Presentation
Low back pain with incidental findings on CT dorsolumbar spine for which CT abdomen with contrast was done.
Patient Data
Rather well circumscribed ovoid shaped soft tissue mass is seen at the right para-spinal peri-renal retro-peritoneal space showing heterogeneous CT architecture of dominant fat density, soft tissue strands & tumoral vessels seen traversing to the renal parenchyma. It is seen abutting the posterior aspect of the right kidney pushing it anteriorly with mild medial rotation. A posterior renal parenchyma cortical defect is seen continuous with the mass. No internal discrete enhancing nodules seen. It measures 3.5 x 7.8 x 11.2 cm in maximal axial and craniocaudal dimensions. The feeder artery of the mass is seen originating from the right renal artery reaching it along its medial aspect.
Another much smaller fat density nodule is seen within the right renal cortex medial aspect measuring 5 mm in diameter and reading a mean attenuation -60 HU.
Case Discussion
Right paraspinal retroperitoneal fat containing soft tissue mass. The differential diagnosis includes exophytic renal angiomyolipoma versus retroperitoneal liposarcoma.
The presence of a defect in the right renal parenchyma, other smaller renal parenchymal fat containing nodule (angiomyolipoma), vascular supply from the renal artery as well as a lack of discrete internal enhancing nodules are in keeping with exophytic renal angiomyolipoma.
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