Hypoechoic perirenal fat in renal transplant recipients.

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.