Diabetic Kidney Disease
What Is Diabetic Kidney Disease?
The kidney is a part of the renal system that plays a crucial role in filtering and modulating the amount of water and electrolytes in the blood, maintaining acid-base balance, stimulating production of red blood cells, and regulating blood pressure.1 Exposure to chronic hyperglycemia in diabetes causes damages to the kidney that can eventually lead to chronic kidney disease (CKD).2
Diabetic kidney disease (DKD) specifically refers to CKD that is caused directly by diabetes, distinguishing itself from CKD that coincides with diabetes.3 DKD is caused by similar pathogenic processes that cause retinopathy and neuropathy.4 In DKD, structural and functional changes to the kidney lead to proteinuria (protein found in urine), hypertension (high blood pressure), and progressive worsening of kidney function.2 While the exact pathophysiology of DKD is still being uncovered, possible causes include insulin resistance, genetics, hyperglycemia, and an autoimmune process. Approximately 30-40% of patients with diabetes will eventually develop DKD.2
How Is Diabetic Kidney Disease Diagnosed?
The hallmark of DKD is proteinuria.2 Diagnostic criteria for DKD include the following:
- Hypertension
- Progressive reduction in estimated glomerular filtration rate (eGFR)
- Persistent albuminuria (>300 mg/day) on at least 2 visits 3-6 months apart
What Are the Stages of Diabetic Kidney Disease?
DKD staging is based on both albuminuria and eGFR.5 Based on the current classification system, both values need to be measured to guide treatment decisions. The level of albuminuria is associated with an increased risk of cardiovascular disease, CKD progression, and mortality. eGFR levels are also important in drug dosage or restrictions.
|
|
Normal to mildly increased <30 mg/g |
Moderately increased 30-299 mg/g |
Severely increased ³300 mg/g |
|
Normal to high (³90) |
1 |
1 |
2 |
|
Mildly decreased (60-89) |
1 |
1 |
2 |
|
Mildly to moderately decreased (45-59) |
1 |
2 |
3 |
|
Moderately to severely decreased (30-44) |
2 |
3 |
3 |
|
Severely decreased (15-29) |
3 |
3 |
4+ |
|
Kidney failure (<15) |
4+ |
4+ |
4+ |
How Is Diabetic Kidney Disease Managed?
As having diabetes is associated with a 10 times higher likelihood of developing CKD that progresses to end-stage renal disease (ie, kidney disease that requires dialysis),6 it is critical for patients with diabetes to undergo intensive treatment to prevent or delay micro- and macrovascular complications. Current management of DKD includes intensive concurrent management of glucose, blood pressure, and lipids along with lifestyle modifications to potentially slow the progression of DKD.4
Glycemic Control – The significant effects of intensive glycemic control on renal function have been reported by various studies.7,8 In particular, the Diabetes Control and Complications Trial (DCCT) randomly assigned 1441 individuals with type 1 diabetes mellitus to either 6.5 years of intensive diabetes therapy or the control group aimed at preventing hyperglycemic symptoms.7 It concluded in its follow-up Epidemiology of Diabetes Interventions and Complications (EDIC) study that intensive therapy was associated with a 50% lowered risk of renal impairment. The study noted that the effect seemed entirely attributable to improved glucose control. Another seminal study of 11,140 patients with type 2 diabetes mellitus reported similar findings, with individuals who received intensive glucose control requiring renal replacement therapy (eg, hemodialysis, peritoneal dialysis, or renal transplantation) less than individuals in the control group.8
Blood Pressure Control – Additionally, multiple studies have demonstrated that lowering blood pressure is effective in increasing the rate of regression of albuminuria and lowering the risk of CKD progression in diabetic patients.9,10 Most notable is the UK Prospective Diabetes Study (UKPDS) where lowering systolic blood pressure from 154 mmHg to 144 mmHg was found to be associated with a 30% decrease in microalbuminuria.10
Blood Lipid Control – Although lowering plasma lipid levels may or may not have a significant effect on renal function, lipid-lowering treatment is generally recommended for all patients with CKD to lower the risk of cardiovascular disease and associated mortality.4
Lifestyle & Dietary Modifications – Intensive lifestyle modifications including healthy weight loss, increased physical activity, Mediterranean-style diet with sodium restriction, and smoking cessation are strongly recommended for patients with CKD.4 Among diabetic patients with CKD, high-protein diet is not recommended. Although consuming protein of more than 20% of daily caloric intake should be avoided, formal protein restriction (<0.8 g/kg body weight/day) is also typically not suggested due to potential health risks and difficulty of adherence.
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