Normal pericardium is seen as a thin curvilinear structure that is surrounded on either side by epicardial and mediastinal fat (Fig.
1).
The two pericardial layers are not separately indidualized.
The pericardium is prominently seen adjacent to the right ventricular free wall,
right atrioventricular groove,
inferior aspect of the left ventricle,
and left ventricular apex.
It is visualized less clearly adjacent to the lateral left ventricular wall because of the paucity of fat. Normal pericardium measures less than 2 mm in cross sectional studies.
The transverse sinus is situated inferior and posterior to the aorta and the pulmonary trunk,
above the left atrium.
The superior extent of the transverse sinus is the superior aortic recess.
The posterior portion of the superior aortic recess manifests on CT as a well-defined crescentic fluid collection adjacent to the posterior wall of the ascending aorta usually at the level of the left pulmonary artery.
It should not be mistaken for adenopathy.(fig.2)
The right pulmonary venous recess is located between the superior and inferior pulmonary veins.
As the pulmonary vein penetrate the fibrous pericardium to enter the left atrium,
a serosal sleeve of pericardium surrounds the vein and also should not be mistaken for adenopathy.
(fig.3)
Pericardial effusion
A fluid collection with attenuation close to that of water is likely to be a simple effusion.(fig.4)
Pericarditis
Inflammation of the pericardium (pericarditis) has a wide range of causes.
Most of them are idiopathic (80%–85%) and are generally presumed to be viral.
Major nonidiopathic causes include tuberculosis,
neoplasia,
and systemic (generally autoimmune) disease.
On CT images,
pericardial layers are thickened and show diffuse enhancement after contrast material administration.
Similar morphologic findings can be shown on MR images when a combination of T1-weighted, T2-weighted and contrast-enhanced images.
(fig. 5 and 6).
In chronic forms of pericarditis,
pericardial layers tend to be irregularly thickened and effusions may be loculated owing the presence of adhesions.(fig.
7)
Constrictive Pericarditis
This is a condition in which the compliance of the pericardium is decreased,
which may result in impaired ventricular filling,
severe diastolic dysfunction,
and right heart failure. The most frequent causes of constrictive pericarditis are cardiac surgery and radiation therapy.
Other causes include infection (purulent or tuberculous),
connective-tissue disease,
uremia,
neoplasm,
or idiopathic condition.
Figures 8 and 9 show a patient with tuberculous constrictive pericarditis.
Pericardial Tumors
Primary disease is rare and include mesothelioma,
angiosarcoma,
liposarcoma,
lymphoma,
fibroma,
teratoma,
hemangioma,
and lipoma.
Secondary disease has been described in up to 10%–12% of patients and may occur by means of direct invasion of neoplasms originating in the lung (figure 10),
mediastinum,
or heart; by hematologic spread (malignant melanoma,
lymphoma,
breast cancer); or, by venous extension (usually renal cell or hepatocellular carcinomas).
Pericardial Cyst
Benign unilocular mass of celomic origin,
usually incidental findings.
usually have thin smooth walls without internal septa.
At CT they have the same attenuation as water.
At MR imaging,
they typically have low or intermediate signal intensity on T1- weighted images and homogeneous high intensity on T2-weighted images.
They do not enhance with the administration of iodinated IV contrast or gadolinium chelates.
They may occur anywhere in the mediastinum,
although they usually are found in the right cardiophrenic angle (figure 11).
Congenital Absence of the Pericardium
Most pericardial defects are partial and occur on the left side.
Infrequently,
defects also occur on the right side or at the diaphragmatic surface.
Normally,
the aortopulmonary window is covered by pericardium and contains some fat.
Left-sided absence of the pericardium allows interposition of lung tissue between the aorta and the main segment of the pulmonary; the heart usually rotates toward the left (figure 12).
Those findings can be identified by CT or MR imaging.