The kidneys are two bean-shaped organs responsible for filtering waste, balancing fluids, regulating blood pressure, and maintaining electrolyte levels. When kidney function declines, toxins build up in the body, potentially leading to acute or chronic kidney failure. Early detection and treatment are critical for protecting long-term kidney health.
Your kidneys are two bean-shaped organs located just below the rib cage, near the center of your back. Roughly the size of your fist, these small but powerful organs perform essential tasks that keep your body in balance.
Each day, your kidneys filter approximately 200 quarts of blood, removing about two quarts of waste products and excess fluid. These waste materials leave the body as urine. Without this filtration system, toxins and fluid would accumulate quickly, disrupting nearly every major organ system.
Understanding how the kidneys function — and what happens when they fail — can help you recognize early warning signs and protect long-term health.
What Do the Kidneys Do?
Each kidney contains approximately one million filtering units called nephrons. These microscopic structures filter blood in three main steps:
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Removing waste products
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Balancing fluids
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Regulating essential electrolytes
In addition to filtering blood, the kidneys also:
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Maintain proper sodium, potassium, and calcium levels
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Help regulate blood pressure
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Support red blood cell production
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Maintain acid-base balance in the body
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Activate vitamin D for bone health
Because the kidneys play so many roles, even minor declines in function can affect multiple systems.
What Is Kidney Failure?
Kidney failure occurs when the kidneys lose the ability to filter waste and excess fluids effectively. When this happens, toxins accumulate in the bloodstream, potentially leading to life-threatening complications.
Kidney failure may develop suddenly (acute kidney failure) or gradually over time (chronic kidney disease progressing to failure).
Several factors can impair kidney function, including:
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Severe dehydration
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Reduced blood flow to the kidneys
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Exposure to toxins or certain medications
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Chronic illnesses such as diabetes
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Physical trauma
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Autoimmune conditions
What Causes Kidney Failure?
Kidney failure is generally caused by one of three main problems: reduced blood flow, direct kidney damage, or blocked urine flow.
1. Reduced Urination or Urinary Blockage
If urine cannot exit the body properly, waste builds up and places strain on the kidneys. Conditions that may block urine flow include:
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Prostate enlargement or cancer
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Bladder cancer
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Colon or cervical cancer
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Kidney stones
Holding urine for prolonged periods does not typically cause kidney failure on its own, but chronic obstruction can lead to serious complications.
2. Loss of Blood Flow to the Kidneys
The kidneys rely on a steady blood supply. Sudden or severe reductions in blood flow can cause acute kidney injury.
Possible causes include:
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Heart attack
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Severe dehydration
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Liver failure or cirrhosis
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Severe burns
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Sepsis or severe infections
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Allergic reactions
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Blood clots
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Uncontrolled high blood pressure
Reduced circulation deprives kidney tissue of oxygen, potentially leading to cell death.
3. Direct Kidney Damage
Certain diseases and conditions directly damage kidney tissue, including:
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Glomerulonephritis
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Lupus
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Vasculitis
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Hemolytic uremic syndrome
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Multiple myeloma
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Scleroderma
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Thrombotic thrombocytopenic purpura
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Long-standing uncontrolled diabetes
Toxins such as heavy metals, certain chemotherapy drugs, nonsteroidal anti-inflammatory drugs (NSAIDs), and excessive alcohol can also damage kidney tissue.
Types of Kidney Failure
Kidney failure is classified based on its cause and progression.
Prerenal Acute Kidney Failure
Prerenal kidney failure occurs when blood flow to the kidneys decreases. The kidney tissue itself is not initially damaged, but reduced circulation prevents proper filtration.
This is the most common type of acute kidney injury and may be reversible if treated promptly. If blood flow is not restored, permanent damage can occur.
Intrinsic (Intrarenal) Acute Kidney Failure
Intrinsic kidney failure occurs when the kidney tissue itself is damaged.
