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

AKIN criteria
Creatinine:

1: 150-200 % of normal level or 25 umol/l increase within 48hrs
2: 200-300 % of normal level

3 :>300% increase or >350μmol/l with acute rise of >45μmol/l*

OR

Urinary Output:

1: 0.5ml/kg/hr 6 hours
2. 0.5ml/kg/hr 12hrs
3. 0.3ml/kg/hr 24hrs or anuria 12hrs

Question 5

How should AKI’s be investigated?

Answer 5

Fluid balance monitoring (stage AKI)

Creatinine (stage AKI)

Urinalysis:
Nitrites +ve send MSU
Blood +ve nephritis screen consider biopsy
Protein +ve consider nephrotic syndrome

VBG: for lactate and acid base

Question 6

How should you manage an AKI?

Answer 6

Treat underlying cause:

• Stop/avoid nephrotoxins and review all drug dosing
• Exclude obstruction (Renal U/S within 24hrs)
• Monitor U/O and repeat creat at least daily until improvement

Question 7

When should you refer to a renal specialist?

Answer 7

Stage 1:

• Uncertain cause
• Complications
• Intrinsic renal disease

Stage 2:
Refer except where cause+ plan clear
+ early improvement

Stage 3:
Always refer

Question 8

At what level of potassium do you worry about arrhythmias?

Answer 8

6.5 (slightly arbitrary number)

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

Treat underlying cause

Question 11

What are the main pre-renal causes of AKI?

Answer 11

Dehydration
Shock
Heart and Liver failure

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