Acute tubular necrosis: causes, diagnosis and recovery in the UK

The NHS describes acute kidney injury (AKI) as when something suddenly causes your kidneys to stop working as well as they should. AKI is a syndrome with several possible causes rather than a single disease. NICE Clinical Knowledge Summaries groups these causes as pre-renal (reduced blood flow to the kidneys, the most common), intra-renal (structural damage within the kidney) and post-renal (obstruction to the flow of urine). Acute tubular necrosis belongs to the intra-renal group, where it appears in the list of tubular causes.

In ATN the cells lining the kidney tubules are damaged, so the kidney cannot clear waste and balance fluid and salts properly. Patient.info explains that tubular injury is typically seen after prolonged ischaemia or exposure to nephrotoxins. CKS adds that intra-renal damage may result from persistent pre-renal or post-renal causes damaging the kidney cells, which is why a pre-renal problem that is not corrected in time can progress to tubular injury.

The NHS lists many things that can cause AKI, including infections or sepsis, dehydration, low blood pressure or blood loss, blockages, long-term conditions affecting the kidneys, heart or liver, certain medicines and the dye used in some scans. Kidney Research UK describes reduced blood supply to the kidney caused by bleeding, heart failure, infection and dehydration as one of the main routes.

For tubular injury specifically, Patient.info lists prolonged ischaemia and nephrotoxins. Kidney Research UK adds that high doses of contrast used in X-rays, particularly when injected into arteries, and drugs or toxins can damage the kidney directly. CKS lists nephrotoxic drugs such as some antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs), proton pump inhibitors, allopurinol, iodine-based contrast and chemotherapy under toxins.

• Severe infection or sepsis, or major blood loss, causing prolonged low blood pressure.

• Severe dehydration from vomiting, diarrhoea or being unable to drink.

• Kidney-toxic medicines such as aminoglycoside antibiotics or cisplatin chemotherapy.

• Radiocontrast dye used in some scans, especially in people already at risk.

• Muscle breakdown (rhabdomyolysis) releasing myoglobin, which CKS lists as a tubular cause.

The NHS says anyone can get AKI but that it is more common if you are 65 or older, have had AKI before, have recently had surgery or take illegal drugs. North Tees and Hartlepool NHS Foundation Trust adds chronic kidney disease, sepsis, diabetes, severe pancreatitis and heart failure as conditions that increase risk, and notes that AKI normally happens as a complication of another serious illness.

Patient.info reports that stage 1 AKI occurs in more than 15% of emergency hospital admissions and that community-acquired AKI is thought to be up to three times more common than hospital-acquired AKI, which is why kidney function is checked routinely in people who are acutely unwell.

The NHS says many people do not get symptoms of AKI, especially if it is mild. If symptoms occur they may include peeing a lot less than usual, feeling very thirsty, feeling or being sick, swollen feet or legs, feeling tired, dizzy, confused or sleepy, and feeling breathless, especially when lying down. Kidney Research UK notes that the most obvious sign is a reduction in urine volume, but that some forms of AKI, particularly those caused by back pressure, can continue to pass normal amounts of urine.

Because symptoms are non-specific and often overshadowed by the illness that triggered the problem, AKI is often diagnosed when blood tests are done for another reason, according to the NHS.

The NHS says AKI is diagnosed using a blood test for creatinine, and that a doctor may also ask for a urine sample, check your pulse and blood pressure and arrange an ECG or scans such as an X-ray, CT or ultrasound. Kidney Research UK lists measuring creatinine in the blood, measuring urine output, testing the urine for infection, inflammation, protein or blood, ultrasound to look for back pressure and, sometimes, a kidney biopsy.

Patient.info explains that it is important first to identify the cause because this affects management, particularly when there is a treatable cause such as obstruction, low fluid volume, nephrotoxic drugs or glomerulonephritis. The history of medicines, including over-the-counter and recreational drugs and herbal remedies, matters, so tell the doctor everything you take. In some people a kidney specialist is involved. The NHS says you may be referred to a nephrologist or admitted to hospital if the AKI is severe or the cause is unclear.

Patient.info states that there is no specific treatment for AKI so management is largely supportive: treating the cause where possible, monitoring fluid and electrolyte balance closely and optimising fluid therapy. The NHS describes treatment as depending on how bad the AKI is and what is causing it, and says it may need hospital care. It may include medicine for infection, to raise blood pressure or reduce swelling, stopping or changing medicines that could be harming the kidneys, fluids through a drip, a catheter, and surgery to remove a blockage.

If AKI is severe, the NHS says the kidneys may need help to clean the blood using a machine (dialysis), usually just for a few days or weeks until the kidneys recover. North Tees explains that medicines are reviewed on diagnosis and some may be temporarily stopped to let the kidneys recover.

The NHS says AKI is serious and can be life-threatening if not treated, but many people recover fully within a few weeks with no long-term effects, and more serious AKI can take several months. You will have regular blood tests and check-ups afterwards. Some people end up with permanent kidney damage, which can cause chronic kidney disease, and the NHS says this is more likely if the AKI was severe or you already had other long-term health problems.

Kidney Research UK adds that chronic kidney disease can develop two to three years after an episode of AKI, and that very occasionally a small proportion of people do not recover and end up with end-stage kidney disease. Patient.info reports that the prognosis varies with the setting, the cause and other illnesses, and that early detection improves it.

If you have had AKI before or are at higher risk because of age or medicines, the NHS suggests staying hydrated, with enough fluids that your pee is pale and regular, especially in hot weather or when being sick or having diarrhoea, speaking to a doctor before taking any new medicines or supplements, and knowing the symptoms and when to get medical help. Patient.info adds that avoiding nephrotoxic drugs and contrast in at-risk people reduces risk, which is why clinicians review medicines during acute illness.

AKI is managed in the NHS through GPs, acute hospital teams and, where needed, renal units. It is largely a hospital and acute-care problem, so private routes are less relevant, although private hospitals also treat it. Follow-up kidney function tests are usually arranged through your GP or renal team.