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Applied CP 2 > Renal Functional Imaging > Flashcards

Renal Functional Imaging Flashcards

1
Q

prep

A

well hydrated - minimum 300-500 ml water prior to scan

void before imaging

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2
Q

RP(s) and dose

A

MAG3 or DTPA
90-370 MBq

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3
Q

imaging protocol

A

flow and dynamic, then statics of pre-void, post-void and injection site

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4
Q

what are the 2 sequential phases that are imaged?

A
  1. renal perfusion (flow)
  2. function (dynamic)
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5
Q

normal renal scan

A
  • prompt and symmetrical perfusion in both kidneys within 2-5 secs of seeing the abdominal aorta
  • peak activity seen at 2-5 min
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6
Q

bladder visible by ____

A

4-8 mins

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7
Q

time to peak (Tmax)

A

2-5 mins

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8
Q

what is the 20 min/peak ratio?

A

measures residual cortical activity (transit time in kidney) at t=20 mins and at max counts
then cts at 20 mins divided by max cts

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9
Q

20 min/max ratio

A

<0.35 normal

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10
Q

what is the differential cortical retention?

A

% retained in each kidney at 15 or 20 mins

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11
Q

what is considered abnormal differential cortical retention?

A

difference of more than 20%

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12
Q

normal value of T1/2 excretion

A

=< 20 mins
8-12 mins is typical

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13
Q

what is the T1/2 excretion?

A

time for half the peak activity to be cleared from the kidney

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14
Q

what range is appropriate for differential/relative renal function?

A

45:55

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15
Q

pathologies seen in diuretic renal scan (lasix)

A
  • hydronephrosis (obstructive or non-obstructive)
  • horseshoe kidney
  • renal/crossed ectopia
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15
Q

pathologies seen in regular renal scans

A
  • acute glomerulonephritis
  • renal artery
  • vein thrombosis
  • renal trauma (contusion, rupture, urine leak)
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16
Q

pathologies seen in ACEI/captopril scans

A

RVH caused by RAS

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17
Q

symptoms of acute glomerulonephritis

A
  • oliguria, proteinuria, hematuria
  • HTN
  • edema
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18
Q

what does acute glomerulonephritis look like with MAG3/DTPA?

A

uni/bilateral delayed excretion = elongated excretory phase on the renogram

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19
Q

what does acute glomerulonephritis look like with DMSA/Gluco?

A

photopenic cortex = poor function

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20
Q

NM appearance of renal artery embolus

A

with MAG3/DTPA = absent flow, function, and uptake

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21
Q

NM appearance of RVT

A
  • with MAG3/DTPA: decreased flow, enlarged kidneys, prolonged renal parenchymal transit time
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22
Q

NM appearance of renal contusion/trauma

A
  • infarcted area that improves over time!
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23
Q

nm appearance of renal rupture or fx

A

tearing = break in continuity of renal contour

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24
Q

what RP is best to determine renal rupture/fx?

A

delayed morphological imaging = DMSA

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25
Q

indications for diuretic renal imaging

A
  • hydronephrosis
  • eval distension of renal pelvis and ureter
  • differentiating cause of distension: functional vs. mechanical obstruction
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26
Q

hydronephrosis

A

dilation of renal pelvis and ureters

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27
Q

what causes hydronephrosis?

A
  • congenital malformations
  • mechanical obstruction
  • inflammatory obstruction
  • nerve damage
  • VUR, UTIs
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28
Q

which diuretic is most commonly used for functional renal scintigraphy? when do we use it? what is its mechanism of action?

A

lasix
various times, can be F15, F20 or right away (F0)
it inhibits absorption of sodium in loop of henle = less water going back to blood so more is excreted

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29
Q

what is used if the patient has a sulpha allergy?

A

ethancrynic acid

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30
Q

mechanical causes of distension

A
  • nephrolithiasis
  • extrinsic masses that press on the ureter
  • infection
  • mechanical obstruction
31
Q

functional causes of distension

A
  • VUR
  • previous obstruction
  • infection
  • congenital disorders
32
Q

dose of Lasix

A

max 40 mg IV over 1-2 mins

33
Q

when does administering lasix result in better discrimination between obstruction and non obstruction? why?

A

F15
allows for maximal diuresis effect

34
Q

when does administering lasix result in better visualization or natural urinary drainage? why?

