DMST 343 (Vasc 3) - Renal and Mesenteric Vasculature

What is the anatomical relationship between the LRV and the SMA?

The LRV is posterior to the SMA

What is the anatomical relationship between the RRA and the IVC?

The RRA is posterior to the IVC

What are the segmental arteries?

Within the kidney, the renal artery divides into several segmental arteries, which branch into the interlobar arteries

What are the interlobar arteries?

Branches of the segmental artery that enter the parenchyma and pass through the renal columns, between the pyramids

What are the arcuate arteries?

Branches of the interlobar arteries and are wrapped around the pyramids

What are the interlobular arteries?

Branches of the arcuate arteries that project into the renal cortex

What is the "banana peel"?

An image of the aorta in a coronal plane where you can see both the RRA and the LRA branching off the side

What is a normal waveform for the Prox aorta?

Low (moderate) resistance, monophasic, 60-100cm/s

What is a normal waveform for the aorta distal to the renals?

High resistance, multiphasic

What is a normal waveform for the renal artery?

Low resistance, 75-125cm/s

Does the velocity of renal arteries increase or decrease as it gets closer to the kidney?

Decrease

What is an ESP?

Early systolic peak (compliance peak)

Reflects the elasticity of the arterial wall

T/F: there is an ESP on abnormal waveforms

False

T/F: the absence of an ESP always indicates an abnormal waveform

False

Should you use a high or low sweep speed on the renal arteries?

High

What is a RAR?

Renal artery ratio

Compares the highest renal artery PSV to the Prox ao PSV

What is the normal RAR?

<3.5

What should the AT be of a normal segmental/interlobar/arcuate artery?

Acceleration time <100ms

What should the RI be of a normal segmental/interlobar/arcuate artery?

<0.75

What is the normal for an RI?

RI = (S-D)/S

What is the most common cause of secondary HTN?

Renal artery stenosis

What is the most correctable cause of HTN?

RAS

How does RAS cause HTN?

Decreased flow in the renin-angiotensin system

What is the renin-angiotensin system?

- Stenosis causes decreased flow/pressure in the kidneys

- Low pressure in kidney release renin

- Renin is converted to angiotensin III

- This causes vasoconstriction, sodium retention and increased thirst

- The result is HTN

What is the most common cause of RAS?

Atherosclerosis

What is the second most common cause of RAS?

FMD

What are some risk factors of RAS?

Age

DM

High cholesterol

Smoking

CAD

PAD

How does a patient with RAS present (S/S)?

- New onset or chronic HTN

- Abdominal bruit

- Decreased renal function

- Recurrent CHF

- Discrepant renal size

- HTN in kids

Duplex U/S has ______% accuracy for identifying RAS

80-90%

What is the PSV of a RAS of >/= 60%?

> 180cm/s

What is the RAR of a RAS do

> 3.5

At what percentage of RAS is post-stenotic turbulence not seen?

<60%

What is a tell tale sign in the waveform that a RAS is >80%?

ESP is lost

RAS indirect assessment picks up most RAS >____%

60

What are some signs of a renal artery occlusion?

Small kidney (<9cm)

Low flow in intrarenal arteries

What portion of the renal artery is the most likely to get stenosed?

Proximal

What does the string of pearls sign indicate?

FMD

What is FMD?

Fibromuscular dysplasia - widening and narrowing of a vessel

In what demographic is FMD most common in?

Female, child bearing age

Is FMD of the renal arteries usually unilateral or bilateral?

Bilateral

If RAS starts at the mid renal artery, what is suspected?

FMD

What two things can cause renal vein thrombosis?

- Intraluminal thrombus

- Extrinsic compression

What is the most common predisposing factor for renal vein thrombosis?

Primary renal disease

What are all of the predisposing factors for renal vein thrombosis?

Primary renal disease

Hypercoaguable states

Tumours

Abdominal surgery/trauma

What are some S/S of renal vein thrombosis?

Depends on cause but generally:

- Pain

- Hematuria

- Nausea and vomiting

- PE

- Renal failure s/s

Why can chronic renal vein clot be difficult to detect?

Because chronic clot can mimic normal flow in grayscale

What is the appearance of acute renal vein thrombosis?

Dilated vein

Renal enlargement

What is nutcracker syndrome?

When the LRV is compressed by the SMA against the aorta

What is the U/S appearance of nutcracker syndrome?

High velocity flow

Colour bruit

What can cause medical renal disease?

- Glomerulonephritis

- PCKD

- Acute tubular necrosis

- Obstructive hydronephrosis

- Diabetic neuropathy

What is medical renal disease?

Disease causing flow changes to the parenchymal arteries

An RI of > 0.7 is predictive of what?

Medical renal disease

What is medical renal disease AKA?

Parenchymal dysfunction

Why would CES be used for a renal study?

