A sudden change in kidney function can prevent the kidneys from adequately filtering waste and maintaining the body’s balance of fluids and minerals. This condition, most often referred to as acute kidney injury, can develop within hours or days and range from relatively mild changes in kidney function to sudden, severe kidney failure. Prompt medical evaluation is important because identifying and treating the underlying problem may allow the kidneys to recover and help reduce the risk of lasting damage.
Acute kidney injury is common among people who are hospitalized or critically ill. Research suggests that about one in five adults worldwide develops AKI during a hospital stay. In the United States, older adults may be especially vulnerable to sudden kidney injury.
What Is Acute Kidney Injury?
AKI is a rapid decline in how well the kidneys work. Healthy kidneys continuously filter the blood, removing waste and excess fluid while helping maintain the right balance of electrolytes and other substances in the body. If kidney function suddenly declines, these normal processes can be disrupted.
Acute kidney injury may be mild or progress to severe kidney dysfunction. Its severity can be determined based on changes in kidney function, including blood creatinine levels and urine output. More severe cases may cause dangerous fluid, electrolyte or acid-base imbalances and sometimes require temporary dialysis.
AKI is serious, but it does not necessarily indicate a permanent loss of kidney function. Some patients recover fully, particularly when the cause is identified and addressed quickly. Others may have residual kidney damage or an increased risk of future kidney problems. The likelihood of recovery depends on factors such as the cause and severity of the injury, how quickly treatment begins and the patient’s overall health.
Is Acute Kidney Injury the Same as Acute Kidney Disease?
Not exactly. Although the terms are sometimes used interchangeably in general conversation, acute kidney disease refers to a wider range of abnormalities in kidney function or structure that are present for up to three months. In contrast, acute kidney injury describes changes that develop within seven days.
As such, AKI falls within the broader spectrum of acute kidney disease. Older terminology, such as acute renal failure, may also be used to describe a sudden loss of kidney function, particularly when the injury is severe. Today, however, healthcare professionals generally use the term “acute kidney injury” because it encompasses a wider range of kidney dysfunction, including milder changes that would not traditionally have been classified as kidney failure.
Acute Kidney Injury vs. Chronic Kidney Disease (CKD)
The primary difference between AKI and CKD is how quickly the problem develops and how long it persists. Acute kidney injury develops suddenly, often in response to an illness, injury, medication or another identifiable trigger. With timely treatment, kidney function may recover substantially or completely.
On the other hand, chronic kidney disease involves abnormalities in kidney structure or function that persist for at least three months. CKD generally develops or progresses over a longer period and may cause permanent loss of kidney function.
An individual can have both conditions. For instance, a patient who already has CKD may develop AKI during an illness or hospitalization. Existing kidney disease can make the kidneys more vulnerable to acute injury.
Can Acute Kidney Injury Lead to Chronic Kidney Disease?
Yes. Although many patients regain kidney function after AKI, an episode can increase the risk of developing CKD later. The risk may be greater after severe or repeated episodes of acute kidney injury, when kidney function does not fully return to its previous level or when the patient already has kidney disease or another health condition that affects the kidneys.
For this reason, recovery from the immediate illness is not always the end of AKI care. Follow-up testing can help determine how well the kidneys have recovered and identify persistent changes that may require ongoing monitoring or treatment.
What Causes Acute Kidney Injury?
AKI can occur if the kidneys do not receive enough blood, kidney tissue is directly damaged or urine flow is blocked. More than one problem may occur at the same time. For example, a patient who is seriously ill with an infection may become dehydrated, experience low blood pressure and develop inflammation that affects the kidneys.
Reduced Blood Flow to the Kidneys
The kidneys need an adequate supply of blood and oxygen to function properly. A significant or prolonged decrease in blood flow can cause acute kidney injury and, without timely treatment, may eventually damage kidney tissue.
