Sonography - Portal Venous Hypertension

Best Practices In Sonography

Sandra L.Hagen-Ansert, M.S., RDMS, RDCS
Charleston, South Carolina

Michael S. Getsinger RT®, RDMS, RVT
Charleston, South Carolina

Table of contents

Sonography - Portal Venous Hypertension

Type of Examination

Abdominal Doppler of the Hepatic Portal Circulation

Definition

Acute or chronic hepatocellular disease can block the flow of blood throughout the liver, causing it to back up into the hepatic portal circulation. This causes the blood pressure in the hepatic circulation to increase (portal hypertension). In an effort to relieve the pressure, collateral veins are formed that connect to the systemic veins. This is known as varicose veins and occurs most frequently in the area of the esophagus, stomach, and rectum. Rupture of these veins may cause massive bleeding that may result in death.

Objective

To identify the direction and patency of flow in the portal venous system, hepatic veins, and hepatic artery

Indication(s)

  • Suspected portal hypertension secondary to liver disease
  • Portal vein compression or thrombosis
  • Acute onset of hepatic vein occlusion (Budd-Chiari syndrome), constrictive pericarditis, or congestive heart failure with tricuspid regurgitation
  • Congenital/ traumatic/ or neoplastic arterioportal fistula

Limitations/Contraindications

  • bandages, surgical sutures
  • patient unable to suspend respiration
  • patient size
  • excessive bowel gas

Equipment & Supplies

  • Duplex imaging system: LOGIQ 700, LOGIQ 500
  • Transducers: 2-5MHz curved array (may be necessary to use lower frequency or multifrequency to penetrate the liver; the patient may be scanned with one frequency to image hepatic structures and then use a lower frequency Doppler to improve sensitivity and color fill-in. Harmonics may also improve the greyscale image.)
  • System setups for abdominal ultrasound evaluation
  • Ultrasound gel
  • Towels
  • Materials for documentation of the study [video, prints, film]

Patient Preparation & Positioning

  • The abdominal Doppler examination is explained to the patient and any questions are answered.
  • A history is obtained from the patient focusing on risk factors, signs, and symptoms of hepatocellular disease. Previous medical history relating to hepatocellular disease should be noted.
  • Any recent surgical intervention of shunt placement within the portal venous system is documented in the patient history work sheet.
  • The patient is placed initially in the supine position; the patient may be rolled into a slight left lateral decubitus position to obtain a better intercostal window. The images and Doppler evaluation may be obtained in the longitudinal, coronal, oblique, or transverse planes.
  • Breath holding is very important in obtaining good Doppler color and spectral waveforms. Initially scan the patient in shallow respiration to set up your controls and depth. Then instruct the patient to stop breathing when you obtain the Doppler images.

Technique

General Technical Points

  • Place ultrasound gel on the abdomen to ensure good transducer-to-skin contact during the abdominal Doppler imaging examination.
  • The transducer's orientation marker should be pointing toward the patient's right side during the examination when a transverse scan is performed; the orientation marker is directed toward the patient's head when a longitudinal scan is performed.
  • The examination is performed with both gray scale and Doppler evaluation of the portal venous system, the hepatic veins, and hepatic arteries.
  • Remember, the transducer must be PARALLEL to the vessel; the Doppler angle should be less than sixty degrees to obtain the maximum peak systolic velocity.
  • At the end of the examination, the ultrasound gel should be removed from the patient and any excess gel should be removed from the transducer. The transducer should be cleaned using a disinfectant.

Doppler

  • The evaluation of the portal venous system, hepatic veins, and hepatic artery is performed during the Doppler imaging examination.
  • Doppler signals or color Doppler imaging should be obtained from the imaging plane that allows the beam to be as parallel to the vessel as possible.
  • A liver Doppler should also evaluate flow in the extra-hepatic portal venous system, and IVC. These images should be obtained prior to the PW evaluation.
  • Also document the size of the CBD, liver, kidneys, and spleen.
  • Look in the pelvic cavity and lower quadrants for the presence of free fluid.

