Renal injury in the extremely obese patients with normal renal function.

We studied the glomerular architecture in renal biopsies of 95 patients undergoing bariatric surgery for extreme obesity but whose renal function was normal. The comparison group was 40 control patients having protocol biopsies. These latter patients had normal weight and renal function, were non-diabetic, non-hypertensive, and were undergoing nephrectomy or donating a kidney. Logistic regression models determined associations between the clinical and biochemical variables and glomerular lesions. Arterial hypertension, sleep apnea syndrome (SAS), and microalbuminuria were prevalent in the obese patients, as was hyperglycemia to a lesser extent. Focal and segmental glomerulosclerosis was present in only five extremely obese (EO) patients but absent in controls. Increased mesangial matrix, podocyte hypertrophy, mesangial cell proliferation, and glomerulomegaly were more frequent in the obese cohort than in the control group. Body mass index was a significant independent risk factor associated with glomerular lesions in all 135 patients and in the 95 EO patients, whereas SAS was associated with glomerulomegaly only in the EO. Our study shows that EO patients who lack overt clinical renal symptoms have a variety of glomerular abnormalities that correlate with body mass.