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Urinary System > 19) Acute Kidney Injury > Flashcards

19) Acute Kidney Injury Flashcards

(49 cards)

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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?

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A

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

21
Q

How does ischaemic ATN present on microscopy?

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A

Loss of structure on PT

Debris in lumen

22
Q

How do nephrotoxins cause ATN?

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A

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

23
Q

Give some examples of endogenous nephrotoxins:

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A

Myoglobin
Urate (increased in chemo)
Bilirubin

24
Q

Give some examples of exogenous nephrotoxins:

Study These Flashcards
A

Endotoxin
X-ray contrast
ACEi, NSAIDs
Weedkiller

25
What is rhabdomyolysis and how can it cause AKI?
Muscle necrosis due to crush injury - release of myoglobin | Myoglobin filtered and toxic to tubule cells, may cause obstruction and dark urine
26
How can you tell the difference between pre-renal failure and ATN?
Lower osmolarity in ATN as cells can't concentrate | Higher urinary Na+ in ATN as cells can't reabsorb
27
What causes acute glomerulonephritis?
Primary: IgA nephropathy Secondary: Lupus, vasculitis
28
How do haemolytic uraemic syndrome or hypertension cause arteriolar/glomerular damage?
Endothelial damage -> platelet thrombi -> partially obstruct small arteries -> destruction of RBC
29
What can cause interstitial nephritis?
Infection: acute pyelonephritis | Toxin induced: antibiotics, NSAIDs, PPI
30
What is seen microscopically in interstitial nephritis?
Lots of lymphocytes and inflammatory infiltrate, wide space between tubules
31
How does post-renal failure cause AKI?
Obstruction causing rise in intraluminal pressure, dilatation of renal pelvis and decrease in renal function
32
What can cause obstruction leading to post renal failure?
Within lumen obstruction From within wall (likely to cause CKD) Pressure from outside
33
What can cause obstruction within lumen?
Stones, blood clot, tumour
34
What can cause obstruction from within the wall?
Congenital megaureter, stricture (post TB)
35
What can cause obstruction by pressure from outside?
Enlarged prostate, tumour, AAA
36
What investigations can be carried out in AKI?
Serum biochemistry - urea and creatinine Urinalysis - blood, protein, leucocytes Potassium, sodium and calcium
37
What are symptoms of volume depletion?
Cool peripheries, high pulse, low BP
38
What are symptoms of volume overload?
Gallop rhythm, raised JVP, oedema
39
What are the symptoms of sepsis?
Fever, warm peripheries, bounding pulse, low BP
40
What could you examine if you suspect UT obstruction ?
Anuria Palpable bladder Pelvic masses Enlarge prostate
41
What imaging may you use to investigate AKI?
Ultrasound | CXR - fluid overload or infection
42
When would you use a kidney biopsy to investigate AKI?
When pre and post renal AKI ruled out
43
How can AKI be prevented?
Adequate hydration Avoid nephrotoxins Detect early
44
What are risk factors for AKI?
Advanced age, CKD, dehydration
45
How is pre-renal AKI treated?
Fluids - restore volume | Diuretics - pump failure
46
How is intrinsic AKI treated?
Maintain perfusion, avoid nephrotoxins, restrict solutes
47
How is post-renal AKI treated?
Urological intervention
48
What can be used if kidneys aren't functioning after treatment?
Dialysis
49
What is the prognosis for AKI?
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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