B5.079 Prework 1: Renal Imaging

Question 1

pros and cons of conventional radiographs

Answer 1

pros: cheap and quick
cons: poor soft tissue detail & radiation

Question 2

pros and cons of CT

Answer 2

pros: high spatial and contrast resolution, relatively short exam, easy to access
cons: high radiation dose, risks of iodinated contrast

Question 3

pros and cons of nuclear scintigraphy

Answer 3

pros: provides functional data
cons: poor resolution, radiation exposure

Question 4

pros and cons of ultrasound

Answer 4

pros: relatively cheap and quick, no radiation
cons: cant visualize ureters, operator dependent

Question 5

is MRI used for kidney imaging?

Answer 5

not often

2nd or 3rd line only

Question 6

2 main categories of renal imaging

Answer 6

structural: xray, CT, US
functional: nuclear medicine

Question 7

how does a CT of the kidney work

Answer 7

produce cross sectional images of the kidney utilizing an xray source and detector on a rotating gantry
often performed with IV contrast
can produce images in any plane

Question 8

4 phases of renal imagining w contrast

Answer 8

1. pre contrast
2. post contrast: corticomedullary
3. post contrast: nephrogenic
4. delayed: pylographic

Question 9

why are there different phases of renal imaging?

Answer 9

each phase highlights a different portion of the kidney and allows detection of different disease processes

Question 10

pre-contrast imaging uses

Answer 10

renal calcifications

no differentiation

Question 11

corticomedullary phase imaging description

Answer 11

20-40 s after contrast admin

cortex brighter than medulla/pelvis (kidneys perfuse from outside in)

Question 12

nephrogenic phase imaging description

Answer 12

60-120 s after contrast admin

equal distribution of contrast between cortex and medulla

Question 13

pyelographic phase imaging description

Answer 13

minutes to hours after contrast admin

contrast in calices and pelvis

Question 14

early post contrast imaging uses

Answer 14

detects and characterizes solid vs cystic cortical masses

i.e. RCC vs simple cyst

Question 15

delayed contrast imaging uses

Answer 15

evaluates renal pelvis and ureter for mass lesions

i.e. UCC

Question 16

appearance of cyst on post contrast CT

Answer 16

dark, homogenous mass

Question 17

appearance of RCC on post contrast CT

Answer 17

mass with mixed densities throughout, lighter than cyst

Question 18

how does an ultrasound work for kidney imagine

Answer 18

high frequency sound waves are produced by a piezoelectric crystal in a transducer and transmitted into the tissues via a gel medium
transducer also receives reflected sound waves and converts them back into electrical currents for image reconstruction

Question 19

2 main factors in ultrasound image reconstruction

Answer 19

travel time for a reflected beam of sound (depth)

degree to which it is reflected (acoustic impedance)

Question 20

high acoustic impedance on US

Answer 20

fat, air, bone, metal
appear whiter
hyperechoic

Question 21

low acoustic impedance on US

Answer 21

water
appear dark
hypoechoic

Question 22

normal kidney appearance on US

Answer 22

edge is lighter
cortex darker
collection of renal sinus fat in center appears light

Question 23

hydronephrosis on US

Answer 23

dark circles in center of kidney due to urine filled calices

Question 24

use of Doppler imaging on kidney

Answer 24

can determine direction and speed of blood flow within the structure
helps determine is there is vasculature in a mass (RCC vs fluid filled cyst)

Question 25

how does nuclear medicine imaging of the kidney work

Answer 25

utilizes selective binding and/or filtering of various radioactive compounds (radionuclides)
most common renal scintigraphic study is a MAG-3 renal scan

Question 26

what is MAG-3

Answer 26

compound which is partially filtered from the blood via the glomerulus and partially secreted from the tubules
labeled with radioactive technicium

Question 27

uses of renal scintigraphy

Answer 27

can construct an image with radioactivity and also quantitate amount of activity in a given structure over time
evaluates renal function and can be used to determine GFR

Question 28

normal activity vs time curve for a kidney

Answer 28

activity rises to a peak and then begins to decline steadily

decreases faster with administration of Lasix

Question 29

activity vs time curve during hydronephrosis

Answer 29

activity constantly rises and never falls, even with Lasix administration
radioactive material cannot be excreted due to blockage

Question 30

activity vs time curve in nonobstructed but dilated kidney

Answer 30

rises to a peak, but eventually falls off with Lasix infusion