A sudden loss of kidney function causes acute kidney injury. However, kidney failure occurs in end stage chronic kidney disease (CKD). While both conditions cause the kidneys to stop working properly, they are distinct.

Acute kidney injury can be mild, moderate, or severe, depending on how much kidney function a person loses. Typically, doctors can treat it effectively if they catch it early.

Conversely, kidney failure occurs when a person has had CKD for some time and the kidneys cease to function properly. Kidney failure is a serious condition, and a person often needs treatment with dialysis or a kidney transplant to survive.

This article explores the differences between these two conditions that affect the kidneys.

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Acute kidney injury and acute kidney (or renal) failure are the same. Doctors now largely refer to both as acute kidney injury.

However, kidney failure that results from CKD is not the same as acute kidney injury. The key difference is the underlying cause of kidney failure.

The two conditions also differ in outlook. Acute kidney injury is often reversible, while kidney failure is not.

Acute kidney injury can sometimes lead to CKD and kidney failure.

Acute kidney injury

Acute kidney injury is the result of a sudden loss of kidney function, in which a rapid decline in the estimated glomerular filtration rate (eGFR) occurs. eGFR is the rate at which the kidneys filter waste from the blood. It is a measure of kidney function.

As eGFR declines, a person’s levels of serum creatinine, blood urea nitrogen, and electrolytes will change.

Acute kidney injury has many possible causes, including:

  • dehydration
  • sepsis
  • shock
  • organ failure
  • acute kidney inflammation, or glomerulonephritis
  • fluid and blood loss
  • certain medications

People with acute kidney injury often require hospital stays for other reasons, such as major surgery, organ failure, or severe blood or fluid loss.

With early medical intervention, doctors can treat and reverse most cases of acute kidney injury.

Learn more about acute kidney injury.

Kidney failure

Kidney failure is the final stage of CKD. Blood tests measure a person’s levels of creatinine — a waste product in the blood — and eGFR. Doctors define CKD as the presence of kidney damage, or an eGFR of less than 60 ml/min over 3 months or more.

Doctors recognize the following signs of kidney damage:

  • albuminuria, or protein in the urine
  • urine casts, which are cylindrical structures the kidney produces
  • imaging findings
  • atypical kidney biopsy results

Symptoms of kidney disease are often mild. People may experience:

However, some people live with CKD for years, or even decades, with relatively minor or no symptoms. A person may have significantly reduced kidney function before they become aware of their condition.

Kidney disease is progressive. Eventually, the kidneys fail and the person needs renal replacement therapy, which consists of dialysis or transplantation.

Certain health conditions increase the likelihood of developing CKD, including:

Diabetes and hypertension are the two leading causes of kidney failure in the U.S., causing 3 in 4 cases.

Certain risk factors may increase a person’s risk of developing CKD, such as having a family history of the condition.

Learn more about CKD.

Many cases of acute kidney injury happen to people who are already in the hospital for other acute illnesses. Doctors may suspect acute kidney injury if that is the case.

The diagnostic processes for acute kidney injury and kidney failure are similar. Doctors typically diagnose, and possibly differentiate, these conditions based on results from:

  • blood work
  • urine studies
  • biopsy
  • imaging tests
  • a person’s medical history

While treatment for the two conditions may differ, the cause of the disease is an important factor to consider.

For example, a person with acute kidney failure has typically had CKD for some time. When eGFR falls below 60 ml/min, it can be concerning. In this case, doctors might reexamine results from previous exams to determine whether acute kidney injury or CKD — which may have been asymptomatic — is affecting the eGFR.

Treatment for either condition usually requires hospital care. In acute kidney injury, doctors must identify and treat the underlying cause. This may involve:

  • administering fluids for dehydration
  • using medications to regulate blood pressure
  • using medications to balance electrolytes

For CKD, treatment typically involves dialysis or a kidney transplant.

No. Acute kidney injury is often reversible if doctors catch and treat it early. However, it increases a person’s risk of:

A person’s recovery time depends on the cause of acute kidney injury and many other factors, for example, whether the person has preexisting kidney disease.

In more serious cases, people may need dialysis to support their kidneys as they recover.

A 2020 study found that most people with kidney failure resulting from acute kidney injury recovered within 12 months. However, recovery within this time frame was less likely in females than in males and less likely in Black, Asian, Hispanic, and Native American individuals than in white individuals.

Acute kidney injury and kidney failure are two conditions that cause a decline in kidney function. Acute kidney injury has a rapid, sudden onset and results from illness or injury. It is often reversible with prompt treatment.

In contrast, kidney failure is irreversible. It is the end stage of CKD, so the damage occurs gradually.

Doctors may use a range of tests, imaging studies, and biopsies to diagnose either condition.

Treatment for acute kidney injury depends on the underlying cause. CKD often requires long-term management and, eventually, renal replacement therapy.