Acute kidney injury (AKI)

Question 1

What are the 3 criteria for a diagnosis of AKI?

Answer 1

• Rise in creatinine of ≥ 25 micromol/L in 48 hours
• Rise in creatinine of ≥ 50% in 7 days
• Urine output of < 0.5ml/kg/hour for > 6 hours

Question 2

The severity of an AKI is staged according to which 2 things?

Answer 2

• Highest creatinine rise
• Longest period/severity of oliguria

Question 3

AKI usually occurs in patients that are suffering with an acute illness i.e. infection or having a surgical operation. Name 3 risk factors that would predispose them to develop an AKI

Answer 3

• Chronic kidney disease
• Heart failure
• Diabetes
• Liver disease
• Older age (above 65 years)
• Cognitive impairment
• Nephrotoxic medications i.e. NSAIDS, ACEi
• Use of a contrast medium i.e. during CT scans

Question 4

1) Prerenal causes of AKI are due to inadequate blood supply to the kidneys - name a cause of this
2) Name a renal cause of AKI
3) Post renal causes of AKI are due to the obstruction of urine leaving the kidney - how does this lead to an AKI?
4) Name a cause of this
5) Which of these is the commonest cause of AKI?

Answer 4

1) Dehydration, hypotension (shock), heart failure, haemorrhage, renal artery stenosis
2) Glomerulonephritis, interstitial nephritis, acute tubular necrosis
3) The back-pressure of urine into the kidney impairs kidney function
4) Renal stone, masses i.e. cancer in the abdomen or pelvis, ureter or uretral strictures, enlarged prostate or prostate cancer
5) Pre-renal

Question 5

Urinalysis is one of the main investigations for AKI. Name 2 of the things urinalysis would look for, and what would their presence/elevated level of show?

Answer 5

• Leukocytes + nitrates = infection
• Protein + blood = acute nephritis
• Glucose = diabetes

Question 6

Name 2 signs/symptoms/features of AKI

Answer 6

• Decreased urine output
• Rise in molecules that the kidney normally excretes (i.e. potassium, creatinine, urea)
• Fluid overload
• Pulmonary and peripheral oedema
• Arrhythmias due to potassium imbalance
• Pericarditis or encephalopathy due to urea rise

Question 7

1) Name 1 preventative measure for developing AKI
2) How is AKI managed (3)?

Answer 7

1) Avoiding nephrotoxic drugs where possible, ensuring correct fluid management in unwell patients.
2) Treatment of cause + supportive management (review of px drugs, ensure correct fluid balance). Dialysis in severe cases

Question 8

Name 2 complications of AKI

Answer 8

• Hyperkalemia
• Fluid overload, heart failure and pulmonary oedema
• Metabolic acidosis
• Uraemia which can lead to encephalopathy or pericarditis

Question 9

An increase in creatinine of what from baseline is considered a stage 1, 2 or 3 AKI?

Answer 9

• Stage 1 = 1.5-1.9 times baseline
• Stage 2 = 2-2.9 times baseline
• Stage 3 = >3 times baseline

Question 10

A reduction in urine output to what is considered stage 1, 2, or 3 AKI?

Answer 10

• Stage 1 = <0.5 ml/Kg/hr for >6 hrs
• Stage 2 = <0.5 ml/Kg/hr for >12 hrs
• Stage 3 = <0.3ml/Kg/hr for >24 hrs

Question 11

A rise in creatinine of what is considered a stage 3 AKI?

Answer 11

> 354 micromol/L

Question 12

1) If there’s raised creatinine and urea, but the creatinine rise is proportionally higher than the urea, what is the most likely cause (AKI or dehydration)?
2) If there’s raised creatinine and urea, but the urea rise is proportionally higher than the creatinine, what is the most likely cause (AKI or dehydration)?

Answer 12

1) AKI
2) Dehydration

Question 13

What investigation is required for patients presenting with an AKI if unknown aetiology?

Answer 13

Renal ultrasound