Acute kidney injury (AKI)
A sudden drop in kidney function over hours to days, so the kidneys can no longer clear waste and balance fluids and salts properly. It is often triggered by dehydration, infection, low blood pressure or certain medicines, and is usually reversible if the cause is treated quickly.
What it is
Acute kidney injury is a rapid loss of kidney function developing over hours to a few days, in contrast to chronic kidney disease which develops over years. The kidneys suddenly cannot filter waste products, control the body's water and salts, or maintain acid-base balance. It is common in people who are acutely unwell, especially in hospital. The causes are grouped in three ways. 'Pre-renal' causes reduce blood flow to the kidneys — dehydration, severe vomiting or diarrhoea, blood loss, heart failure or low blood pressure from serious infection (sepsis). 'Intrinsic' causes damage the kidney tissue itself — from prolonged poor blood flow, certain medicines and toxins, or inflammation of the kidney filters. 'Post-renal' causes block the flow of urine, such as an enlarged prostate, stones or a tumour. AKI is detected on blood tests as a rising creatinine and falling eGFR, often with a fall in urine output; potassium can rise dangerously and the blood can become acidic. Many cases are mild and reversible once the trigger is corrected — rehydration, treating infection, stopping the offending drug or relieving a blockage — but severe AKI can need temporary dialysis and can be life-threatening, and even after recovery it raises the long-term risk of chronic kidney disease.
Key lab markers
- Creatinine — rises, often quickly; the defining laboratory change.
- eGFR — falls as creatinine climbs.
- Urea — rises alongside creatinine.
- Potassium — can rise to dangerous levels; a key safety marker.
- Bicarbonate — falls (metabolic acidosis).
- Urinalysis — can show blood, protein or casts, helping point to the cause.
- Urine output — often falls (though not always).
Symptoms
- Often few symptoms early, detected on blood tests
- Passing less urine than usual
- Swelling of the legs, ankles or around the eyes
- Tiredness, nausea and loss of appetite
- Confusion or drowsiness in severe cases
- Shortness of breath if fluid builds up
- Symptoms of the trigger — infection, dehydration or blockage
Related lab panels
When to discuss with a doctor
Acute kidney injury needs prompt medical attention because it can worsen quickly and, when severe, becomes an emergency — a dangerously high potassium or heavy fluid overload can be life-threatening and may need urgent treatment or temporary dialysis. It is often first noticed as a rising creatinine on blood tests, sometimes before any symptoms, which is why testing matters when someone is unwell, dehydrated or on medicines that can affect the kidneys. Reduced urine output, new swelling, breathlessness, confusion or feeling very unwell alongside an illness should prompt urgent review. Because many cases are reversible when the cause is found and treated early, speed matters. Mediora.AI can flag a rising creatinine, falling eGFR and rising potassium that signal acute kidney injury, but this is a clinical situation that needs prompt assessment and treatment by a doctor.