The kidneys are essential organs that filter the blood and balance fluids in the body. If they begin to work less efficiently, it can lead to renal failure. There are two types of renal failure: acute and chronic.

The kidneys are two bean-shaped organs on either side of the spine, just below the ribcage. They have a range of essential functions, including filtering waste products and excess substances from the bloodstream, regulating the body’s balance of fluids and electrolytes, and helping control blood pressure.

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), renal failure happens if someone has less than 15% kidney function. Acute renal failure can sometimes progress into the chronic type.

This article explores the different types of renal failure, including their symptoms, causes, diagnosis, and treatments for both.

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Acute renal failure or acute kidney injury (AKI) refers to a sudden and often reversible loss of kidney function. The condition affects the kidneys’ ability to filter waste products, excess fluids, and electrolytes from the bloodstream.

This type of renal failure can happen suddenly, often within a few hours or days.

Doctors categorize acute renal failure into several subtypes based on its underlying causes:

  • Pre-renal: A reduction in blood flow to the kidney plays a role in causing this subtype. It is the leading cause of kidney injury. Factors that reduce blood flow to the kidneys include:
  • Intrinsic or renal: This subtype occurs due to direct damage to the kidney tissue. Common causes of it include:
  • Post-renal: Post-renal AKI occurs when a physical obstruction prevents the flow of urine from the kidneys and to the bladder. Obstruction can occur due to:


The symptoms of acute renal failure can vary depending on its severity and underlying cause. Common symptoms and signs include:


Doctors categorize acute renal failure into four stages based on the level of kidney dysfunction:

  • Stage 1: Early stage failure. There may be no symptoms.
  • Stage 2: Oligo-anuria, meaning a person urinates less frequently. This leads to fluid retention, waste production accumulation, increased blood pressure, and potential heart failure.
  • Stage 3: Kidney function slowly recovers, but there may still be a substantial loss of water and electrolytes. If this stage lasts for longer than 3 months, a person may have progressed to chronic kidney disease.
  • Stage 4: Restitution or return of kidney function.


Diagnosing acute renal failure typically involves a combination of:


Treatment for acute renal failure depends on its underlying cause, severity, and stage. Standard treatment approaches include:

  • addressing the underlying cause, such as correcting dehydration or discontinuing nephrotoxic medications
  • supportive care to manage symptoms and maintain fluid and electrolyte balance
  • dialysis to temporarily take over the kidneys’ filtering function until they recover

Learn more about acute renal failure.

Chronic renal failure, also known as chronic kidney disease (CKD), is a long-term and progressive decline in kidney function. Unlike acute renal failure, CKD develops gradually over months or years and is characterized by a persistent loss of the kidney’s ability to filter waste products and maintain electrolyte balance.


Common contributing factors and causes include:


Doctors categorize chronic renal failure into different stages based on the level of kidney function and the presence of complications:

  • Stage 1 — Kidney damage with normal GFR: There is mild kidney damage in this early stage, but the glomerular filtration rate (GFR) — a measure of kidney function — remains normal.
  • Stage 2 — Mildly reduced GFR: Kidney function is mildly reduced in this stage and has a slightly lower than average GFR. Some individuals may experience mild symptoms or complications.
  • Stage 3 — Moderately reduced GFR: Kidney function is moderately reduced, and individuals may experience noticeable symptoms and complications.
  • Stage 4 — Severely reduced GFR: In this stage, kidney function is significantly impaired, and individuals are at high risk of experiencing complications and symptoms.
  • Stage 5 — End stage renal disease (ESRD): This is the most advanced stage of chronic renal failure. Kidney function is severely compromised, and individuals often require kidney replacement therapy, such as dialysis or a transplant, to sustain life.


Chronic renal failure may not exhibit noticeable symptoms in its early stages. As CKD progresses, individuals may experience a range of symptoms, which can include:

  • fatigue and weakness
  • nausea and vomiting
  • persistent itching
  • foamy or bubbly urine
  • increased or decreased urination
  • blood in the urine (hematuria)
  • swelling in the legs, ankles, or face (edema)
  • a loss of appetite
  • muscle cramps
  • high blood pressure
  • difficulty sleeping
  • cognitive changes and trouble concentrating


Doctors diagnose chronic renal failure through a combination of a medical history review, physical examination, and laboratory tests.

Key diagnostic markers include:

Just as with acute renal failure, imaging studies are useful to assess kidney size and structure.


Treatment for CKD aims to slow the progression of the disease, manage its symptoms, and address underlying causes. The severity of the disease can play a role in choosing the most appropriate treatment method.

Common approaches include:

A person with CKD should also make dietary modifications to adjust their sodium, potassium, phosphorus, and protein intake.

Learn more about CKD.

There are two types of renal failure. Acute renal failure happens rapidly, often as a result of dehydration, medications, or infections. The outlook for acute renal failure tends to be favorable, as individuals have the potential to recover completely.

Conversely, chronic renal failure is more gradual kidney failure, spanning weeks or months. This form of renal failure is typically progressive, leading to long-term consequences if people do not manage it appropriately.