Doppler Technique

  • The pulse repetition frequency (PRF) allows one to record lower velocities as the PRF is lowered; as the PRF is increased, the lower velocities are filtered out to record only the higher velocity signal.
  • The PRF may be changed with the scale control on the Doppler panel (look at the color bar on the left side of the monitor, the PRF will change as the "scale" on the Doppler control is changed.
  • The PRF increases as imaging depth increases and decreases as depth decreases. Flow within the normal hepatic venous system is low; therefore a lower PRF is necessary to record the flow pattern. As the flow increases beyond 40 cm/sec, the PRF should be increased to prevent aliasing. (Aliasing may also be reduced by scanning at a lower frequency).
  • The Doppler sample volume should be smaller than the diameter of the lumen. If you have difficulty finding the vessel, increase the width of the sample volume to locate the flow, and then reduce the volume width to clean up the spectral waveform.
  • The Doppler angle correction should be less than 60 degrees to display the peak spectral velocity.
  • Wall filters help to eliminate "noise" or low level Doppler shifts seen within the vessel.

Types of Doppler:

  • Pulse wave provides quantitative information from a selected location
  • Color Doppler Velocity
  • Dependent on direction of flow, velocity, and angle to flow
  • Important to angle color box as parallel to vessel as possible
  • Positive Doppler shift shows flow towards the transducer; negative shows flow away from transducer on color bar
  • Laminar flow distinguished from turbulent flow by varying shades of color
  • Color Doppler Energy
  • Relies on echo amplitude
  • Each energy signal is assigned a hue that is related to number of blood cells in the sample volume (displayed on color bar)
  • Different hues represent number of blood cells in sample volume, not the velocity
  • CDE not dependent on velocity, direction or angle of flow

Color Doppler Technique

  • Color Doppler gain
  • Color Doppler scale
  • Angle the color box (sample volume)
  • Decrease the size of the color box

Doppler Measurement

  • Peak systolic velocity (calculate highest velocity in cm/sec)
  • Resistive Index (RI): subtract the end diastolic velocity from the peak systolic velocity and divide by the peak systolic velocity. Normal or low resistive RI measures <.7.

Doppler Observations

Hepatic Artery

  • Low resistance waveform; forward flow in diastole above baseline
  • Vessel is tortuous; flow may appear to move toward and away from the transducer.
  • Systolic window with narrow bandwidth with parabolic flow profile
  • Spectral fill-in of systolic window due to small vessel diameter
  • High resistance waveforms may indicate veno-occlusive disease

Portal Venous System

  • Continuous low velocity phasic signal; phasic means that the velocity increases and decreases with respirations giving the signal a smooth wavelike appearance
  • Normal flow is termed hepatopedal (toward the liver)
  • Reversed flow is hepatofugal.
  • Portal venous thrombosis or post op anastomosis from a liver transplant can cause an abnormal portal vein signal: results from decreased vessel lumen size which reduces the pressure, and consequently increases the velocity of flow through the narrowed region - "choppy" appearance as result of increased velocities.
  • NOTE: The hepatic artery and portal vein flow should be in the same direction as the hepatic artery runs parallel with the portal vein.

Hepatic Venous System

  • Multi-phasic pulsatile flow pattern secondary to proximity of the right atrium with flow above and below the baseline due to close proximity to the right atrium which results in hemodynamic changes
  • Right sided heart failure may cause the hepatic veins to become pulsatile and dilated.
  • Increased intrahepatic pressure or venous obstruction demonstrates a more continuous or monophasic signal

Inferior Vena Cava

  • Continuous waveform with respiratory variations; become more pulsatile as it empties into the right atrium.
  • Best imaged with a slight cranial-caudal sweep in the longitudinal plane with the patient in deep inspiration
  • Anastomosis from surgical transplantation may alter the normal flow into the IVC
  • Thrombosis can cause the IVC waveform to appear monophasic with high velocities ("choppy" appearance). Evaluate for thrombus in the renal veins as well.
  • If a surgical shunt is present, be sure to check the patient's history to find out the specific type of shunt (portal/cava or mesenteric/cava) is in place.

