Characteristics of nephropathy in severely obese Japanese patients complicated with type 2 diabetes mellitus: a cross-sectional cohort study

Purpose We aimed to investigate the characteristics of kidney disease in severely obese Japanese patients with type 2 diabetes mellitus (T2DM). Methods This was a cross-sectional study of severely obese patients (body mass index ≥35 kg/m 2 ) with T2DM treated at Jinnouchi Hospital, Kumamoto, Japan. Results A total of 3128 T2DM patients visited the hospital during the survey period, of whom 55 patients (1.7%) were severely obese and 50 patients were enrolled. In terms of diabetic nephropathy (DN), twenty-five patients were stage 1 (non-DN, 50.0%), sixteen were stage 2 (32.0%), five were stage 3 (10.0%), and four were stage 4 (8.0%). There were significant differences in the presence of urinary occult blood ( P = 0.01) and history of cardiovascular disease (CVD) ( P = 0.04) between patients with DN (stages 2–4) and those without DN (stage 1). The presence of urinary occult blood (odds ratio [OR], 4.96; 95% confidence interval, 1.32–18.6; P = 0.02) was significantly associated with the presence of DN according to multivariate logistic regression analysis with forced inclusion of age, sex, and CVD history. Conclusions Urinary occult blood may be a significant independent factor associated with the presence of nephropathy in severely obese Japanese patients with T2DM. The presence of urinary occult blood could thus be an important pathogenic factor in obesity-related nephropathy in patients with T2DM.