Renal Injury
Renal injury, also called acute kidney injury, is when your kidneys suddenly stop working properly. It can happen over hours or days, and while it can be mild, it may also become severe enough to require immediate medical attention. The good news is that many people recover kidney function with quick treatment.
Table of contents
- What is renal injury?
- Symptoms of renal injury
- Causes and risk factors
- How is renal injury diagnosed?
- Treatment approaches
- Recovery and outlook
- Prevention
What is renal injury?
Acute kidney injury, AKI, acute renal failure, acute kidney failure
Renal injury, also known as acute kidney injury or AKI, is when your kidneys suddenly lose their ability to work properly. This can happen over a few hours, days, or in some cases, weeks[1][4][5]. Your kidneys are responsible for filtering waste and extra fluid from your blood. When they can’t do this job, harmful waste products and fluids build up in your body[1].
AKI is not the result of a physical blow to the kidneys, despite what the name might suggest[4]. It is usually seen as a complication of another serious illness[4]. The condition ranges from minor loss of kidney function to complete kidney failure[4].
Acute kidney injury is different from chronic kidney disease, where the kidneys gradually lose function over a long period of time[4]. Many people with AKI can recover kidney function over time, though this could take days, weeks, or months[6].
- Kidneys
AKI is a common condition, especially among hospitalized patients. It can be seen in up to 7% of hospital admissions and 30% of intensive care unit (ICU) admissions[5]. Acute kidney injury affects over 750,000 people in the United States each year[3].
Symptoms of renal injury
The first and most noticeable symptom of acute kidney injury is often making less urine than usual[6][19]. However, immediately after the kidney damage occurs, blood test results may still be normal, and decreased urine output may be the only sign[5].
Early symptoms of AKI may include[1][4][6]:
- Less urine output than normal
- Fluid buildup, which causes swelling in the legs, ankles, or feet
- Shortness of breath
- Tiredness or extreme fatigue
- Confusion or trouble thinking clearly
- Nausea (feeling sick) or vomiting
- Pain in the belly or side below the ribs
- Drowsiness
- Diarrhea
- Feeling dehydrated
If acute kidney injury gets worse and is not treated, additional symptoms may develop, including muscle cramps, seizures, and changes in breathing[1][6].
It’s essential that AKI is detected early and treated promptly. Without quick treatment, abnormal levels of salts and chemicals can build up in the body, which affects the ability of other organs to work properly[4]. If the kidneys shut down completely, this may require temporary support from a dialysis machine or could lead to death[4].
You should see your doctor urgently or go to your local hospital emergency department if you notice you are suddenly making less urine than usual together with other symptoms of acute kidney failure[6].
Causes and risk factors
Main causes
Most cases of AKI are caused by reduced blood flow to the kidneys, usually in someone who is already unwell with another health condition[4]. This reduced blood flow could be caused by[4]:
- Low blood volume after bleeding, excessive vomiting or diarrhea, or severe dehydration
- The heart pumping out less blood than normal as a result of heart failure, liver failure, or sepsis (a severe infection)
- Certain medicines that reduce blood pressure or blood flow to the kidneys, such as ACE inhibitors, certain diuretics, or NSAIDs (non-steroidal anti-inflammatory drugs like ibuprofen)
AKI can also be caused by a problem with the kidney itself, such as inflammation of the filters in the kidney, the blood vessels, or other structures. This may be caused by a reaction to some medicines, infections, or the liquid dye used in some types of X-rays[4].
Sometimes AKI results from a blockage affecting the drainage of the kidneys, such as an enlarged prostate, a tumor in the pelvis (such as an ovarian or bladder tumor), or kidney stones[4].
Common causes of AKI include serious infection, blood loss, and some medicines[19].
Who is at risk?
You’re more likely to get acute kidney injury if you[4]:
- Are aged 65 or over
- Already have a kidney problem, such as chronic kidney disease
- Have a long-term disease, such as heart failure, liver disease, or diabetes
- Are dehydrated or unable to maintain your fluid intake on your own
- Have a blockage in your urinary tract (or are at risk of this)
- Have a severe infection or sepsis
- Are taking certain medicines, including NSAIDs such as ibuprofen, or blood pressure medicines such as ACE inhibitors or diuretics
- Are given aminoglycosides (a type of antibiotic usually only given in hospital), especially if you’re dehydrated or ill
Acute kidney injury is most common in people who are in the hospital, especially those who need intensive care[1].
