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

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

Posted: 16 August 2025Updated: 16 August 2025 Guideline-Aligned (High Confidence) Clinically Reviewed
Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX

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 ,,.

  • Direct Clinical Indicators:
    • A significant reduction in urine output, known as oliguria (less than 0.5 ml/kg/hour) .
    • 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 ,,.
    • New onset or a significant worsening of existing urological symptoms .
    • Signs of fluid imbalance such as oedema (swelling) or evidence of hypovolaemia (low blood volume) ,,.
    • Low blood pressure (hypotension) .
  • Systemic Signs and Complications:
    • A general deterioration in the patient's clinical condition or worsening early warning scores ,,.
    • The presence of sepsis ,,.
    • Symptoms or complications related to uraemia, which can include uraemic encephalopathy (brain dysfunction due to kidney failure) or pericarditis (inflammation of the heart lining) ,,.
    • Pulmonary oedema (fluid in the lungs) ,,.
    • Elevated potassium levels in the blood (hyperkalaemia), especially if serum potassium is 6.0 mmol/L or more ,,.
    • Signs of fluid overload or metabolic acidosis .
    • Symptoms or signs of a multi-system disease affecting the kidneys and other organs, such as AKI symptoms accompanied by a purpuric rash .
  • 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 . 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 .
    • A history of previous acute kidney injury .
    • Underlying conditions such as heart failure , liver disease , , or diabetes .
    • Suspected or known urinary tract obstruction ,,.
    • 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 .
    • Recent exposure (within the past week) to iodine-based contrast media .
    • Neurological or cognitive impairment or disability, which may limit a patient's access to fluids due to reliance on a carer .
    • Age 65 years or over .
    • Severe diarrhoea, particularly bloody diarrhoea in children and young people .
    • Haematological malignancy .

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