CASE 13657 Published on 05.05.2016

Morgagni hernia containing omental fat: differential diagnosis with prominent epicardial fat pad

Section

Chest imaging

Case Type

Clinical Cases

Authors

Eleonora Tricarico1, Francesco Tricarico2, Carlo Florio3

(1) University of Bari Medical School,
DIM - Section of Diagnostic Imaging;
Piazza Giulio Cesare 11
70124 Bari, Italy;
Email:eleonoratric@gmail.com
(2) P. O. San Paolo,
Dpt of Diagnostic Imaging,
Via Caposcardicchio,
70123 Bari, Italy
(3) C. B. H. Mater Dei,
Dpt of Diagnostic Imaging,
Via Hahnemann
70124 Bari, Italy
Patient

50 years, male

Categories
Area of Interest Mediastinum ; Imaging Technique CT
Clinical History
A 50-year-old male patient underwent chest CT for the suspicion of a pulmonary nodule detected on chest radiograph. Another finding on lateral chest radiograph was a triangular opacity in the low retrosternal space, suspected to be prominent epicardial fat pad. The patient did not present with any symptoms.
Imaging Findings
Chest CT (computed tomography) did not show any pulmonary abnormalities. The retrosternal opacity seen on chest radiograph (Fig. 1) corresponded to prominent soft tissue with fat density, which obliterated the right cardio-phrenic angle (Fig. 2). At first, the finding was considered to be prominent epicardial fat pad, but, after careful evaluation, an opening in the anterior portion of the right hemidiaphragm was seen, with continuity between the right cardio-phrenic fat and the intra-abdominal fat (Fig. 3). Furthermore, the prominent fat tissue mildly displaced the lateral wall of the right atrium (Fig. 2c). Sagittal-CT images clearly showed fine linear densities within the fat tissue which cross the diaphragmatic opening and reach the anterior mediastinum, representing omental vessels (Fig. 3b). The diagnosis of Morgagni hernia containing omental fat tissue was made.
Discussion
The "epicardial fat pad" corresponds to adipose tissue located in the cardio-phrenic space which is the most basal mediastinal region and is delimited by the base of the heart, diaphragm, and chest wall [1]. A prominent epicardial fat pad may be idiopathic, but is more frequently seen in overweight patients and in certain clinical conditions, i. e. Cushing syndrome and prolonged steroid therapy. A prominent epicardial fat pad leads to an opacity of the cardio-phrenic space on chest radiograph and is quite easily diagnosed as such. In case of diagnostic doubts, CT or MRI (magnetic resonance imaging) may confirm the diagnosis or show other abnormalities of the cardio-phrenic space, i.e. cystic lesions, solid lesions and fat-containing lesions like a Morgagni hernia [1].
Morgagni hernia was first described in 1769 and is characterised by herniation of abdominal viscera into the thorax through the foramen of Morgagni, which is located immediately adjacent to the xiphoid process of the sternum and arises from the failure of closure of the septum transversarium of diaphragm with the seventh costochondral arch. Some authors refer to this type of defect occurring on the right as “Morgagni’s gap” and the one that is located on the left as “Larrey’s gap” [2]. Morgagni hernia represents only 2-3% of congenital diaphragmatic hernias. Herniation of abdominal viscera (colon, omentum, liver, and, less frequently, small bowel or stomach) occur over time through a pre-existing diaphragmatic defect [3]. This abnormality may be asymptomatic or manifests with non-specific symptoms and, in severe cases, with bowel ostruction [4]. In patients with Morgagni hernia chest radiographs may lead to an opacity at the cardio-phrenic angle on p.a. projection and of the retrosternal space on lateral projections.
CT-findings are useful to differentiate a Morgagni hernia containing omental fat from a prominent epicardial fat pad: in case of Morgagni hernia the fat tissue of the cardio-phrenic angle may displace the lateral wall of the heart, while the epicardial fat pad does not lead to a mass-effect thus does not displace the adjacent structures. Furthermore, in case of a Morgagni hernia CT is able to demonstrate the defect of the anterior portion of the right hemidiaphragm and the omental vessels that pass through this defect.
Differential Diagnosis List
Morgagni hernia containing omental fat
Prominent epicardial fat pad
Fat-containing mediastinal lesion
Cystic mediastinal lesion
Solid mediastinal lesion
Final Diagnosis
Morgagni hernia containing omental fat
Case information
URL: https://www.eurorad.org/case/13657
DOI: 10.1594/EURORAD/CASE.13657
ISSN: 1563-4086
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