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
What can be some issues with using IV contrast for CT?
- Risk of contrast induced nephropathy
- Allergy
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
