Acute Kidney Injury

Question 1

Define AKI?

Answer 1

An acute decrease in kidney function which is usually reversible.

Note: previously AKI was referred to as acute renal failure

Question 2

List the common causes of AKI’s?

Answer 2

Any cause of renal damage can lead to AKI.

Pre-renal (hypovolaemia)
Renal
Post Renal

In the community 90% cases are pre-renal.
In hospital majority of cases are also pre-renal.

Question 3

List the life threatening complications of an AKI?

Answer 3

Severe fluid overload aka severe pulmonary oedema.
Metabolic Acidosis
Hyperkalaemia

Uraemic complications:
Pericarditis
Encepalopathy

Question 4

Describe how AKI’s are diagnostically confirmed?

Answer 4

Stage 1

• 150-200% increase of serum creatinine or 25mmol in 8hrs
• urine output <0.5ml/kg/hr for 6hrs

Stage 2

• 200-300% increase in serum creatinine
• urine output <0.5ml/kg/hr for 12hrs

Stage 3

• > 300% increase or >350mmol with acute rise >45mmol in 48hrs
• urine output <0.3ml/kg/hr

Question 5

How should AKI’s be investigated?

Answer 5

Urine dip and analysis

BP- hypotension(pre renal) or HTN (CKD)

Bloods

• FBC
• CRP
• U&Es
• LFTs
• Clotting
• CK
• Phosphate
• bicarbonate

ABG
ECG
Renal USS or CT for obstruction
Renal biopsy if uncertainity

Question 6

How should you manage an AKI?

Answer 6

Treat underlying cause:

Stop all nephrotoxic drugs
Restrict potassium intake
Pre renal cause- treat shock with IV fluids
Post renal cause- refer to nephrology

Question 7

When should you refer to a renal specialist?

Answer 7

Stage 3 AKI
No known cause
Complications of AKI
CKD stage 4/5

Question 8

At what level of potassium do you worry about arrhythmias?

Answer 8

6.5

Look for ECG changes.

Question 9

What are the ECG changes associated with hyperkalaemia?

Answer 9

Tall tented T waves

Flat P waves

Wide QRS

Question 10

Describe how you would treat hyperkalaemia and what each intervention does?

Answer 10

Calcium gluconate: protects the heart (ECG should go back to normal)

Insulin (+ dextrose) and Salbutamol: Moves K temporarily into cells

Removal of potassium from body

• calcium resonium
• loop diuretics
• dialysis

Question 11

What are the main pre-renal causes of AKI?

Answer 11

Dehydration
Shock
Heart failure
Renal artery stenosis

Question 12

What are the main renal causes of AKI?

Answer 12

Glomerulonephritis (IgA nephropathy/minimal change disease)

Acute Tubular Necrosis (hypoperfusion/rhabdomyolysis/gentamicin)

Acute interstitial nephritis (usually drug reactions)

Question 13

Describe how you would investigate for the renal causes of AKI and what you might find on testing?

Answer 13

Glomerulonephritis: Urinalysis should see protein +/- blood

Acute tubular necrosis: Urine MCS should show casts aka (dead tubular cells)

Acute interstitial nephritis: Renal biopsy

Question 14

What are the main post renal causes of AKI?

Answer 14

Luminal: Stones, blood clots, strictures

Mural: Tumour

Extramural: Prostate, tumours

Question 15

How can you investigate for post renal causes of AKI?

Answer 15

On exam make sure you do a DRE in males

Renal US to look for dilation.

CT KUB if looking for a stone.

Question 16

What are the general management points for an AKI?

Answer 16

Check fluid balance:

• Start a fluid chart.
• If you think they are dry start fluid.
• If you think they look overloaded speak to renal as this needs specialist care.

Daily U&Es

Treat underlying cause