A 61-year-old Caucasian man was referred for a cardiology review after his general practitioner found an abnormal electrocardiogram (ECG) on a routine examination. A repeat ECG at the outpatient department was normal, but further investigations revealed a raised left hemidiaphragm (fig 1) and echocardiography showed a large pericardial cyst. Computed tomography (CT) scan of the thorax identified a cyst measuring 8.9 cm with some compression of the pulmonary artery (figs 2–4). The CT images also showed some compression of the left phrenic nerve as the possible cause of the raised hemidiaphragm.

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Figure 1

Chest x ray showing raised left hemidiaphragm.

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Figure 2

Pericardial cyst in sagittal view (CT reconstruction).

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Figure 3

Pericardial cyst in coronal view (CT reconstruction).

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Figure 4

Pericardial cyst in coronal view (CT reconstruction).

The patient is currently under follow-up by the cardiothoracic team as he has decided against an operation to remove the cyst and plicate the left diaphragm at present.

Pericardial cysts are benign and rare intrathoracic abnormalities that occur in 1 person per 100 000. They make up 7% of all mediastinal tumours. The cyst wall is made of connective tissue and the inner surface is lined with a single layer of mesothelial cells. They contain a clear water-like fluid. The size of the cysts can vary from 2–28 cm (according to case reports). Patients with pericardial cysts are usually asymptomatic, but when symptoms occur they range from atypical chest pain and dyspnoea to persistent cough.1

The management options include observation, percutaneous drainage and surgical resection, depending on the size of the cyst and severity of symptoms.