18. Renal Imaging Flashcards
what imaging modality is best for renal cysts?
ultrasound. kidney size helps prognosis
how early will hydronephrosis be evident on US after obstruction?
not evident for 1-2 days post-obstruction. takes a few days to develop
what imaging modality is usually preferred for diagnosing renal obstruction?
ultrasound
CT: contrast or non-contrast best for nephrolithiasis?
non-contrast. because contrast can obscure stones
what imaging modality can show early signs of renal obstruction?
contrast CT
what renal structures can contrast CT highlight in particular?
vascular structures
what’s one problem with CT contrast?
it is nephrotoxic. be careful particularly with patients who already have low renal function
generally, what 4 things are we evaluating the kidney for with imaging?
- obstruction w hydronephrosis
- stones
- renal masses
- renal vasculature
how does the CT contrast move through the kidney: what lights up first?
arteries –> cortex –> veins –> collecting systems
what is the appearance of urine with contrast CT?
dark unless contains contrast (contrast is bright white)
by comparing the kidneys over time with contrast (as the contrast goes through phases), what can you discern?
asymmetric function, whether one kidney has delayed function
if one kidney is processing contrast more slowly than the other, what are possible causes?
- decr GFR
- decr inflow of contrast due to prob with afferent arteriole
if kidney is stretched (collecting system enlarged( is the obstruction acute or chonic?
chronic (stretch takes time)
if something enhances (takes in contrast), what can we conclude? does that make us more or less concerned?
if it takes up contrast, then generally it receives blood flow and it’s “alive”. we care more about this type of mass than about one that is not taking up contrast.
if a mass does not enhance, what can we conclude?
no blood flow, just a cyst. water, essentially.
