Module 1: Renal Vasculature Flashcards
where do the renal arteries arise from
- arise from the aorta just distal to the SMA
what is the pathway of the RRA
- arise from anterolateral aspect of the aorta traveling posterior to IVC
what is the pathway of the LRA
- arises from lateral or posterolateral aspect of the aorta
can renal arteries be duplicated
- yes
in what directions doe the renal arteries branch into
- anterior and posterior vessel
- travel anterior and posterior to the renal pelvis
how many anterior segmental arteries are there
- 4
how many posterior segmental arteries are there
- 1
what do the segmental arteries branch into
- interlobar arteries in the parenchyma
what do the interlobar arteries branch into and where
- arcuate arteries
- corticomedullary junction
what do the arcuate arteries branch into and where
- interlobular arteries
- peripheral cortex
protocol for renal assessment
- asses kidney size (8-12cm)
- arteries seen in transverse anterior midline
- RRA followed transverse from midline
- LRA followed coronally
- asses entire length of the vessel
what three factors add to the difficulty of the renal interrogation
- artery depth
- respiration
- abdominal gas
what is the pathway of the LRV
- passes between the aorta and the SMA entering left side of IVC
what two smaller veins drain into the LRV
- left suprarenal
- left gonadal
which renal vein is shorter right or left
- RRV
on which side are more accessory veins commonly found
- right
what is the flow pattern in the aorta proximal to the renal arteries
- low resistance
- sharp systolic upstroke with forward flow above t the baseline throughout diastole
- feeding low resistance vascular bed
what is the normal velocity of flow in the aorta suprarenaly
- 80-100cm/sec
what is the flow pattern in the aorta distal to the renal arteries
- high resistance
- reverse flow component
what is the flow pattern in the main renal artery
- low resistance forward flow
- sharp systolic peak
- supplies low resistance vascular bed
what is the normal velocity of the main renal artery
- 74-127cm/sec
where is the main renal artery sampled ideally
- prox mid and distal
what velocity in the main renal artery suggests a stenosis >/= 60%
- > 180cm/sec
what is the normal renal artery PSV to aortic ratio (RAR)
< 3.5
what is the normal flow pattern in the segmental artery
- sharp systolic upstroke and dicrotic notch
- looks like distal renal artery with slower velocities due to multiple branches
normal characteristics of segmental artery flow
- presence of ESP
- AT < 0.07s
- RI < 0.75
abnormal characteristics of segmental artery flow
- AT > 0.1s
- tardus parvus waveform
- loss of ESP
- flatted systolic upstroke
- reduced color flow in kidney unilaterally
where are the interlobar arteries found and where are they sampled
- found between the collecting system calyces
- upper mid and lower pole of each kidney
what is the normal flow patterns of the interlobar arteries
- like segmental waveform
- 30-40cm/s
what is another name for the arcuate and interlobular arteries collectively and where are the found
- parenchymal arteries
- cortical region of kidney
what is the normal velocity of the parenchymal arteries
- 20-30cm/s
what is the end diastolic ration (EDR) used for
- determine an increase in resistance
what is the EDR equation
- end diastolic velocity (EDV) / peak systolic velocity (PSV)
what is the normal and abnormal EDR values
normal: >/= 0.33
abnormal: < 0.23
what is the flow pattern of the renal veins near the IVC
- pulsatile flow due to proximity to the heart
what is the flow pattern of the renal veins distal to the IVC
- phasic flow
what condition can be caused by stenosis or occlusion in the renal arteries
- renal ischemia leading to hypertension causing parenchymal damage
what ultrasound tool helps to indicate presence of a stenosis
- color flow
what ultrasound tool helps to quantify stenosis severity
- doppler spectral
what reduction in diameter indicates a hemodynamically significant stenosis in the renal arteries
- 50-60%
in what three conditions should renal artery stenosis be thoroughly investigated in
- young patients with hypertension
- patients with uncontrollable hypertension
- patients with renal insufficiency and discrepant kidney size
what is the most common cause of stenosis in patients >50
atherosclerosis
what is a common cause fo stenosis in patients < 40
fibromuscular dysplasia (FMD)
what are 4 less common causes of stenosis in the renal arteries
- vasculitis
- neurofibromatosis
- congenital bands
- extrinsic compression
what is the most correctable cause of hypertension
- renal artery stenosis
what PSV and renal/aortic ration indicates significant stenosis
- PSV >180cm/s
- RAR >3.5
what acceleration time AT suggests a renal stenosis of >60%
AT >0.07sec
what intervention is often used to persevere patency of the vessels
- stents
what are 4 signs of severe renal artery stenosis
