17) Imaging of GIT Flashcards
What types of imaging can be used for the GIT?
X-ray - abdominal and erect chest Contrast studies Ultrasound CT/MRI Angiography
What types of contrast studies are there?
Barium swallow, enema and meal
Water soluble studies
What imaging types are low dose radiation?
Ultrasound, MRI
What imaging types are high dose radiation?
Barium enema, CT
What are the risks of radiation in imaging?
Carcinogenesis
Genetic
Developmental risk to foetus
Why would an abdominal X-ray be requested?
Acute abdominal pain (sometimes)
Small or large bowel obstruction (used as triage)
Acute exacerbation of IBD
How is an abdominal X-ray taken?
Patient on back, X-ray from above
What features can be seen on an AXR?
Bowel gas pattern
Soft tissue structures
Bones
When can hollow tube be seen on X-ray?
If gas filled of gas and fluid filled
Slow transit time in colon and stomach so will be gas filled
When it can be seen, what are the features of the small bowel on AXR?
Central position
Valvulae conniventes - lines across entire bowel lumen
What are the features of the large bowel on AXR?
Peripheral position
Haustra
Faeces and gas
Transverse colon hangs down into pelvis
What is the rule of 3/6/9 in abnormal gas patterns?
Small bowel obstruction if dilated >3cm
Large bowel obstruction if dilated >6cm
Caecum (if ileocaecal valve working) obstruction if dilated >9cm
What causes small bowel obstruction?
Adhesions, hernias, tumours, inflammation
How does small bowel obstruction present?
Vomiting (early)
Distension
Absolute constipation (late)
Colicky pain
What causes large bowel obstruction?
Colorectal carcinoma (unless proven otherwise)
Diverticular stricture
Hernia
Volvulus
How does large bowel obstruction present?
Distension
Pain
Absolute constipation
Vomiting (late)
What is a volvulus?
Loop of intestine twisting around itself or around its mesentery
What is the most common volvulus?
Sigmoid volvulus
What can be the outcome of a volvulus?
Bowel loop dilates and can cut off its blood supply (in mesentery) or perforate
What can be the treatment for a sigmoid volvulus?
Sigmoidoscopy - passed through twist
What inflammation can be seen on AXR?
Mucosal thickening
Featureless colon (UC)
Bowel wall oedema
Describe the features of toxic megacolon:
Microvascular ischaemia Mucosa sloughs off Colonic dilatation Oedema Pseudopolyps
What is thumb printing?
Oedematous thickened haustra due to active inflammation (UC)
What other organs may be seen on an AXR?
Liver, spleen, kidneys, bladder
What other abnormalities may be see on an AXR?
Stones
Masses
Calcification - chronic pancreatitis, vascular
Foreign bodies
What condition can a chest X-ray be used to diagnose?
Perforated bowel
Why does a chest X-ray need to be used in perforated bowel?
To see diaphragm being elevated from viscera, with air/gas in the peritoneal cavity
What can cause a perforated bowel?
Peptic ulcer Diverticular Tumour Obstruction Trauma
When is barium contrast study used and when is water soluble contrast study used?
Barium if healthy
Water soluble if going into surgery
What can a barium swallow be used for?
Visualise aspiration, used in elderly
What can a barium enema be used for?
Injected rectally, check if anastomoses have healed in removed rectum where ileostomy has been used
What is the L1 plane of a CT called?
Trans-pyloric plane
What are the advantages of MRI scans?
No radiation
Good spatial and contrast resolution - differentiating between different tissues
What can be visualised using ultrasound?
Gall stones
Common bile duct dilation
Liver, portal vein and appendix
How is a GI angiography carried out?
Inject radio opaque contrast IV, then use imaging to visualise blood supply
What can a GI angiography be used to see?
Bleeding
Ischaemia
What can GI stenting be used for?
Removing blockages