Potential causes of reduced blood flow to the kidneys include:
- Severe dehydration – Vomiting, diarrhea, excessive sweating or inadequate fluid intake can reduce the amount of fluid circulating throughout the body.
- Significant blood loss – A serious injury, internal bleeding or complications of surgery can decrease blood volume and kidney circulation.
- Sepsis – The body’s extreme response to infection may cause changes in circulation, inflammation and dangerously low blood pressure that contribute to kidney injury.
- Heart problems – Heart failure, heart attack or another condition that impairs the heart’s ability to pump blood effectively can limit blood flow to the kidneys.
- Certain medications – Some drugs can affect blood flow within the kidneys, particularly in an individual who is dehydrated, has low blood pressure or already has impaired kidney function.
AKI caused by reduced kidney blood flow is sometimes called prerenal acute kidney injury. Kidney function may improve when circulation is restored promptly, but a severe or prolonged reduction in blood flow can lead to direct kidney damage.
Direct Damage to the Kidneys
Acute kidney injury can also develop when a disease, medication, toxin or another problem damages the kidney tissue. This is known as intrinsic or intrarenal acute kidney injury.
Possible causes of direct damage to the kidneys include:
- Sepsis or another severe infection
- Inflammation within the kidneys, such as glomerulonephritis or interstitial nephritis
- Certain prescription and over-the-counter medications, including NSAIDs such as ibuprofen and naproxen and certain antibiotics
- Iodinated contrast material used for certain imaging tests, especially in individuals with risk factors for kidney injury
- Severe muscle damage that releases substances into the bloodstream that can injure the kidneys
Although the use of certain medications can sometimes lead to kidney injury, those medications are not unsafe for everyone. The risk of AKI depends on factors such as the specific medication and dosage used and the individual’s hydration status, existing kidney function and other health conditions. It is important to talk with a healthcare provider before stopping or changing a prescribed medication.
Blocked Urine Flow
A blockage can prevent urine from draining normally. The resulting pressure within the urinary system can interfere with kidney function. This condition is known as postrenal acute kidney injury or obstructive kidney injury.
Potential causes of blocked urine flow include:
- A kidney stone or urinary tract stone
- An enlarged prostate
- A blood clot in the urinary tract
- A tumor that blocks or compresses part of the urinary tract
- Narrowing or another abnormality of the urinary tract
- A problem that prevents the bladder from emptying properly
A kidney stone will not always cause AKI. The risk of sudden kidney failure is greater when an obstruction significantly interferes with urine drainage, such as when both kidneys are affected or when an individual has only one functioning kidney. Promptly relieving an obstruction can improve the likelihood that kidney function will recover.
What Causes Sudden Kidney Failure?
Sudden kidney failure can occur if an acute injury becomes severe enough that the kidneys can no longer adequately perform essential functions. Historically called acute renal failure, this severe loss of kidney function can result from:
- A major drop in blood pressure or blood flow
- Severe dehydration or blood loss
- Sepsis or another severe infection
- Major surgery, trauma or critical illness
- Direct kidney damage from certain diseases, medications or toxins
- A significant blockage in the urinary tract
Sudden kidney failure does not necessarily mean kidney function is permanently lost. Depending on the cause and severity of the injury and how quickly treatment begins, kidney function may partially or fully recover.
What Are the Risk Factors for Acute Kidney Injury?
Certain health conditions, medications and medical treatments can make some individuals more vulnerable to AKI. Risk factors include:
- Older age, particularly when other health conditions are present
- Chronic kidney disease or reduced kidney function
- Diabetes
- Heart disease, including heart failure
- High blood pressure
- Liver disease
- Hospitalization or critical illness, especially when intensive care is needed
- Major surgery, particularly if the procedure can affect blood pressure or circulation
- Certain medications or combinations of medications that can affect kidney function
- Certain imaging procedures that use iodinated contrast material, particularly in individuals who already have impaired kidney function or other risk factors
Having one or more risk factors does not mean an individual will develop AKI. However, the healthcare team may monitor kidney function more closely during an illness, hospitalization or medical procedure when the patient is at increased risk.