- decreased renal size (renal atrophy)
- renal infarct (hypoechoic area within the kidney)
- renal hypo perfusion
- narrowed artery with area of aliasing and increased PSV
what are 2 signs of renal artery occlusion
- decreased kidney size
- no main artery visualized
- absent or very low flow and dampened intrarenal flow
what 2 other conditions can cause increased resistance in the kidneys
- urinary tract obstruction
- acute or chronic parenchymal disease
what are 2 common signs and symptoms of patients with acute RV thrombosis
- pain
- hematuria
what are 2 ultrasound findings of RV thrombosis
- enlarged kidney and altered parenchymal echogenicity
- enlarged renal vein with absent doppler signal
what are the signs and symptoms of chronic RV thrombosis
- asyptomatic
- nephrotic syndrome
- hematuria
in what 2 ways can the RV become blocked
- intraluminal thrombus
- extrinsic compression
what is the most common factor causing RV thrombosis
- primary renal disease
what 5 other factors can cause RV thrombus
- hyper coagulable states
- renal, IVC, Ovarian tumor thrombus
- abdominal surgery
- trauma
- dehydration
what is the eventual progression of RV thrombosis
- leads to parenchymal disease»_space; renal failure
can venous flow still be present in the kidney in the presence of and RV thrombus
- yes
- due to collateral vessels
what is the standard treatment for chronic renal failure
- renal transplants
what is an allograft
- any tissue transplanted from one human to another
where can a renal allograft be harvested from
- living, related donor
- brain dead donor
where is the transplanted kidney often located
- right iliac fossa between peritoneum and iliac muscle
is the native kidney and ureter removed after a transplant
- no they are left in place
what can develop on the native kidneys of long term dialysis patients
- cysts
- neoplasms
where is the allografted ureter placed and what does it form
- passes obliquely through the muscular layer of the bladder
- non refusing UV junction
how is the allografted vein anastomosed
- end to side anastomoses to the iliac vein
what is the appearance of the transplanted kidney compared to the native kidney
- very similar
what are 3 considerations to take when scanning the post transplanted kidney
- cortex may appear more echogenic due to superficial placement of kidney
- kidney may enlarge over a period of a month following transplant
- slight dilation of the collecting tubules (hydro) is common
when should a baseline post transplant study be done
- within 72 hours after surgery
what are 7 complications that can occur with a kidney transplant
- rejection
- acute tubular necrosis
- perigraft fluid
- pseudo aneurysm
- AV fistula
- venous/arterial thrombosis
- arterial stenosis
when can rejection be diagnosed sonographically
- should not be diagnosed with ultrasound unless several rejection abnormalities present
what will doppler look like with a rejection
- high resistance doppler waveforms minimal diastolic flow
- RI >/=0.7
what causes acute tubular necrosis post surgery
- ischemia
how is doppler affected with acute tubular necrosis
- not usually altered
- increase in PI maybe
are perigraft fluid collections commonly seen
- yes post op
what are 4 different types of perigraft fluid collections
- hematomas
- seromas
- abscesses
- urinomas
how is color doppler used when a fluid collection is identified
- use to see if there is active bleeding into the collections
where do most pseudo aneurysms occur and what from
- renal parenchyma
- arterial laceration after biopsy
- can also be seen near arterial anastomosis site
what should we try to identify in the neck of the pseudoaneurysm
- high velocity jet
what causes an AV fistula
- biopsy trauma
are AV fistulas symptomatic or asymptomatic
- asymptomatic
what condition can AV fistulas be associated with
sustained hypertension
what color and spectral doppler information can be obtained from an AV fistula
- coordinations doppler identifies fistula as a bright spot in renal parenchyma due to disturbed flow
- high velocity inferrer flow in the feeder artery appears like a bruit
are venous/arterial thrombosis common after transplants
- no
when does thrombosis occurs with a transplant
- immediately post op
what will venous arterial thrombus look like on ultrasound
- enlarged kidney
- renal vein distended
- absent flow signal in renal vein/artery
what is the most common vascular complication in transplant patients
- arterial stenosis
where is transplant stenosis usually located and why does it occur
- site of anastomosis
- due to a surgical issue
will older transplants have more or less stenosis
- long segment of stenosis due to scarring or hyperplasia
what will doppler look like with an arterial stenosis post transplant
- increased velocity in stenotic segment
- post stenotic turbulence and distal dampening in severe stenosis
