Native & Transplant Livers Vasculature Flashcards
What artery is the primary blood supplier of the liver?
Hepatic artery
What % of blood from the HA feeds the liver?
30%
Whats the flow pattern of the HA?
Low resistance flow pattern
How is the proximal HA best visualized?
In transverse at the level of the celiac axis
How is the distal HA best visualized?
Intercostally at the level of the MPV
Why is fill in of the spectral windows seen within the vessels?
Due to the small diameter
Is there specific PSV criteria?
No
What exams is the intrahepatic artery included in?
Liver duplex exams
Pre and post liver transplant studies
To rule out veno-occlusive dx in bone marrow transplant pts
Will the HA appear normal if the celiac axis is occluded? Why?
Yes due to collateralization
Where does collateralization occur?
Through the pancreaticoduodenal network of vessels that surround the pancreas and duodenum
Where do the hepatic veins dump into the IVC?
Just inferior to the diaphragm
Intracostal scans are used to best visualize what part of the IVC?
Intrahepatic portion
What kind of waveform does the IVC have with respiratory variations?
Spontaneous waveform
What are some factors that cause the size of the IVC to vary?
Size or pt, respiration and right arterial pressure
What happens to the IVC it moves more proximal (near the heart)?
Becomes pulsatile
What happens to the IVC as you move more distal (towards LEs)?
Becomes phasic with respiration
What is the most common accessory HV?
RHV
Are accessory hepatic veins common to visualize?
No, they are common but difficult to visualize
How does the RHV run within the right lobe?
Runs coronally b/w the anterior and posterior segments of the right lobe
How does the LHV run within the left lobe?
Runs between the medial and lateral segments of the left lobe
Does the caudate lobe have its own drainage from the IVC?
Yes
What HV commonly join together before entering the IVC?
LHV and MHV
In the case of agenesis what HV is usually absent?
RHV
What scanning approach do you use to visualize the hepatic veins?
Transverse, subxiphoid scan plan
What is the flow pattern of the HVs?
Multi-phasic, pulsatile flow pattern
When is the patency of the vein most important?
When the Budd-Chiari syndrome is suspected
What happens to the HVs when affects by CHF?
HVs dilate
What type of blood does the portal venous system drain?
Nutrient rich blood from bowel and spleen
Where does the portal vein begin?
Junction of the splenic and SMV
Where does the portal vein enter the liver?
Porta hepatis and branches into the right and left segments
What are other tributaries of the portal system?
Coronary vein and IMV
How is the portal vein best visualized?
In an oblique plane- intercostal approach may be used
What is scanning the liver vasculature dependent on?
Body habitus
What type of flow does the portal vein have?
Low velocity, cont. signal with subtle phasic variations
What is the velocity of the portal vein?
15-40cm/sec
What is the mean velocity of the portal vein?
15-18cm/sec
What is normal flow in the portal vein and its tributaries?
Toward the liver- hepatopetal
When does flow within the portal system increase?
Post-pradially
What is cavernous transformation of the portal vein?
numerous collaterals in the porta hepatis in the event of a thrombosis
MPV will not be visualized
What is portal hypertension?
Elevated pressure in the portal venous system
What does portal hypertension cause?
Impedance of blood flow through the liver
What are the causes of portal hypertension?
Volume overload or increased resistance to flow
When can portal hypertension occur? (3)
- Pre-hepatic
- Intrahepatic
- Post-hepatic
What is the most common portal hypertension?
Intrahepatic
What conditions can causes of pre-hepatic portal hypertension?
Portal or splenic thrombosis
Portal or splenic vein invasion
Extrinsic compression by tumor
What conditions can cause intrahepatic hypertension?
Hepatocellular dx- cirrhosis
Hepatitis
Fatty infiltration
What conditions can cause post-hepatic hypertension?
Thrombosis of hepatic veins (Bud Chiari) or IVC
CHF
Right sided heart dx
What are the risk factors for portal hypertension? (2)
Chronic liver dx that precedes fibrosis or cirrhosis
Heart dx resulting in increased right sided pressures
What conditions can cause chronic liver dx that precedes fibrosis or cirrhosis? (6)
- Viral hepatitis: chronic Hep B or C
Alcoholic liver dx - Autoimmune disorders: primary biliary cirrhosis, primary sclerosing cholangitis
- Metabolic and genetic disorders- hemochromatosis, Wilsons dx
- Schistosomiasis
- Non-alcoholic steatohepatits (NASH)
- Sarcoidosis
What conditions can cause heart dx resulting in increased right sided heart pressure? (3)
- Tricuspid regurgitation
- CHF
- Constrictive pericarditis
What are the clinical signs for portal hypertension?