What Are the Potential Complications of Acute Kidney Injury?
AKI can disrupt the kidneys’ ability to remove waste and excess fluid from the body and maintain a healthy balance of electrolytes and acids in the blood. While some complications may improve as kidney function recovers, severe or prolonged AKI can cause life-threatening problems and increase the risk of lasting kidney damage.
Potential complications of acute kidney injury include:
- Fluid buildup – If the kidneys cannot remove enough fluid from the body, excess fluid may accumulate and cause swelling. If fluid builds up in the lungs, it can cause difficulty breathing.
- Electrolyte imbalances – AKI can cause abnormal levels of potassium, sodium and other electrolytes. A dangerously high potassium level can interfere with the heart’s normal rhythm.
- Acid buildup in the blood – Impaired kidney function can lead to metabolic acidosis, a condition in which the body cannot adequately maintain its normal acid-base balance.
- Waste buildup – Waste products that the kidneys normally filter from the blood can accumulate and, in severe cases, contribute to symptoms such as nausea, confusion and extreme fatigue.
- Heart and circulation problems – The kidneys and heart work closely together to regulate fluid balance, blood pressure and circulation. Severe kidney dysfunction can place strain on the cardiovascular system, particularly in individuals who already have heart disease.
- Need for dialysis – A patient with severe AKI may require temporary dialysis to remove waste and excess fluid or correct dangerous electrolyte and acid-base imbalances while the kidneys recover.
- Chronic kidney disease – AKI can increase the risk of developing CKD, particularly after severe or repeated episodes or when kidney function does not fully recover.
- Long-term kidney failure – In some cases, kidney damage may be permanent and progress to kidney failure that requires ongoing dialysis or, eventually, a kidney transplant.
The risk of complications depends on the cause and severity of AKI, the patient’s overall health and how quickly the underlying problem can be treated. Individuals who already have chronic kidney disease, heart disease or another serious health condition may face a greater risk.
What Are the Warning Signs and Symptoms of Acute Kidney Injury?
AKI symptoms can vary widely. Some individuals may notice changes in urination, swelling or fatigue, while others have few or no obvious symptoms. In some cases, acute kidney injury is first detected through blood testing or urine output monitoring during a hospital stay or an evaluation for another health issue.
Possible signs and symptoms of acute kidney injury include:
- Decreased urine output, although some individuals with AKI continue to produce a normal amount of urine
- Swelling in the legs, ankles or feet due to fluid retention
- Unusual tiredness or weakness
- Nausea or loss of appetite
- Shortness of breath, particularly if excess fluid accumulates in or around the lungs
- Confusion or difficulty concentrating
- Chest pain or pressure, which can occur with serious complications
- Rapid weight gain caused by fluid retention
As kidney function worsens, decreased urination, fluid retention, nausea, weakness or other symptoms may become more noticeable. Severe AKI can lead to significant shortness of breath, changes in mental alertness and other signs of potentially dangerous complications.
Symptoms can also differ depending on the cause of the kidney injury and the patient’s age and other medical conditions. For example, an older adult with AKI may develop confusion, while an individual with heart disease may experience worsening swelling or shortness of breath. Because these symptoms can also occur with many other conditions, testing is often necessary to determine whether the kidneys are involved.
Acute Kidney Injury Symptoms That May Require Immediate Care
AKI can develop rapidly, and certain symptoms may indicate severe kidney dysfunction or another medical emergency. It is important to seek immediate medical attention for symptoms such as:
- Little or no urine output
- Severe or rapidly worsening shortness of breath
- Chest pain or pressure
- New or severe confusion, extreme drowsiness or difficulty staying alert
- Fainting or loss of consciousness
- Severe weakness, particularly when accompanied by an abnormal or irregular heartbeat
- Rapidly worsening swelling or other signs of significant fluid buildup
Prompt evaluation is especially important after a serious illness, severe dehydration, major surgery or another event that could affect kidney function.
