Pericardial cyst is a rare and benign abnormality. Many patients harboring pericardial cysts are asymptomatic. However, serious, even fatal, complications can arise, such as cardiac failure. Small cysts and asymptomatic cases may be managed conservatively. Surgical resection is recommended if the cysts are large or compress neighboring organs, or the symptoms are troubling or dangerous.
Pericardial cyst occurs rarely, with one person affected in 100,000  . The cysts constitute less than ten percent of mediastinal masses and about a third of mediastinal cysts . They range in size from about 2 cm to almost 30 cm , with a layer of mesothelial cells lining them . The cysts are usually congenital , and originate from the pericardial coelom as the result of abnormal embryonic development . They are most often found at the right cardiophrenic angle . Alternative names include springwater cyst because the fluid inside the cysts has been characterized as crystal clear . Otto Pickhardt performed the first resection of a pericardial cyst and found an orange-sized, shiny cyst  .
Most patients are asymptomatic and the cysts are discovered on radiographs or echocardiograms obtained for unrelated reasons. Symptoms, if they occur, are most often caused by compression of neighboring structures. The most frequent symptoms of pericardial cysts are chest pain, dyspnea, and cough.
Rare but serious complications can arise. One of these is cardiac tamponade, which is usually caused by rupture of the cyst inside the pericardium , or by hemorrhage from the cyst  . Chest pain and signs of respiratory tract infection have been reported . Pulmonary stenosis, right ventricular outflow obstruction, and infection of the cyst can also occur . Giant cysts have been described, one that slowly grew to a size that held two and a half liters of fluid , and another that resulted in the unusual symptom of recurrent syncope because of compression of the right ventricle . A pericardial cyst may infrequently erode adjacent structures, such as the superior vena cava , or partially erode into the right ventricular wall . The cysts can occasionally resolve without intervention.
Imaging methods include plain radiography, echocardiography, computed tomography (CT) scans, and magnetic resonance imaging (MRI). Computed tomography is regarded as the method of choice, because it is helpful in determining the location of lesions, and detects pericardial thickening, and other defects  . CT can distinguish masses derived from mediastinal structures from those arising outside the mediastinum. CT scans can also differentiate cystic structures from solid ones. In problematic cases, injection of contrast material into the cyst may aid in the diagnosis . Most pericardial cysts show well-defined, non-enhancing attenuation on CT scans ; however, protein content in the cysts interferes with attenuation. Hemorrhagic cysts show hyperattenuation.
MRI is also helpful in diagnosis and follow-up examinations. It yields a high signal intensity on T2 weighted images, and a low signal intensity on T1 weighted images. This is altered in cysts containing a high concentration of protein. Diffusion weighted images may be useful in certain cases .
Ultrasound techniques are not the generally favored method for diagnosing pericardial cysts, although echocardiography can be a useful tool for determining the location of the cyst, and for differentiating it from other structural anomalies . Echocardiography has the advantage over CT in that no ionizing radiation is involved .