Acute renal failure, now more commonly referred to as acute kidney injury (AKI), is a sudden decline in kidney function that develops over a short period.
When the kidneys suddenly become less effective at filtering blood, waste products and fluid can accumulate. Electrolyte and acid-base disturbances may also develop.
Acute kidney injury can range from mild to severe. Some patients recover kidney function after the underlying cause is treated, while severe cases may require temporary or, in some circumstances, longer-term kidney replacement therapy.
Understanding the types of acute renal failure helps doctors identify where the problem originates and choose appropriate treatment.
At Prabhakar Bhurke Clinic, Dr. Sandip Prabhakar Bhurke, super specialist nephrologist and transplant physician, provides specialist evaluation and management of acute and chronic kidney conditions.
The 3 Main Types of Acute Renal Failure
Acute kidney injury is broadly classified according to where the primary problem occurs:
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Prerenal acute kidney injury
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Intrinsic renal acute kidney injury
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Postrenal acute kidney injury
These categories are based on the underlying mechanism rather than simply the severity of kidney dysfunction.
1. Prerenal Acute Kidney Injury
Prerenal AKI occurs when the kidneys do not receive adequate blood flow or effective circulation.
In this situation, the kidney tissue may initially be structurally intact, but insufficient blood supply reduces the kidneys' ability to filter blood.
Common Causes of Prerenal AKI
Possible causes include:
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Severe dehydration
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Significant blood loss
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Prolonged vomiting or diarrhea
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Severe infection
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Low blood pressure
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Heart failure
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Conditions causing reduced circulating blood volume
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Certain medicines that affect kidney blood flow
Example
A person with severe diarrhea and vomiting may lose a substantial amount of fluid. If dehydration becomes severe, blood flow to the kidneys may decrease, resulting in acute kidney injury.
Why Early Treatment Matters
Prerenal AKI can sometimes improve significantly when the underlying circulatory or fluid problem is recognized and corrected promptly.
However, prolonged inadequate blood flow can eventually cause actual kidney tissue injury.
2. Intrinsic Renal Acute Kidney Injury
Intrinsic renal AKI occurs when there is direct injury to the kidney tissue itself.
Different parts of the kidney can be affected, including the tubules, glomeruli, interstitium or blood vessels.
Common Causes of Intrinsic AKI
Examples include:
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Acute tubular injury
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Certain glomerular diseases
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Acute interstitial nephritis
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Kidney inflammation
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Severe infections
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Some medications
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Exposure to certain toxins
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Prolonged ischemic injury
Acute Tubular Injury
Acute tubular injury is an important cause of intrinsic AKI.
It can occur after:
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Severe low blood pressure
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Major surgery
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Severe infection
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Significant blood loss
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Certain medications or toxic exposures
The kidney's tubules become injured and may temporarily lose their ability to function normally.
Acute Interstitial Nephritis
This is an inflammatory condition affecting the kidney's interstitial tissue.
It can sometimes occur as a reaction to medications or infections.
Possible associated symptoms may include:
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Fever
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Rash
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Changes in kidney function
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Urinary abnormalities
Not every patient develops all of these symptoms.
Glomerular Causes
Some inflammatory diseases affecting the kidney's filtering units, called glomeruli, can cause AKI.
These conditions may be associated with:
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Blood in urine
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Protein in urine
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Swelling
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High blood pressure
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Rapidly worsening kidney function
Specialist evaluation is important because treatment depends on the underlying disease.
3. Postrenal Acute Kidney Injury
Postrenal AKI develops when urine cannot flow normally out of the kidneys because of an obstruction.
The obstruction increases pressure within the urinary system and can impair kidney function.
Common Causes of Postrenal AKI
Possible causes include:
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Kidney or ureteric stones
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Enlarged prostate
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Urinary tract obstruction
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Tumors
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Blood clots
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Urethral blockage
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Certain structural abnormalities
Kidney Stones and AKI
A single kidney stone does not always cause kidney failure.
However, significant obstruction can become dangerous, particularly when:
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Both urinary pathways are affected
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A person has only one functioning kidney
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Severe obstruction is present
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Infection occurs behind the obstruction
Postrenal AKI may improve when the obstruction is identified and appropriately relieved.