How Is Acute Kidney Injury Diagnosed?
AKI is diagnosed by evaluating how quickly kidney function has changed, usually through blood tests and urine output. The healthcare team will also look for the underlying cause so treatment can begin as quickly as possible.
Tests and evaluations used to diagnose acute kidney injury may include:
- Creatinine blood test – Creatinine is a waste product that healthy kidneys filter from the blood. A rise in the blood creatinine level over a short period may indicate that kidney function has declined. The healthcare team may compare current and previous test results to determine how quickly the change occurred.
- Urine output monitoring – Producing significantly less urine than expected over several hours can be a sign of AKI. However, some individuals continue to produce a normal amount of urine despite having an acute kidney injury.
- Urine testing – A urinalysis can detect blood, protein and other substances that may provide clues about the cause of kidney injury. Additional urine tests may be performed if certain kidney diseases are suspected.
- Imaging – A kidney ultrasound is often used when a urinary tract blockage is suspected. Other imaging tests may be appropriate depending on the possible cause of AKI.
- Additional blood tests – The healthcare team may check the blood levels of potassium, sodium, bicarbonate and other substances to identify electrolyte or acid-base imbalances and assess the severity of AKI.
- Kidney biopsy – In select cases, a small sample of kidney tissue may be examined under a microscope. A biopsy is generally reserved for situations in which the cause of AKI remains uncertain or a specific type of kidney disease is suspected.
An estimated glomerular filtration rate (eGFR) may also appear with creatinine results. While eGFR is commonly used to assess kidney function, it is less reliable for evaluating AKI when creatinine levels are changing rapidly. The healthcare team will therefore consider changes in creatinine, urine output and the overall clinical picture rather than relying on a single eGFR result.
To determine what caused the kidney injury, the healthcare team may also review recent illnesses, fluid losses, medications, medical procedures and existing health conditions. Identifying the cause is an important part of the diagnostic process because AKI can result from problems as varied as dehydration, infection, direct kidney damage and urinary obstruction.
How Is Acute Kidney Injury Treated?
AKI treatment can vary based on the cause of the sudden decline in kidney function and the severity of the injury. The immediate goals are to address the underlying cause, support the kidneys while they recover and prevent potentially dangerous complications.
Treatment options for acute kidney injury may include:
- Managing fluids – A patient who is dehydrated or has lost blood may need fluids given through a vein. If excess fluid has accumulated because the kidneys cannot remove it effectively, treatment may instead focus on limiting fluid intake or using medications to help manage the buildup.
- Treating infection or another underlying illness – Prompt treatment of sepsis, severe infection, a heart problem or another condition affecting kidney function can be an important part of recovery.
- Relieving a urinary blockage – A kidney stone, enlarged prostate or another obstruction may require treatment to restore urine flow.
- Adjusting medications – The healthcare team may temporarily stop, adjust or replace medications that could be contributing to kidney injury. The patient should not stop prescription medications without medical guidance.
- Correcting electrolyte and acid-base imbalances – Treatment may be needed if AKI causes dangerous changes in potassium, acid levels or other substances in the blood.
- Dialysis – Severe AKI may require dialysis if the kidneys cannot adequately remove waste and excess fluid or maintain a safe balance of electrolytes and acids.
Treatment for sudden kidney failure often takes place in a hospital, particularly when kidney function is severely impaired or AKI occurs alongside another serious illness. Kidney function, urine output, fluid balance and blood chemistry may be monitored closely so treatment can be adjusted as the condition changes.
When Is Dialysis Needed for Acute Kidney Failure?
Dialysis may be needed if severe AKI causes complications that cannot be safely controlled with other treatments. Rather than relying on a single creatinine level to make this determination, the healthcare team will consider the patient’s overall condition and whether the kidneys can still perform essential functions.
