Chempath 18: Assessment Of Renal Function 1 Flashcards

1
Q

What is considered the best measure of Kidney function ?

A

GFR

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2
Q

List 3 criterias that need to be fulfilled for a marker of clearance to be an accurate representation of GFR ?

A
  • The marker is not bound to serum proteins
  • The marker is freely filtered by the glomerulus
  • The marker is not secreted or reabsorbed by tubular cells
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3
Q

Name an endogenous markers that is measured clinically to estimate GFR ?

A

Creatinine

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4
Q

Apart from haematuria what else can cause a +ve dipstick result for blood ?

A

Myoglobinuria

Seen in rhabdomyolysis

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5
Q

What does the measure SG tell you on the urine dipstick ?

A

Specific gravity

Its a measure of urine concentration

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6
Q

Which marker of multiple myeloma can be detected in the urine ?

A

Bence jones proteins

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7
Q

A 50 year old, known alcoholic, presents generally unwell, seemingly intoxicated, with acute kidney injury. Urine microscopy reveals calcium oxalate Chrystals. What is the diagnosis?

A

Ethylene glycol poisoning (anti-freeze)

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8
Q

List 4 different methods of imaging the renal/urological system ?

A

Ultrasound KUB
IV Urogram (paediatrics looking for anatomical defects)
CT KUB
MRI KUB

KUB = kidney ureter bladder

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9
Q

Which mode of imaging is considered gold standard for identification of kidney stones ?

A

CT KUB

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10
Q

Normal GFR

A

120ml/min

Age related decline of 1mL/min/year

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11
Q

What is clearance

A

Can be used to measure GFR

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

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12
Q

How do you calculate clearance

A

Of 3 criteria fulfilled, clearance = GFR

C = (U x V) / P
Where u = urinary concentration
V = volume
P = plasma concentration

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13
Q

What is inulin

A

Marker used in research tool to measure GFR

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14
Q

What are clinically viable measures of GFr

A

Single injection plasma clearance measurements using

  • Cr- EDTA
  • Tc - DTPA
  • Iohexol

Give injection and measure urine collection using a gamma counter or take blood samples and look at the progressive reduction in radioactivity

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15
Q

Give examples of exogenous markers of GFR

A

Blood urea
Serum creatinine (from muscle cells, small amount of intestinal absorption)
CDK- epidemiology collaboration
Cystatin C

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16
Q

What 4 factors affect the rate of generation of creatinine

A

Muscularity
Age
Sex
Ethnicity

17
Q

What is the best way to measure GFR

A

Serum creatinine is an insensitive marker
Cystatin C is better
Constant rate infusion is a research tool
EGFR/ creatinine clearance is the best compromise in practice

18
Q

How can we measure urine protein:creatinine ratio

A

Quantitative assessment of the amount of proteinuria

Spot urine PCR correlates well with 24hr urine collection

19
Q

Types of urine examination

A
Single sampling:
Dipstick testing
Microscopic investigation
Proteinuria quantification 
Electrolyte estimation 

24 hour collection:
Creatinine clearance estimation
Stone forming elements

20
Q

What diagnosis would be suspected if a patients urine microscopy reveals calcium oxalate crystals

A

Ethylene glycol poisoning
Gets converted to oxalis acid
Precipitates with calcium in the renal tubules and ureters

21
Q

Different types of renal imaging

A
Plain KUB films 
IV urogram 
Ultrasound KUB 
CT KUB - 1st choice for kidney stones 
MRI KUB
Functional imaging - static and dynamic renograms
22
Q

name 2 equations that estimate GFR

A

overestimate - cockroft-gault
underestimate - MDRD

uses age, weight, sex, ethnicity

23
Q

why is inulin only used in research

A

requires a steady state infusion and difficult to assay