Diabetes and Kidney Disease

Diabetes is a leading cause of kidney disease; 1 in 3 adults with diabetes also have kidney disease.  Diabetic kidney disease may also be known as DKD, chronic kidney disease (CKD), kidney disease of diabetes, or diabetic nephropathy (DN).

What is Diabetes?

Diabetes mellitus is a chronic condition which causes blood glucose levels (blood sugar) to become too high. There are two types: type 1 in which the body’s immune system attacks cells in the pancreas that make the hormone insulin, and type 2, in which the body either does not make enough insulin or cannot respond effectively to lower blood glucose. Type 2 is much more common than type 1, accounting for 9 out of 10 of all people with diabetes. Type 1 diabetes often arises in childhood, whereas type 2 commonly appears in adulthood.  

Because both conditions cause high blood sugar, both can cause a similar range of complications.  Among these is kidney disease, peripheral nerve problems, for example in the feet, and cardiovascular disease.  

What is Diabetic Nephropathy (DN)?

Kidneys are essential to health and function by filtering salts, waste products such as urea, acids, and excess fluids out of the blood. They are also responsible for making urine and maintaining a healthy balance of water, salts, and minerals in your blood.  

Sustained high blood glucose levels damage the fine blood vessel clusters (glomeruli) and tiny filters in structures called nephrons in the kidney.  Other risk factors increasing the likelihood of DN include:

• High blood pressure
• African American, Native American, or Hispanic ancestry 
• Smoking
• Not following your diabetes eating plan
• Eating foods high in salt
• Not being active
• Being overweight
• Heart disease
• A family history of kidney failure 

Risk can be mitigated somewhat by eating healthily, exercising, giving up smoking, and achieving good glycaemic control (a blood glucose between 3.5 and 7.8 mmol/l).

Damage to the nephrons reduces the ability of the kidneys to filter waste and fluid (kidney disease), and can eventually lead to kidney failure (when kidney function has fallen to 15% of normal). It can also cause the barrier between the blood and the urine to become leaky, resulting in protein from the blood appearing in the urine (proteinuria). This disease process is progressive and is called diabetic nephropathy (DN).

In the early stages of DN, your symptoms are so mild you may not notice them. In later stages, signs and symptoms may include:

• Worsening blood pressure control
• Protein in the urine
• Swelling of feet, ankles, hands or eyes
• Increased urination
• Reduced need for insulin or diabetes medicine
• Confusion or mental fog
• Breathlessness
• Loss of appetite
• Nausea and vomiting
• Persistent itching
• Fatigue

As blood pressure control worsens, this causes further damage to the kidneys, speeding the progression of DN.

Diagnosing Diabetic Nephropathy

There are two tests which are performed routinely in people with diabetes to check for kidney problems. A simple urine test done to check whether protein has leaked into the urine is called the albumin: creatinine ratio, or ACR. Kidney filtration function is tested by estimating the glomerular filtration rate (eGFR). This involves a blood test which tests for a waste product called creatinine and uses it to calculate the eGFR using other factors including age, ethnicity, and gender. Depending on age, an eGFR of 90 or more indicates normal kidney function, and a value of 60 or below is regarded as kidney disease. As DN progresses, kidney function will gradually diminish, and eGFR will fall through the following stages:

Treating Diabetic Nephropathy

The treatment type used will depend on the stage kidney disease has reached. One treatment arm may include medication to help control blood pressure using classes of drugs called ACE inhibitors (e.g., ramipril, enalapril) or Angiotensin Receptor-Blockers (ARB’s), such as losartan or candesartan. Both drug classes help to prevent further kidney damage in addition to lowering blood pressure.

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