Epipericardial Fat Shadows in Differential Diagnosis

As any one who has seen an appreciable number of autopsies can testify, the accumulation of sizable quantities of adipose tissue outside the pericardium of obese individuals is a commonplace occurrence. It is also common knowledge that these epipericardial fat pads frequently are visible roentgenologically along the left heart border, at times completely obliterating the left cardiophrenic angle. What is apparently not so widely recognized is the fact that large extrapericardial fat deposits occasionally produce well defined roentgenographic shadows adjacent to the right heart border. In this location they sometimes present particularly difficult diagnostic problems. The literature on the subject of pericardial fat is widely scattered and surprisingly meager. As long ago as 1910, Schwarz (1) described the frequent fluoroscopic observation of triangular shadows of increased density obscuring the left cardiophrenic angle in some of his obese patients. Because these shadows were less dense than that produced by the heart itself, Schwarz concluded that they represented fat tissue, a fact which he repeatedly confirmed at autopsy. A few additional references to Schwarz's observations followed (2, 3, 4), and then, in 1936, McGinn and White (5) re-emphasized the importance of recognizing epipericardial fat deposits to avoid errors in roentgenologic estimation of heart size. During the same year, Kautz and Pinner (6) stated that “after reviewing a large roentgenologic material and evaluating the very few observations in the literature, we reached the conclusion that under certain circumstances extrapericardial fat bodies may be visualized roentgenologically.” These authors then presented the roentgenologic and anatomic findings in a patient with prominent fat shadows at both cardiophrenic angles and listed some of the intrathoracic conditions with which these fat bodies might be confused. Our current interest in right epipericardial fat deposits is largely centered around the problem they present in photofluorography. The opportunity to view literally thousands of chest roentgenograms afforded by the increasingly popular mass survey methods employing miniature film has made the roentgenologist acutely aware of a number of insignificant normal variations in the appearance of intrathoracic structures. At times, some of these findings are extremely difficult to distinguish from clinically important lesions. The wide anatomic and physiologic variations in the size and shape of the heart, the frequent unexplained accentuation of the undivided portion of the pulmonary artery or of peripheral vascular markings in the upper portions of the lungs, and the startling prominence of the innominate artery buckled outward by a tortuous thoracic aorta, are just a few of many examples which might be mentioned.