Abstract

PURPOSE:

To evaluate ultrasonographic (US) findings of morphologies, anatomic locations, and causes of hypoechoic rims that mimic disease and appear around native kidneys of asymptomatic renal allograft recipients.

MATERIALS AND METHODS:

Annual, routine abdominal US examinations of 170 renal allograft recipients were performed. US scans of 23 (13.5%) of these patients showed a hypoechoic rim. CT examination of the perirenal space was performed for 18 of these 23 patients to confirm the US findings.

RESULTS:

For 11 of these 18 patients, the hypoechoic rims on US scans corresponded to low-attenuation, septated perirenal fat on CT scans; for seven, the perirenal space appeared to be a homogeneous, fat-filled compartment. Low-attenuation fat in the perirenal space was separated by bridging septa. Patients with hypoechoic rims were significantly older than those without (57 years +/- 10 vs 48 years +/- 12, P = .001).

CONCLUSION:

Hypoechoic rims are frequently found in asymptomatic renal allograft recipients. They correspond not to disease but to low-attenuation perirenal fat divided into compartments by bridging septa.