Ch 22 Renal Vasculature Flashcards
What is a post-stenotic signal?
-Signal taken immediately distal to a stenosis
-Waveform shows decreased PSV
What is the renal-aortic velocity ratio?
PSV of RA / PSV of Ao
-Recorded at the level of the celiac or SMA
-Used to identify RA stenosis
RA stenosis is m/c due to ___ or ___?
Atherosclerotic disease or medial fibromuscular dysplasia
What is a RA stent used for?
Helps hold stenotic artery open, is inserted during arterial dilation (angioplasty)
What is the renal cortex?
-Outermost area of kidney tissue beneath the renal capsule
-The fibrous covering of the kidney
What is the renal hilum?
Area where RA, RV + ureter enter/exit kidney
What is the renal medulla?
-Middle area of kidney b/w sinus + cortex
-Contains pyramids
What is the renal ostium?
Opening of RA from aortic wall
What is renal parenchymal disease?
Medical disorder affecting tissue function of kidneys
What is the renal sinus?
-Central echogenic cavity in kidney
-Contains RA, RV, collecting + lymphatic systems
What is the SSN?
Indentation at base of neck where neck joins sternum
What is the symphysis pubis/pubic bones?
Prominence of pelvic bones noted in lower abdomen
RA stenosis is the m/c cause of what 3 things?
-Secondary hypertension
-Chronic renal insufficiency
-Incident end stage renal disease
2 main S/S of RA stenosis?
-Azotemia (buildup of nitrogen + creatinine in blood)
-Discrepant renal size > 1.5cm
Location of kidneys?
-Retroperitoneal
-B/w T12 + L3
Which kidney sits more inferior?
RT (due to liver)
Normal kidney length + width?
Length: 9-13cm
Width: 5-7cm
(note: size decreases with age)
What is the m/c organ anomaly?
Horseshoe kidneys
Horseshoe kidneys are joined at their ___ poles by an isthmus of tissue, anterior to Ao at L4 or L5?
Lower poles
When a horseshoe kidney is present, the renal arteries may be supplied by what 3 arteries?
-Distal Ao
-CIA
-IMA
What is the m/c congenital anomaly of the urinary tract?
Duplex collecting system (partial duplication is m/c)
Differentiate b/w complete + partial duplication with duplex collecting systems?
Complete:
-2 pelvicalyceal units
-2 ureters
-2 ureters insert separately into bladder
Partial: (m/c)
-Renal pelvis is bifid
-1 or 2 ureters (converge into 1 along course to bladder)
-1 ureter inserts into bladder
List the 4 renal segments?
Hilum:
-where RA, RV + ureter enter/exit
Sinus:
-contains RA, RV, collecting + lymphatics
-made of fat + fibrous tissue
-echogenic
Cortex:
-outermost area where urine is produced
-lies b/w pyramids
-isoechoic to liver
Medulla:
-12-18 pyramids that carry urine from cortex into pelvis
-hypoechoic
___ plane is an important surface landmark for sonographic localization of RA’s?
Transpyloric (b/w SSN + symphysis pubis)
RA’s branch from lateral Ao approx ___ cm below transpyloric plane?
2cm
What color will the RT + LT RA’s have with CD?
RT: red
LT: blue
What is the course of the RRA + LRA?
RRA:
-courses anterolaterally + then posterior to IVC + RRV
LRA:
-originates more cephalad, passes posterior to LRV + is crossed by IMV
RA’s give rise to how many branches that supply blood to segments of the kidney?
2-5 branches
At the hilum, the RA divides into a ___ anterior branch + a ___ posterior branch?
Large anterior, small posterior
The ant + post RA branches give rise to what 3 arteries within the renal parenchyma?
-Interlobar
-Arcuate
-Interlobular
RAs lie b/w the ___ + ___ in the hilum?
RV + ureter
Order:
anterior: RV
mid: RA
posterior: ureter
What is the course of the RRV + LRV?
RRV:
-short course from hilum to IVC
LRV:
-courses anterior to Ao, below SMA
Is RA stenosis m/c found in men or women?
Men
Atherosclerotic lesions m/c affect the ___ + ___ of the RA?
Ostium + prox third of RA
What is the 2nd m/c cause of renovascular disease?
Medial fibromuscular dysplasia
Medial FMD m/c affects which segments of the RA?
Mid-to-distal segments
Medial FMD m/c affects males or females?
