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

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

1
Q

What is a normal GFR?

WHat is the age related decline in GFR?

A

120mls/ min

1ml/hour/year

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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

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17
Q

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

A

CT

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18
Q

What options are available for functional imaging of the kidney?

A

Static and dynamic renograms

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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)

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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

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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) - this bypasses the need to synthesise vitamin D altogether
  3. PTH suppression (cinacalcet)
35
Q

What is clearance?

When does clearance= GFR?

A

The volume of plasma that can be completely cleared of a marker substance ina. unit of time

Clearance=GFR if: marker is not bound to serum proteins, freely filtered by the glomeurlus and not secreted/reabsorbed by tubular cells

36
Q

What is the gold standard measure of GFR?

Why si it not used widely?

A

inulin

*requires a steady state infusion and difficult to assay so it’s reserved for research purpses only*

37
Q

What is used in clinical practice to measure GFR? How is it calculated?

A

Creatinine

*because the absolute levels vary so much, you measure the trend over time*

Equations: Cockcroft-Gault and MDRD - take account of diff combinations of age, weight, sex and ethnicity

38
Q

What does urine specific gravity measure?

A

Concentration of solute

*higher urine specific gravity = higher solute concentration*

normal rage: 1.005-1.030

39
Q

What does blood on urine dip signify?

A

Positive for blood: haematuria or myoglobinuria

Negative for blood: can reliably exclude haematuria

40
Q

What has 24-hour urine collection been superceded by? *for the measurement of proteinuria*

A

Protein:creatinine ratio

41
Q

For measurement of GFR is a single urine sample enough?

A

No- need to do 24 hour protein collection

42
Q

What stones do you get in ethylene glycol poisoning?

A

Calcium oxalate stones

*because ethylene glycol consists of glycolic acid and oxalic acid; when oxalic acid combines wih calcium it forms calcium oxalate stones*

43
Q

When would you see RBC on urine microscoy?

A

Stones or UTI

44
Q

When would you see white blood cells on urine microscopy?

A

UTI or glomerulnephritis

45
Q

When would you see casts on urine microscopy?

A

Glomeruloneprhitis

46
Q

What is the definition of AKI?

A

Rise in serum creatinine over 26 within 48h
• A 50% or greater rise in serum creatinine known or presumed to have occurred
within the past 7 days • A fall in urine output to less than 0.5mL/kg/hour for more than 6 hours.
o Be wary that prostate and bladder pathology can cause this too

47
Q

Indications for dialysis?

A

Acidosis (metabolic)

  1. Electrolyte disturbance e.g. refractory hyperkalaemia
  2. Intoxication e.g. lithium, aspirin
  3. Overload (fluid) e.g. pulmonary oedema
  4. Uraemic encephalopathy

(AEIOU)

48
Q

How do you define end stage kidney failure?

A

GFR<15

49
Q

Commonest causes of chornc kidney disease

A

Diabetes
• Atherosclerotic renal disease
• Hypertension
• Chronic Glomerulonephritis
• Infective or obstructive uropathy
• Polycystic kidney disease

50
Q

Biggest mortality in CKD?

A

Vascular calcification and subsequent atheroscleorsiss

51
Q

What are the 4 types of renal bone disease?

A

Osteitis fibrosa cystica: osteoclastic bone resorption

Osteomalacia: decreased bone mineralisation due to the low vitamin D

Adynamic bone disease: oversuppression of PTH

  • this happens when you overtreat the hyperparathyroidism

Mixed renal osteodystrophy

52
Q

Which iliac fossa is the transplanted kidney usually in?

A

Right iliac fossa

chemical pathology (22 decks)

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