liver normal
for liver function tests explained (lfts).
liver anatomy
scanning probe positions
parasagittal ultrasound scan plane.
the liver and rt kidney are visualised in this view.
intercostal ultrasound liver scan plane.
the middle and right hepatic veins are visualised in this view.
subcostal scan plane. the probe is angled cephalad under the ribs to avoid any bowel or ribs shadowing over the liver.
the right portal vein is shown coursing transversely in this view.
scan plane left lobe of liver. the probe is in the epigastric region just below the sternum. it is angled cephalad to view the left lobe in its entirety. the probe may need to be angled towards the left side to see the most medial edge of the left lobe.
the portal vein should have constant forward flow into the liver (hepatopetal flow) .as seen in this image, the colour is red ,which is set for movement towards the probe. be very careful to make sure you look at the colour box on the side of the image to know the setting.
because the hepatic veins drain into the ivc immediately prior to the right atrium, they have phasic flow reflective of cardiac motion.
scan protocol
role of ultrasound
to assess the:
- size
- capsular contour (smooth, coarse, lobulated)
- parenchymal echogenicity
- vascularity
- biliary tree
- masses or collections
limitations
- obesity and patients with severe cases of metabolic disorders such as haemochromatosis and fatty infiltration will reduce detail and the diagnostic yield of the scan.
patient preparation
- ideally, fast the patient for 6 hours to reduce bowel gas and prevent gall bladder contraction.
equipment setup
- depending on the size of the patient a curved linear array 2-6mhz.
- if there is nodularity of the liver border then a linear array with a 7-12mhz frequency will better appreciate this. good colour / power / doppler capabilities when assessing vessels or vascularity of a structure.
- be prepared to change focal zone position and frequency output of probe (or probes) to adequately assess both superficial and deeper structures.
common pathology
- fatty liver
- liver cysts
- haemangioma
- portal hypertension
- portal vein thrombosis
- hepatic vein thrombosis
- liver abscess/collection
- cirrhosis
- trauma
- metastases
- hcc
- abscess
scanning technique
begin by doing a full survey sweep through the liver.
you will need the patient to take deep inspirations to fully visualise the superior borders of the liver.
look in transverse up and down the left lobe from a subcostal approach. look in transverse through the right lobe subcostally or intercostally.
roll the patient in a left lateral decubitus position for assessment of the rt lobe only after checking for fluid. bowel gas can overlie the liver in a subcostal approach, so getting the patient to distend their abdomen can help with visualisation. also looking intercostally between each rib space can ensure thorough visualisation.
look for:
- homogeneous v’s attenuative(normal v’s fatty)
- smooth v’s coarse echotexture
bmode image here
- size: to measure the size of the liver, use a sagittal approach in the mid clavicular line. measure from the diaphragm to the inferior border on bmode image. this can be very subjective. also look at the lower edge of liver in relation to the rt kidney.it should finish half way down the kidney. bmode image an enlarged liver will have rounded borders.
once you have thoroughly scanned though the liver, then start taking images.
normal liver measurements
- we need to be able to determine such conditions as hepatomegaly , splenomegaly, renal impairment and abdominal aortic aneurysm.
- it needs to be a consistent measurement to be able to compare sizes over time.
- the calipers need to be positioned in the same position between sonographers for accuracy.
- the upper border lies in the right midclavicular line at the 5th intercostal space.
- most people have the lower border extending to the lower costal margin.
- if it is measured in the midhepatic line with a large field of view it should measure <16cm (ref : ultrasonic determination of hepatomegaly. j clin ultrasound 1981gosink bb)
from the posterior diaphragm to the lower anterior edge. however organ size increases with gender, age ,height, weight and body surface area.
- if the measurement is made from the anterior diaphragm to the lower edge of the liver in the midclavicular line it should be no >13cm (ref ultrasonography .an introduction to normal structure and functional anatomy:wb saunders; 1995.curry ra and tempkin bb.)
midclavicular
if the measurement is made from the ant diaphragm to the lower edge of the liver in the midclavicular line it should be no >13cm
midhepatic
measured in the mid-hepatic line with a large field of view it should measure <16cm from the post diaphragm to the lower anterior edge.
basic hardcopy imaging
any liver series should include the following minimum images;
- longitudinal
- left lobe
- caudate lobe
- ivc
- porta hepatis
- comparison to rt kidney
- transverse
- left lobe
- left hepatic vein
- left portal vein
- right portal vein
- middle and right hepatic vein.
- demonstrate hepatopetal flow in portal vein.
- demonstrate hepatic vein flow
- document the normal anatomy. any pathology found in 2 planes, including measurements and any vascularity.
please note that an image must not be taken if it does not have a vessel in it ie. portal or hepatic vein because you must be able to identify which segment of the liver the image has been taken in. look at the direction of flow in the portal vein by scanning intercostally to get optimal directional flow with colour doppler use spectral doppler to demonstrate hepatopetal or hepatofugalflow. in a fatty liver the hepatic veins can be assessed and a spectral doppler used to visualise the normal waveform with the atrial contraction.- remember that the images are only a sample of what you have seen.if you miss the pathology then it does not matter how perfect the images are.
- longitudinal