Your doctor will try to find out what has caused your child’s kidneys to suddenly stop working. AKI may be related to other health conditions or problems. In some children, there is more than one cause.
Types of AKI
There are three types of AKI:
- pre-renal AKI – there is not enough blood flow to the kidneys
- renal AKI – there is a problem inside the kidneys
- post-renal AKI – there is a problem that affects how the urine leaves the kidneys; this is usually caused by a blockage.
Pre-renal AKI
In pre-renal AKI, there is not enough blood flow to the kidneys because the blood pressure is too low.
Following are some of the causes of pre-renal AKI in children. Not all children who have these get AKI.
Dehydration
If there is not enough water in the body, this is called dehydration. This can happen in children who have severe vomiting or diarrhoea, because they lose a lot of water.
Some children get AKI because they have dehydration and are taking some medicines. If your child has severe vomiting or diarrhoea, your doctor may stop these medicines. These include:
- non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen
- medicines that lower blood pressure (called ACE inhibitors and Angiotensin receptor blockers)
- medicines that help flush out extra water (called diuretics).
Other causes
- A large amount of bleeding (haemorrhage) – for example, after an accident
- An infection in the blood (septicaemia)
- Nephrotic syndrome – when the kidneys leak a lot of protein in the urine, causing parts of the body to swell (oedema)
- Other conditions, including hepatorenal syndrome (when the liver stops working) and heart failure (when the heart cannot pump as much blood around the body)
Renal AKI
In renal AKI, there is a problem inside the kidneys. This is also called intrinsic AKI or intra-renal AKI.
These are some of the causes of renal AKI in children. Not all children who have these get AKI.
- Conditions that affect the kidneys – these include haemolytic uraemic syndrome (HUS), glomerulonephritis and interstitial nephritis
- Conditions that affect different parts of the body, including the kidneys – these include vasculitis, liver disease and problems associated with treating cancer
- Pre-renal AKI that is not recognised and successfully treated
Haemolytic uraemic syndrome (HUS)
Haemolytic uraemic syndrome (HUS) is the most common cause of renal AKI in children. It usually happens after an infection in the gut, when children also get diarrhoea. Most children recover from these infections, but some get HUS and/or have AKI.
When a part of the body is damaged, the body makes blood clots, which are like clumps of blood. These help heal wounds, such as a cut in the skin. In HUS, the body makes blood clots in the wrong places, and these can damage the kidney.
Glomerulonephritis
Glomerulonephritis is a group of diseases that affect the kidneys. The tiny filters of the kidney – the glomeruli – are damaged. Children with glomerulonephritis have blood and protein in their urine, and may get swelling of their body, especially around the face and legs.
Interstitial nephritis
In interstitial nephritis (also known as tubulo-interstitial nephritis), some parts of the kidney become inflamed (swollen). These include the renal tubules, the long tubes that carry the liquid that will become urine. This causes pressure to rise inside the kidneys. There is less blood flow into the kidney, which leads to AKI.
It is often not possible to know why the inflammation happens. But, in some children, certain medicines can lead to interstitial nephritis. These include:
- some antibiotic medicines, which are used to treat infections
- ibuprofen.
Other problems affecting the kidneys
- Acute tubular necrosis (ATN) – the kidneys do not get enough oxygen from the body. This damages the renal tubules so they stop working.
- Renal vein thrombosis– the renal vein, the blood vessel that carries blood out of the kidney, is blocked with a blood clot.
Conditions that affect different parts of the body
- Vasculitis – the blood vessels become inflamed or swollen, especially in the skin. Some types of vasculitis also affect the blood vessels in the kidneys.
- Hepatitis – the liver becomes inflamed. This causes changes in chemicals in the blood, which can lead to AKI.
- Tumour lysis syndrome – this is a problem that happens in some children who are being treated for cancer.
- Rhabdomyolysis – this means there is a rapid breakdown in muscle cells. Chemicals are released into the blood, which can damage the kidney.
Post-renal AKI
Post-renal AKI is caused by an obstruction, or a blockage, in the urinary system. This obstruction affects how urine leaves the body when we go to the toilet.
It is often due to a structural problem. This means that one or more parts of the urinary system have not developed, or been made, normally. Children with structural problems are usually born with them. They are sometimes found out during an ultrasound scan before birth.
These are some of the causes of post-renal AKI in children. Not all children who have these get AKI.
- Posterior urethral valves (PUV) – a blockage in the back part of the urethra (nearest the bladder) in some boys
- Pelviureteric junction (PUJ) dysfunction – a blockage between the renal pelvis (in the kidney) and the ureter
- Vesicoureteric junction (VUJ) dysfunction – a blockage between the ureter and the bladder
- Kidney stones – these are like small crystals, or clumps, which may cause pain and block parts of the urinary system
The blockage needs to affect both kidneys before it can cause post-renal AKI. If a child has only one working kidney, it would need to affect that kidney.
Some babies are born with structural problems – doctors call these congenital conditions. Occasionally, children get structural problems later in life – these are acquired conditions.