Acute kidney injury (AKI) means that the kidneys suddenly come under strain and they function less effectively. This can cause toxic waste products to build up in the blood and they change the balance of essential salts like potassium and sodium. It is essential it’s recognised and treated promptly, to ensure the kidneys have a chance to recover without permanent damage. It can prove life-threatening if left untreated. AKI is diagnosed on a blood test, which will show that creatinine, a substance excreted by the kidneys, is raised, indicating the kidneys are not doing their job. Urea may also be raised, eGFR (estimated glomerular filtration rate) may be low, and potassium may be raised. AKI is also known as acute renal failure. The name AKI is misleading in that it doesn’t mean you have received a physical injury or blow as such.
Sudden illness can cause AKI, such as sepsis, gastroenteritis, severe COVID-19 and other severe infections such as pneumonia, urinary tract infection (UTI) or pyelonephritis (kidney infection). The burden of infection causes dehydration, which prevents the kidneys functioning normally in filtering out waste products to leave the body in the urine. Certain antibiotics may be given in acute illness that can further stress the kidneys. If this is spotted – usually on blood tests during a hospital stay – these antibiotics will be changed to others and you will be given a drip for rehydration. Some medication is filtered by the kidneys (other medication is processed via the liver). This can cause a kidney strain in some people, so certain medications are monitored with blood tests before starting and shortly afterwards. If your condition is stable on a particular dose, your kidney function will be monitored once or twice a year thereafter if you remain on it long-term. One such medication is lithium, which is used to treat bipolar disorder. Painkillers such as ibuprofen, naproxen or other NSAIDs (non-steroidal anti-inflammatory drugs) can stress the kidneys, as can certain water tablets (diuretics) or anti-hypertensives.
Anyone can get AKI if dehydrated or with a severe infection. People more vulnerable to AKI include those over 65 years old or those with any existing kidney condition. Chronic kidney disease (CKD) is one such condition, where the kidneys gradually and permanently lose function over a period of time, and this means there is less margin to keep the kidneys functioning if you suddenly become unwell. Another is damage to the kidneys from a blockage, such as kidney stones or an enlarged prostate. Other long-term conditions can make you more vulnerable to AKI if you are unwell or dehydrated, including diabetes, heart failure or liver disease.
Whether AKI has been detected on bloods done while a hospital inpatient or in the community, your treating doctor will assess the results and consider possible causes, including any new medications. Depending on the severity, those at home may be referred to hospital for further tests and possible treatment. Hydration levels will be assessed and intravenous fluids may be prescribed via a drip. If you have a blockage in your urinary tract system causing the AKI, you may have a catheter fitted temporarily. If your potassium is very high, this poses an immediate threat to your heart, so your medical team will reverse this with medication or further fluids. You will be closely monitored with blood tests and possibly urine tests, and kidneys will usually recover within a few days or weeks. Your doctor may order an ultrasound, to check for any structural damage as a consequence of the AKI, or if this is thought to be a cause.
AKI can range from mild disease to complete failure to function. As you are likely to be unwell with an acute illness, it can be difficult to tease apart these symptoms from those of AKI, but it can add to feelings of fatigue or sleepiness, nausea or vomiting, confusion and signs of dehydration like dry lips and mouth or passing less urine. If you have severe AKI that is not correcting itself during hospital treatment, this may require dialysis for a short time to recover. Most people make a full recovery but some people suffer lasting damage to their kidney function, and this is then termed CKD.