AKI Flashcards
What is the NICE criteria for AKI?
- Rise in creatinine of >25 micromol/L in 48 hrs
- Rise in creatinine >50% in 7 days
- Urine output of <0.5 ml/kg/hr for >6 hrs
What is acute kidney injury?
An acute drop in kidney function. Diagnosed by measuring creatinine
How can causes of AKI be classified? Which is most common?
- Pre-renal (most common)
- Renal
- Post-renal
What are pre-renal causes of AKI?
Inadequate blood supply to the kidneys
- Hypovolaemia/sepsis
- Cardiorenal disease
- Renovascular disease
What on U+Es would indicate pre-renal AKI?
- Raised urea:creatinine ratio (>100:1)
- Urea and creatinine are both freely filtered at the glomerulus
- Urea is reabsorbed, creatinine is not reabsorbed
What are causes of a raised urea:creatinine ratio?
- Pre-renal AKI
- Dehydration
- Corticosteroids
- GI haemorrhage
- Protein rich diet
What is a complication of pre-renal AKI?
Acute tubular necrosis
What are renal causes of AKI?
Intrinsic disease leading to reduced filtration of blood
- Glomerulonephritis
- Acute interstitial nephritis
- Acute tubular necrosis
What on U+Es would indicate renal AKI?
- Decreased urea:creatinine ratio (<40:1)
- Urea unable to be reabsorbed -> excreted like creatinine -> ratio closer to one
What are causes of a decreased urea:creatinine ratio?
- Intrinsic renal damage
- Severe liver damage
- Malnutrition, low protein diet
- Pregnancy
- Rhabdomyolysis
- SIADH
Acute tubular necrosis:
1. What is it?
2. Causes?
3. Investigations?
4. Recovery?
- Necrosis of the epithelial cells of the renal tubules
- Ischaemia due to hypoperfusion (dehydration, shock, HF) or nephrotoxins (aminoglycosides, radiocontrast)
- Urinalysis - muddy brown casts
- Recovery usually takes 1-3 weeks
What are post-renal causes of AKI?
Obstruction to the outflow of urine causing back-pressure into the kidney
- Kidney stones
- Massess
- Ureter or uretral strictures
- Enlarged prostate or prostate cancer
What is the first step of treating AKI?
Correcting the underlying cause:
- IV fluids in pre-renal AKI
- Stop nephrotoxic meds and antihypertensives that reduce filtration pressure
- Relieve obstruction in post-renal AKI
What are complications of AKI?
- Hyperkalaemia
- Fluid overload
- Metabolic acidosis
- Uraemia -> encephalopathy/pericarditis
What are indications for renal replacement therapy in AKI?
- Acidosis - <7.2
- Electrolyte abnormalities - hyperkalaemia, hypercalcaemia, hyponatraemia
- Intoxicants - e.g. lithium
- Overload - acute pulmonary oedema
- Uraemia - Ur>60, uraemic pericarditis/encephalopathy
