Acute Kidney Injury

Question 1

Acute kidney injury

Answer 1

A rapid loss (<48hrs) of kidney function (eGFR) due to reduced blood flow, harmful substances or urinary track obstruction. It is diagnosed on increased blood urea, creatinine and failure to produce urine (oligouria over 6hr or more)

Question 2

Causes of AKI

Answer 2

Pre-renal –> Reduced perfusion, rhabomyolysis
Renal –> Glomerular, Atheroembolic, tubular necrosis
Obstructive/Post-renal –> BPH & stones

Question 3

Reduced Perfusion leading to AKI

Answer 3

Can be hypovolaemic (bleeding or cutaneous loss) or hypotensive (HF, shock, Drugs, dehydration)
Renal ischemia due to stenosis or embolism
Urea is much higher than creatinine & urinary Na is low –> Responds to fluid therapy

Question 4

Rhabomyolysis leading to AKI

Answer 4

Major Muscle necrosis (trauma, extertion, immobility) or drugs (statins or neuroleptics)
Causes heme-pigment toxicity with raised CK, brown urine without RBCs
Treat with fluid and bicarbonate (myoglobin is more soluble in alkali)

Question 5

Glomerular Causes of AKI

Answer 5

Any kind of active urinary sediment (myoglobin or immune complexes) will cause damage and the presence of blood, protein and red cell casts in the urine

Question 6

Atheroembolic Disease leading to AKI

Answer 6

May cause a pre-renal AKI due to stenosis/embolism
May also occur post-angiography with allergy like symptoms.
Presents with sterile pyuria and eosinophila

Question 7

Acute tubular Necrosis

Answer 7

Follows any form of hypoperfusion

Can be atheroembolic or toxic (rhabomyolytic or drugs) –> particularly gentamicin, contrast, antivirals, antifungals

Question 8

Sign of Acute Tubular necrosis

Answer 8

‘Muddy brown epithelial cell casts’ are pathognomic

Question 9

Treatment of Renal AKI

Answer 9

Does not respond to fluids
Will take weeks to recover to baseline
High urinary sodium

Question 10

Obstructive causes of AKI

Answer 10

Must occur in both kidneys for AKI to occur
Most commonly Stones or BPH
Will lead to retention and painful anuria (<50ml/day)

Question 11

Management of obstructive AKI

Answer 11

USS urgently and catheterise to relieve obstruction
Watch for large volumes of diuresis
Monitor output and replace electrolytes

Question 12

Indications for Haemodialysis after AKI

Answer 12

Ureamia (>30mmol/L)
Refractory fluid overload
Metabolic acidosis
Severe hyperkalaemia

Question 13

Hyperkalaemia post AKI

Answer 13

> 6.5mmol/L
Palpitations and ECG changes
May need Dialysis

Question 14

Metabolic acidosis

Answer 14

pH 7.1 or below
Increased Resp rate
Monitor and replace electrolytes
May need Dialysis

Question 15

Refractory fluid overload

Answer 15

Can be a consequence of AKI or treatment for AKI
Will present with crackles, orthopnoea and hypoxia
Treat with diuretics

Question 16

Ureamia

Answer 16

Can cause encephalopathy or pericarditis
Can present as confusion, or pleuritic central chest pain with a pericardial rub
Requires Dialysis