Prerenal vs Intrinsic vs Postrenal AKI
| Type | Main Problem | Common Examples |
|---|---|---|
| Prerenal AKI | Reduced kidney blood flow | Dehydration, blood loss, low blood pressure |
| Intrinsic renal AKI | Direct kidney tissue injury | Tubular injury, glomerular disease, interstitial nephritis |
| Postrenal AKI | Urine flow obstruction | Stones, enlarged prostate, tumors, urinary blockage |
A patient can also have more than one contributing mechanism at the same time.
What Are the Symptoms of Acute Renal Failure?
The symptoms of AKI can vary depending on its severity and cause.
Possible symptoms include:
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Reduced urine output
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Swelling in the legs or face
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Fatigue
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Nausea
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Vomiting
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Loss of appetite
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Breathlessness
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Confusion
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Weakness
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Changes in urine
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Flank or abdominal discomfort in selected cases
Importantly, some people with AKI may initially have few or no obvious symptoms.
That is why kidney-function testing is important when AKI is suspected.
How Is Acute Kidney Injury Diagnosed?
Doctors generally combine medical history, physical examination, laboratory tests and imaging.
Blood Tests
Blood tests may assess:
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Serum creatinine
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Urea
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Potassium
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Sodium
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Bicarbonate
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Other relevant parameters
A rising creatinine can indicate worsening kidney function, but the result needs to be interpreted in the context of previous kidney function and the patient's overall condition.
Urine Tests
Urinalysis can provide clues about the underlying cause.
Doctors may look for:
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Blood
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Protein
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White blood cells
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Urinary sediment abnormalities
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Other findings suggesting a particular kidney disorder
Kidney Ultrasound
Ultrasound can help identify:
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Kidney size
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Structural abnormalities
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Urinary obstruction
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Hydronephrosis
Other imaging may be considered when clinically appropriate.
Medical History
Information about recent:
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Vomiting or diarrhea
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Blood loss
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Infection
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Surgery
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Medication use
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Kidney stones
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Urinary symptoms
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Chronic diseases
can help identify the likely type of AKI.
How Is Acute Renal Failure Treated?
There is no single treatment for every type of AKI.
Treatment focuses on finding and correcting the underlying cause while supporting kidney function.
Treatment of Prerenal AKI
Depending on the cause, treatment may involve:
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Correcting fluid loss
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Treating low blood pressure
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Managing severe infection
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Addressing heart-related problems
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Reviewing medications that may be contributing to kidney dysfunction
Fluid treatment must be individualized. Giving excessive fluid can be harmful in some patients, particularly those with certain heart or kidney conditions.
Treatment of Intrinsic AKI
Treatment depends on the specific kidney injury.
It may involve:
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Removing or stopping an offending medicine when appropriate
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Treating infection
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Managing blood pressure
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Correcting electrolyte abnormalities
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Treating specific inflammatory or immune-mediated kidney diseases
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Providing supportive kidney care
Some conditions require additional investigations or specialized treatment.
Treatment of Postrenal AKI
The priority is to identify and relieve the urinary obstruction.
Depending on the cause, management may involve:
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Urinary catheterization
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Treatment of a stone
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Urological procedures
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Stent placement
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Nephrostomy
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Treatment of prostate obstruction
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Management of another structural blockage
The exact approach depends on the location and severity of the obstruction.
When Is Dialysis Needed in Acute Kidney Injury?
Not every patient with AKI requires dialysis.
Kidney replacement therapy may be considered when severe complications develop, such as:
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Persistent severe hyperkalemia
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Severe metabolic acidosis that cannot be adequately controlled
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Significant fluid overload
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Certain severe uremic complications
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Other life-threatening metabolic abnormalities
The decision is based on the overall clinical situation rather than a single creatinine value.
In some cases of AKI, dialysis may be temporary while the kidneys recover.
Can Acute Renal Failure Be Reversed?
In many cases, AKI can improve when its cause is identified and treated promptly.
The possibility and extent of recovery depend on factors such as:
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Cause of AKI
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Severity of kidney injury
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Duration of kidney dysfunction
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Age and overall health
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Presence of previous kidney disease
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Presence of severe infection or other organ problems
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Timeliness of treatment
Some patients recover nearly normal kidney function, while others may have residual kidney impairment or progress to chronic kidney disease.
Who Is at Higher Risk of Acute Kidney Injury?