what are the 9 indications for a fistula or graft doppler ultrasound
- inadequate dialysis
- thromboses access
- perigraft mass
- upper extremity swelling
- decreased thrill or pulse
- suspected steal
- infection
- bleeding
- post revision follow up
what are the 3 methods of evaluation of grafts or fistulas
- duplex ultrasound
- arteriography
- fistulography
where should we sample the PSV during the graft protocol
- native artery prox
- arterial anastomoses
- graft
- venous anastomosis
- venous outflow
where should we sample the PSV during the fistula protocol
- sample 2-3 sites distal to arterial anastomoses
what measurement should we be doing when interrogating fistulas and grafts
- volume flow
what is the volume flow equation
Q(ml/min) = TAV x area x 60
how do we rule out steal from native circulation with duplex ultrasound
- assess retrograde flow in the inflow artery distal to anastomosis
what type of thrombus is commonly seen with dialysis graft patients
- SCV thrombus
- rule out with upper extremity DVT exam
what is the normal flow pattern of the arterial limb
- high velocity
- continuous forward flow through diastole
- marked spectral broadening
what is the normal flow pattern of the venous limb
- slightly lower velocities than arterial limb
- mosts common site of stenosis /thrombosis
what is the normal PSV in a graft/fistula
100-400cm/s
what is the normal EDV in graft/fistula
60-200cm/s
what would an occlusion look like in a graft/fistula
- no flow detected in graft
- no flow in vein distal to fistula
- high resistance in artery leading to graft or fistula
- low venous outflow
what is the criteria (PSV and velocity ratio) for > 50% graft stenosis
- PSV > 400cm/s
- VR >/= 2:1 (50%) ; 3:1 (75%)
what is the criteria ( PSV and velocity ratio) for >50% fistula stenosis
- PSV > 400cm/s
- VR >/= 2:1 (50%); 3:1 (75%)
+ outflow cephalic vein >/= 3:1
graft flow volumes- what does < 350ml/min indicate
poor dialysis, pending graft failure
graft flow volumes - what does < 500 ml/min indicate
increased risk of graft failure
graft flow volumes - what does > 800ml/min indicate
normal flow range
graft flow volumes - what does > 1500ml/min indicate
possible congestive heart failure
AV fistula flow volumes - what does >500ml/min with 4mm outflow vein indicate
adequate dialysis
AV fistula flow volumes - what does >800ml/min indicate
normal
what are the 8 most common abnormalities seen with grafts and fistulas
- venous flow obstruction
- venous anastomosis stenosis
- pseudo aneurysms
- diffuse aneurysmal dilation
- hematoma
- perigraft abscess
- intimal flaps
- arterial anastomotic stenosis
what 4 things is ultrasound used for with dialysis grafts and fistulas
- identify graft lesions and monitor them
- initial baseline exams for follow up studies
- to help assess the maturity of an AV fistula graft
- identify grafts in jeopardy of failure
what is hemodialysis
- removal of certain elements from the blood through a semipermeable membrane while being circulated outside the body
what kind of vessel is required fro hemodialysis
- requires an easily accessed vessel than can tolerate multiple punctures and high flow
what is an AV fistula
- surgically created by connecting and artery and vein together to accomplish high flow situation where blood flows directly from the high pressure artery to a low pressure vein
what is a AV graft
- surgically inserted prosthetic graft or vein conduit connecting and artery and vein
what 6 things are hemodialysis grafts evaluated for with ultrasound
- stenosis
- thrombosis
- aneurysms
- pseudo aneurysms
- hematomas
- arterial steal from hand
what is the most common cause of graft failure in the first month of insertion
thrombosis of graft
are PSV’s or PSV ratios used more frequently when determining severity of stenosis
- PSV ratios
what is the normal PSV ratio for dialysis grafts
<2.0
what is the normal PSV ration for dialysis fistulas
< 3.0
arterial inflow in graft/fistula waveform above and below anastomosis
- above = low resistance
- below = high resistance
gray scale signs of abnormal grafts/ fistulas
- decreased lumen
- color jet
- increased velocities and post stenotic turbulence indicated significant stenosis
waveforms of abnormal grafts/fistulas
- decreased venous spontaneity and phasicity suggests obstruction in the outflow vein
- evaluate spontaneity, phasicity, and pulsatilityof the SCV and internal jugular veins
what abnormal PSV and PSV ratio indicate a >50% at venous anastomosis of a prosthetic graft
- PSV > 400cm/s
- PSV ratio >/= 1.9
what abnormal PSV ratio indicates >50% stenosis at the arterial inflow or venous outflow of a fistula
- PSV ratio > 2.0
what abnormal PSV ratio indicates >50% stenosis at the fistula anastomosis
- PSV ratio >3.0
what volume flow rate indicated suboptimal graft performance
<800 ml/min
what volume flow rate indicates suboptimal fistula performance
< 500 ml/min
