Acute Kidney Injury

Question 1

What is acute kidney injury?

Answer 1

Sudden deterioration of renal function over hours or days

Question 2

What is oliguria?

Answer 2

Production of small amounts of urine
100-400ml

Question 3

What is anuria?

Answer 3

Failure of kidneys to produce urine
<100ml

Question 4

Three categories of causes of acute kidney injury

Answer 4

Pre renal
Intrinsic renal
Post renal

Question 5

Risk factors of AKI

Answer 5

• older age >65
• sepsis
• CKD
• heart failure
• diabetes
• liver disease
• cognitive impairment > leading to reduced fluid intake
• meds e.g. diuretics, ACE inhibitors, NSAIDs
• radiocontrast agents

Question 6

Causes of pre renal cute kidney injury

Answer 6

• Sepsis
• Hypovolaemia
• Shock
• Renal artery stenosis
• NSAIDs
• Congestive cardiac failure
• ACE inhibitors
  . generally cause a decreased blood supply to kidneys

Question 7

Causes of intrinsic renal acute kidney injury

Answer 7

Acute tubular necrosis
Acute interstitial nephritis
Glomerulonephritis
Rhabdomyolysis
Haemolytic uraemic syndrome

Question 8

Causes of post renal acute kidney injury

Answer 8

Obstruction of urine
Bilateral calculus of ureters
Ureteric/urethra stricture
Tumour
Retro-peritoneal fibrosis
Benign prostatic hyperplasia

Question 9

Diagnosis of AKI

Answer 9

• rise in creatinine for >25mmol/L in 48 hours
• rise in creatinine of >50% in 7 days
• urine output <0.5nl/kg/hr over >6 hours

Question 10

Complications of acute kidney injury

Answer 10

• Metabolic acidosis
• Hyperkalaemia
• Ureamia > encephalopathy + pericarditis
• Volume overload > heart failure + pulmonary oedema

Question 11

Urine volume in oliguria

Answer 11

100-400ml a day

Question 12

Urine volume in anuria

Answer 12

<100ml a day

Question 13

Staging of acute kidney injury

Answer 13

Stage 1
- serum creatinine: 1.5-1.9 times baseline
- urine output: <0.5ml/kg/h for 6-12 hours

Stage 2
- serum creatinine: 2-2.9 times baseline
- urine output: <0.5 ml/kg/h for >12 hours

Stage 3
- serum creatinine: 3 times baseline
- urine output: <0.3ml/kg/h for >24hours or anuria for >12 hours

Question 14

Stage 1 AKI

Answer 14

• serum creatinine: 1.5-1.9 x baseline
• urine output: 0.5ml/kg/h for 6-12 hours

Question 15

Stage 2 AKI

Answer 15

• serum creatinine: 2-2.9 x baseline
• urine output: <0.5ml/kg/h for >12 hours

Question 16

Stage 3 AKI

Answer 16

• serum creatinine: 3 x baseline
• urine output: <0.3ml/kg/h for >24hours or anuria for >12 hours

Question 17

Treatment of pre-renal AKI

Answer 17

Treat the cause

• IV fluids for hypovolaemia
• stop potentially nephrotoxic meds e.g. NSAIDs, ACEi
• diuretics

Question 18

Treatment of intrinsic renal AKI

Answer 18

• correct electrolytes
• renal replacement therapy (dialysis)
• call nephrology

Question 19

Treatment of post renal AKI

Answer 19

• urinary or supra-pubic catheter
• ureteric stents
• nephrostomy

Question 20

Management of AKI

Answer 20

• stop nephrotoxic agents
• treat underlying cause
• fix any electrolyte imbalances
• ensure volume status + perfusion pressure (IV fluids if dehydrated | diuretics if overloaded)
• monitor urine output + daily bloods

Question 21

How can AKI cause metabolic acidosis?

Answer 21

Unable to make more bicarbonate in intercalated cells or glutamine

Question 22

Symptoms of a patient with failing kidneys?

Answer 22

• palpitations
• deceased urine output
• fatigue
• vomiting (to resolve acid base imbalance)
• oedema (volume overload)
• confusion (end stage)

Question 23

What meds do you want to stop if a patient has an AKI?

Answer 23

Stop the DAMN meds

Diuretics
ACE inhibitors
Metformin
NSAIDs

Question 24

What is acute tubular necrosis?
What is it due to?

