is small calcifications which may be a helpful imaging finding in the diagnosis of a hydatid cyst. Relationship of hydatid cysts with adjacent structures can be depicted by MRI. Hydatid cysts present as a hypointense mass on T1- weighted images and hyperintense on T2-weighted images. A hypointense rim around the mass on T2-weighted images represents pericyst. Daughter cysts are characterized by cystic structures that are attached to the internal wall of the cyst with fluid signal intensity. 

       Treatment of pericardial hydatid cyst can be accomplished with surgical excision of the cystic lesion. Medical treatment (e.g., albendazole and mebendazole) is complimentary for disseminated cases and for prophylaxis.