It is sudden damage to the kidneys that causes them not to work properly. It can range from minor loss of kidney function to complete kidney failure.
Acute renal failure (ARF) normally occurs as a complication of another serious illness and is not the result of a physical blow to the kidneys.
This type of kidney damage is usually seen in older people who are unwell with other conditions, and the kidneys are affected as well.
It is essential that ARI is detected early and treated promptly. The role of the kidneys is:
- Filtering – removing waste and water from the blood (such as urine, through the bladder).
- Cleanse the blood.
- Keep bones healthy.
- Take care of blood pressure.
- Stimulate the bone marrow to make blood.
Without prompt treatment, abnormal levels of salts and chemicals can build up in the body, affecting the ability of other organs to function properly.
If the kidneys shut down completely, this may require temporary support from a dialysis machine or lead to death.
Symptoms of acute kidney failure
In the early stages of ARF, there may not be any symptoms. The only possible warning sign may be that the person is not producing much urine, although this is not always the case.
However, someone with ARF can deteriorate rapidly and suddenly experience any of the following:
- Nausea and vomiting
- High blood pressure
- Abdominal pain.
- Slight back pain.
- Accumulation of fluid in the body (edema).
Even if the disease does not progress to complete kidney failure, ARF should be taken seriously. It has an effect on the whole body, changes the way the body handles some drugs, and can make some existing illnesses more serious.
ARF is different from chronic kidney disease, where the kidneys gradually lose function over a long period of time.
Which are the risk factors?
You are more likely to have an ARI if:
- You are 65 years of age or older.
- You already have a kidney problem, such as chronic kidney disease.
- You have a long-term illness, such as heart failure, liver disease, or diabetes.
- You are dehydrated or unable to maintain your fluid intake independently.
- You have a blockage in your urinary tract (or are at risk for this).
- You have a severe infection or sepsis.
- You are taking certain medications, including non-steroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen) or blood pressure medications, such as ACE inhibitors or diuretics.
- You are given aminoglycosides, a type of antibiotic; again, this is only a problem if the person is dehydrated or sick, and they are usually only given in a hospital setting.
It is estimated that ARF affects between 13 and 18% of people admitted to hospital. It can affect both adults and children.
Most cases of ARF are caused by reduced blood flow to the kidneys, usually in someone who is already ill with another health condition.
This reduced blood flow could be caused by:
- Low blood volume, excessive vomiting or diarrhea, severe dehydration.
- The heart pumps less blood than normal as a result of heart failure, liver failure, or sepsis, for example.
- Problems with the blood vessels, such as inflammation and blockage in the blood vessels within the kidneys (a rare condition called vasculitis).
- Certain drugs, which can affect the blood supply to the kidney, other drugs can cause unusual reactions in the kidney.
ARF can also be caused by a problem with the kidney itself, such as glomerulonephritis. This can be caused by a reaction to some medications, infections, or contrast media (such as the liquid dye used in some types of X-rays).
It can also be due to a blockage that affects the drainage of the kidneys, such as:
- An enlarged prostate.
- A tumor in the pelvis, such as an ovarian or bladder tumor.
- Kidney stones
When should ARI be suspected?
A doctor may suspect ARF in people who are known to be at risk and who suddenly become ill or develop symptoms that suggest complications of ARF.
ARF can also be suspected in people who have been sick for a while and have:
- Chronic kidney disease
- A disease of the urinary system.
- New or worsening urinary symptoms.
- Symptoms or signs of a disease affecting the kidneys and other organs.
Diagnosis of acute kidney failure
AKI can be diagnosed after measuring urine output and taking blood tests.
Blood levels of creatinine, a chemical waste product produced by muscles, will be measured. Healthy kidneys filter creatinine and other waste products from the blood and these are excreted in the form of urine.
It is a quick and easy marker of kidney function, with higher blood creatinine levels indicating poorer kidney function.
In adults, a diagnosis of ARF can be made if:
- The blood creatinine level has increased from the baseline value for that person (by 26 micromoles per liter or more in 48 hours)
- Blood creatinine level has increased over time (by 50% or more in the last 7 days)
- You are passing much less urine (less than 0.5 ml per kg per hour for more than 6 hours)
- In children and adolescents, doctors should use the plasma creatinine level to calculate the estimated glomerular filtration rate (estimated glomerular filtration rate).
Investigating the underlying cause
Urine can be tested for protein, blood cells, sugar, and waste products, which can give clues to the underlying cause.
Doctors also need to know about:
- Any other symptoms, such as signs of sepsis or signs of heart failure.
- Any other medical condition.
- Any medication that has been taken in the past week, as some medications can cause ARI.
- An ultrasound should reveal whether the cause is a blockage in the urinary system, such as an enlarged prostate or bladder tumor.
Treatment of ARF depends on the underlying cause and extent of the disease. In most cases, treating the underlying problem will cure the ARF.
General practitioners can handle mild cases in people who are not yet in the hospital, and the hospital can:
- Advise to stop any medications that may be causing the situation or making it worse, it may be safe to resume some of these when the problem is fixed.
- Treat any underlying infection.
- Advise on fluid intake to prevent dehydration (which could cause or worsen ARF).
- Perform a blood test to monitor creatinine and salt levels to check how well a person is recovering.
- Refer to a urologist (genitourinary surgeon) or nephrologist (kidney specialist) if the cause is unclear or if a more serious cause is suspected.
Admission to the hospital is necessary in cases where:
- There is an underlying cause that needs urgent treatment, such as a urinary blockage or if the person is seriously ill. Most people need hospital care to treat the underlying cause, which allows the ARF to improve.
- There is a risk of urinary blockage due to prostate disease, for example.
- The person’s condition has deteriorated, and regular blood and urine tests are needed to monitor how well their kidneys are working.
- The person has an ARI complication
Most people who recover from ARF end up with a level of kidney function that is very similar to what they had before they got sick, or they have normal kidney function.
However, some people continue to develop chronic kidney disease or long-term kidney failure as a result. In severe cases, dialysis may be necessary, where a machine filters the blood to remove hazardous waste, salt, and water.
Those at risk for ARF should be monitored with regular blood tests if they become ill or start taking new medications. It is also useful to check how much urine you are passing.
Any warning signs of ARF, such as vomiting or low urine output, require immediate investigation for disease and treatment. People who are dehydrated or at risk for dehydration may need drip fluids.
Any medication that appears to make the problem worse or directly damage the kidneys should be stopped, at least temporarily.
The National Institute for Excellence in Health and Care (NICE) has produced detailed guidelines for preventing, detecting, and managing ARI.
The most serious complications of acute kidney injury are:
- High levels of potassium in the blood, in severe cases, this can cause muscle weakness, paralysis, and heart rhythm problems.
- Fluid in the lungs (pulmonary edema).
- Acidic blood (metabolic acidosis), which can cause nausea, vomiting, drowsiness, and shortness of breath.