Ascites, splenomegaly, GI bleed, jaundice, abnormal LFTs
What is the most common sign of cirrhosis?
Jaundice
Are all pts symptomatic when they have portal hypertension?
No, some are asymptomatic
What is an example when manifestations of liver dx and conditions associated with its cause?
Pancreatitis if alcohol related
What are additional pt history/signs of portal hypertension?
Variceal hemorrhage (hematemesis and melena) Bacterial peritonitis
What can be concluded in a physical examination of portal hypertension? (4)
- Jaundice
- Splenomegaly (can lead to low platelet counts)
- Dilated abdominal wall veins
- Hepatic encephalopathy (confusion due to poor liver function)
2-D sonographic evaluation includes documentation of what?
- Portal vein diameter >13mm (normal <13mm)
- Cavernous transformation (intra-abdominal collaterals)
- Portocaval anastomoses
- Dilation/recanalization of the umbilical vein
- Splenomegaly (>13cm)
Duplex evaluation includes documentation of the following…
Color flow or lack of color flow within vessels including collaterals
Direction of flow
Loss of phasic variations (response to respirations)
Presence or absence of thrombosis
Mean velocity
Waveform changes
CHF
Why are we looking for color flow or lack of color flow within vessels and collaterals?
Shows potency of MPV and branches
How does the waveform change in pts with portal hypertension?
Changes to bi-phasic and ultimately reverses as pressure increases
Why mights power doppler be needed to document vessel fill in?
Due to tortuosity of vessels and collaterals
Portal vein thrombosis can occur in pts with what sort of conditions?
- Liver dx
- Hypercoagulable states
- Intestinal inflammation (appendicitis/diverticulitis)
What does portal vein thrombosis cause?
Increased resistance in portal venous circulation
How does a portal vein thrombosis appear on US?
Enlarged or normal vein that is filled with low level echo or is anechoic
Lack of flow
When is collateral flow with portal vein thrombosis?
Chronic portal vein thrombosis
What happens to the HA when PVT is present?
Enlarged HA and flow
Can tumors (hepatocellular or pancreatic carcinoma) invade the portal vein?
Yes- presence of arterial flow within thrombosis may be documented
What may seen at the site of obstruction in a PVT?
Partial blockage, increased velocities and disturbed flow patterns
What is seen in patent segments distal to a PVT?
Continuous flow with no respiratory changes
Is portal vein occlusion permanent?
Yes
What do fibrotic changes cause when portal vein occlusion is permanent?
Cause vessel to virtually disappear sonographically
What are the 3 pitfalls to be aware of when scanning a portal vein occlusion?
- Undetected anechoic tumor/thrombus
- Low velocity flow undetected
- Inadequate doppler age precluding detection of flow
When does hepatic vein occlusion mostly occur?
Hyper coagulable states- polycythemia or hemogloblinuria leading to thrombosis
What are other reasons for hepatic vein occlusion to occur?
Cirrhosis or tumor invasion
What are the clinical manifestations of Budd-chiari syndrome?
- Hepatomegaly
- Abdominal pain
- Acute development of ascitis
- Abnormal liver function tests
- Splenomegaly and collaterals may be evident in chronic areas
When is hepatic vein occlusion considered a positive finding?
Presence of thrombosis or tutors with absence of flow
What may be seen in hepatic vein occlusion when veins are narrowed?
Focal evaluation of velocity and turbulence
In hepatic vein occlusion what do the collaterals connect?
Patent hepatic veins to portal system
Why should the IVC be evaluated when considering a HV occlusion?
To rule out thrombosis or tutor causing secondary obstruction to the HVs
Describe the normal flow of the portal veins
Low velocity, hepatopedal flow with respiration variation
Max velocity vary within 15-30 cm/s
Describe the normal flow of the HA
Low resistance flow
PSV range 70-150cm/s
Describe the flow of the HV
Multiphasic flow pattern
What occurs with right sided heart failure/tricuspid regurgitation?
Increased HV and PV pulsatility
What occurs with portal hypertension?
