Indian Journal of Medical Microbiology, Vol. 26, No. 1, January-March, 2008, pp. 80-81
Hydatid cyst of mediastinum
Sehgal S, Mishra B, Thakur A, Dogra V, Loomba PS, Banerjee A
Department of Microbiology, G.B. Pant Hospital, New Delhi -110 001
Date of Submission: 17-Nov-2005
Code Number: mb08019
AbstractWe report a case of hydatid cyst of the mediastinum in a 32-year-old female patient who was admitted with chest pain. CT scan reported posterior mediastinal mass towards the right side. Surgical exploration revealed a loculated cyst in posterior mediastinum on the right side, adherent to the overlying lung and underlying bone. Posterolateral thoracotomy was performed for cyst aspiration and excision. The patient was discharged on albendazole.
Keywords: Hydatid cyst, hydatid disease, mediastinal cyst, mediastinal echinococcosis
Hydatid disease caused by Echinococcus granulosus , E. multilocularis and E. oligarthrus is an uncommon parasitic disease.  The disease poses a serious problem in India, where it is endemic. The primary hosts for the infecting organism are the members of the Canidae family, usually dogs, wolves and coyotes. The intermediate hosts are sheep, cattle and deer. Humans enter the cycle through infected canine faeces. Liver and lungs are the most common sites of infection, but it can also be seen elsewhere in the body.  Extrapulmonary location of the disease in the thorax is very rare. Intrathoracic extrapulmonary locations are generally the mediastinum, pleura, pericardium and chest wall.  We report a case of posterior mediastinal mass, which was provisionally diagnosed as bronchogenic cyst and later confirmed to be hydatid cyst of the posterior mediastinum.
Case ReportA 30-year-old lady was admitted to the cardiovasculothoracic surgery (CTVS) department with complaints of chest pain for the past 6 months. Pain started at the back radiating to the right lateral side of the chest below the nipple. Pain was constant and had a pinprick quality in nature without any change for the last six months. There was no history of trauma, fever, syncope, haemoptysis, haematemesis and dyspnoea on exertion. Laboratory tests were normal except for mild leucocytosis. CT scan of thorax showed a well-defined lobulated cystic lesion 6.2 x 4 x 4.2 cm in size at the right posterior mediastinum [Figure - 1]. The mass lesion was compressing the posterior segment of the upper lobe of the right lung; otherwise, the lung appeared normal. Abdominal ultrasonography (US) revealed a normal liver, spleen and gall bladder. A preoperative diagnosis of bronchogenic cyst was made. Posterolateral thoracotomy was performed and the lung retracted. The cyst was found adherent to the lung. The fluid aspirating from the cyst was straw-coloured and contained some particulate matter. Hence, it was sentfor microscopy to the Microbiology Department. Total cyst excision was performed, and the postoperative stay of the patient in the hospital was uneventful. Microscopy of the aspirated cystic fluid showed hooklets of Echinococcus granulosus . The patient was discharged on albendazole (400 mg once daily for one month).
Hydatid disease has been acknowledged as an important clinical entity since ancient times.  The disease is a serious problem in India, where it is endemic. Although hydatid cysts are mostly seen in the liver and lungs, they may also be located in various tissues of the body. , Extrapulmonary but intrathoracic hydatid cysts are very rare.  Cysts of bronchogenic, pleuropericardial, thymic, intramural, oesophageal, lymphangioma, anterior meningocele and enteric origin, as well as other rare types, may be found in the mediastinum of adults and children.  In one study, out of 1,619 intrathoracic hydatid cysts, only eight (0.5%) were situated in the mediastinum.  Primary hydatid cyst of the mediastinum, although extremely rare, is a distinct clinical entity, which must be considered in a patient with mediastinal mass in endemic regions.  In general, mediastinal echinococcosis is neither clinically nor radiologically distinguishable from other mediastinal cystic lesions.  Diagnosis can be reached after the combined assessment of clinical, radiological, historical and laboratory data of patients, as in the case presented here.
In conclusion, although very rare, hydatid disease should be considered in the differential diagnosis of a cystic lesion of the mediastinum, especially in endemic regions. Chest CT is the most efficient method of diagnosing these lesions. Surgical removal remains the treatment of choice for mediastinal echinococcosis. To avoid recurrence, additional adjuvant medical therapy is recommended.
Copyright 2008 - Indian Journal of Medical Microbiology
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