Common causes include:
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Acute tubular necrosis
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Acute glomerulonephritis
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Acute interstitial nephritis
This form of kidney injury often results from prolonged oxygen deprivation, infections, medications, or autoimmune reactions.
Chronic Kidney Failure
Chronic kidney failure develops gradually over months or years. As functional nephrons are lost, remaining nephrons attempt to compensate by working harder — a process called hyperfiltration.
Over time, hyperfiltration causes further damage and scarring. Chronic kidney disease may not produce noticeable symptoms until approximately 70 percent of kidney function is lost.
Chronic kidney failure can be classified as:
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Chronic pre-renal failure
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Chronic renal failure
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Chronic post-renal (obstructive) failure
Chronic Intrinsic Kidney Failure
This form results from long-term direct kidney damage, often due to persistent inflammation, lack of oxygen, or prolonged exposure to toxins.
Symptoms of Kidney Failure
Kidney failure symptoms vary depending on severity and type. Some individuals may not notice symptoms until the condition is advanced.
Common symptoms include:
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Reduced or difficult urination
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Swelling in the legs, ankles, or feet
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Fatigue or excessive drowsiness
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Shortness of breath
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Chest pain or pressure
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Persistent nausea
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Confusion
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Seizures (in severe cases)
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Coma (in life-threatening cases)
If you experience these symptoms, seek medical attention immediately.
Treatment Options for Kidney Failure
Treatment depends on the cause and severity of kidney failure.
Dialysis
Dialysis is a procedure that filters waste and excess fluid from the blood when the kidneys can no longer perform this function.
There are two primary types:
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Hemodialysis (machine-based blood filtration)
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Peritoneal dialysis (using the abdominal lining as a filter)
Dialysis can extend life and relieve symptoms but does not cure kidney failure. Patients may also need to follow dietary restrictions, such as limiting sodium and potassium intake.
Kidney Transplant
A kidney transplant involves replacing a failed kidney with a healthy donor kidney.
Advantages include:
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Elimination of dialysis
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Improved quality of life
However, transplant recipients must take lifelong immunosuppressive medications to prevent rejection. These medications increase infection risk and may cause side effects.
Transplants are not always successful, and waiting times for donors can be long.
Kidney Cancer and Warning Signs
Kidney cancer often does not cause symptoms in its early stages. As tumors grow, symptoms may include:
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Blood in the urine
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A lump in the side or abdomen
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Persistent side pain
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Swelling in the legs
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Unexplained weight loss
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Prolonged fever
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Fatigue
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Anemia
Early detection improves treatment outcomes. Any persistent or unusual symptoms should be evaluated by a healthcare professional.
Protecting Kidney Health
Preventive measures include:
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Staying hydrated
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Managing blood pressure
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Controlling blood sugar
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Limiting NSAID overuse
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Avoiding excessive alcohol
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Reducing exposure to environmental toxins
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Maintaining a balanced diet
Regular checkups are especially important for individuals with diabetes, hypertension, or a family history of kidney disease.
FAQs
What do the kidneys do?
The kidneys filter waste from the blood, balance fluids and electrolytes, regulate blood pressure, and support red blood cell production.
What are the first signs of kidney failure?
Early signs may include fatigue, swelling in the legs or ankles, changes in urination, nausea, and shortness of breath.
Can kidney failure be reversed?
Acute kidney failure may be reversible if treated quickly. Chronic kidney failure is usually progressive and not fully reversible.
What causes sudden kidney failure?
Sudden kidney failure can result from severe dehydration, blood loss, infection, heart problems, or exposure to toxic substances.
Is dialysis permanent?
Dialysis may be temporary in cases of acute kidney injury. In chronic kidney failure, dialysis is often long-term unless a transplant occurs.
What are the symptoms of kidney cancer?
Symptoms may include blood in the urine, persistent side pain, unexplained weight loss, fatigue, and swelling in the legs.