Ultrasound assessed peri-renal fat: an index of sub-clinical atherosclerosis.

OBJECTIVE

Overweight/obesity has predicted cardiovascular disease (CVD) risk for long with its standard measure of body mass index (BMI), which later was found to mis-classify risk oftentimes. This is because it does not differentiate between fat and whole body mass. The finding that fat especially visceral fat was more culpable shifted attention to ectopic fat as a more precise measure of CVD risk. Peri-renal fat (PRF) is one such ectopic foci, which is hardly used despite the relative ease of assessment. We assessed PRF to correlate it with carotid intima media thickness (CIMT) to see if there was any significance in order to obviate need for heavy equipment in CVD risk assessment.

METHODS

This is secondary analysis of data generated in the course of studying sub-clinical atherosclerosis in apparently normal individuals. Subjects underwent routine anthropometry to determine BMI. They then underwent abdominal ultrasound studies wherein PRF was measured as the size of the echogenic strip between the posterior part of the liver and the right kidney. The CIMT was measured using the same equipment but a different transducer, as the distance between the intima and medial layers of the right common carotid artery 1 cm proximal to the carotid bulb.

RESULTS

The 221 subjects (82 M, 139 F) had mean ages of 37.01±10.97 and 36.86±11.62 years respectively. PRF correlated significantly with CIMT, age and all anthropometric measures. A PRF level of 0.26 cm turned out to be a significant value that determined presence of sub-clinical atherosclerosis deriving from the receiver operating characteristic curve analysis.

CONCLUSION

PRF has shown to be correlated significantly with indices that predict atherosclerosis. Being an ectopic fat focus, its local and systemic effects on the kidney increase systemic vascular resistance and CVD. Since it can easily be measured on abdominal ultrasound, a test readily available and requiring lower level skills it should be used to advantage. Levels above 0.26 cm should prompt initiation of curative or preventive action to control CVD in the population.