Duplex Imaging Technique

Terminology:

  • Left hepatic vein - LHV
  • Left hepatic artery - LHA
  • Left portal vein - LPV
  • Right hepatic vein - RHV
  • Right hepatic artery - RHA
  • Right portal vein - RPV
  • Common (main) hepatic artery - CHA
  • Main portal vein - MPV
  • Middle hepatic vein - MHV

The hepatic vessels should be imaged at four anatomical locations:

  • Midline, beneath the xyphoid for the LHV, LHA, and LPV;
  • Mid-clavicular and intercostal at the portal hepatis for the MHA and MPV;
  • Lateral and intercostal at the right lobe for the RHA and RPV;
  • Subcostal and midclavicular for the RHV and MHV.

Hepatic Vasculature Technique Summary

Vessel Image Plane Technique
LHV Transverse / Longitudinal
  • Locate the left lobe of the liver.
  • Identify the inferior vena cava and angle steeply towards the diaphragm.
  • The LHV and MHV should be seen as they drain into the IVC.
LPV Transverse, coronal, intercostals, decubitus
  • Locate horizontal segment of PLV, adjust transducer to obtain steepest angle for Doppler (parallel to the vessel), and zoom in on the LPV
LHA Transverse
  • Usually found posterior to horizontal segment of LPV.
  • After interrogating the PLV, look for LHA with color Doppler (expand color box to cover the LPV and adjacent liver tissue).
  • Place PW cursor/ sample volume in area of LHA (suspend respiration); watch for "flashing" of signal as it comes in and out of view with respiration.
  • Look for LHA on deep inspiration.
  • If you can't get the signal in the periphery of the liver, move to another location closer to the main portal vein.
Common HA Longitudinal - porta hepatis

Use same technique as described for LHA

 

  • Transplant recipient patients: usually only able to Doppler HA at the porta hepatis
  • Include extra-and intrahepatic segment of HA
  • Difficult to image site of anastomosis
MPV Longitudinal - porta hepatis
  • If shunt is present, anastomosis site easier to identify (more prone to thrombosis); be sure to investigate the MPV proximal, within, and distal to anastomosis.
IVC Longitudinal, coronal - slightly to right of midline; suspend breath. Angle transducer in cephalad to caudal sweep to record flow
  • May be difficult to obtain good angle because of horizontal location on transverse plane.
  • If shunt is present, evaluate site of anastomosis carefully (proximal, within, and distal)
  • Look carefully for presence of internal echoes that represents thrombosis.
  • If you suspect thrombus is present, and the Doppler signal is very "choppy" with high velocity and little phasicity, the likelihood of thrombus is good.
  • Be sure to follow the IVC all the way into the right atrium of the heart.
SV Transverse
  • Evaluate SV from the splenic hilum to the portal-splenic confluence
RHA Transverse, Anterior to right posterior portal branch.
  • Use same techniques as mentioned to Doppler the RPV and RHA.
  • If you are unable to locate the RHA in the periphery of the liver, move closer to the trunk of the adjacent PV.
  • If you can't find the RHA at the right posterior portal branch, try looking for it at the level of the right anterior PV branch.
RPV Anterior, intercostals approach; one rib space away from window for porta hepatis
  • To locate right posterior branch of RPV, begin with the MPV at the porta hepatis
  • Follow the MPV into the liver until you see the RPV.
  • The posterior branch extends posteriorly into the right lobe. It is easier to obtain a good Doppler angle if you use a more anterior, intercostals approach.
  • Make small movements with the probe to get into the right posterior portal branch.
RHV Transverse, subcostal
  • Place the probe just below the level of the xyphoid with a steep angulation toward the diaphragm.
  • Locate the IVC; the RHV will be seen in the right lobe of the liver in a horizontal plane as it empties into the IVC.
MHV Transverse, subcostal
  • Place the probe just below the level of the xyphoid with a steep angulation toward the diaphragm.
  • Locate the IVC; the MHV will be seen in a vertical plane as it separates the right lobe from the left lobe of the liver as it empties into the IVC.

