(Figs 1a and 1b)
(Figs 2a and 2b)
(Figs 1a and 1b)
(Figs 2a and 2b)
Click on Images for Enlarged View
Findings: The PA and lateral chest (Figs 1a and 1b) shows a well circumscribed mass in the right cardiophrenic angle. A CT scan shows this to be a predominantly fat-containing mass (2a). Lower images show this mass to be contiguous with the mesenteric fat, and there is a large anterior defect in the diaphragm (2b).
Diagnosis: Morgagni hernia.
Discussion: The differential if a cardiophrenic angle mass includes pericardial fat, lipoma, pericardial cyst, Morgagni hernia and thymoma.
The presence of fat and demonstrated continuation with the more inferior mesenteric fat is diagnostic of a Morgagni hernia. The added CT finding of a diaphragmatic defect is further supportive of the diagnosis.
The Morgagni hernia is the result of a failure of fusion of the pars sternalis of the diaphragm. It was first described by Morgagni in a post mortem examination in the 1500s. It was later described by Larrey, Napolean’s chief surgeon. While the presence of bowel in an anterior cardiophrenic mass is felt to be the classic presentation of the Morgagni hernia, most of these hernias contain only mesenteric fat. Before CT scanning, the diagnosis was often made by barium exam, which would generally show upward deviation of the transverse colon. Occasionally, small bowel is demonstrated in the hernia.
Currently, CT and MRI are the imaging modalities of choice. While cross-sectional imaging with CT will establish the diagnosis, currently spiral CT with sagittal reconstructions can help better define the diaphragmatic defect.
MRI has also been shown to be a sensitive method of establishing the diagnosis, by both imaging in a coronal plane and often demonstrating the presence of mesenteric vessels continuous with the mass.
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