Renal Arteries Flashcards
Renal Arteries anatomy in terms of location? Think left and right? 3
- From the aorta just distal to the RMA
- RRA comes off anteriolateral aorta and passes posterior IVC
- LRA comes of lateral and posterolateral aorta
20% of kidneys supplied by what?
Duplicated or accessory arteries
Renal arteries divided how in the renal pelvis?
Vessels that lie anterior and posterior to the renal pelvis, each supplying a different segment
How many segments of the renal arteries are there?
- 4 anterior segmental arteries
- 1 posterior segmental arteries
Segmental arteries branch into what?
Interlobar arteries that reach into the parenchyma
Segmental arteries terminate in what?
Arcuate arteries that lie at the cortico- medullary junction
Interlobar arteries branch off what?
Arcuate arteries in the peripheral cortex
What doe we do with the kidney before evaluating vessels? 2
- Assess kidney size and morphology
- Normal is 9-13 cm, can be as small as 8cm
What is the usually approach for interrogation of the renal arteries? 2
- Transverse, anterior, midline
- RRA can usually folow this way, but a coronal approach may be needed to follow the LRA
What factors contribute to the success of the renal artery exam? 3
- Artery depth
- Respiration
- Abdominal gas
What is usually done for renal artery exams in terms of patient prep?
12 hour fast and scanning in the morning possible to study 90% of patients
In terms of interrogation of the renal arteries, it is important to do what?
Assess the entire length of the vessel to avoid missing lesions
What probe is generally used for Renal artery exams?
2.5-3 MHz probe
LRV passes between the aorta and SMV entering what?
The left side of the IVC
LRV receives which veins?
Left suprarenal and left gonadal vein
Which Renal vein is shorter?
RRV is shorter than the left and extended directly to the hilum
The RRV does not accept what?
No tributaries but it is more common to find accessory veins draining directly into the IVC
Suprarenal (proximal) aortic signal has what kind of flow characteristics?
Low resistance, monophasic waveform because it is feeding a low resistance vascular bed up to this point
What is the velocity of the suprarenal (proximal) artery?
80-100 cm/sec
Distal to the renal arteries what happens to the pattern changes?
Pattern changes to a high resistance multiphasic with a reverse flow component
What are some normal flow characteristics of the renal artery? 3
- Normal low resistance
- Early systolic peak/ compliance peak, may be seen on the upstroke to systole
- 74-127 cm/s
What parts of the renal artery do we assess? (With U/S)
Origin, mid, distal
In the renal artery, what is considered abnormal in terms of velocity and stenosis?
> 180 cm/sec, indicates stenosis >60^
What is the renal artery PSV to Aortic PSV ratio (RAR)?
Normally <3.5
Segmental artery’s have how many branches?
Multiple
What is the doppler waveform of segmental arteries like?
Similar to distal renal artery but with lower velocities
What is the normal segmental artery look like? (Think waveform)
Sharp systolic upstroke and ESP
What does abnormal segmental artery spectral look like?
Delayed AT and rounded peak
Where are Interlobar arteries located?
Between collecting system calyces
In terms of Interlobar arteries, doppler signals are obtained where? 3
- Upper
- Mid
- Lower poles
Where are arcuate and lnterlobular attires located?
Cortical region of the kidney and are called the parenchymal arteries
Where are the renal veins located and what is their normal flow characteristics like? 3
- Near the IVC
- Multiphasic pattern due to proximity to the IVC and heart
- Dismally they have phasic flow, vessel diameter changes with respiration
Stenosis or occlusion of renal artery may cause what?
Ischemia leading to hypertension
Renal artery stenosis is the most common cause of what? 3
- Secondary hypertension
- Chronic renal insufficiency
- End stage renal disease
Renal artery stenosis can cause what kind of damage?
Parenchyma damage
In terms of renal artery stenosis/ occlusion, Colour flow does what?
Locates the arteries and detects flow disturbances which indicates stenosis
In terms of renal artery stenosis/ occlusion, doppler spectral determines what?
Quantifies stenosis severity
Hemodynamically significant stenosis have a >60% diameter reduction
What are some situations where renal artery stasis should be investigated in? 9
- Sudden onset or acceleration of chronic hypertension
- Unexplained renal insufficiency
- Abdominal bruit
- Azotemia - elevation of nitrogen, creatinine and other waste in your blood
- Decreased serum potassium
- Recurrent congestive heart failure
- Pulmonary edema
- Unilateral strophic kidney and discrepancy renal size greater than 1.5 cm
- Hypertensive children
Renal artery stenosis can result from several conditions including what? 9
- Atherosclerosis - Most common (90%) , older population >50
- FMD - usually <40 year olds
- Dissection extending into the renal arterie s
- Aneurysms of the main or segmental arteries
- Aortic coarctation proximal to the renal artery origins
- Arteriovenous fistula
- Arteritis (vasculitis)
- Extrinsic compression of the renal artery and/or vein by tumor/masses
- Radiation
What is the most correctable cause of hypertension?