Diagnostic Criteria - Hepatic Vascular Imaging

Interpretation
Grayscale Compression
Doppler Signal
Color Doppler
Portal Veins:
A. Normal No intraluminal echoes; bright, echogenic borders Low velocity signal with respiratory variation Smooth fill in of color
B. Thrombosis Enlarged or normal portal venous system with low level echoes within the lumen; may appear isoechoic with the liver. Decreased low velocity to absent Doppler waveform; look for hepatofugal flow Decreased to absent color flow
C. Portal Hypertension Enlargement of the portal venous system.

Recannilization of the umbilical vein

Look for hepatofugal flow in portal venous system Hepatofugal flow with good color fill of lumen
D. Cavernous Transformation Multiple vascular channels near the portal hepatis and/or splenic hilum.

Thrombosis of the extrahepatic portal vein (may be difficult to image)

Look for recannalized umbilical vein

Continuous low velocity flow Color fills dilated collateral vessels; portal vein is difficult to fill with color
Hepatic Artery:
A. Normal Follow course of portal vein to image hepatic artery anterior.

Enlarge/res image size to visuage artery

Proximal HA best seen at level of celiax axis

Distal HA seen in intercostals coronal view at level of MPV and CBD

Low resistance waveform with systolic and diastolic component Increase gain slightly to fill in vessel lumen with color
B. Thrombosis Increased low level echoes within the lumen Obstruction would cause increased velocity waveforms Turbulence or absence of flow if complete obstruction is present
Inferior Vena Cava:
A. Normal Low level intraluminal echoes within the lumen returning into right atrium; changes with respiration Continuous triphasic waveform with respiratory variations Color fills lumen
B. Thrombosis Increased echogenicity of low level echoes filling lumen

Evaluate renal veins for extension of thrombus

Decreased Doppler waveform secondary to degree of thrombosis Decreased color within lumen; color will outline the area of thrombus/obstruction
C. Right sided heart failure Dilation of lumen that does not change with respiration Multiphastic, pulsatile flow Color fills lumen of hepatic veins and inferior vena cava
D. Thrombosis/ Budd Chiari Low level echoes within the lumen of the hepatic veins; may completely restrict blood flow into the inferior vena cava

Caudate lobe enlargement may be suspicious of thrombosis of hepatic veins

Decreased flow signal Decreased color fill in of hepatic veins; IVC may appear collapsed with decreased blood return.

Image Correlation

Click on image for larger view

Interpretation
Gray scale Compression
Doppler Signal
Color Doppler
Portal Veins:
A. Normal
Normal-Gray scale Compression
Normal-Doppler Signal
B. Thrombosis
Thrombosis-Gray scale Compression
Thrombosis-Color Doppler
C. Portal Hypertension
Portal Hypertension-Gray scale Compression
Portal Hypertension-Doppler Signal
D. Cavernous Transformation
Cavernous Transformation-Doppler Signal
Cavernous Transformation-Color Doppler
Hepatic Artery:
A. Normal
Normal-Gray scale Compression
Normal-Doppler Signal
B. Thrombosis
Thrombosis-Doppler Signal
Inferior Vena Cava:
A. Normal
Normal-Gray scale Compression
B. Thrombosis
Thrombosis-Gray scale Compression
C. Right sided heart failure
Hepatic Veins:
A. Normal
Normal-Gray scale Compression
Normal-Doppler Signal
Normal-Color Doppler
B. Thrombosis/ Budd Chiari
Thrombosis/ Budd Chiari-Gray scale Compression
Thrombosis/ Budd Chiari-Doppler Signal

References

Dahnert, Wolfgang, Radiology Review Manual, 3rd Edition, Williams & Wilkins, 1995.

DeJong, Robert, The Use of Doppler in the Abdomen, The Johns Hopkins Hospital, 1998.

Hagen-Ansert SL, Textbook of Diagnostic Ultrasonography, 5th Ed. Mosby, 2001.

Kurtz, AB and Middleton WD, Ultrasound: The Requisites, Mosby, 1996.

Rumack CM, Wilson SR and Charboneau JW, Diagnostic Ultrasound, 2nd Ed, Mosby, 1998.

Thibodeau, GA and Patton, KT. The Human Body in Health & Disease, 2nd Edition, Mosby, 1997.