Partial or complete absence of the pericardium

Imaging description Pericardial defects may be congenital, posttraumatic, or post-surgical [1]. Congenital pericardial defects are rare and most often occur on the left [1–3]. Extent of congenital pericardial absence is variable and complete absence of the entire pericardium is exceptionally rare [2]. In fact, the term “complete absence” is at times used to refer to large partial defects that result in cardiac displacement into the left pleural cavity [2]. Congenital defects are attributed to premature atrophy of the left common cardinal vein, which cuts off blood supply to the developing pericardium [2, 3]. On CT and MRI, partial absence of the pericardium may be small enough that normal pericardial position is maintained but the heart is at risk of herniation through the defect with or without incarceration. Large partial defects and complete absence of the pericardium show leftward and/or posterior displacement of the heart on CT and MRI [1, 4, 5] (Figures 65.1 and 65.2). Partial or complete defects may allow interposition of lung tissue between the aorta and the main pulmonary artery or between the base of the heart and the diaphragm, which can help to make the diagnosis on imaging [1, 3–5]. A portion of the heart, such as the left atrium, may bulge through the defect on imaging [1]. The actual pericardial defect may be directly visualized on CT or MRI, although normal intact pericardium may not be readily visualized over the left atrial appendage or left ventricle [4].