Diabetic Nephropathy

Article by Carolien Koreneff, CDE, Diabetes NSW & ACT.

Diabetes is the leading cause of kidney disease in Australia. According to a report by the Australian Institute of Health and Welfare, about 1 out of 4 adults with diabetes has Diabetic Nephropathy, or diabetes kidney disease, and diabetic nephropathy was the leading cause of treated ESKD, accounting for 37% of new cases in 20141. End Stage Kidney Disease (ESKD) attributed to diabetic nephropathy has steadily increased over the past 15 years.

The main job of the kidneys is to filter and remove wastes and extra water out of the blood, by making urine. The kidneys also help control blood pressure. When the nephrons in the kidneys are damaged, they can’t filter blood like they should, which can cause wastes to build up in the body.

Kidney damage caused by diabetes usually occurs slowly, over many years. Although one can take steps to protect the kidneys and to prevent or delay kidney damage, kidney disease is often called a ‘silent disease’, as up to 90% of kidney function can be lost before symptoms appear. As a result, many people are unaware that they have the condition1,2.

 

Types of nephropathy

We refer to ‘Acute kidney injury’ (AKI) if the kidneys recover normal function within three months. AKI is usually caused by injury or trauma to the kidney which restricts the blood supply or due to severe inflammation.

‘Chronic kidney disease’ is where there is a loss of healthy kidney function for more than three months. Chronic kidney disease is the most common form of kidney disease; there are five recognised stages.

Another term often used when talking about nephropathy is End Stage Kidney Disease (ESKD); this is the most severe form of kidney disease, where people usually require dialysis or a kidney transplant to survive.

 

How does diabetes cause kidney disease?

Hyperglycaemia (high blood glucose levels), as well as hypertension (high blood pressure) – a common complication of diabetes, can damage the capillary blood vessels in the nephron and thereby cause nephropathy. Other risk factors include: smoking, high salt (sodium) intake, inactivity, being overweight or obese, heart disease, having a history of renal calculi and family history of kidney failure.  As many of these risk factors are modifiable CKD is largely preventable.  Kidney disease is not reversible, but it is treatable if caught early.

Image 1 shows data which highlights the number of people in Australia who are at risk of kidney disease (bottom tear) and those with CKD in its various stages3. It is estimated that 1 in 9 Australians have CKD.

 

A new system for staging CKD was introduced to Australia in 20124. This new system factors in albuminuria, has a better correlation with progression and resulted in quantification of risk for both CKD progression and cardiovascular events. The following image highlights the stages of CKD:

How do we detect CKD?

There are 3 areas of focus in regards to CKD detection2,3,4:

  1. Test the kidney function by doing a blood test to check the estimated Glomerular Filtration Rate (eGFR) as this may fall substantially before serum creatinine is outside of the normal range and a fall in eGFR always precedes kidney failure. Early detection and treatment can reduce the rate of progression of kidney failure and cardiovascular risk by between 20 and 50%. A normal level of eGFR in healthy adults is >90 mL/min/1.73m2 and declines with age. The eGFR is reported by all Australian pathology labs.

 

  1. The preferred method to test for albuminuria (both in people with and without diabetes) is by doing a first void or random spot urine test for albumin to creatinine ratio (ACR). Albuminuria is present if at least two out of three ACR tests are positive. CKD is present if the ACR is consistently elevated for 3 months.  A normal level of ACR is <2.5mg/mmol for males and <3.5mg/mmol for females5. An ACR of 2.5-25mg/mmol in males or 3.5-35mg/mmol in females is considered microalbuminuria. Levels exceeding 25mg/mmol in males or >35mg/mmol in females is termed macroalbuminuria2.

 

  1. Check the patient’s blood pressure. Generally blood pressure targets are set at <140/90 mmHg for those with CKD3. People with diabetes and/or microalbuminuria should maintain a BP target of <130/80mmHg. Two types of blood pressure medicines, ACE inhibitors and ARBs, play a special role in protecting kidneys6,7. Each has been found to slow kidney damage in people with diabetes who have high blood pressure and diabetic nephropathy.

For more information on kidney disease we recommend the following resources:

  1. https://kidney.org.au/
  2. Chronic Kidney Disease (CKD) Management in Primary Care (4th edition) – provides best practice recommendations for detecting and managing CKD in primary care: https://kidney.org.au/uploads/resources/chronic-kidney-disease-management-in-primary-care-4th-edition-handbook_2020-07-16-064708.pdf

 

References:

  1. https://www.aihw.gov.au/getmedia/83cc1bdd-557f-4d9d-9deb-3fe65069c07e/ah16-3-8-kidney-disease.pdf.aspx
  2. https://www.racgp.org.au/afp/2012/december/ckd-in-the-elderly/
  3. https://www.slideserve.com/chun/general-practitioner-workshop-powerpoint-ppt-presentation
  4. https://kidney.org.au/uploads/resources/chronic-kidney-disease-management-in-primary-care-4th-edition-handbook_2020-07-16-064708.pdf
  5. https://baker.edu.au/-/media/documents/impact/ausdiab/reports/ausdiab-report-2012.pdf?la=en
  6. https://pubmed.ncbi.nlm.nih.gov/8413456/
  7. https://pubmed.ncbi.nlm.nih.gov/11565517/
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