Retrocrural herniation of the perinephric fat mimicking lipoma
Presentation
No specific chest symptoms just cough and wheeze. No history of trauma or previous operation.
Patient Data
The CT scout image shows soft tissue density mass lesion close to the left wall of the descending aorta at the level of diaphragmatic cupola and inferior cardiac border, CT angiography will be needed to exclude the possibility of aortic aneurysm.
In axial reconstruction a fatty density left retrocrural well defined mass seen bowing the diaphragmatic crus anteriorly and displacing the intercostal vessels posteriorly and hemiazygos medially which appears markedly attenuated. Note the presence of a small left crural defect connecting the fatty mass with the perinephric fat.
In coronal images the left crural defect is seen clearly with definite connection between the retrocrural fatty mass and the perinephric fat, multiple string like vessels pass from the perinephric space inside the retrocrural fatty mass forming tuft-like appearance.
The sagittal images confirm the data, the feeding vessel seen crossing inside the fatty retrocrural mass, the defect is difficult to be visualized due to the plane pass with its axis.
The homogeneity of the fatty mass with absent faint trabeculation suggesting the possibility of normal fat rather than lipomatous changes.
No other pathological finding could be detected.
Case Discussion
The retrocrural lipoma is a rare but important site for occurrence of lipoma as it is liable to malignant transformation, normally the retrocrural space contains a crescent rim of fat that support the retrocrural content; azygos, hemiazygos and cisterna chyli.
Here an un expected herniation of the left perinephric fat in the left side of the retrocrural space is suggected rather than lipoma due to the presence of left crural defect with concomitant multiple string like vessels running between the two spaces.
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