- TDS

- Flow detection improves

- Improves mass differentiation

Why aren't MRA and CTA scans done on patients with renal insufficiency?

The contrast agent may be nephrotoxic

What is hemodialysis?

A process used to filter the blood and act as a nephron when a patient has end-stage renal disease

Explain how hemodialysis works

The blood is pumped out of the body, into a machine and is filtered through a semi-permeable membrane outside of the body. The clean blood is pumped back into the body

Why is an AV connection required for hemodialysis?

Why are grafts/fistulas created as distal as possible for hemodialysis?

To allow proximal access if the initial attempt fails

What is the most common type of fistula created for dialysis? Where is it?

Brescia-Cimino fistula

It is at the wrist

What is the role of sonography with hemodialysis grafts and fistulas?

- Pre-op:

- assess arteries and veins for fistula suitability

- Post-op:

-assess for stenosis/occlusion of AVF/graft

- non-stenotic indications

What is involved in the pre-op assessment for hemodialysis grafts/fistulas?

Full UE arterial & venous study, plus vessels in the forearm

What is the most common complication of AVF/grafts?

Stenosis

What is the most common cause of graft/fistula failure in the first month?

Thrombosis

What are some non-stenotic indications for a post-op assessment of hemodialysis grafts/fistulas?

- AVF maturity

- Pesudoaneurysm

- Hematoma

- Peri-graft abscess

- Aneurysmal fistula dilation

Do you need high or low flow settings for graft and fistula assessments?

High flow settings (increased scale, low gains)

What is the normal flow before and within a graft/fistula?

Low resistance

Constant, antegrade flow

What is needed to calculate the outflow volume of a graft/fistula?

- Time averaged velocity (3 cycles)

- Fistula diameter

Is there a higher rate of flow through a graft or fistula?

Graft

What is the normal flow ratio of a fistula at the anastomosis?

< 3

What is the normal flow ratio of a fistula at the draining vein?

< 2

What is the normal flow ratio of a graft?

< 2

What is the normal PSV in a graft/fistula?

< 400cm/s

What is seen on 2D with a stenotic fistula (>/=50%)?

- Intraluminal echoes

- Thickened walls

What is seen on colour with a stenotic fistula (>/=50%)?

- Reduced lumen fill

- Disturbed colour flow

What is seen on spectral with a stenotic fistula (>/=50%)?

- Velocity > 400cm/s

- Ratio > 2 for feeding artery or outflow vein

- Ration > 3 @ anastomosis

What is seen on 2D with an occluded fistula?

- Echogenic lumen

What is seen on colour with an occluded fistula?

- No flow

What is seen on spectral with an occluded fistula?

- Absent waveform

- Proximal arterial flow, high resistance

What is an arterial steal with a graft/fistula?

The graft steals from a more caudal artery

When does an arterial steal with a graft/fistula occur?

When the venous outflow exceeds inflow from the artery

What kind of flow in the distal artery is seen with an arterial steal with a graft/fistula?

Retrograde

What are the symptoms with an arterial steal with a graft/fistula?

Usually asymptomatic but can cause pain, weakness, paresthesia and hand ischemia

T/F: arterial steals with a graft/fistula are common

True

What is the treatment of choice for chronic renal failure?

Renal transplant

What can cause chronic renal failure?

DM

PCKD

Glomerulonephritis

HTN

Atherosclerosis

Systemic lupus erythematosus

What is a renal allograft?

Kidney transplant

Where are kidneys for transplants harvested from?

Living donor or cadaveric donor

Where are transplanted kidneys places?

Right ililac fossa

What is the non-refluxing UV junction?

Where the donor ureter is placed into the bladder (through the bladder muscle)

Where are the renal arteries and veins anastomosed with a kidney transplant?

External iliac artery and vein

What is the sonographic appearance of a transplanted kidney?

- Cortex may appear more echogenic (d/t the lack for attenuation over it)

- Enlarged (~13-14cm)

- Mild hydronephrosis

Why are transplanted kidneys enlarged?

D/t compensatory enlargement (taking over for 2 kidneys)

When is the baseline U/S done post-op of a kidney transplant?

1-2 days

Do the arterial velocities increase or decrease as you sample deeper into the arterial vasculature of the kidney?

Decrease

What are some kidney transplant complication?

- Fluid collections

- Hydronephrosis

- Acute tubular necrosis (ATN)

- Rejection

- AV fistula

- Peseudoaneurysm

- Arterial stenosis

- Venous thrombosis

T/F: fluid collections post-op kidney transplant are common

True

What are some examples of what the fluid collection post-op kidney transplant could be?

Hematoma/Abscess/Urinoma/Lymphoma, etc.

What can cause hydronephrosis post kidney transplant?

Ureters may be compressed d/t scarring or external compression

What does ATN stand for?

Acute Tubular Necrosis