AAA Assessments Flashcards
AA & IVC scanning
Td: low frequency, curvilinear (C5-2)
1- transverse view approx 3-4 cm above umbilicus; top to bifurcation
2- longitudinal assessment of proximal AA & IVC
3- coronal plane view of AA, throughout its length, to obtain more accurate measurements
4- Iliac arteries; viewed in longitudinal & transverse planes
Heal-toeing: helps to get better colour views
Endoleak types
Type I (attachment site):
- proximal (1a) & distal (1b) leaks due to inadequate seal between device $ aortic/iliac wall.
- colour flow; often in form of jet at point of leak
Type II (collateral):
- some filling via lumbar vessels, inf+ mesenteric art+, or accessory art+
- may have Inflow only, some have Outflow via a second branch
- many will seal spontaneously after a month or two!!
Type III (tears):
- tears between limb & main body or tears in graft (rare!!)
Type IV (porosity):
- sweating or increased porosity of graft material, will gradually increase sac size in first month
- not possible to image in real time, serial surveillance scans show changes in diameter
- less common w newer graft technology
Type V (endotension):
- increase in max diameter with No identifiable endoleaks
Scanning AAA repair & EVAR; settings
Optimise to detect low velocity flow:
- reducing PRF or colour scale to 1-1.5 kHz
- increasing colour sensitivity/gain
- using Power Doppler
- setting wall filter to Minimum level
AAA Repair Vs EVAR
AAA Repair:
- open surg+ repair
- aneurysm opened, cleaned, & graft inserted into sac
- 7-10 days Hosp, 3-4 months recovery
EVAR:
- guide wire insertion of tailor made graft through femoral arteries
- 2 days Hosp, 2wks recovery
Scanning AAA rep+ & EVAR; technique
- obtain transverse image in middle of aneurysmal sac
- follow graft proximally to assess, ensuring bifurcation visible initially
- follow distally to aortic bifurcation
- anechoic areas in aneurysmal sac should be noted, could represent blood flow, & should be scrutinised carefully w colour flow imaging!
- Colour flow imaging over whole transverse view of AA
- record Max diameter (coronal plane)
- record prox+ neck (transverse) to monitor progression or aneurysmal Dx
- Colour flow imaging in longitudinal section (sagittal & coronal planes) to examine Flow thru graft & areas of stenosis (eg; kinking of graft)
- Spectral Doppler: assess the flow in graft limbs, & any abnormal areas, are shown on colour flow imaging
- Examine Sac for endoleaks in longitudinal orientation
Spectral Doppler AAA
Blind ending in the AAA;
- only one point of communication w No Outflow = Type II endoleak
- will create to-&-fro wave pattern
Separate entry & exit:
- net flow depicted in one directional wave form
EVAR Complications
Iatrogenic injury at catheter insertion site (of CFA)
- arteriovenous fistula
- pseudoaneurysm
- haematomas
- intimal flaps
- dissection
Abnormal IVC appearances
Tba
Anatomic variants of IVC
- persistence if the L precursor of the IVC can result in paired vena cavae or a L sided IVC
- if paired vena cavae; duplication often terminated at level of L renal vein, tho can extend superiorly & drain into azygos vein
- intra-hepatic portion of IVC can be congenitally absent; if so, under US hepatic veins can be seen directly draining into R atrium
Clinical indications for IVC scan
- checking for DVT; from lower limbs or iliac veins
- assess position of an IVC (canal) filter (inserted to prevent formation of PE)
- aorto-caval fistula; result of trauma/surg/enlarged AAA
- neoplastic obstruction;
Intra luminal tumours: arise from hepatic or renal veins & May obstruct/thromboses the IVC
Extrinsic tumours: partially or completely obstruct the IVC - resulting in dilated collateral veins & distension of distal IVC & iliac veins
IVC scan prep & technique
Scan prep:
- fasted for 6-8hrs prior, to eliminate overlying bowel gas
- Pt supine on exam table w head slightly elevated
Td:
- low freq+ curvilinear Td to allow adequate penetration
Technique:
- complete survey of transverse & longitudinal planes req+; from diaphragm to confluence of iliac veins
- Transverse: IVC has elliptical cross section- as the Td moves inferiority the IVC tributaries must be assessed
- Include: common iliac & external iliac veins in both Longitudinal & Transverse views
- Assess patency: cannot compress these veins, so need to use colour & spectral Doppler to assess. Phasicity of flow can be assessed by valsalva manoeuvre
AAA Scan Protocol
Transverse superior/mid:
- AA 1-2cm below level of celiac axis or SMA origin
- add anteroposterior measurement to confirm an aneurysm
Transverse distal AA:
- 1-2 cm above bifurcation
- add anteroposterior measurement when confirming an aneurysm
Transverse AA: 1-2 cm below bifurcation
Longitudinal AA:
- at the level of the celiac axis or SMA origin OR 1-2 cm below
- measurements anteroposterior
Longitudinal distal AA:
- w 1-2 cm above bifurcation
- w Measurement
AAA scan: indications
Hx: lower back pain, flank pain, or abdo pain w or without haemodynamic instability;
- palpable or pulsation abdo mass or abdo bruit
- Fam Hx of AAA
- follow-up of prev AAA
AAA US may be advised in:
- men >/= 65yrs
- women >/= 65yrs w cardiovasc* risk factors
- Pts >/=50yrs w Fam Hx aortic &/or peripheral vasc* aneurysmal Dx
- Pts w personal Hx peripheral vasc* aneurysmal Dx
- smokers
- hypertensive Pts
- Pts w connective tissue Dx (eg; Marian Synd*)
AAA US: contraindications
- body habit is may inhibit accurate assessment of AA
- difficult access: drains, scarring etc
AAA US: Tds, preset & positioning
Tds selection:
- curvilinear Tds will usually allow sufficient depth due to narrow freq range
- linear probe may be useful in very thin Pts, where necessary
- vector probes may be of limited value here
Preset:
- AAA setting
- abdo-gen or vasc-abdo/gen
- advanced settings may give better liminal definition but at the cost of depth of field (eg; harmonics & compound imaging)
- frame rate degradation is not an issued for AAA due to the static nature of the region of interest
Positioning:
- start w Pt in supine position
- L Lat decubitus may be useful for visualisation of the renal artery origins & bifurcation. May also shift bowel anteriorly & reduce limitations caused by overlying bowel gas.
