Kidneys

Question 1

NM renal radiotracers

Answer 1

Tc 99m DTPA, MAG3, DMSA

Question 2

Tc99m DTPA

Answer 2

DTPA measures GFR and renal perfusion

excreted by glomerular filtration; identical extraction fraction to inulin

Question 3

Tc99m MAG3

Answer 3

evalute renal plasma flow and renal perfusion; cannot measure GFR

filtered/excreted by tubules; better images in renal insufficiency/obstruction

Question 4

Tc99m DMSA

Answer 4

evaluate for renal scarring in kids with pyelonephritis; collecting system not imaged

cortical agent; allows anatomic imaging of cortex; SPECT imaging

Question 5

renal cortical imaging

Answer 5

evaluate for pyelonephritis/scarring in peds using Tc99m DMSA

normal: no acute pyelo
positive: focal cortical defect, multifocal cortical defects, diffusely decreased radiotracer

Question 6

renogram

Answer 6

time-activity curve to chart renal uptake/excretion

10mCi Tc99m MAG3 administered, imaged in 3 phases

1) flow phase (sharp upslope)
2) cortical function phase (defined peak); first 3 min
3) clearance phase (rapid excretion); lack of pelvicalyceal clearance suggests hydronephrosis

Question 7

ACE inhibitor renogram

Answer 7

used for renal artery stenosis; stop use of ACE for 2 d-1 week prior to access; IV access maintained in cause fluid resuscitation needed

normal: GFR should decrease after administration of ACE
positive: post ACE inhibitor renogram is abnormal

Question 8

diuretic renogram

Answer 8

Tc99 MAG3 to distinguish between obstruction and nonobstructive causes of hydronephrosis ; renal function and urodynamics

after 20 min imaging, IV lasix 40 mg administered; fixed mechanical obstruction should show no change

non-obstructive hydronephrosis will allow drainage of kidneys

clearance times
<10 min: normal
10-20 min: borderline
>20 min: obstruction

Question 9

causes of false positives for diuretic renogram

Answer 9

dehydration, distended bladder, renal failure (no response to diuretics)

Question 10

radionuclide cystography (RNC)

Answer 10

evaluate for pediatric reflux; less radiation than cystourethrogram

inject radionuclide (DTPA, pertechnetate, sulfure colloid) into bladder and monitor reflux

Question 11

RNC grading of reflux

Answer 11

RNC grade 1: minimal; confined to ureter

RNC grade 2: moderate, reflux extends superiorly to pelvicalyceal system

RNC grade 3: severe, tortuous ureter and dilated intrarenal system