Acute kidney injury (AKI)

Question 1

Definition of acute kidney injury (AKI)

Answer 1

An abrupt (<48 hours) reduction in kidney function defined as:

• An absolute increase in serum creatinine by >26.4umol/L
• OR increase in creatinine by >50%
• OR reduction in urine output

Question 2

What are the 3 classes of cause of AKI?

Answer 2

Pre-renal - Impaired blood flow
Renal - Damage to renal cells
Post-renal - Obstruction

Question 3

Pathophysiology of pre-renal AKI

Answer 3

Reversible volume depletion causes a reduction in perfusion to the kidneys - leads to oliguria (<0.5 mls/kg/hr) and increase in creatinine

Question 4

What are some types of cause of pre-renal AKI?

Answer 4

• Hypovolaemia
• Hypotension
• Renal hypo perfusion

Question 5

What are some causes of hypovolaemia in pre-renal AKI

Answer 5

Haemorrhage
Volume depletion (D+V, Burns)

Question 6

What are some causes of hypotension in pre-renal AKI?

Answer 6

Cardiogenic shock
Distributive shock (Sepsis, anaphylaxis)

Question 7

What are some causes of renal hypo perfusion in pre-renal AKI?

Answer 7

NSAIDs/COX2
ACEi/ARBs
Hepatorenal syndrome

Question 8

How does ACEi cause AKI?

Answer 8

• Renin reduces renal perfusion and increases angiotensin II, which causes efferent arteriole vasoconstriction, to maintain GFR
• ACE inhibitors decrease levels of angiotensin II and so decrease efferent arteriole vasoconstriction, therefore slightly lowering GFR
• If there is a co-morbid reduction in renal perfusion, GFR can fall rapidly, causing AKI

Question 9

What are some types of cause of renal AKI?

Answer 9

• Vascular
• Glomerular
• Interstitial nephritis
• Tubular injury

Question 10

What can occur if pre-renal AKI goes untreated?

Answer 10

Acute tubular necrosis

Question 11

What are some vascular causes of renal AKI?

Answer 11

Vasculitis (GPA)
Renovascular disease (Like peripheral vascular disease for the kidneys)

Question 12

What is a glomerular cause of renal AKI?

Answer 12

Glomerulonephritis (And therefore any causes of GN)

Question 13

What are some causes of interstitial nephritis in renal AKI?

Answer 13

• Drugs
• Infection (TB)
• Systemic (sarcoid)

Question 14

What are some causes of tubular injury in renal AKI?

Answer 14

• Ischaemia
• Drugs (gentamicin)
• Contrast
• Rhabdomyolysis

Question 15

What is the pathology of post-renal AKI?

Answer 15

AKI due to obstruction of urine flow leading to back pressure and thus loss of concentrating ability

Question 16

What are some causes of post-renal AKI?

Answer 16

• Stones
• Cancers
• Strictures
• Extrinsic pressure

Question 17

What are some patient factors that increase risk of AKI?

Answer 17

• Older age
• Male
• CKD
• Diabetes
• Cardiac failure
• Liver disease
• Peripheral vascular disease
• Previous AKI

Question 18

What are some exposures that can increase risk of AKI?

Answer 18

• Hypotension
• Hypovolaemia
• Sepsis
• Deteriorating NEWS
• Recent contrast
• Exposure to certain medications

Question 19

What classification system is used in AKI cstaging?

Answer 19

KDIGO staging

Question 20

What are some symptoms of AKI

Answer 20

• Constitutional symptoms - anorexia, weight loss, fatigue, lethargy
• Nausea and vomiting
• Itch
• Fluid overload - oedema, SOB

Question 21

What are some signs of AKI?

Answer 21

• Fluid overload including HTN, oedema, pulmonary oedema, pleural effusion
• Uraemia including itch, pericarditis
• Oliguria

Question 22

What are some investigations required in AKI?

Answer 22

U+E
Bloods
Urinalysis
USS
Immunology

Question 23

What blood tests are required in AKI?

Answer 23

• FBC - Anaemia
• Coagulation screen - Abnormal clotting
• Bicarbonate
• Bone profile

Question 24

What specific tests are required if myeloma is the suspected cause of AKI?

Answer 24

Protein electrophoresis
Bence-Jones protein

Question 25

How is pre-renal AKI managed?

Answer 25

Assess for hydration Fluid challenge for hypovolaemia

Question 26

How is hydration assessed in pre-renal AKI?

Answer 26

- Clinical observations (BP, HR, UO) - JVP, cap refil, oedema - Pulmonary oedema

Question 27

How is fluid challenge completed in hypovolaemia in pre-renal AKI

Answer 27

- Crystalloid (0.9% NaCl) or colloid (Gelofusin) - no NOT use 5% dextrose - Give bolus of fluid then reassess and repeat as necessary - Ig >1000mls IN and no improvement, seek help

Question 28

What are some management options in pre-renal and renal AKI?

Answer 28

- Fluid resuscitation - Treat underlying causes - Stop nephrotoxins - Dialysis is remains anuric and uraemic

Question 29

How is post-renal AKI managed?

Answer 29

- Relieve obstruction - catheter, nephrostomy - Refer urology if ureteric stenting required

Question 30

What are some urgent indications for haemodialysis in AKI?

Answer 30

- Hyperkalaemia >7 or >6.5 unresponsive to medical therapy - Severe acidosis - pH <7.15 - Fluid overload e.g. pulmonary oedema - Urea >40, pericardial rub/effusion

Question 31

What are some complications of AKI?

Answer 31

- Hyperkalaemia - Fluid overload (pulmonary oedema) - Severe acidosis (pH <7.15) - Uraemic pericardial effusion - Severe uraemia(Ur >40)

Question 32

What is acute tubular necrosis?

Answer 32

Refers to tubular cell death and acute deterioration in renal function

Question 33

What is the most common cause of acute tubular necrosis?

Answer 33

Ischaemia: - Hypotension - Shock - Malignant hypertension - Polyarteritis nodosa - HUS

Question 34

What are some other causes of acute tubular necrosis?

Answer 34

Toxins or drugs Post renal ATN (Obstruction)