Renal artery stenosis
What are some things we can do to interprete a renal artery stenosis <60%? 4
- Grayscale may demonstrate atherosclerotic plaque
- COlour flow helps identify disturbed flow and lumen narrowing
- With narrowing <60% it is not yet severe enough to cause a decrease in pressure and flow distal to the lesion
- Post- stenotic turbulence is not present
How do we interpret renal artery stenosis >60%? 4 (What do we see?)
- PSV increases significantly
- Post stenotic turbulence is present
- PSV of >180 cm/sec and renal/aortic ratio (RAR) of >3.5 indicate significant stenosis
- Renal infarcts (hypoechoic ares within the kidney) may be seen
How do we interpret renal artery stenosis >80%? 4 (How does the waveform look like?)
- Systolic upstroke is delayed
- Early system peak (ESP) is lost
- PSV decreases dismally, monophasic (tarsus parvus)
- In the absence of elevated renovascuar resistance diastolic flow will be maintained
How do we interpret renal artery occlusion? 3( how do we confirm it, what is the renal flow like?)
- Confirmed by usuing optimized spectral, colour, and power doppler to demonstrate the abscence of flow
- Non- visualization of the main renal artery
- Absent or very low flow and dampened renal flow (hypoperfusion)
In terms of a renal artery occlusion, the kidney is supplied by adrenal and ureteral collaterals, what is seen in the renal medulla and cortex?
Low velocity doppler signals
In terms of a renal artery occlusion, What is the PSV of the cortex and what is the renal length?
PSV in the cortex is usually <10cm/sec and renal length is often less than 9cm
In terms of interpretation of renal artery occlusion, we should avoid a false- positive diagnose of renal artery occlusion when we see what?
When there is poor visualization of the kidney and the artery
In terms of intrinsic parenchymal dysfunction, we need to do what?
Obtain spectral waveforms throughout the parenchymal vessels in the media and cortex of the kidney
What is the normal intrinsic parenchymal dysfunction waveform?
Low resistance
In terms of intrinsic parenchymal dysfunction, what is the abnormal waveform?
High resistance waveform, associated with parenchymal dysfunction/ medical renal disease
In terms of abnormal intrinsic parenchymal dysfunction, the degree of Reno vascular resistance can be determined by what?
RI
RI of what is indicative of medical renal disease?
> 0.8
Urinary tract obstruction, acute and chronic parenchymal disease can cause what to happen in the kidney?
Increased resistance within the kidney
What is the most common outcome from renal vein thrombosis?
Primary renal disease
RV thrombosis is also caused by what? 8 (Besides the main cause)
Other conditions such as
1. Hypercoaguable states
2. Renal
3. IVC
4. IVC or ovarian tumor thrombus
5. Abdominal surgery
6. Surgery
7. Trauma
8. Dehydration
Renal veins may be blocked by what? 2
Intraluminal thrombus or by extrinsic compression
Renal vein thrombosis causes what? (2, disease and what it leads to)
Parenchymal disease and leads to renal failure
What does renal veins look like normally with u/s? 2
- Anechoic lumen
- Respirophasicity throughout all visualized segments
What does abnormal renal veins look like? 3
- Intraluminal echoes
- Continuous, non phasic, low velocity flow seen proximal to thromboses Venous segments
- Minimally phasic flow is seen dismally if the thromboses segment has recanalized or if collaterals have developed
If the renal veins are severely damaged by thrombosis, what can be seen happen to the renals? 2
- Renal atrophy may be seen
- May have increased echogenicity compared to the normal contra lateral organ
Chronic RV thrombosis presents as what? (asymptomatic/ symptomatic or diseases)
Asymptomatic or presents with nephrotic syndrome (hydro Proteinuria) or hematuria
How does Acute RV thrombosis present in terms of S/S? 3
- Pain and hematuria
- Vein is often dilated and respirophasic flow is absent
- Kidney is usually enlarged with a variable echogenic pattern throughout the medulla and cortex
What is nutcracker syndrome? 2 (what it looks like, and what is the spectral look like?)
- Left renal vein is compressed by the mesentery or SMA
- High velocity signal associated with a colour bruit may be seen in the vein as it crosses anterior to the aorta
In terms of renal stents, lesions occur most frequently where?
In the proximal renal artery and are amenable to Percutaneous transluminal angioplasty (PTA) with or without stenting
What does contrast arteriography provide?
Anatomical information