Acute Kidney Injury (Complete)

Question 1

Define acute kidney injury

Answer 1

Acute reduction in renal function

Presents within 7 days of insult, lasts for more than 24 hours.

Characterised by:
Oliguria
Raised serum creatinine and urea

Question 2

AKI causes can be divided into which 3 categories? What is the pathophysiology behind each category?

Answer 2

Pre-renal causes (Hypoperfusion and ischaemia)

Intrinsic causes (Damage to the kidney itself)

Post-renal causes (Obstruction)

Question 3

Give 2 examples of pre-renal causes of AKI

Answer 3

(Tends to be iscahemia related causes)

• Shock: (e.g. hypovolaemia secondary to vomitting or diarrhoea, cardiogenic, distributive shock [e.g. sepsis])
• Renovascular diseases: Renal artery stenosis

Question 4

List 6 examples of interstitial causes of AKI

Answer 4

• Acute glomerulonephirits (Inflammation of the glomeruli)
• Acute tubular necrosis (Necrosis of the tubules of the nephrons)
• Interstitial nephritis (Inflammation of interstitium sorrounding the nephrons)
• Haemolytic uraemic syndrome (small vessels in the kidney become damaged or inflammed)
• Rhabdomyolysis
• Tumor lysis syndrome (large number of cancer cells death leading to release of harmful contents)
• Drugs (e.g. ACE, ARB, Diuretics)

Question 5

List 3 examples of post-renal causes of AKI

Answer 5

Kidney stones in ureter or bladder

Benign prostatic hyperplasia

External compression of ureter (e.g. tumor)

Question 6

Are pre-renal, renal or post-renal causes the most common in AKI?

Answer 6

Pre-renal causes

Question 7

Define acute glomerulonephritis

Answer 7

Acute inflammation of the glomeruli of the kidneys

Question 8

Define acute tubular necrosis

Answer 8

Necrosis of the tubules of the nephrons of the kidney

Question 9

Define interstitial nephritis

Answer 9

Inflammation of the interstitium (Space between the nephrons)

Question 10

Define haemolytic uraemic syndrome

Answer 10

Syndrome which develops due to small vessels in the kidney become damaged or inflammed, resulting in small blood clot formation and hence occlusion.

Question 11

What are the 8 main risk factors for acute kidney injury?

Answer 11

Aged 65 and over

Chronic kidney disease

Chronic disease (e.g. DM) or other organ failure (e.g. heart, liver)

Previous AKI

Nephrotoxic drugs within the past week (e.g. NSAIDs, ACE inhibitors, ARBs, Diuretics)

Use of iodinated contrast agents within the past week

Renal transplant

Requires a carer e.g. disaibility or impairement: Which may mean limited access to fluids because of reliance on a carer

Question 12

List 5 examples of nephrotoxic drugs which can increase likelihood of developing an AKI.

Answer 12

NSAIDs

ACEi

ARBs

Diuretics

Aminoglycosides (type of broad-spectrum ABs -mycins/cins)

Question 13

Pateints with risk of AKI and require investigation using contrast agents are given what to minimise risk?

Answer 13

IV fluids

Question 14

What are the aetioligical manifestations of an AKI? (3)

Answer 14

Oliguria

Increase in unexcreted waste products such as: Pottasium, urea, creatinine.

Fluid overload (due to osmotic gradient of unxecreted waste products)

Question 15

What are the main signs/symptoms of acute kidney injury? (4)

Answer 15

Oliguria (<0.5ml/kh/hr)

Pulmonary and peripheral oedema

Arrythmias (secondary to pottasium and acid-base dysregulation)

Features of uraemia: E.g. encephalopathy, pericarditis, pruritis, nausea, fatigue.

Question 16

What are the main investigations to order in patients suspected of AKI?

Answer 16

Bedside:
ECG (due to hyperkalaemia)
Urine dipstick (urinalysis and MCS)
Urine output monitoring (dont catheterise)

Bloods:
FBC
LFTs
U&Es
Creatinine
Glucose
Clotting
Calcium
ESR
ABG
Blood culture (if sepesis suspected)

Imaging:
CXR (pulmonary oedema)
Renal US

Special test:
Glomerulonephritis screen if cause still unknown

Question 17

What are the main findings on investigation can present in paients with AKI?

Answer 17

Elevated serum urea

Elevated serum creatinine

Hyperkalaemia

Question 18

What ECG findings can show in patients with AKI? (4)

Answer 18

Signs of hyperkalaemia such as:

Peaked T-waves

Prolonged PR

Widened QRS

Atrial arrest

Question 19

What findings on a FBC can present in AKI?

Answer 19

Leukocytosis (suggests infection cause such as sepsis)

Low platelets (Points towards haemolytic uraemic syndrome and other rare causes)

Anaemia (can present in AKI secondary to haemolytic uraemic syndrome, vasculitis, myeloma)

Question 20

Why is urinalysis, MCS useful when investigating for AKI?

Answer 20

Helps to look for intrinsic causes of AKI or UTI causes

Question 21

Why is ABG needed for patients with suspected AKI? What are two potential findings in ABGs in these patients?

Answer 21

Due to buildup of acidic waste products and reduced kidney function, patient at risk of a metabolic acidosis.

May also show hypoxia if person have oedema due to AKI.

Hypoxia and acidosis

Question 22

Whys is a renal US useful in patients suspected of AKI? When should it be ordered?

Answer 22

Can observe renal size and check for conditions such as hydronephrosis indicating obstructive cause.

Order US within 24 hours if no identifiable cause for the deterioration or are at risk of urinary tract obstruction

Question 23

What diagnostic criteria should be met alongside investigation findings to diagnose a person with AKI?

Answer 23

Either one of 3:

1) Rise in serum creatinine of 26 micromol/litre or greater within 48 hours

2) 50% or greater rise in serum creatinine known or presumed to have occurred within the past 7 days

3) Fall in urine output to less than 0.5 ml/kg/hour for more than 6 hours in adults

Question 24

What is the management plan for patients with AKI?

Answer 24

ABC approach: Sit up and oxygen if pulmonary oedema, IV fluids of hypovolaemic.

Suspend any nephrotoxic medications (e.g. NSAIDs, ACE, ARB, Diuretics, aminoglycosides)

Suspend renally excreted drugs: E.g. metformin, Digoxin [AF], lithium.

Continous monitoring: for fluid status, electrolytes and urine output.

Treat life threatening complications: E.g. sepsis, hyperkalaemia

Treat underlying causes:

Post-renal: IV fluids if hypovolaemic, IV ABs if sepsis

Intrinsic causes: Nephrology review

Post-renal causes: Catheterisation and urology review

In severe cases: Dialysis

Question 25

What are the indications for dialysis in patients with acute kidney injury? (5)

Answer 25

AEIOU:

A: Acidosis (severe acidosis with pH less than 7.2)

E: Electrolyte imbalance (persistent hyperkalaemia)

I: Intoxication (poisoning)

O: Oedema (refractory pulmonary oedema)

U: Uraemia (encephalopathy or pericarditis)

Question 26

What managemet options are available for patients with hyperkalaemia?

Answer 26

IV calcium gluconate (Stabilises cardiac membrane)

Combined insulin/dextrose infusion (Increases K+ intracellular uptake)

Nebulised salbutomol (Increases K+ intracellular uptake)

Calcium resonium (Increases K+ excretion)

Loop diuretic (Increases K+ excretion)

Dialysis (Increases K+ excretion)