Acute kidney injury needing dialysis: what renal replacement therapy involves

Acute kidney injury (AKI) is when something suddenly causes the kidneys to stop working as well as they should. Kidney Care UK describes it as a sudden drop in kidney function that can range from a small loss of function to complete failure, and says it normally happens as a complication of another condition. It is not the same as chronic kidney disease, which does not get better but can be slowed or managed with treatment.

The NHS lists many possible causes: infections or sepsis, dehydration, low blood pressure or blood loss, blockages such as kidney stones, long-term conditions affecting the kidneys, heart or liver, some medicines, and the contrast dye used in some scans. Most AKI is managed by treating the cause, using fluids, stopping or changing medicines that may be harmful, or relieving a blockage.

Dialysis comes into the picture only when the kidneys need more help than this. The NHS says that if AKI is severe, the kidneys may need help to do their job of cleaning the blood, which can be done using a machine during dialysis.

NICE sets out the situations in which people should be referred immediately for renal replacement therapy. These are when any of the following are not responding to medical management: high potassium (hyperkalaemia), metabolic acidosis, symptoms or complications of uraemia such as pericarditis or encephalopathy, fluid overload, or fluid on the lungs (pulmonary oedema).

NICE also says that the decision to start should rest on the condition of the person as a whole and not on an isolated blood result, and that where there are significant other health conditions, whether dialysis would offer benefit should be discussed with the person and the multidisciplinary team. Before starting, the specialist should discuss the treatment with the person, or their family or carers, as soon as possible.

The NICE quality statement stresses speed: people who need and wish to have dialysis should be referred immediately to avoid delay, and prompt access offers potential benefits including shorter hospital stays, reduced mortality and improved long-term outcomes.

The NHS describes two types of dialysis. In haemodialysis, blood is filtered by a machine. In peritoneal dialysis, blood is filtered by passing it through the natural lining inside the tummy. Your care team can discuss which type is most suitable.

The NHS explains that in haemodialysis a machine is attached to a blood vessel using a thin tube and the blood flows into the machine and is cleaned before flowing back into the body. It describes the long-term arrangement, where a fistula is created around 10 weeks before starting and sessions take around 4 hours, most people needing 3 sessions a week. Acute kidney injury is treated differently from long-term kidney failure, and the arrangements for a short course in hospital are decided by the kidney or intensive care team, so these details describe long-term dialysis rather than a short stay.

Both main types can leave you feeling tired and sick after a session, and haemodialysis can also cause muscle cramps and dizziness during or shortly after a session, according to the NHS. Talk to the care team if side effects are a problem, as they may be able to help.

The NHS says AKI is a serious condition and can be life-threatening if not treated, but many people recover fully within a few weeks with no long-term effects. If it is more serious, it can take several months to recover. Dialysis in this setting is usually just for a few days or weeks until the kidneys recover.

Kidney Care UK says most people with AKI make a full recovery and do not need any long-term treatment, and that the GP will monitor kidney function and blood pressure for at least three years after an episode of AKI. It also advises checking with a doctor before taking any new medicine or herbal supplements in case they could damage the kidneys.

The NHS says some people end up with permanent kidney damage and chronic kidney disease, which is more likely if AKI was severe or if there are other long-term health conditions. Chronic kidney disease is a lifelong condition that increases the risk of cardiovascular disease and may mean regular dialysis, but the NHS says it can often be managed through lifestyle changes.

The NHS notes that many people do not get symptoms, especially if AKI is mild. If they do, they may include passing much less urine than usual, feeling very thirsty, feeling or being sick, swollen feet or legs, feeling tired, dizzy, confused or sleepy, and breathlessness, especially when lying down. The NHS advises asking for an urgent GP appointment or getting help from NHS 111 if you think you may have symptoms of AKI.

The NHS lists factors that make AKI more likely: being aged 65 or older, having had AKI before, having recently had surgery, and taking illegal drugs. For people at higher risk, it advises staying hydrated, speaking to a doctor before taking any new medicines or supplements, and knowing the symptoms to watch for.