Figure 1-2: Axial T1-weighted in and out of phase images demonstrate a high signal mass in the mid-aspect of the left kidney in the area of partial nephrectomy. There is also some thickening of the para-renal fascia.

Figure 3: Pre-contrast 3D GRE images demonstrate a left renal mass with decreased signal intensity. This decreased signal intensity is similar to that of the subcutaneous and retroperitoneal fat and is, therefore, consistent with a mass composed of fat.

Figure 4: Post-contrast 3D GRE images demonstrate that the left renal mass does not enhance. Enhancement in the thickened left para-renal fascia is consistent with post-surgical changes and fat.

Renal omental fat packing following partial left nephrectomy for RCC.

Nephron-sparing surgery is becoming more commonly performed and it is important to be familiar with the post-operative appearance of a kidney after partial nephrectomy. Sometimes, omental fat may be placed in the post-operative nephrectomy site and can be mistaken for AML. Ancillary findings such as adherence of the post-operative kidney to the posterior peritoneum and adjacent scarring are suggestive of this diagnosis when pertinent clinical history is not available.