Renal Vasculature Flashcards
What are the triangular-shaped structures within the inner portion of the kidney that carry urine from the cortex to the renal pelvis?
Renal pyramids
The RRA courses (blank) from the Ao, then passes (blank) to the IVC?
Anterolateral; posterior
What vessel courses anterior to the Ao, posterior to the SMA, and anterior to both renal arteries?
A) Splenic vein
B) RRV
C) LRV
D) IMV
C
What renal artery segments does atherosclerotic disease typically occur?
Origin to proximal third
At what level is spectral doppler with PSV needed from the aorta for use in the renal-aortic ratio?
Proximal - at level of celiac axis and SMA
When comparing renal length from side to side, how much of a difference suggests compromised flow in the smaller kidney?
3 cm
Using what angle of insonation are flow patterns within the kidney parenchyma typically obtained with a spectral doppler?
0 degrees
What is the normal spectral Doppler waveform in the renal artery?
Low resistance, high diastolic flow with velocities in the range of 90-120 cm/s
What will NOT occur on spectral doppler distal to significant stenosis or renal artery?
Increased peak systolic velocity
What is measured to determine acceleration time?
Onset of systole to the early systolic peak/initial compliance peak
During renal evaluation, the LRV near the hilum of the kidney has continuous, non-phasic low-flow velocity. What might this suggest?
Proximal renal vein thrombosis
Patients with sudden onset of chronic hypertension, azotemia, unexplained renal insufficiency, or pulmonary edema should be evaluated for what?
Renal artery stenosis
The renal arteries lie below what plane?
Transpyloric
The left renal vein courses posterior or anterior to the Ao?
Anterior
When kidney parenchymal disease is present, what will happen to the resistance and diastolic flow?
Increased resistance; decreased diastolic flow
Diagnostic criteria for identifying renal artery stenosis are based on the ratio between what structures? What must the ratio be to diagnose disease?
Renal-aortic ratio. Must be greater than 3.5 to diagnose.
What typically occurs to the velocity in a stented renal artery?
Increases
What is the most common cause of renal artery stenosis in a pediatric patient?
FMD
For renal artery stenosis, what are the PSV and percent of stenosis correlations?
- PSV >180cm/s with distal turbulence correlates with a >60% stenosis
- PSV >180cm/s without distal turbulence correlates with a <60% stenosis
- Renal-aortic ratio (RAR) greater than 3.5 correlates with a >60% stenosis
- Acceleration index at renal hilum <3.78 or acceleration time >100ms is consistent with stenosis.
Intrinsic renal parenchymal disease is characterized by what parameters?
- Increased resistance
- RI greater than 0.8
- Diastolic to systolic ratio less than 0.3
Does the RRA course anterior or posterior to the IVC?
Posterior
FMD typically causes stenosis in what segments of the renal artery?
Mid-distal
What is the classic appearance of FMD in the renal artery?
“String of pearls”
What pathology is being observed with the renal-aortic ratio?
Renal artery stenosis - greater than 3.5 indicates stenosis
Renal artery stenosis is typically caused by what two things?
- Atherosclerosis
- FMD
What is the term for the opening of the renal artery from the aortic wall?
Renal ostium
What most common cause of secondary hypertension, chronic renal insufficiency, and incident end-stage renal disease?
Renal artery stenosis
Presentation of renal artery stenosis?
- Sudden onset of hypertension
- Azotemia
Which kidney is more inferior?
Right
What is the normal renal length?
9-13cm
Between which vertebrae are the kidneys seen?
T12-L3
What is the most common anomaly of the kidney?
Horseshoe kidney - isthmus lies anterior to the Ao
In the case of horseshoe kidney, the renal arteries may be supplies by what 3 other arteries?
- Distal Ao
- IMA
- Iliac arteries
Where do the renal arteries lie in relation to the renal veins?
Renal arteries are posterior to the veins
What is the most common congenital anomaly of the kidney?
Duplicated collecting system
What is the pathway of flow through the kidney beginning at the Ao?
