Acute kidney injury

Question 1

What happens in acute kidney injury?

Answer 1

There is rapid reduction in kidney function taking hours to days.

Question 2

How is AKI diagnosed?

Answer 2

One of 3 out of:
1. Rise in creatitine >26nmol/L over 48 hours
2. Rise in creatinine >1.5x baseline cr
3. Urine output <0.5ml/kg/hr for >6 hours.
(PTS, lecture 20.2.18)

Question 3

Describe the pathogenesis of AKI.

Answer 3

Can be pre-renal, renal or post-renal:
1. Pre-renal: hypoperfusion due to MI/hypotension/sepsis etc.
2. Acute tubular necrosis (commonest), autoimmune disease, glomerulonephritis
3. Post-renal: UT obstruction due to stones/malignancy/extrinsic compression.
(lecture 20.2.18)

Question 4

Give 3 symptoms of AKI.

Answer 4

Depends on underlying cause and severity.

1. Nausea, vomiting
2. Postural hypotension
3. Confusion

Question 5

Give 3 signs on AKI.

Answer 5

Depends on underlying cause and severity.

1. Oligo/anuria
2. Polyuria due to decreased fluid reabsorption.
3. Dehydration
4. Confusion
5. Hypertension
6. Urinary retention (large painless bladder)

Question 6

What investigations would you do if you suspect AKI?

Answer 6

Serum creatinine, urine output
Volume status - fluid overload?
Full examination
Liver enzymes
Clotting 
Urine dipstick
Renal USS
(PTS)
 If person is elderly and has been lying down, check creatinine kinase (CK), to exclude rhabdomyolysis. (lecture)

Question 7

Describe the management of AKI.

Answer 7

Stop nephrotoxic drugs
Aim for euvolaemia
Treat underlying cause
Manage complications eg hyperkalaemia with insulin/dextrose or salbutamol nebuliser with calcium gluconate (cardio-protective).

Question 8

Give 3 risk factors for AKI.

Answer 8

Age
CKD
Cardiac failure
Peripheral vascular disease
Diabetes

Question 9

Give 3 potential complications of AKI.

Answer 9

Hyperkalaemia is the main one
Pulmonary oedema
Uraemia

Question 10

Give 3 classes of nephrotoxic drugs and give the brief mechanism of nephrotoxicity.

Answer 10

1.ACEIs/ ARBS dilate efferent arterioles, decreasing GFR.
2. NSAIDs inhibit cyclo-oxygenase which causes constriction of the afferent arteriole, decreasing GFR.
3. Aminoglycosides - increase risk of acute tubular necrosis, a common cause of AKI.
This is why you need to check renal function before using these drugs.
(PTS)