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Urinary System > 19) Acute Kidney Injury > Flashcards

19) Acute Kidney Injury Flashcards

1
Q

What is oliguria?

A

Little urine, less than 500ml/day

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2
Q

What is anuria

A

No urine, less than 100ml/day, indicates blockage

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3
Q

What is acute kidney injury?

A

Abrupt decline in actual GFR (days to weeks)

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4
Q

What does AKI affect?

A

Upset in ECF volume, electrolyte and acid base homeostasis

Accumulation of nitrogenous waste products

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5
Q

Why is AKI hard to diagnose?

A

Serum creatinine has a delayed build up (5 days) after kidney function decline

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6
Q

How is AKI defined? (3 definitions)

A

Increase in serum creatinine by ≥ 26.5 μmol/L within 48 hours
Increase in serum creatinine by ≥1.5 times baseline within 7 days
Urine volume <0.5 ml/kg/h for 6 hours

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7
Q

How is AKI staged?

A

3 stages, with each stage a higher increase in serum creatinine
Stage 3 may include initiation of renal replacement therapy

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8
Q

What are the 3 general causes of AKI?

A

Pre-renal failure
Intrinsic renal failure
Post renal failure (obstruction)

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9
Q

What is pre-renal failure?

A

Decreased renal perfusion

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10
Q

What can cause pre-renal failure?

A

Hypovolemia
Heart failure
Systemic vasodilation
Impaired renal autoregulation

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11
Q

How does the kidney maintain renal blood flow normally, when renal perfusion decreases?

A

Autoregulation to dilate AA and constrict EA, therefore maintaining GFR

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12
Q

What can cause impaired autoregulation?

A

If BP falls below 80mmHg
Diseases of afferent arteriole
Interfering drugs - NSAIDs and ACEi/ARB

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13
Q

What can occur if pre-renal failure isn’t promptly treated?

A

Acute tubular necrosis

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14
Q

What can cause intrinsic renal failure?

A

Acute tubular necrosis - ischaemic, toxic
Glomerular and arteriolar disease
Interstitial disease

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15
Q

What can cause ATN?

A

Ischemia
Nephrotoxins
Sepsis

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16
Q

Why is ATN a misnomer?

A

Cells damaged without immediate reversal but not necrosed

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17
Q

What can’t the damaged cells in ATN do?

A

Cannot reabsorb water and salt

Can’t expel excess water

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18
Q

Why shouldn’t fluid resuscitation be used in ATN?

A

May get fluid overload due to damaged cell function

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19
Q

What causes ischaemic ATN?

A

Reduced perfusion

Affects proximal tubule as near hypoxic zone

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20
Q

Where in nephron does ischaemic ATN affect and why?

A

Proximal tubule as near hypoxic zone and requires lots of O2 to function

21
Q

How does ischaemic ATN present on microscopy?

A

Loss of structure on PT

Debris in lumen

22
Q

How do nephrotoxins cause ATN?

A

Damage the epithelial cells lining the tubules causing cell death and shedding into lumen

23
Q

Give some examples of endogenous nephrotoxins:

A

Myoglobin
Urate (increased in chemo)
Bilirubin

24
Q

Give some examples of exogenous nephrotoxins:

A

Endotoxin
X-ray contrast
ACEi, NSAIDs
Weedkiller

25
Q

What is rhabdomyolysis and how can it cause AKI?

A

Muscle necrosis due to crush injury - release of myoglobin

Myoglobin filtered and toxic to tubule cells, may cause obstruction and dark urine

26
Q

How can you tell the difference between pre-renal failure and ATN?

A

Lower osmolarity in ATN as cells can’t concentrate

Higher urinary Na+ in ATN as cells can’t reabsorb

27
Q

What causes acute glomerulonephritis?

A

Primary: IgA nephropathy
Secondary: Lupus, vasculitis

28
Q

How do haemolytic uraemic syndrome or hypertension cause arteriolar/glomerular damage?

A

Endothelial damage -> platelet thrombi -> partially obstruct small arteries -> destruction of RBC

29
Q

What can cause interstitial nephritis?

A

Infection: acute pyelonephritis

Toxin induced: antibiotics, NSAIDs, PPI

30
Q

What is seen microscopically in interstitial nephritis?

A

Lots of lymphocytes and inflammatory infiltrate, wide space between tubules

31
Q

How does post-renal failure cause AKI?

A

Obstruction causing rise in intraluminal pressure, dilatation of renal pelvis and decrease in renal function

32
Q

What can cause obstruction leading to post renal failure?

A

Within lumen obstruction
From within wall (likely to cause CKD)
Pressure from outside

33
Q

What can cause obstruction within lumen?

A

Stones, blood clot, tumour

34
Q

What can cause obstruction from within the wall?

A

Congenital megaureter, stricture (post TB)

35
Q

What can cause obstruction by pressure from outside?

A

Enlarged prostate, tumour, AAA

36
Q

What investigations can be carried out in AKI?

A

Serum biochemistry - urea and creatinine
Urinalysis - blood, protein, leucocytes
Potassium, sodium and calcium

37
Q

What are symptoms of volume depletion?

A

Cool peripheries, high pulse, low BP

38
Q

What are symptoms of volume overload?

A

Gallop rhythm, raised JVP, oedema

39
Q

What are the symptoms of sepsis?

A

Fever, warm peripheries, bounding pulse, low BP

40
Q

What could you examine if you suspect UT obstruction ?

A

Anuria
Palpable bladder
Pelvic masses
Enlarge prostate

41
Q

What imaging may you use to investigate AKI?

A

Ultrasound

CXR - fluid overload or infection

42
Q

When would you use a kidney biopsy to investigate AKI?

A

When pre and post renal AKI ruled out

43
Q

How can AKI be prevented?

A

Adequate hydration
Avoid nephrotoxins
Detect early

44
Q

What are risk factors for AKI?

A

Advanced age, CKD, dehydration

45
Q

How is pre-renal AKI treated?

A

Fluids - restore volume

Diuretics - pump failure

46
Q

How is intrinsic AKI treated?

A

Maintain perfusion, avoid nephrotoxins, restrict solutes

47
Q

How is post-renal AKI treated?

A

Urological intervention

48
Q

What can be used if kidneys aren’t functioning after treatment?

A

Dialysis

49
Q

What is the prognosis for AKI?

A

Recovery with 2-3 weeks
Infection and dialysis increase mortality
Increase risk of death for year after

Urinary System (10 decks)

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