Acute kidney injury vs chronic kidney disease – what’s the difference?

Acute kidney injury vs chronic kidney disease – what’s the difference?

Even though both are kidney diseases, they are quite different in terms of causes, symptoms and treatment. This is why it is important to do two things: (1) distinguish the two, and (2) identify the underlying cause based on medical assessment, urine and blood tests, and (often) a renal (kidney) ultrasound. Both diseases affect both kidneys.

Renal ultrasound – needed in many cases of AKI and CKD

Note. Both AKI and CKD are not diagnoses. They are syndromes (groups of diseases) with specific causes. Your doctors need to find the cause.

So. Acute kidney injury vs chronic kidney disease – what’s the difference? Here goes. Let’s start with the basics.

Acute kidney injury (AKI)

• Caused by a short-term illness – especially infection, medication, blood loss (e.g. trauma) or obstruction (to the drainage of urine from the kidneys or bladder)
• Decline in kidney function – is rapid, usually over hours or days. Episodes typically last 10-14 days, but can be  2-3 day, or weeks. If dialysis is required for more than 3 months, end-stage renal disease (ESRD; stage 5 CKD) is assumed. This is rare
• Onset of symptoms – can be rapid, and severe. Patients look unwell, with findings dominated by the underlying cause (e.g. after a heart operation)
• Treatment –  focused on reversing the underlying cause
• Short-term dialysis – is necessary in a small number of cases
• Reversibility – it is usually reversible.

Chronic kidney disease (CKD)

• Caused by a long-term illness – e.g diabetes, chronic glomerulonephritis, or a condition that you are born with (e.g. polycystic kidney disease, PKD)
• Decline in kidney function – is gradual, usually over months, years or decades
• Onset of symptoms – slow, and symptoms may not appear until the damage is at a late stage. Patients look well
• Treatment – focused on controlling (rather than reversing) the underlying cause, and slowing progression
• Long-term dialysis or a kidney transplant – is necessary in a small number of cases (about 1 in 100)
• Reversibility – it is usually non-reversible.

AKI on CKD

Some patients have both. In other words they have a background of CKD, that is rapidly worsened by an AKI episode. This can be called ‘AKI on CKD’. Kidney function usually returns to the baseline level, when the AKI is treated. In a few patients, the kidney function does not recover that well and kidney function is reset a new lower level.

Who should look after you?

It depends. [“No, really. How many times have we heard that?” CKDEx Ed]. Well, it does.

AKI – patients can usually be looked after by the patent’s current hospital team, with the advice of kidney specialists (nephrologists) or intensive care doctors, if necessary. A few patients will need to be transferred to a kidney ward (at that hospital, or another) or intensive care – especially if dialysis and/or a kidney biopsy is necessary.

CKD – patients with milder CKD (CKD1-2 or CKD3A) can usually be looked after by their GP. For more advanced CKD (CKD3B or CKD4-5), patients need to be looked after by a nephrologist. A few (with CKD3B or 4) can be discharged back to their GP if stabilised.

Patients with CKD5 are by definition in long-term kidney failure – requiring dialysis, or a transplant, or supportive care – and will therefore always need long-term care by a nephrologist.

Summary

We have described, acute kidney injury vs chronic kidney disease – what’s the difference. We hope it has been helpful.

Last Reviewed on 10 April 2024