At a Glance

Presentation Acute Kidney Injury
Medical Emergency Hyperkalaemia
Most Common Cause Pre-renal AKI
Must Not Miss Obstructive Uropathy
Immediate Test ECG
Clinical Priority Treat Life-threatening Complications

Red Flags

Potassium >6.5 mmol/L Anuria Pulmonary oedema Uraemic encephalopathy Pericarditis Severe metabolic acidosis Hypotension Rapidly rising creatinine

PACES Approach

① Confirm AKI ② Treat hyperkalaemia immediately ③ Assess volume status ④ Classify AKI ⑤ Identify and treat the underlying cause

Acute Kidney Injury Framework

Pre-renal
Hypovolaemia
Sepsis
Heart failure
Intrinsic Renal
ATN
AIN
Glomerulonephritis
Post-renal
Urinary retention
Stones
Malignancy
Life-threatening
Hyperkalaemia
Pulmonary oedema
Immediate Investigation
ECG
Urinalysis
Confirm Cause
Renal Ultrasound

Hyperkalaemia Emergency

ECG immediately Calcium gluconate Insulin + Dextrose Stop nephrotoxins Repeat potassium Consider dialysis

Overview

Acute Kidney Injury (AKI) is a medical emergency characterised by a sudden deterioration in renal function. The immediate priorities are to identify life-threatening complications such as hyperkalaemia, pulmonary oedema and severe metabolic acidosis, followed by determining whether the cause is pre-renal, intrinsic renal or post-renal. Early recognition and prompt management can prevent irreversible kidney damage and reduce mortality. The uploaded PACES scenario emphasises urgent assessment of hyperkalaemia, careful volume assessment, review of nephrotoxic medications and consideration of dehydration and drug-induced acute interstitial nephritis as key causes. :contentReference[oaicite:2]{index=2}

Structured History

Presenting Symptoms

Assess Volume Status

Symptoms of Uraemia

Features of Fluid Overload

Drug History

Past Medical History

Examination

Differential Diagnosis

Pre-renal AKI (Hypovolaemia) Acute Tubular Necrosis Acute Interstitial Nephritis Glomerulonephritis Obstructive Uropathy Contrast Nephropathy Drug-induced AKI Sepsis-associated AKI Rhabdomyolysis

Investigations

Immediate Investigations

Blood Tests

Urine Assessment

Imaging

Diagnosis

Acute Kidney Injury

Acute Kidney Injury is diagnosed by an acute deterioration in renal function with or without oliguria. The first priority is recognising life-threatening complications such as hyperkalaemia, pulmonary oedema, severe metabolic acidosis and uraemic complications. The underlying cause should then be classified as pre-renal, intrinsic renal or post-renal to guide definitive management. In the uploaded PACES scenario, dehydration with ongoing diuretic therapy is the most likely cause, although antibiotic-associated acute interstitial nephritis should also be considered. :contentReference[oaicite:1]{index=1}

Management

Stabilise Immediately Treat hyperkalaemia promptly with ECG monitoring, intravenous calcium gluconate if indicated, insulin with dextrose, and continuous reassessment of potassium levels.
Treat the Cause Restore intravascular volume if hypovolaemic, stop nephrotoxic medications, adjust drug doses for renal impairment and relieve urinary obstruction when present.
Monitor Closely Insert a urinary catheter when appropriate, maintain accurate fluid balance charts, repeat renal function and electrolytes regularly, and involve nephrology early if recovery is delayed or dialysis is likely.

Explaining to the Patient

"Your blood tests show that your kidneys are not working as well as they were when you came into hospital. The good news is that many cases of acute kidney injury improve once the underlying cause is treated. Our immediate priority is to correct the high potassium level because this can affect the heart, while identifying why the kidneys have become impaired. We will monitor you closely, adjust your medications and involve the kidney specialists if necessary."

Examiner's Corner

How do you classify Acute Kidney Injury?
  • Pre-renal: Reduced renal perfusion due to hypovolaemia, sepsis, heart failure or hypotension.
  • Intrinsic renal: Acute tubular necrosis, acute interstitial nephritis, glomerulonephritis or vascular disease.
  • Post-renal: Urinary tract obstruction due to prostatic enlargement, stones, tumours or ureteric obstruction.
How do you differentiate Pre-renal AKI from Intrinsic Renal AKI?
Feature Pre-renal AKI Intrinsic AKI
Urinary sodium <20 mmol/L >40–50 mmol/L
Urine osmolality >500 mOsm/kg <350 mOsm/kg
Urine concentration Preserved Impaired
Typical cause Hypovolaemia / Sepsis ATN / AIN / GN
What are the indications for dialysis (Renal Replacement Therapy)?
  • Refractory hyperkalaemia
  • Refractory metabolic acidosis
  • Pulmonary oedema not responding to medical treatment
  • Uraemic encephalopathy
  • Uraemic pericarditis
  • Certain toxin ingestions where dialysis is indicated
What do urinary casts indicate?
  • Red cell casts: Glomerulonephritis
  • White cell casts: Acute interstitial nephritis or pyelonephritis
  • Muddy brown granular casts: Acute tubular necrosis
  • Hyaline casts: May be seen with dehydration and are often non-specific
Common Viva Questions
  • What are the causes of Acute Kidney Injury?
  • How do you assess fluid status?
  • How would you manage severe hyperkalaemia?
  • Which medications commonly cause AKI?
  • When should nephrology be involved?
  • When should a urinary catheter be inserted?
  • What are the indications for renal replacement therapy?
Important Clinical Pearls
  • Always obtain an ECG immediately when potassium is ≥6.0 mmol/L or rapidly rising.
  • Treat life-threatening hyperkalaemia before determining the exact cause of AKI.
  • Review medications carefully and stop nephrotoxic drugs where appropriate.
  • Accurate fluid balance and urine output monitoring are essential.
  • Never forget to exclude urinary tract obstruction with renal ultrasound.

Pathfinder Pearls

Treat hyperkalaemia before chasing the cause Always review fluid status Think pre-renal first Stop nephrotoxic medications Check the ECG immediately Insert a catheter if urine output is uncertain Renal ultrasound excludes obstruction Monitor glucose after insulin treatment

Common Pitfalls

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