Urinary19 - Acute Kidney Injury (AKI)

Question 1

Acute Kidney Injury

Diagnostic Criteria
Risk Factors
Investigations
Management

Answer 1

1. ) Diagnostic Criteria - 3 stages using serum creatinine
   - ↑50% (x1.5) over 2-7 days (normal is 60-120)
   - stage 1: x1.5-2, stage 2: x2-3, stage 3: >x3/>350mM
2. ) Risk Factors
   - diabetes, CKD, IHD, HF, ↑age (>75), sepsis
   - medications: ACEi/ARBs, NSAIDs, antibiotics
3. ) Investigations
   - urine dipstick: normal excludes pre-renal causes, protein++ suggests renal, blood++ suggests post-renal
   - bloods: FBC, CRP, U+Es, LFTs, bone profile, CK (if suspecting rhabdomyolysis)
   - urine PCR, MC+S, USS KUB to exclude obstruction
   - investigate potential glomerulonephritis causes
4. ) Management
   - treat underlying cause, stop nephrotoxic substances
   - maintain euvolaemia: IV fluids or diuretics if needed
   - monitor urine output and daily bloods
   - adjust drug dosing to renal function
   - consider dialysis (renal replacement therapy)

Question 2

Causes of AKI

Pre-Renal
Nephrotoxic Renal Causes
Other Renal Causes
Post-Renal
Acute Tubular Injury

Answer 2

1. ) Pre-Renal - can be reversed if recognised quickly
   - decreased circulating blood flow: shock (esp sepsis), congestive HF, liver failure, anti-hypertensices
   - impaired renal autoregulation: NSAIDs, ACEi, ARBs
2. ) Nephrotoxic Renal Causes
   - exogenous: NSAIDs, PPI, cisplatin, radiocontrast dye
   - antibiotics: aminoglycosides, amphotericin B
   - endogenous: rhabdomyolysis (myoglobin is toxic), haemolysis, myeloma
3. ) Other Renal Causes
   - acute glomerulonephritis, sepsis/infection, ischaemia
   - vasculitis, malignant hypertension, TTP-HUS
4. ) Post-Renal - bladder outlet obstruction
   - blockage in the ureters leads to hydronephrosis
   - commonly caused by stones or malignancies
   - oliguria is hallmark of post-renal AKI
5. ) Acute Tubular Injury - damage to tubular cells
   - most common cause is untreated pre-renal AKI causing ischaemia of cells surrounding the tubules
   - proximal tubules most at risk (highest metabolic demand and less well-perfused areas)
   - nephrotoxic substances can also cause ATI (renal)

Question 3

Complications/Indications for Dialysis in AKI (AEIOU)

Acidosis
Electrolyte Distrubance
Intoxication
Oedema
Uraemia

Answer 3

1. ) Acidosis
   - metabolic acidosis refractory to medical therapy
2. ) Electrolyte Disturbance
   - hyperkalaemia (K+ released from damaged cells)
   - hyponatraemia (↓GFR causing fluid overload)
   - hypocalcaemia (↓conversion to active vitD)
3. ) Intoxication
   - lithium, salicylates (aspirin), methanol
4. ) Oedema
   - pulmonary oedema due to fluid overload
5. ) Uraemia - ↓excretion due to ↓kidney function
   - uraemic encephalopathy - N/V, confusion, reduced consciousness, drowsiness
   - uraemic pericarditis