Temporary dialysis may be considered for problems such as:
- Dangerously high potassium levels
- Severe acid buildup in the blood
- Excess fluid that causes serious breathing problems or does not respond adequately to other treatments
- Significant buildup of waste products that causes complications
- Other severe changes that cannot be adequately managed while kidney function is impaired
Hemodialysis is one method that may be used to address acute kidney failure. During treatment, blood passes through a dialysis machine that removes waste and excess fluid before returning the blood to the body. A critically ill patient may receive a slower, continuous form of kidney replacement therapy if appropriate.
Dialysis during AKI is not necessarily permanent. Instead, it may be used to provide temporary support until the kidneys regain enough function to manage the body’s needs on their own.
Treatment, Dialysis and Recovery
Recovery from AKI can vary. In some cases, kidney function may begin to improve within days; in others, recovery can take weeks or longer. The outlook will depend on factors such as the cause and severity of the kidney injury, whether additional organs were affected and the patient’s kidney function and overall health before the illness.
If temporary dialysis is necessary, the healthcare team will monitor blood test results, urine output, fluid balance and other signs of kidney function to determine whether the kidneys are recovering. Dialysis can often be discontinued when kidney function improves enough to safely regulate fluid, electrolytes and waste without this support.
Follow-up will remain important even after the patient feels better or no longer needs dialysis. Periodic blood and urine testing can help determine how much kidney function has returned and whether further monitoring or treatment is needed.
Reversible vs. Permanent Kidney Damage
Acute kidney injury may be reversible, particularly if the cause is identified and treated before extensive kidney damage occurs. For example, kidney function may improve after severe dehydration is corrected or a urinary obstruction is relieved. Recovery, however, is not always complete.
Some patients are left with reduced kidney function after an episode of AKI. Others may develop chronic kidney disease or experience worsening of CKD that was already present. Severe or repeated episodes of AKI can increase the likelihood of long-term kidney problems.
Permanent kidney failure after AKI is possible but is not inevitable. If kidney function does not recover enough to meet the body’s needs, long-term dialysis may be necessary. Kidney transplantation may eventually be considered for an eligible patient who develops irreversible kidney failure, rather than as a treatment for the acute kidney injury itself.
What Is the Prognosis and Long-Term Outlook for Acute Kidney Injury?
The outlook for AKI varies widely. Many patients recover some or all of their kidney function, especially when the cause can be identified and treated promptly. Others may have a lasting reduction in kidney function or an increased risk of CKD and future episodes of AKI.
Recovery depends on several factors, including the cause and severity of the injury, kidney function before AKI developed, coexisting medical conditions and whether the patient was critically ill. A mild episode caused by a reversible problem may have a different outlook than severe AKI associated with sepsis, major surgery or failure of other organs.
After AKI, follow-up care may include:
- Kidney function testing – Periodic blood and urine tests can help determine whether kidney function has returned to its previous level or remains impaired.
- Medication review – The healthcare team can determine whether medications that were stopped or adjusted during AKI can be safely resumed and whether dosages need to change.
- Fluid management – Fluid needs can change during and after AKI. The patient should follow their healthcare team’s recommendations rather than significantly increasing or restricting fluids on their own.
- Protecting overall health – Managing diabetes, high blood pressure, heart disease and other conditions that can affect kidney health may help protect remaining kidney function.
- Avoiding another kidney injury – The patient may be advised to take certain precautions during illnesses that cause vomiting, diarrhea or dehydration and to discuss any medications that could affect the kidneys with the healthcare team.
- Ongoing kidney care when needed – A patient whose kidney function does not fully recover may need continued monitoring or care from a nephrologist.
Even when kidney function appears to recover, an episode of AKI can have implications for future kidney health. Keeping follow-up appointments and completing recommended testing can help identify persistent kidney problems early.
How Can Acute Kidney Injury Affect Daily Life?