- hepatofugal (reverse) flow in MPV, SV or SMV
- slow portal vein flow
- Portal veins altering b/w retrograde and antegrade flow
- MPV >13cm
- SV >10mm
- PVT +/- cavernous transformation
- Patent paraumbilical vein >2.5mm
- Presence of other portosystemic collateral
- Spleen coronal length >13cm
- Presence of ascites
What occurs with the Budd-Chiari syndrome?
- decreased, absent, or reversed flow in any of the HV
- narrowing of IVC
- intrahepatic hepatic venovenous collaterals
- echogenic thrombus in HV or IVC
- dampened spectral tracing in HV
- caudate lobe hypertrophy
What are tributary collaterals?
Pre-exsting vessels that normally drain into the portal, splenic and mesenteric venous system
Flow directed towards the veins
What is the coronary vein also know as?
Left gastric vein
What is the most prevalent portosystemic collateral?
Left gastric vein
What % of retrograde flow occurs in the left gastric vein in pts with portal hypertension?
80-90%
Increased pressure in the left gastric vein indicates what?
Esophageal varices
Presence of a left gastric vein implies what?
Increased risk of vatical hemorrhage - most clinically important
Where is the left hepatic vein located?
Ant to the bifurcation of the CA or post to the common HA or SA
What is the orientation of the left gastric veins?
Oblique plane travelling superior and to the left of the portosplenic confluence
What are developed collaterals?
Vessels that are not normal tributaries but instead develop in the setting of portal hypertension
What is an example of a developed collateral?
Umbilical vein- easiest to identify
What is the umbilical vein?
Remnant from umbilical vein located in the ligamentum teres
Where does the umbilical vein travel?
Umbilicus to the anterior aspect of the umbilical segment of the LPV
Is the umbilicus vein hepatofugal or hepatopedal flow?
Hepatofugal (away from the liver)
What does the umbilical vein measure?
< 3mm and contains no blood
Why do porto-systemic shunts occur?
Effect of portal hypertension- obstructed blood takes secondary route- vessels dilate and become engorged (not built to take large loads- risk of hemorrhage)
Where is a common site of porto-systemic shunts?
Esophagus- giving rise to esophageal varices
Where do gastric varices occur?
Near stomach, under left lobe of the liver, near spleen
Where does the backup of blood flow go?
Into the draining organ- megaly
What is portal systemic shunting?
Change in majority of blood flow to other pathways
Examples of portal systemic shunts
Portocaval, mesocaval and splenorenal
Describe surgical shunts
- Surgical or endovascular to decompress portal system
- Stents are used
- Reduce ascites, prevent hemorrhage of varices and improve quality of life
When are surgical shunts used?
Severe portal hypertension or cirrhosis- risk of GI bleed
Describe transjugular intrahepatic portosystemic shunt (TIPS)
- Installed percutaneously
- Catheter passes down JV into HV through liver to the PV
What is the success rates of TIPS?
90%
What is an early complication of TIPS?
Obstruction or occlusion in the first few weeks due to thrombosis
What is a late complication of TIPS?
Neointimal hyperplasia invading the stent
Is hepatic vein end or beginning a common site of thrombosis?
HV end
Where is there competency flow seen with a TIPS?
HA
What should the peak velocity be within the shunt? What’s the normal range?
At least 50 cm/sec
Normal range 90-190cm/sec
What type of flow is seen within a shunt?
Pulsatile
Portal and splenic vein flow should be hepatopedal
What should the MPV caliber be?
15mm
Within a localized stenosis the velocity gradient is greater then what?
100cm/sec
What is the stent velocity when there is a shunt failure?
< 50cm/sec
What is the abnormal velocity in the PV (outside the TIP shunt)?
< 30cm/sec
What is the flow like within an abnormal TIPS?
Continuous flow or absence of flow
What type of US is used in the pre and post operative assessment of patients?
Duplex US
What included within the pre-operative screening?
- Documentation of patency of PV, HA, HV and IVC
- Other abnormalities (tumours/vasculature)
- Biliary tree status
What’s included within the post-operative assessment?
- Confirm latency of HA (most important), HV, PV, SV, IVC, mesenteric veins
- Flow direction
- Vessel size
- PV can be up to 15mm in a liver transplant pt
What are potential post-transplant complications?
- Rejection, pseudoaneurysm, hepatic infarction, thrombosis of major veins
- Stenosis may be shown at surgical anastomosis at follow up exams
- Viability of liver critical to HA inflow
- Sample HA at the proximal portion and CA due to tortuous path
- Hematoma, abscess formation or AV fistula
Has it been proven form studies that resistance increases in the artery if the graft rejected?
Yes
