The Clinical Characteristics of Normoalbuminuric Renal Insufficiency in Korean Type 2 Diabetic Patients: A Possible Early Stage Renal Complication

It has been recently reported that a considerable portion of diabetic patients with renal insufficiency show normoalbuminuria. As little is known about normoalbuminuric renal insufficiency in the Asian population, we examined its prevalence and clinical characteristics in Korean type 2 diabetic patients. We studied 562 patients with type 2 diabetes from Seoul National University Hospital. The estimated glomerular filtration rate (eGFR) was calculated by the Modification of Diet in Renal Disease formula and the degree of albuminuria was evaluated by spot urine albumin-creatinine ratio. Of 562 patients, 151 (26.9%) patients had renal insufficiency (eGFR <60 mL/min/1.73 m(2)). Among them, 44 (29.1%) patients had normoalbuminuria. After excluding the patients using renin-angiotensin system (RAS) inhibitors, the prevalence of normoalbuminuric renal insufficiency was 35.3% (18 of 51 patients). Compared with micro- and macroalbuminuric renal insufficiency, normoalbuminuric renal insufficiency was associated with the female predominance, shorter duration of diabetes, lower prevalence of diabetic retinopathy, and lower prevalence of using antihypertensive drugs except RAS inhibitors. The prevalence decreased progressively with an increase in the duration of diabetes and an increase in the severity of retinopathy. Normoalbuminuric renal insufficiency was prevalent in Korean type 2 diabetic patients. The association with a shorter duration of the diabetes and a lower prevalence of retinopathy suggests that it might be an early stage renal complication.