Q: What are the screening, prevention, and treatment recommendations for nephropathy in patients with type 2 diabetes?
Kidney disease or nephropathy (albuminuria >30 mg/24 hours) is a potentially serious complication of diabetes, occurring in 20% to 40% of patients with diabetes. It is the leading cause of end-stage renal disease. According to the American Diabetes Association (ADA, 2015), screening for nephropathy should occur at least annually for all patients with type 2 diabetes by assessing urine albumin excretion by measuring the urine-albumin-to-creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR). Until recently, a UACR between 30-299 mg/24 hours was classified as microalbuminuria and a UACR >300 mg/24 hours was classified as macroalbuminuria. The ADA has now recommended a change in the terminology used to describe kidney disease, because albuminuria occurs on a continuum. Therefore, the old nomenclature has been replaced by the term "albuminuria" (UACR >=30 mg/g).
The UACR and eGFR tests are important for patients with diabetes because persistent increased UACR (30-299 mg/g) is a known marker for the development of kidney disease and cardiovascular disease risk. However, because variability in urinary albumin excretion is not uncommon, the ADA recommends that two of three specimens collected within a 3- to 6-month period be abnormal (>=30 mg/g) before diagnosing a patient with microalbuminuria. Factors that may elevate urinary albumin excretion include exercise within 24 hours of the test, fever, infection, hyperglycemia, congestive heart failure, and marked hypertension (ADA, 2015).
Another recent change in prevention of nephropathy relates to the use of an angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB). These antihypertensive medications used to be prescribed to patients with diabetes, even in the absence of a diagnosis of hypertension, in hopes of slowing down the onset or progression of nephropathy. However, the ADA (2015) now recommends that only those patients diagnosed with hypertension or an abnormal UACR be started on these drugs.
There are a number of things that can be done to prevent the progression of the disease. Patients need to strive for optimum glucose and blood pressure control. Multiple studies have demonstrated that when patients are able to attain near normal glucose control the onset and/or progression of the disease can be delayed. For patients with diabetes and hypertension the ADA recommends treating to a goal of at least <140/90 mmHg (or lower, such as a systolic of <130 mmHg, if this can be achieved without undue burden). Second, regular monitoring of eGFR, creatinine, urinary albumin excretion, potassium, and other lab values is also recommended. Keep in mind, once the eGFR is <30 mL/min/1.73 m2 referral to a nephrologist is recommended (ADA, 2015).
Another change in the ADA recommendations is related to protein intake for patients with diabetes and nephropathy. Reducing protein intake below the recommended daily allowance of 0.8 g/kg/day (based on ideal body weight) is not required. However, if the patient has nephropathy that is progressing, despite use of an ACE inhibitor or ARB and achieving glucose and blood pressure control, and the dietary protein intake is high, then protein limitation should be considered.
Finally, while it is known that physical activity can increase urinary protein excretion there is no evidence that vigorous exercise increases the rate of progression of nephropathy; therefore, there is no need to restrict exercise in patients with diabetes and nephropathy (ADA, 2015).
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