A

F20, 30 or Fmax

35
Q

non obstructed hydronephrosis is seen as…

A

post lasix, collecting system washes out = renogram curve declines

36
Q

obstructed hydronephrosis is seen as…

A

post lasix, little change in collecting system activity = rising renogram changes very little or not at all

37
Q

T1/2 excretion post lasix
T1/2 <10 = …

A

no obstruction

38
Q

T1/2 excretion post lasix
T1/2 10-20 = …

A

indeterminate

39
Q

T1/2 excretion post lasix
T1/2 >20 = …

A

obstruction

40
Q

difference between acute/subacute high-grade and chronic high-grade obstruction

A

acute = blood flow and function is maintained
chronic = decreased blood flow and function

41
Q

false positives for diuretic scans

A
  • dehydration
  • poor underlying renal function
  • back pressure from noncompliant bladder
  • interstitial dose
  • large volume in dilated pelvis
  • use of diclofenac
42
Q

what is renovascular hypertension (RVH)?

A

HTN caused by blockage/occlusion of renal artery

43
Q

what is HTN?

A

BP >140/90

44
Q

symptoms of RAS

A
  • uncontrollable HTN (nonresponsive to meds)
  • headache
  • stroke
  • BP wildly erratic (exceeds sys 200 mmHg)
  • common under 30 or over 55
45
Q

causes of RAS

A
  • atherosclerosis
    -thromboembolism
  • fibromuscular dysplasia
  • pressure from external mass on renal artery
46
Q

prep
discontinue ACE, how long? why?

A

short acting 3 days
long acting 5-7 days

it can reduce sensitivity of test

47
Q

prep
discontinue diuretics, how long? why?

A

2-3 days
volume depletion cna reduce specificity of test

48
Q

why does fasting need to be done for captopril studies?

A

it interferes with absorption of captopril therefore false neg can happen

49
Q

dose of captopril

A

50 mg, PO

50
Q

when do you give captopril?

A

1 hr prior to RP injection

51
Q

dose of enalapril

A

0.04 mg/kg, max 2.5 mg IV over 3-5 mins

52
Q

when do you give enalapril?

A

10-15 mins prior to RP injection

53
Q

ACEI Neg exam
peak activity …

A

<5 mins

54
Q

ACEI Neg exam
half time excretion

A

8-12 min

55
Q

ACEI Neg exam
20min:peak ratio

A

<0.35

56
Q

RVH with MAG3
post capto
renogram results

A

post captopril = adequate uptake and secretion but decreased excretion due to decreased GFR

57
Q

RVH with MAG3
NM image results

A

increase cortical retention

58
Q

RVH with DTPA
post capto
renogram results

A

post captopril = fall in peak function, decrease in uptake and excretion

59
Q

scale for renograms
grade 0

A

normal

60
Q

scale for renograms
grade 1

A

mild abnormalities
time to peak >5 min
delayed excretion, 20 min: max >0.3

61
Q

scale for renograms
grade 2

A

more exaggerated delay in Tmax and parenchymal washout

62
Q

scale for renograms
grade 3

A

progressive parenchymal accumulation
(no washout)

63
Q

scale for renograms
grade 4

A

renal failure with measurable kidney uptake

64
Q

scale for renograms
grade 5

A

no uptake

65
Q

false negatives for ACEI scans

A
  • didn’t stop ACEI therapy
  • didn’t fast
66
Q

ACEI Renography
high probability

A

unilateral deterioration of renogram curve post captopril

67
Q

ACEI Renography
intermediate probability

A
  • small or poorly functioning kidney
  • abnormal baseline renogram that is unchanged after ACEI
68
Q

ACEI Renography
low probability

A
  • normal ACEI renogram with normal indices
  • grade 2 renogram that’s unchanged or improves after ACEI
69
Q

generic name ethacrynic acid

A

Edecrin

70
Q

generic name furosemide

A

lasix

71
Q

trade name Vasotec

A

enalapril

72
Q

blocks conversion of angiotensin I to angiotensin II

A

captopril and enalapril

73
Q

administered IV 40 ug/kg over 3-5 mins

A

enalapril

74
Q

1 mg/kg administered IV for peds

A

Lasix

Applied CP 2 (12 decks)

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