The effects of AKI on daily life can vary depending on the severity of injury, the underlying illness and how quickly kidney function recovers. A mild, short-lived episode may have minimal lasting impact, while recovery from severe AKI or a lengthy hospitalization can temporarily affect the patient’s energy, independence and normal routines.
Possible mental, emotional and social effects include:
- Fatigue and reduced stamina while recovering from AKI and the illness that caused it
- Changes in daily routines related to medications, follow-up appointments, laboratory testing or dietary and fluid recommendations
- Stress or uncertainty about whether kidney function will fully recover or whether another episode could occur
- Emotional strain related to dialysis, particularly when it is needed during a serious illness
- Time away from work, school or other responsibilities during hospitalization and recovery
- Greater reliance on family members or caregivers if additional support is needed
Recovery is different for each patient. The healthcare team can offer guidance about returning to daily activities and managing any ongoing kidney-related needs. A patient who experiences persistent anxiety, low mood or difficulty adjusting after a serious illness can also discuss these concerns with the team.
Can Acute Kidney Injury Be Prevented?
Not every case of AKI can be prevented. However, taking steps to protect kidney function may reduce the risk, particularly for individuals who have chronic kidney disease or other factors that make the kidneys more vulnerable to sudden injury.
Ways to help lower the risk of acute kidney injury include:
- Preventing dehydration – Maintain adequate fluid intake and pay attention to fluid loss during vomiting, diarrhea, fever or prolonged heat exposure. Individuals who have kidney disease, heart failure or other conditions that can affect fluid balance should ask their healthcare team how much fluid is appropriate for them.
- Using medications safely – Take prescription medications and over-the-counter drugs as directed. Some medications, including nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen, can increase the risk of kidney injury in certain circumstances, particularly during dehydration or illness.
- Asking about medication management during an illness – Vomiting, diarrhea or difficulty eating and drinking can affect fluid balance and kidney function. Individuals who take medications for conditions such as hypertension, heart disease or diabetes should ask their healthcare team if any adjustments may be necessary during an acute illness.
- Managing existing health conditions – Controlling diabetes, high blood pressure, heart disease and chronic kidney disease appropriately can help protect kidney health.
- Discussing kidney health before certain medical procedures – Individuals at increased risk of AKI should make their healthcare team aware of any existing kidney problems and other risk factors before surgery or imaging procedures that may involve iodinated contrast material.
- Seeking care for significant illness or fluid loss – Persistent vomiting or diarrhea, severe infection and other illnesses can lead to dehydration or changes in circulation that affect the kidneys. Timely medical care may help prevent kidney problems from becoming more severe.
Individuals who have previously experienced AKI may be at increased risk of another episode. Knowing what caused the initial injury, keeping healthcare providers informed about that history and completing recommended kidney function testing can help guide future care.
The TGH Difference for Acute Kidney Injury
AKI can develop quickly, but timely diagnosis and treatment may help restore kidney function and reduce the risk of lasting damage. At Tampa General Hospital, patients with acute kidney injury have access to specialized kidney care for conditions ranging from relatively mild changes in kidney function to severe kidney failure.
TGH’s Nephrology Program takes a patient-focused, multispecialty approach to kidney care. Our nephrologists collaborate with other specialists and healthcare providers to identify what is affecting kidney function and develop an individualized treatment plan. Depending on the patient’s needs, care may include close monitoring, fluid and electrolyte management, medication adjustments, treatment of the underlying cause or dialysis.
Tampa General is recognized by U.S. News & World Report as a High Performing Hospital for Acute Kidney Failure for 2025-26. For patients who develop irreversible kidney failure, TGH also offers access to advanced kidney care through its Transplant Institute and Kidney and Pancreas Transplant Center.
If you are experiencing symptoms of acute kidney injury or have concerns about your kidney function, it is important to talk with a healthcare provider. Contact Tampa General Hospital to learn more about our kidney care services and schedule an appointment with a nephrology specialist.