Chemical Pathology 14 - Acute and Chronic Renal failure 1 & 2 Flashcards

1
Q

What is a normal GFR?

A

120mls/ min

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2
Q

What are the roles of the proximal and distal convoluted tubules?

A

Proximal: bulk resorption of glomerular filtrate
Distal: fine tuning of composition of filtrate

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3
Q

What is the gold-standard measure of GFR?

A

Inulin clearance

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4
Q

What is the most clinically-viable measure of GFR?

A

51Cr-EDTA and 99Tc-DTPA

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5
Q

How can plasma creatinine be used to estimate GFR?

A
Clearance = P(U x V) 
P = plasma concentration
U = urinary concentration
V = plasma volume
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6
Q

What would invalidate a creatinine-based measurement of GFR?

A

If function is not in a steady state

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7
Q

Why does plasma urea have a limited clinical value for measuring renal function?

A

Because it can be affected by many things so is highly variable

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8
Q

Describe the movement of creatinine from blood to urine

A

Freely filtered

Actively transported into urine by tubular cells

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9
Q

What equation can be used to refine your interpretation of creatinine clearance?

A

Cockcroft Gault Equation

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10
Q

What is the equation for estimated creatinine clearance?

A

((1.23 x (140- age) x weight))/ serum creatinine

Adjust by 0.85 if female

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11
Q

What is cystatin C, and why is it particularly useful?

A

Alternative to creatinine clearance

Largely unaffected by muscle mass/ gender/ age

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12
Q

In what condition does cystatin C not give a reliable result for GFR estimation?

A

Hypo/ hyperthyroidism

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13
Q

How can proteinuria be quantified?

A

Spot urine measurement

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14
Q

What can a 24-hour urine collection be used for?

A
  1. Creatinine clearance estimation
  2. Examination for stone-forming elements
  3. Proteinuria quantification (but this can also be done on spot urine testing)
  4. Electrolyte estimation (but this can also be done on spot urine testing)
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15
Q

What is the first choice of imaging in a suspected renal stone?

A

Abdo X ray

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16
Q

What is the first choice of imaging to assess renal blood flow?

A

USS with doppler

17
Q

What is the first choice of imaging in investigating renal structural abnormalities?

A

CT

18
Q

What options are available for functional imaging of the kidney?

A

Static and dynamic renograms

19
Q

Recall the increases in creatinine that define each stage of AKI

A

Stage 1: 1.5-1.9 x the reference
Stage 2: 2-2.9 x the reference
Stage 3: >=3 x the reference (or >354)

20
Q

Systematically recall some differentials for pre-renal AKI

A

Water loss: diuresis/ vomiting
Selective ischaemia: renal artery stenosis
Blood loss: road traffic accident/ drugs affecting renal blood flow
Oedematous states: heart failure

21
Q

Recall 5 drug classes that can predispose to pre-renal AKI and the mechanism of each of these

A

NSAIDs - decrease afferent arteriolar dilatation
Calcineurin inhibitors - decrease afferent arteriolar dilatation
ACE inhibitors: decrease efferent constriction
ARBs: decrease efferent constriction
Diuretics: affect tubular function and pre-load

22
Q

When does AKI become only partially reversible?

A

When acute tubulr necrosis occurs

23
Q

Recall 3 differentials for the causes of post-renal AKI

A

It’s an obstructive pathology:

  1. Stone in renal pelvis
  2. Bilateral ureteric obstruction (BPH)
  3. Blocked urinary catheter
24
Q

Systematically recall some causes of intrinsic renal AKI

A

Vascular causes (vasculitis/ vasculitides)
Glomerular (glomerulonephritis)
Tubular (ATN)
Interstitial (analgesic nephropathy)
Big proteins that clog up nephron - myoglobin (rhabdomyolysis), immunoglobin (amyloidosis, myeloma)
Toxins (contrast/ drugs)

25
Q

What is the most common cause of intrinsic renal AKI?

A

Acute tubular necrosis

26
Q

What are the 2 best measures of AKI severity?

A

Creatinine

Urine output

27
Q

How is CKD stage 1 defined?

A

Kidney damage with normal GFR (>90)

28
Q

How is CKD stage 5 defined?

A

End-stage - GFR <15

29
Q

What is the best measure of prognosis in CKD?

A

Albumin creatinine ratio

30
Q

What is the most common cause of CKD?

A

Diabetes by a long mile

31
Q

How can CKD cause a failure of homeostatsis?

A
  1. Can cause acidosis due to reduced H+ excretion

2. Can cause hyperkalaemia due to reduced K+ excretion

32
Q

How can CKD cause a failure of hormonal function?

A
  1. Can lead to a normochromic normacytic anaemia due to failure of EPO production
  2. Can cause renal bone disease due to failure of PTH action
33
Q

How can end-stage CKD affect the heart?

A

CKD –> less PTH action –> calcium elevated –> cardiac myocyte dysfunction –> uraemic cardiomyopathy

34
Q

How should renal bone disease be treated (3 ways)?

A
  1. Phosphate control (phosphate binding drugs)
  2. Vitamin D receptor activators (eg 1 alpha calcidol)
  3. PTH suppression (cinacalcet)