AKI

Question 1

What is the NICE criteria for AKI?

Answer 1

• 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

Question 2

What is acute kidney injury?

Answer 2

An acute drop in kidney function. Diagnosed by measuring creatinine

Question 3

How can causes of AKI be classified? Which is most common?

Answer 3

• Pre-renal (most common)
• Renal
• Post-renal

Question 4

What are pre-renal causes of AKI?

Answer 4

Inadequate blood supply to the kidneys
- Hypovolaemia/sepsis
- Cardiorenal disease
- Renovascular disease

Question 5

What on U+Es would indicate pre-renal AKI?

Answer 5

• Raised urea:creatinine ratio (>100:1)
• Urea and creatinine are both freely filtered at the glomerulus
• Urea is reabsorbed, creatinine is not reabsorbed

Question 6

What are causes of a raised urea:creatinine ratio?

Answer 6

• Pre-renal AKI
• Dehydration
• Corticosteroids
• GI haemorrhage
• Protein rich diet

Question 7

What is a complication of pre-renal AKI?

Answer 7

Acute tubular necrosis

Question 8

What are renal causes of AKI?

Answer 8

Intrinsic disease leading to reduced filtration of blood
- Glomerulonephritis
- Acute interstitial nephritis
- Acute tubular necrosis

Question 9

What on U+Es would indicate renal AKI?

Answer 9

• Decreased urea:creatinine ratio (<40:1)
• Urea unable to be reabsorbed -> excreted like creatinine -> ratio closer to one

Question 10

What are causes of a decreased urea:creatinine ratio?

Answer 10

• Intrinsic renal damage
• Severe liver damage
• Malnutrition, low protein diet
• Pregnancy
• Rhabdomyolysis
• SIADH

Question 11

Acute tubular necrosis:
1. What is it?
2. Causes?
3. Investigations?
4. Recovery?

Answer 11

1. Necrosis of the epithelial cells of the renal tubules
2. Ischaemia due to hypoperfusion (dehydration, shock, HF) or nephrotoxins (aminoglycosides, radiocontrast)
3. Urinalysis - muddy brown casts
4. Recovery usually takes 1-3 weeks

Question 12

What are post-renal causes of AKI?

Answer 12

Obstruction to the outflow of urine causing back-pressure into the kidney
- Kidney stones
- Massess
- Ureter or uretral strictures
- Enlarged prostate or prostate cancer

Question 13

What is the first step of treating AKI?

Answer 13

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

Question 14

What are complications of AKI?

Answer 14

• Hyperkalaemia
• Fluid overload
• Metabolic acidosis
• Uraemia -> encephalopathy/pericarditis

Question 15

What are indications for renal replacement therapy in AKI?

Answer 15

• Acidosis - <7.2
• Electrolyte abnormalities - hyperkalaemia, hypercalcaemia, hyponatraemia
• Intoxicants - e.g. lithium
• Overload - acute pulmonary oedema
• Uraemia - Ur>60, uraemic pericarditis/encephalopathy

Question 16

Which drugs should be stopped in AKI as may worsen renal function?

Answer 16

• NSAIDs
• ACE-In
• ARBs
• Aminoglycosides
• Diuretics

Question 17

Which drugs may need to be stopped in AKI as increased risk of toxicity (but don’t worsen renal function)?

Answer 17

• Metformin
• Lithium
• Digoxin