What is CKD (chronic kidney disease)?

What is CKD (chronic kidney disease)?

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It is surprisingly difficult to answer.

This is partly because chronic kidney disease (CKD) is not a diagnosis. It is a syndrome (group of diseases) with many specific causes (diagnoses). Nonetheless .. here goes.

Key points

1. Chronic Kidney Disease (CKD) is defined as a
   • Gradual loss of kidney function over time, or ..
   • Structural abnormality of the kidneys, with normal renal function.
2. CKD is not a diagnosis. It is a syndrome with a cause(s) – you need to find out what is causing it
3. CKD affects approximately 10-15% of adults in the UK to some degree. However, most cases are mild (Stages 1-3B) and age-related
4. CKD is associated with an increased risk of cardiovascular disease and hypertension, and can cause end-stage renal failure (ESRF; i.e. need for dialysis or a kidney transplant) in 1% of cases (rare)
5. Early detection and management can slow disease progression and reduce complications.

Ok then ..  tell me more about how CKD is defined

Here is a quite complex ‘doctors definition of CKD’

1. ‘Functional CKD’ = an estimated glomerular filtration rate (GFR; see below) of <60 mL/min – that is present for at least three months (i.e. measured at least twice), with or without evidence of kidney damage (a higher GFR means better kidney function)
2. ‘Structural CKD’ = evidence of kidney damage with or without decreased GFR – that is present for at least three months, as shown (by 1 or more of):

• Albuminuria (protein in urine),
• Haematuria (blood in urine, after exclusion of urological causes)
• Structural abnormalities (e.g. polycystic kidneys on renal ultrasound)
• Pathological abnormalities (e.g. on kidney biopsy)
• Electrolyte and other abnormalities due to tubular disorders
• History of kidney transplantation.

This definition is based on the 2024 KDIGO CKD guideline (Stevens, 2024).

Stages of CKD/GFR

CKD is graded into stages 1, 2, 3A, 3B, 4 and 5 – from minor to severe kidney disease.

Who needs to be referred to a nephrologist?

• If your GFR falls below 60 ml/min (Stage 3A CKD), your GP should discuss you with a hospital based kidney disease specialist (called a nephrologist)
• If your GFR is less than 30 ml/min (Stage 4 CKD) you should see a nephrologist
• A GFR below 15 ml/min (Stage 5 CKD) indicates that you need to start a treatment for kidney failure (dialysis or a kidney transplant).

Summary

We have described what is CKD. We hope it has been helpful.