Acute kidney injury (AKI)

What Is Acute Kidney Injury (AKI)?

Acute Kidney Injury (AKI), also known as acute renal failure, is a sudden loss of kidney function that develops over hours or days. It causes a rapid build-up of waste products like creatinine and urea in the blood and disrupts the body’s ability to maintain fluid, electrolyte, and acid-base balance.

AKI is common in hospitalized patients, especially those in intensive care units, and requires prompt detection and treatment.

What Causes Acute Kidney Injury?

AKI can be triggered by a wide range of factors, often classified into three categories:

1. Prerenal (Before the Kidneys)

Low blood pressure (hypotension)
Severe dehydration
Heart failure
Blood loss or shock

2. Intrinsic (Within the Kidneys)

Acute tubular necrosis (ATN)
Glomerulonephritis
Nephrotoxic medications (e.g., NSAIDs, some antibiotics)
Sepsis

3. Postrenal (After the Kidneys)

Urinary tract obstruction
Kidney stones
Enlarged prostate

Signs and Symptoms of AKI

AKI may not always present symptoms in early stages, but common signs include:

Decreased urine output
Swelling in legs, ankles, or around the eyes
Fatigue or confusion
Shortness of breath
Nausea or loss of appetite

In severe cases, AKI can lead to seizures, coma, or death if left untreated.

Key Lab Tests for Diagnosing AKI

Blood and urine tests are essential for diagnosing and monitoring acute kidney injury. Key biomarkers include:

Serum Creatinine – Elevated levels are a primary indicator of kidney dysfunction.
Blood Urea Nitrogen (BUN) – Often elevated when kidney function is impaired.
Estimated Glomerular Filtration Rate (eGFR) – Measures how well your kidneys filter waste.
Urine Output – Decreased output may indicate kidney injury.
Urinalysis – Helps detect protein, blood, or sediment in urine.
Electrolytes (Sodium, Potassium) – Imbalances often accompany AKI.

Stages of AKI (Based on Creatinine and Urine Output)

Stage	Serum Creatinine	Urine Output
Stage 1	1.5–1.9× baseline or ≥0.3 mg/dL increase	<0.5 mL/kg/h for 6–12 hours
Stage 2	2.0–2.9× baseline	<0.5 mL/kg/h for ≥12 hours
Stage 3	3.0× baseline or ≥4.0 mg/dL	<0.3 mL/kg/h for ≥24 hours or anuria for ≥12 hours

Can AKI Be Reversed?

Yes, in many cases, acute kidney injury is reversible, especially if caught early and the underlying cause is treated quickly. Recovery may take days to weeks, and some individuals may require temporary dialysis during recovery.

Preventing Acute Kidney Injury

To reduce your risk of AKI:

Stay well hydrated, especially during illness or hot weather
Avoid overuse of NSAIDs (ibuprofen, naproxen)
Monitor and manage chronic conditions like diabetes and high blood pressure
Inform healthcare providers of kidney concerns before imaging tests or surgery
Get regular check-ups and lab tests if at risk

Frequently Asked Questions (FAQ)

What is the most common cause of AKI?
Low blood flow to the kidneys (prerenal AKI) is the most common cause, often due to dehydration, blood loss, or heart failure.

How is AKI diagnosed?
AKI is diagnosed using blood tests like creatinine and BUN, urine output tracking, and kidney imaging when needed.

Can AKI lead to chronic kidney disease (CKD)?
Yes. If left untreated or severe, AKI can result in permanent kidney damage and increase the risk of developing chronic kidney disease.

Does AKI require dialysis?
Severe cases may require temporary dialysis to support kidney function until recovery.

How fast can AKI develop?
AKI can develop within a few hours or over a couple of days, depending on the cause and the individual's health status.

Track Your Kidney Health with Lab Data

At HealthMatters, you can upload your lab results and track key kidney biomarkers like creatinine, BUN, eGFR, and more. Our platform helps you monitor changes over time and understand how your kidney function is trending.