What is diabetic nephropathy (diabetic kidney disease)? How do I protect my kidney function?

Up to 50% of people living with diabetes can develop signs of renal (kidney) damage in their lifetime. In Canada, diabetes is the leading cause of kidney disease. This article provides an overview of:


What is diabetic nephropathy (kidney disease) | Beyond Diabetes Nutrition - Lucy Zhang, Registered Dietitian



What is diabetic nephropathy?

Diabetic nephropathy (diabetic kidney disease) is a microvascular complication of diabetes. High blood sugar over a long period of time causes damage to the small, delicate blood vessels of our kidneys.


Diabetic nephropathy follows a pattern of slowly increasing albuminuria (albumin protein in the urine), followed by a decrease in kidney function. This can eventually lead to end stage renal disease (ESRD), also known as kidney failure.




How is diabetic nephropathy diagnosed?


The earlier that the signs and symptoms of chronic kidney disease are detected, the better chances you have to reduce the chance of progression to advanced kidney disease and the need for dialysis or a kidney transplant.


Understanding your kidney lab tests: ACR, eGFR | Beyond Diabetes Nutrition - Lucy Zhang, Registered Dietitian

There are two lab tests used to screen for kidney damage:



Albumin-to-creatinine ratio (ACR)

Albumin-to-creatinine ratio (ACR) is a urine test that detects the presence of albumin (a protein) in the urine. Albuminuria (the presence of albumin in urine) is the earliest clinical sign of diabetic nephropathy.


If you are living with diabetes, your doctor will likely order a urine ACR test on an annual basis. The earlier kidney disease is detected, the better the chance of slowing or stopping its progression.

  • ACR < 2 mg/mmol Normal

  • ACR 2 - 20 mg/mmol Microalbuminuria

  • ACR > 20 mg/mmol Overt nephropathy

Keep in mind, there are a number of factors that can cause a temporary increase in albuminuria. If your urine ACR is over 20 mg/mmol, your doctor will likely order two repeats of urine ACRs performed over the next three months. Two out of the three urine samples have to show high urinary albumin levels to confirm albuminuria.



Estimated Glomerular Filtration Rate (eGFR)

A blood test called estimated glomerular filtration rate (eGFR) is commonly ordered as part of your routine blood work to measure kidney function. Levels of creatinine (a waste product that our kidneys have to filter out) is measured in the blood, which allows calculation of eGFR.


eGFR is used to determine the stage of kidney disease. You can think of eGFR as % of kidney function. As kidney function decreases, the eGFR number gets lower.


Diagnosis of chronic kidney disease (CKD) is typically made if eGFR is equal to or less than 60 mL/min or ACR is equal to or greater than 2.0 on at least two out of three urine samples.


Stages of chronic kidney disease | Beyond Diabetes Nutrition - Lucy Zhang, Registered Dietitian



What can I do to protect my kidney function?

Keeping blood sugar and blood pressure within target range, along with making certain dietary changes and the use of medications shown to be protective of kidney function can help to slow or stop the progression of diabetic nephropathy.


How to protect kidney function | Beyond Diabetes Nutrition - Lucy Zhang, Registered Dietitian

Glycemic (blood sugar) control

  • For most adults, the target HbA1C is < 7.0%.

  • In general, target blood sugar across the day are:

  • Fasting blood sugar: 4 - 7 mmol/L

  • Blood sugar 2 hours after eating: 5 - 10 mmol/L

NOTE: Depending on your age and health conditions, your doctor may recommend an individualized target range.



Blood Pressure

  • For most people with diabetes, target blood pressure is: < 130/80 mmHg



Nutrition Recommendations

Reduce sodium intake to 1500 - 2000 mg/d

Following a low sodium diet helps to support management of high blood pressure


Limit intake of phosphate additives

Phosphorus is a mineral found naturally in many foods (e.g. meat, dairy, whole grains, beans and lentils). You do not need to limit naturally occurring phosphorus.


However, it is a good idea to avoid foods with phosphate additives even if your blood phosphorus levels are in the normal range. Phosphorus from food additives is extremely well absorbed and may damage the kidneys. Phosphate additives are used in many processed foods as a preservative, to enhance flavour, or to improve the look and texture of the product.


Foods that commonly contain phosphate additives:

  • Pre-seasoned meats

  • Fast food

  • Processed meats (deli meats, sausage, bacon, etc.)

  • Processed cheeses (Processed cheese slices, Cheez Whiz, Velveeta, etc.)

  • Cola, dark sodas, and some ice teas

The best way to check for phosphate additives is to look at the ingredients list. Try to avoid products with the words "phosphate" or "phosphoric acid" listed under ingredients.


Keep to moderate protein intake

If you have protein in the urine, it is recommended to avoid excessive protein intake. Protein is still important for preserving lean muscle mass, meal balance, and supporting the immune system! Instead, stick to the recommended protein intake for most adults of 0.8g protein per kilogram of body weight.




Take Medications as Prescribed

Diabetes Medications: SGLT2 inihibitors.

Sodium glucose co-transporter-2 (SGLT2) inhibitors are a class of medications used to help improve blood sugar control in adults with type 2 diabetes. This class of medications include canagliflozin, dapagliflozin, and empagliflozin. These medications work to lower blood sugar by increasing the amount of sugar you pass in your urine.


SLGT2 inhibitors have been shown to demonstrate renal protective (protective of the kidneys) and cardioprotective (protective of the heart), resulting in slower rates of kidney function decline.


Blood Pressure Medications: ACE and ARBs

The use of an angiotensin converting enzyme (ACE) inhibitor or an angiotensin receptor blocker (ARB) can reduce the risk of developing CKD in people with diabetes and can help to slow the progression of CKD. These medications are considered kidney protective and heart protective.






References

Lipscombe L, Butalia S, Dasgupta K, et al. Pharmacologic Glycemic Management of Type 2 Diabetes in Adults: 2020 Update. Can J Diabetes 2020;575-591.


McFarlane P, Cherney D, Gilbert RE, et al. Diabetes Canada 2018 Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada: Chronic Kidney Disease in Diabetes. Can J Diabetes 2018;42(Suppl 1):S201-209.


The Kidney Foundation of Canada. Book One: Living with Reduced Kidney Function (5th Ed.): Your Diet and Nutrition for Kidney Health. Montreal: The Kidney Foundation of Canada. 2015.



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