What are the key clinical signs and symptoms that should prompt me to suspect acute kidney injury (AKI) in a patient?

The key clinical signs and symptoms that should prompt suspicion of acute kidney injury (AKI) in a patient encompass direct indicators, systemic manifestations, and specific patient risk factors ¹,²,³.

• Direct Clinical Indicators:
  • A significant reduction in urine output, known as oliguria (less than 0.5 ml/kg/hour) ³.
  • The presence of blood (haematuria) or protein (proteinuria) in urine, particularly when detected by urine dipstick analysis and without signs of urinary tract infection or catheterisation trauma ¹,²,³.
  • New onset or a significant worsening of existing urological symptoms ³.
  • Signs of fluid imbalance such as oedema (swelling) ³ or evidence of hypovolaemia (low blood volume) ¹,²,³.
  • Low blood pressure (hypotension) ³.
• Systemic Signs and Complications:
  • A general deterioration in the patient's clinical condition or worsening early warning scores ¹,²,³.
  • The presence of sepsis ¹,²,³.
  • Symptoms or complications related to uraemia, which can include uraemic encephalopathy (brain dysfunction due to kidney failure) or pericarditis (inflammation of the heart lining) ¹,²,³.
  • Pulmonary oedema (fluid in the lungs) ¹,²,³.
  • Elevated potassium levels in the blood (hyperkalaemia), especially if serum potassium is 6.0 mmol/L or more ¹,²,³.
  • Signs of fluid overload ³ or metabolic acidosis ³.
  • Symptoms or signs of a multi-system disease affecting the kidneys and other organs, such as AKI symptoms accompanied by a purpuric rash ³.
• Patient Risk Factors and Conditions that Increase Suspicion:

  Suspicion of AKI should also be raised in patients with acute illness who have pre-existing conditions or recent exposures ³. These include:

  • Chronic kidney disease (CKD), particularly those with an estimated glomerular filtration rate (eGFR) less than 60 ml/min/1.73m2 or stage 3B, 4, or 5 CKD ³.
  • A history of previous acute kidney injury ³.
  • Underlying conditions such as heart failure ³, liver disease ³, (Elom et al., 2025), or diabetes ³.
  • Suspected or known urinary tract obstruction ¹,²,³.
  • Recent use (within the past week) of certain medications that can cause or worsen kidney injury, such as non-steroidal anti-inflammatory drugs (NSAIDs), aminoglycosides, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), and diuretics, especially if the patient is hypovolaemic ³.
  • Recent exposure (within the past week) to iodine-based contrast media ³.
  • Neurological or cognitive impairment or disability, which may limit a patient's access to fluids due to reliance on a carer ³.
  • Age 65 years or over ³.
  • Severe diarrhoea, particularly bloody diarrhoea in children and young people ³.
  • Haematological malignancy (Canet et al., 2015).