Answer 24

Damage + necrosis of the epithelial cells of renal tubules due to:
- ischaemia due to hypoperfusion
- nephrotoxins e.g. gentamicin, radiocontrast agents

Question 25

What is used to confirm acute tubular necrosis?

Answer 25

**Muddy brown casts on urinalysis** Renal tubular epithelial cells may also be seen

Question 26

What is acute interstitial nephritis? What is it due to?

Answer 26

**Acute inflammation of the interstitium** due to an immune reaction assocaited with: - drugs *e.g NSAIDs* - infection *e.g. E.coli, HIV* - autoimmune conditions *e.g. SLE, sarcoidosis*

Question 27

Management of acute interstitial nephritis

Answer 27

Treat underlying cause Steroids can reduce inflammation + improve recovery

Question 28

Are ACEi nephrotoxic?

Answer 28

- No but they should be stopped during an AKI as they reduce filtration pressure - They have a protective effect on the kidneys long term

Question 29

Investigations of AKI

Answer 29

- urine dipstick - daily FBCs, U&Es, LFTs, bone profile (phosphate + Ca) + CRP - urine PCR - USS KUB - to rule out obstruction

Question 30

Indications for renal replacement therapy in AKI

Answer 30

- hyperkalaemia refractory to medical therapy - metabolic acidosis refractory to medical therapy - fluid overload refractory to diuretics - uraemic pericarditis - uraemic encephalopathy

Question 31

What further investigations are needed if protein + blood are detected on urine dipstick in patient with AKI and why?

Answer 31

- **c-ANCA + p-ANCA** - vasculitis - **anti-GBM, ANA, C3 + C4** - lupus nephritis - **serum immunoglobulins + electrophoresis** - myeloma

Question 32

What is haemolytic uraemic syndrome? What is it due to? What is the classic triad?

Answer 32

- Involves thrombosis in small blood vessels in the body due to shiga toxins from E.coli or shigella. . Triad of: - microangiopathic haemolytic anaemia - acute kidney injury - thrombocytopenia

Question 33

How can haemolytic uraemic syndrome cause the classic triad?

Answer 33

- formation of blood clots uses platelets > **thrombocytopenia** - the thrombi partially obstructs small blood vessels + damage RBCs > **microangiopathic haemolytic anaemia** - the thrombi reduces kidney perfusion + damage the RBCs > **acute kidney injury**

Question 34

Presentation of haemolytic uraemic syndrome

Answer 34

- E. coli + shigella cause gastroenteritis > bloody diarrhoea - fever - pallor or jaundice - bruising - abdominal pain - oliguria - lethargy - confusion

Question 35

Management of haemolytic uraemic syndrome

Answer 35

- stool culture to establish causative organism - blood transfusion - IV fluids - anti hypertensive meds - haemodialysis

Question 36

What does muscle cell death release?

Answer 36

Myoglobin Potassium Phosphate Creatine kinase

Question 37

Causes of Rhabdomyolysis

Answer 37

- prolonged immobility - extremely rigorous exercise beyond person’s fitness level - crush injuries - statins - seizures

Question 38

Presentation of Rhabdomyolysis

Answer 38

- muscle pain, swelling + weakness - oliguria - red-brown urine (Myoglobinuria) - fatigue - N+V - confusion

Question 39

Investigations of Rhabdomyolysis

Answer 39

- Creatine kinase levels - U&Es - potassium levels + ECG - urine dipstick for presence of blood (for myoglobin in urine)

Question 40

Management of Rhabdomyolysis

Answer 40

- **IV fluids** *0.9% sodium chloride - **treatments of hyperkalaemia** . Possible options but have risks: - IV sodium bicarbonate to increase urinary pH - IV mannitol to increase urine output + reduce oedema

Question 41

Prevention of AKI

Answer 41

- regular creatinine monitoring if at risk - review for neprhotoxic drugs - educate patient on symptoms of AKI - explain risk of AKI is increased with acute illness, diarrhoea, vomiting

Question 42

Treatment of hyperkalaemia

Answer 42

- IV calcium gluconate - combined insulin/dextrose infusion - nebulised salbutamol - oral calcium resonium

Question 43

What acid base status can diarrhoea cause?

Answer 43

Metabolic acidosis Normal anion gap (or hypokalaemia)

Question 44

What acid base status can vomiting cause?

Answer 44

Metabolic alkalosis Can cause hypokalaemia