How is renal injury diagnosed?
A doctor may suspect AKI if you are in an “at risk” group and suddenly fall ill, or if you develop symptoms of the condition[4].
Blood tests
AKI is usually diagnosed with a blood test to measure your levels of creatinine, a chemical waste product produced by the muscles. If there’s a lot of creatinine in your blood, it means your kidneys are not working as well as they should[4][7]. Blood tests may also show fast-rising levels of urea, which helps show how your kidneys are working[7].
Urine tests
You may be asked to give a urine sample. Urine can be tested for protein, blood cells, sugar, and waste products, which may give clues to the underlying cause[4][7]. Measuring how much urine you pass in 24 hours may help find the cause of your kidney failure[7].
Other tests
Doctors also need to know about any other symptoms (such as signs of sepsis or heart failure), any other medical conditions, and any medicine that has been taken in the past week, as some medicines can cause AKI[4].
Imaging tests such as ultrasound and CT scans can show your kidneys and may reveal if the cause is a blockage in the urinary system, such as an enlarged prostate or bladder tumor[4][7].
In some cases, your healthcare professional may suggest removing a small sample of kidney tissue for lab testing. This is called a biopsy. A needle is put through your skin and into your kidney to remove the sample[7].
Treatment approaches
Treatment for acute kidney injury most often means a hospital stay[7]. Most people with acute kidney injury are already in the hospital. How long you’ll stay depends on the reason for your AKI and how quickly your kidneys recover[7].
Treating the underlying cause
Treatment involves finding the illness or injury that damaged your kidneys. Your treatment depends on the cause[7]. It might involve stopping a medicine that’s damaging your kidneys[7].
General treatment may include[4][19]:
- Increasing your intake of water and other fluids if you’re dehydrated
- Antibiotics if you have an infection
- Stopping certain medicines (at least until the problem is sorted)
- A urinary catheter, a thin tube used to drain the bladder if there’s a blockage
Supportive care
General management principles for acute kidney injury include determining your fluid status, fluid replacement with fluids given through a vein if needed, treatment of fluid overload with medicines called diuretics, stopping medicines that can harm the kidneys, and adjusting prescribed drugs according to kidney function[12].
Additional supportive care measures may include making sure you get proper nutrition and controlling blood sugar levels if you have diabetes[12].
Dialysis
If kidney function is severely reduced, you may need a treatment called dialysis. Dialysis does the work of healthy kidneys to remove waste and fluids for a short time[19]. If you are in an intensive care unit, you may get kidney dialysis in the ICU[19].
When to see a specialist
A kidney specialist (nephrologist) should be consulted when there is an inadequate response to supportive treatment, when there is AKI without a clear cause, for severe AKI (stage 3 or higher), if you have preexisting advanced chronic kidney disease, if renal replacement therapy is needed, or in other situations requiring expert care[12].
Recovery and outlook
Most people with acute kidney injury make a full recovery[4]. Kidney function may return to normal if the cause of AKI is treated quickly[19]. Your chance of a full recovery depends on what caused the problem, how quickly the cause was treated, and what other medical problems you have[19].
Many people recover kidney function over time. This could take days, weeks, or months[6]. Once you begin to recover, you will start to make a lot of urine before returning to a normal rate[6].
However, some people go on to develop chronic kidney disease after AKI[4]. For some people, acute kidney injury can cause death, or it can cause permanent damage and lead to chronic kidney disease[6].
It’s important to have follow-up care after AKI. Be sure to make and go to all appointments, and contact your doctor or nurse advice line if you are having problems[19]. Watch closely for changes in your health, and contact your doctor if you do not get better as expected[19].
Prevention
While not all cases of acute kidney injury can be prevented, there are steps you can take to reduce your risk[19]:
- Talk to your doctor about how much fluid you should drink
- Eat a balanced diet. Talk to your doctor or a dietitian about what type of diet may be best for you. You may need to limit sodium, potassium, and phosphorus
- Do not smoke. Smoking can make your condition worse
- Limit alcohol
- Review all of your medicines with your doctor. Do not take any medicines, including NSAIDs such as ibuprofen or naproxen, unless your doctor says it is safe for you to do so
- Make sure that anyone treating you for any health problem knows that you have had AKI
If you plan to take any over-the-counter medicines such as painkillers or nutritional supplements, check with a doctor or pharmacist first. These can sometimes affect your kidneys or interfere with your prescribed medicine[4].