Ao -> RA -> Interlobar A -> Arcuate A -> Interlobular A -> Afferent arteriole -> Efferent arteriole -> Capillaries -> Interlobular V -> Arcuate V -> Interlobar V -> RV -> IVC
Atherosclerotic lesions of the renal arteries typically affect what segments?
Ostium to the proximal third
Is renal artery stenosis more common in men or women?
Men
What is the second most common cause of renovascular disease?
FMD
What segments does FMD usually affect in the renal arteries?
Mid-distal - more common in women - more often on RT side
What appearance is seen with RA FMD?
String of beads
What segments of the renal arteries can be examined when patient is supine vs when patient is RLD or LLD?
Supine - prox to mid segments
RLD or LLD - mis to distal segments and kidneys
Spectral waveforms are recorded from the abdominal aorta at the level of what?
Celiac trunk and SMA
Where do the renal arteries lie in relation the LRV?
Immediately inferior
What is the normal doppler signal in RA an Ao?
RA - low resistance with high end-diastolic flow
Ao - high resistance with low end-diastolic flow
Comparing kidneys side to side, a difference in how many cm suggests compromised flow on the side with the smaller kidney?
1cm
What is the PSV range of the Ao?
60-100 cm/s
What does the ESP (early systolic peak) represent in the renal artery waveform?
Elasticity of the arterial wall - as disease progresses, we lose that ESP
What is the normal doppler waveform seen in the renal veins?
- spontaneous
- phasic
- flow towards IVC
- Velocity: b/w 15- 30 m/s
Post-stenotic turbulence will NOT be seen in a stenosis less than what percent?
60%
What happens to the renal artery waveform if there is a stenosis >80%?
- Loss of sharp systolic peak/delayed upstroke
- PSV will decrease DISTALLY - tardus parvus waveform
What will doppler waveforms demonstrate with a renal artery occlusion?
Absence of flow in the main renal artery
What is the PSV and renal length seen with chronic RA occlusion?
PSV <10cm/s
length <9cm
What is intrinsic parenchymal destruction also called?
Medical renal disease
In the case of medical renal disease, what will be seen on doppler waveform within the RA?
High resistance and low end-diastolic flow
How to calculate resistive index?
(PSV - EDV)/PSV
What RI indicates medical renal disease?
Greater than 0.8
Calculate the RI when the PSV = 250cm/s and EDV = 67cm/s
0.73
Doppler reveals a PSV of 300cm/s and a EDV of 120cm/s. Does this patient have medical renal disease?
- Calculate the RI
- Does this patient have medical renal disease?
- Calculate RI: 0.6
- Does this RI indicate disease? NO, it is below 0.8
How do we evaluate indirect renal hilum?
Acceleration index (AI) and acceleration time (AT)
Is AI or AT more accurate?
AT
How do we calculate AI and AT?
AI - Slope of systolic upstroke/transmitted frequency
AI of 291cm/s squared or less = stenosis
AT - Calipers placed at onset of systole and early systolic peak
AT greater than 100ms suggests proximal renal artery disease
When should the renal-aortic ratio (RAR) NOT be used?
When AO PSV exceeds 100 cm/s or is less than 40 cm/s
If a patient has increased cardiac output, will a possible stenosis be over or underestimated?
UNDER
If a patient has decreased cardio output, will a possible stenosis be over or underestimated?
OVER
What may be seen with a re-stenosis of a renal artery stent?
- high-velocity, post-stenotic turbulence, and dampening of the distal waveform
- PSV threshold value of >240 cm/s
- stent–aortic ratio of 3.2 or greater
What is the typical length of a pediatric kidney?
4-6cm
In renal vein thrombosis, what will be seen in the doppler waveform proximally and distally?
Proximal to thrombosed venous segment: Continuous, non-phasic, low-velocity flow
Distal to thrombosed segment: no flow or minimal, phasic flow if venous collaterals have developed
What will be seen on doppler with renal arteries in the case of renal vein thrombus?
Retrograde, blunted diastolic flow components throughout the renal parenchyma
