Am Fam Physician. 2000;61(5):1486-1488
Renal disease in patients with type 2 diabetes mellitus (formerly known as non–insulin-dependent diabetes mellitus) is becoming increasingly recognized. In the United States, the percentage of patients with these concurrent conditions increased from 27 percent in 1982 to 36 percent in 1992. End-stage renal disease was thought to occur mainly in patients with type 1 diabetes mellitus (formerly known as insulin-dependent diabetes mellitus), but much evidence shows that the risk of renal disease is similar in both groups of patients. Ritz and Orth reviewed the current epidemiology, risk factors and treatment recommendations for nephropathy in patients with type 2 diabetes.
The majority of patients with diabetic renal disease and microalbuminuria have nodular glomerulosclerosis (Kimmelstiel-Wilson syndrome). However, some patients have minimal glomerular changes on pathology and, in some cases, the glomeruli appear to be normal. Atherosclerosis of the renal artery produces ischemia in some patients. About 20 percent of patients have a nondiabetic form of renal disease.
Longitudinal and cross-sectional studies have identified a number of factors that may increase the risk of progression to end-stage renal failure in patients with type 2 diabetes. These factors include a family history of nephropathy, elevated blood pressure, poor glycemic control, smoking, and black or Native American race. Less-defined risk factors are male sex, high intake of dietary protein and hyperlipidemia.
Several large studies have found that hypertension and an abnormal circadian blood-pressure profile are strongly correlated with albuminuria and may predict renal and cardiovascular events. Evidence shows that lowering blood pressure in patients with type 1 diabetes attenuates the loss of renal function. As a result, the National Kidney Foundation recommends that patients with diabetic or nondiabetic renal disease should have a target blood pressure of 125/75 mm Hg. The recent U.K. Prospective Diabetes Study found that moderately lowering blood pressure led to major reductions in the risk of renal and cardiovascular events. Researchers noted that blood pressure control was more beneficial than tight glucose control in preventing adverse secondary outcomes. Because patients with diabetes tend to retain sodium, the authors recommend the use of a diuretic. Usually a thiazide or potassium-sparing diuretic will work synergistically with an angiotensin-converting enzyme (ACE) inhibitor. However, the authors note that lowering the blood pressure to protect the nephrons is more important than the type of antihypertensive agent used.
Patients with diabetes who have microalbuminuria (urinary albumin excretion rate of 30 to 300 mg per 24 hours) are at high risk for renal complications. These patients also have a higher risk for cardiovascular events. A 1995 consensus statement recommended that diabetic patients with microalbuminuria be treated with an antihypertensive medication, preferably an ACE inhibitor, regardless of their blood pressure. However, there is still no evidence from placebo-controlled studies to prove that decreasing albumin excretion with an ACE inhibitor will reduce the risk of end-stage renal disease in patients with type 2 diabetes.
A high rate of micro- and macrovascular complications occur in patients with type 2 diabetes. These complications include foot problems, impotence, diarrhea, constipation, retinopathy, coronary heart disease and cerebrovascular disease. Assessment for these complications through questioning and other screening methods should be done on a regular basis during office visits.
The authors conclude that diabetic nephropathy and deterioration of renal function are to a certain extent preventable. Anticipatory creation of a vascular access should be made in patients who exhibit progressive decline in renal function based on measured creatinine clearance. This access allows for fewer complications when the need for dialysis arises. Acute renal decompensation in patients with diabetic nephropathy can be prevented by limiting the use of radiocontrast agents in cardiac studies. Kidney transplantation remains an option for diabetic patients if they do not have significant underlying vascular disease.