Females aged 25-50
Medial FMD m/c affects the RRA or LRA?
RRA
Medial FMD has what known appearance?
String of pearls
What is the nutcracker syndrome (aka mesenteric compression syndrome)?
When the LRV gets compression by the SMA
(LRV is b/w SMA + Ao)
RAs lie immediately inferior to which vessel?
LRV
How to achieve the banana peel view?
-Pt in LLD
-Image Ao in SAG
-Heel toe probe for a 0 degree doppler angle
-RAs seen as they arise off lateral Ao walls
How to identify the RRA + LRA?
RRA:
-easy to follow from hilum to Ao
LRA:
-hilum at 5 o’clock = will course slightly to RT before entering kidney
-hilum at 7 o’clock = will course slightly to LT before entering kidney
Differentiate b/w accessory/duplicated RAs vs polar RAs?
Accessory: enter hilum
Polar: course to surface of kidney
___ arteries are the only low-resistance vessels distal to the SMA?
Renal
Where should we use spectral doppler on the kidney to assess renal perfusion?
-Sample throughout upper, mid + lower poles of the renal sinus, medulla + cortex
-Keep highest PSV + EDV from each segment
Kidney length should always be measured during deep ___?
Inspiration
A difference >1cm b/w kidneys suggests what?
Compromised flow on side with smaller kidney
Revascularization is unlikely when kidney length is ___ cm?
<9cm
The prox Ao carries blood to ___ resistance vascular beds?
Low-resistance (liver, spleen, kidneys)
The mid Ao (inf to RAs) carries blood to ___ resistance vascular beds?
High-resistance (lumbar arteries + lower extremity arteries)
Differentiate b/w RA stenosis <60% + >60%?
Stenosis <60%:
-No post stenotic turbulence
-Increase in PSV <180 cm/s
Stenosis >60%:
-Has post stenotic turbulence
-Increase in PSV > 180 cm/s
-Parvus tardus signal
What would doppler signals show if there was RA occlusion?
-Absent flow in main RA
-Low amplitude + velocity signals in medulla + cortex (due to blood supply from adrenal + ureteral collaterals)
What would the PSV in the cortex be with chronic RA occlusion?
< 10 cm/s
What would the kidney length be with chronic RA occlusion?
<9cm (atrophic)
What is intrinsic parenchymal dysfunction (aka medical renal disease)?
An accumulation of interstitial cellular infiltrates + edema, resulting in impedance to arterial inflow to kidney + increased renovascular resistance
Spectral doppler in the presence of renal disease will show ___ resistance flow patterns?
High-resistance
Formula for resistive index?
PSV - EDV / PSV
RI > ___ indicates medical renal disease?
> 0.8
Is AI or AT more accurate?
AT
What is acceleration index (AI)?
Slope of systolic upstroke / transmitted frequency
(AI < 291 cm/s suggests prox flow-reducing RA stenosis)
What is acceleration time (AT)?
Time interval b/w onset of systole + initial compliance peak
(AT > 100 ms suggests prox RA disease)
A renal-aortic ratio of ___ indicates significant RA stenosis (>60%)?
> 3.5
When should we NOT use the renal-aortic ratio?
When Ao PSV is:
>100 cm/s (increased CO = underestimation)
or
<40 cm/s (decreased CO = overestimation)
What would the PSV + stent-aortic ratio be with RA stents?
PSV: >240 cm/s
Ratio: >3.2
What imaging plane are prox RA stents best seen in?
TRV
Pediatric kidney length?
4-6cm
How do pediatric kidneys differ from adults?
-Lower in abdomen
-Cortex lobulations
-Parenchyma more echogenic
-Pyramids prominent
-Sinus less echogenic
RA stenosis in peds is diagnosed on what 3 criteria?
-Elevated PSV
-Delayed systolic upstroke
-Presence of post stenotic turbulence
RV thrombosis should be suspected in pt’s with what 2 things?
-Hypercoagulable states
-Suspicion of RCC or Wilms tumor with extension into RVs or IVC
SF of acute vs chronic thrombosis?
Acute: dilated RV + enlarged kidney
Chronic: contracted RV + kidney atrophy
If RV thrombosis is present, how will the RAs appear on spectral?
Retrograde + blunted diastolic flow
If RV thrombosis is present, how will spectral doppler appear prox + dist to it?
Prox: continuous, non-phasic, low velocity flow
Dist: no/minimal flow, phasic if collaterals present
