Acute Kidney Injury (AKI) in Children
Acute kidney injury (AKI) is a sudden and often reversible loss of kidney function. It is a critical condition in children that can lead to severe fluid and electrolyte disturbances. The key to management is prompt diagnosis and identification of the underlying cause.
Aetiology and Classification
AKI is categorised based on its aetiology, which helps guide management.
Prerenal AKI: This is the most common cause of AKI in children. It’s caused by a reduction in blood flow to the kidneys, leading to a drop in glomerular filtration rate.
Dehydration: A common cause, especially in gastroenteritis.
Haemorrhage: Significant blood loss from trauma or surgery.
Sepsis: Widespread vasodilation and reduced cardiac output.
Intrinsic Renal AKI: This is caused by direct damage to the kidney itself.
Glomerulonephritis: Inflammation of the glomeruli.
Acute Tubular Necrosis (ATN): Often follows a period of prolonged prerenal AKI or a severe insult like sepsis.
Haemolytic Uraemic Syndrome (HUS): A key cause of intrinsic AKI in children.
Postrenal AKI: This is caused by an obstruction in the urinary tract that prevents urine from draining from the kidneys.
Posterior Urethral Valves: A congenital cause in male infants.
Stones: Renal or ureteric stones.
Clinical Assessment
History:
Fluid Intake and Output: The key is to assess the child’s urine output. A reduced urine output (oliguria) or no urine output (anuria) is a major red flag.
Signs of Dehydration: A history of vomiting, diarrhoea, or fever suggests a prerenal cause.
Medications: Enquire about any medications, such as NSAIDs, that can affect kidney function.
Examination:
Hydration Status: Assess the child for signs of dehydration (e.g., sunken eyes, prolonged capillary refill time).
Blood Pressure: Hypertension can be a sign of fluid overload or a primary renal disease.
Fluid Balance: Look for signs of fluid overload, such as oedema or a palpable bladder.
Investigations
Urine Analysis:
Urine Output: The most important clinical sign to monitor.
Urinalysis: Check for blood and protein, which can suggest a glomerular cause.
Bloods:
U&Es: A rising urea and creatinine is the hallmark of AKI.
Electrolytes: Monitor for hyperkalaemia, which is a life-threatening complication.
Other: A full blood count and inflammatory markers may help identify a cause like sepsis or HUS.
Imaging:
Renal Tract Ultrasound: This is a key investigation to rule out a postrenal cause and assess the size of the kidneys.
Management
Management is based on the underlying cause.
Prerenal AKI: The primary treatment is to correct the fluid deficit with a fluid challenge.
Intrinsic and Postrenal AKI: This requires a more specialist approach.
Fluid and Electrolyte Management: Close monitoring of fluid balance and correction of electrolyte abnormalities, particularly hyperkalaemia.
Renal Support: In severe cases, dialysis may be required to support kidney function.
Paediatric Nephrology: All children with intrinsic or postrenal AKI should be managed in a specialist paediatric unit in consultation with a paediatric nephrologist.