18 Imaging of GI Tract Flashcards
Why might you request an abdominal x-ray for a patient?
Patient presents with:
- Acute abdominal pain
- Suspected bowel obstruction
- Exacerbations of IBD
- Renal colic (CT first line)
DONE AP
How should you use to assess an abdominal x ray? (ABDO X)
ABDO X
- Air
- Bowel
- Dense structures/bones
- Organs and soft tissues
- External
Which bowel should you not see gas in?
- Small bowel, has a fast transit time so will only see fluid
- Colon will have lots of gas as slower transit time
Why is an AXR a higher radiation dose than a CXR?
Has to go through more structures to produce an image
How do the large and small bowel differ on x-ray?
- Small: central position and have lines that cross the entire wall (valvulae conniventes)
- Large: peripheral and have incomplete lines (haustra). faeces is visible as slow transit time
What diameter indicates bowel obstruction on x-ray? (3,6,9 rule)
- Small: >3cm
- Large: >6cm
- Caecum: >9cm
What is the presentation and common causes of small bowel obstruction? (may be extramural,
ASHVITA
- Adhesions (most common)
- Stenosis
- Hernia
- Volvulus
- Inturssusception
- Atresia
What is the presentation and common causes of large bowel obstruction?
- Colorectal carcinoma (60%)
- Diverticular stricture (20%)
- Volvulus (5%)
- Hernia
What is this abdominal x-ray showing?
- Sigmoid volvulus coffee bean sign
- Starts in LIF and goes to RUQ
- Can be ischaemic or perforate
What is this abdominal x-ray showing? How might it be caused?
- Toxic megacolon
- Colonic dilation, oedema (thumbprinting thick haustra due to inflammation) and pseudopolyps
- Common in UC and C.Diff
What is being shown on this abdominal x-ray?
- Lead pipe colon
- Loss of haustra
- Common in UC due to chronic inflammation
Label the viscera on the abdominal x-ray.
X-rays can identify calcification, what are some examples of calcification you may see on an abdominal x-ray?
- Renal calculi
- Vascular calcification
- Pancreatic calcification following chronic inflammation
What is this abdominal x-ray showing?
Cannot see psoas so AAA
(abdominal aortic aneurysm)
What is the abnormality on this x-ray?
Foreign body (cholecystectomy clip)
What are some causes of bowel perforation?
How can you image for a bowel perforation?
- Erect CXR
- Will see free gas under the diaphragm
How can we view hollow viscera on abdominal x-ray?
- Water or barium contrast
- Swallow test and follow through
How can we view the large intestine clearer on an AXR?
Contrast Enema
(x-ray study that uses a water soluble contrast agent containing iodine or barium to show the structure of the rectum, colon and large intestine)
How can we get a high resolution picture of the abdomen? Why might this option not be chosen?
- Abdominal CT augmented with contrast
Danger: - High radiation dose
How can CTs replace a colonoscopy?
- Images from CT scan can be reformatted and produce a 3D image of the anatomy so virtual colonoscopy
Why may we use an MRI to image the abdomen?
+ Very detailed high contrast images
+ No radiation
- However very time consuming
Why is an ultrasound used for abdominal imaging, and what is it most commonly used to image?
+ Cheap and portable
- User dependant
- Often used to:
- visualise the biliary tree for gallstones and dilated bile ducts
- guided biopsy
What is being displayed here
- GI Angiography using contrast CT
Label the following parts of this MRI.
What parasite causes persistent diarrhoea?
Giardia!
Causes villous atrophy due to damage of small intestine, goes back into cyst stage to start the cycle again
