Obesity and Chronic Kidney Disease

The association between obesity and chronic kidney disease seems to be mediated by hypertension and diabetes in many — but not all — cases.

Several years ago, U.S. researchers published a biopsy-based case series that involved 71 patients with obesity-related glomerulopathy (ORG), which is characterized by glomerular enlargement, frequent (but not universal) presence of focal segmental sclerosis, and substantial proteinuria. An increasingly recognized association between obesity and kidney disease is the subject of three new reports. A case series from China involved 90 obese patients who had renal biopsy findings consistent with ORG; no patients had diabetic or hypertensive nephropathy. Mean 24-hour urine protein excretion was 1.5 g. Mean serum creatinine level was 0.9 mg/dL, and about half the patients had elevated creatinine clearance, suggesting that hyperfiltration is an early finding in ORG patients. Framingham Heart Study researchers followed 2676 adults (baseline obesity prevalence, 12%). During an average follow-up of 19 years, obesity at baseline was associated significantly with subsequent development of stage 3 chronic kidney disease (odds ratio, 1.7). However, after adjustment for diabetes and hypertension, the association became statistically insignificant (OR, 1.1).

In another study, researchers analyzed data from two other large U.S. epidemiologic studies in which more than 13,000 adults were followed for an average of 9 years. In multivariable analyses, waist-to-hip ratio, but not body-mass index, was associated with development of chronic kidney disease. This association was somewhat attenuated, but remained significant, after adjustment for diabetes and hypertension.

Comment:

Taken together, these studies suggest that the association between obesity and kidney disease is complex. In most cases, the association likely is mediated by coexisting diabetes and hypertension. But in others, obesity could cause glomerular injury directly by mechanisms that are not fully understood. Because waist-to-hip ratio — an indicator of visceral obesity — was a better predictor than BMI, metabolic abnormalities particularly associated with visceral obesity presumably predispose to chronic kidney disease.

-Allan S. Brett, MD