AKI can affect anyone, but the risk may be higher in people with:
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Chronic kidney disease
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Diabetes
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Heart disease
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High blood pressure
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Older age
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Severe infections
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Major surgery
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Significant dehydration
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Recurrent kidney stones
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Urinary obstruction
Patients with pre-existing kidney disease require particular care when they become acutely unwell.
How Can Acute Kidney Injury Be Prevented?
Not all AKI can be prevented, but some risk can be reduced.
Stay Appropriately Hydrated
Preventing severe dehydration is important, particularly during illnesses involving vomiting, diarrhea or significant fluid loss.
Use Medicines Carefully
Some medicines can affect kidney function in susceptible individuals. Do not stop prescribed medicines without discussing them with your doctor, but inform healthcare professionals about all medicines and supplements you take.
Manage Chronic Conditions
Good management of:
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Diabetes
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Blood pressure
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Heart disease
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Existing kidney disease
can reduce overall kidney risk.
Treat Urinary Problems Promptly
Persistent urinary obstruction, stones or prostate-related urinary problems should be medically evaluated.
When Should You Seek Urgent Medical Attention?
AKI can become serious quickly.
Seek urgent medical evaluation if you experience:
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Very little or no urine
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Severe breathlessness
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Rapidly increasing swelling
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Persistent vomiting
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Severe weakness
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Confusion
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Fainting
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Severe dehydration
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High fever with signs of serious infection
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Sudden worsening of kidney-function test results
People with known kidney disease should have a lower threshold for seeking medical advice when they become acutely unwell.
Acute Kidney Injury Care at Prabhakar Bhurke Clinic
At Prabhakar Bhurke Clinic, Dr. Sandip Prabhakar Bhurke, super specialist nephrologist and transplant physician, provides individualized evaluation for acute and chronic kidney conditions.
Depending on the patient's situation, assessment may include:
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Kidney-function testing
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Urine examination
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Electrolyte monitoring
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Medication review
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Fluid-status assessment
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Ultrasound or other imaging
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Evaluation for infection
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Assessment for urinary obstruction
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Management of AKI complications
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Dialysis evaluation when clinically indicated
The goal is to identify the underlying mechanism of kidney injury and provide appropriate treatment as early as possible.
Frequently Asked Questions About Types of Acute Renal Failure
What are the three types of acute renal failure?
The three broad categories are prerenal, intrinsic renal and postrenal acute kidney injury.
What is the most common type of acute kidney injury?
The frequency varies depending on the patient population and clinical setting. Reduced kidney perfusion and intrinsic kidney injury are important causes, while postrenal AKI is particularly important to identify because relieving obstruction can restore urine flow.
Can dehydration cause acute renal failure?
Severe dehydration can reduce blood flow to the kidneys and cause prerenal AKI. Prompt treatment may allow kidney function to recover in many cases.
Can kidney stones cause acute renal failure?
A stone can cause AKI when it produces significant urinary obstruction, particularly when both urinary pathways are affected or when a person has only one functioning kidney.
Is acute renal failure permanent?
Not necessarily. AKI can be reversible, depending on its cause and severity. Some patients recover kidney function, while others may have lasting kidney impairment.
Does acute kidney injury always require dialysis?
No. Many people with AKI do not need dialysis. Dialysis is considered when serious complications cannot be adequately managed with other treatments.
Conclusion
Understanding the types of acute renal failure helps explain why sudden kidney-function decline can happen for very different reasons.
Prerenal AKI is related to inadequate kidney blood flow, intrinsic renal AKI involves direct injury to kidney tissue, and postrenal AKI results from urinary obstruction. Identifying the correct mechanism is essential because treatment differs considerably between these categories.
Early evaluation is particularly important when there is reduced urine output, severe dehydration, infection, urinary obstruction, rapidly worsening kidney-function tests or other warning signs.
At Prabhakar Bhurke Clinic, Dr. Sandip Prabhakar Bhurke, super specialist nephrologist and transplant physician, provides specialist assessment and management for patients with acute kidney injury and other kidney conditions.
Medical Disclaimer
This article is intended for general educational purposes only and does not constitute medical advice, diagnosis or treatment. Acute kidney injury can be caused by many different conditions, and the appropriate treatment depends on the individual patient's medical history, examination and investigation results. Do not self-treat suspected kidney failure or stop prescribed medicines without medical advice. If you develop very low or no urine output, severe breathlessness, confusion, fainting, persistent vomiting, severe dehydration or rapidly worsening symptoms, seek urgent medical attention.
