Imaging of the GI tract Flashcards
What are the modalities used to image the liver?
- Ultrasound
- CT
- MRI
What are the pros and cons of the use of ultrasound to image the liver?
Pros:
•Repeatable
•Quick
•No radiation
Cons:
•Variable quality
•Least sensitive
What are the pros and cons of using CT to image the liver?
Pros:
• fast
•Reproducable
Cons:
•Limited sensitivity
•Radiation
What are the pros and cons of using MRI to image the liver?
Pros:
•Most sensitive and specific
Cons:
•Slow
•More patient dependent
What is the first line for imaging the liver?
Ultrasound
What is the normal outline of the liver as seen on ultrasound?
Smooth
What is the classical shape of a cirrhotic liver?
- Enlarged caudate lobe
- Enlarged lateral left lobe
- Shrunken medial left lobe
What is the normal echogenicity of the liver on ultrasound
homogeneous
What are the signs of portal hypertension on ultrasound?
- Splenomegaly
- Varices - recanalised umbilical vein
- Ascites
What can you use to measure liver stiffness?
US eleastography
Describe the liver in this ultrasound image
Irregular margin, heterogenous nodular liver texture, indicative of cirrhosis
Discuss this ultrasound image
- Reversal of portal vein blood flow
- Dark space above the liver = ascites
- Relatively normal liver edge
What is the most common cause of a bright liver on ultrasound?
Fat
Compare the brightness of the liver and the kidney in an ultrasound image
- Similar colours
- Renal cortex of the kidney is meant to be a bit brighter than the liver
- If the renal cortex is much darker this indicated a bright liver suggesting fatty liver
What can mimic liver metastases on MRI?
Focal fat
What are the benign causes of focal liver disease/lesions?
- Cysts
- Haemangiomas
- focal nodular hyperplasia
- Adenoma
What are the malignant causes of focal liver disease/lesions?
- Metastases
- Hepatocellualr carcinoma
- Cholangiocaricnoma
Describe a cyst on ultrasound
Black, regular border
Describe cysts on CT
Well defined, dark, dense (if it contains protein and is denser than normal, it may mimic other lesions)
Describe the appearance of cysts on MRI imaging
- T2 weighting: fluid within the cyst is bright
* T1 weighting: fluid is dark
What is the appearance of a haemangioma on ultrasound?
- Round
- Slightly bright
- If round, <3cm and haemogenously bright then almost definitely a haemangioma
- it can appear darker, especially if the liver is brighter i.e. in fatty liver
How can you test if something is a hemangioma?
- MRI
- inject contrast into patients vein
- will be patches of bright as you continue to image due to infiltration into the haemangioma
What lesion on ultrasound is suspicious of a metastases?
Round dark lesion s
Describe the appearance of cholangiocarcinoma on MRI
- Ill defined
- Can draw in the liver capsule
- Hypovascular so don’t tend to become bright on contrast until much later on
What is the first line imaging for the biliary tract?
Ultrasound
If there is no evidence of stones but the common duct is dilated and the patient is jaundiced, what should you do?
CT them to check for pancreatic cancer
How is the small bowel imaged?
- CT and MR enterogrpahy
* both require good patient cooperation including the ability to drink (to distend the bowel)
Describe imaging of the large bowel
- CT colonography
- Bowel cleansing and tagging with iodine
- bowel distension with CO2
- Suprine +/- prone cT scans with IV contrast
- conventional 2D CT read
- CGI images for 3D read (virtual colonoscopy)
Renal cortex appears much darker than the liver suggesting fatty liver
What does this image show?
A cyst
What does this CT image show?
Cyst
What is indicated on this MRI scan (L= T2, R=T1)
Cyst
What is indicated in this ultrasound image?
Haemangioma
What does this ultrasound image show?
Dark round lesions in the liver suspicious of metastases
What is shown in this ultrasound?
Gallstones in the gallbladder
What is shown in this ultrasound?
Gallstone in an inflamed gallbladder (thickened wall)
