Lecture 19– imaging of the GI tract Flashcards
(45 cards)
Imaging available for GI system
- Plain X-rays
- Abdominal x-ray (AXR)
- Erect chest x-ray (CXR)
- Contrast studies
- Barium swallow/enema
- Barium meal/follow through
- Water soluble contrast studies
- US
- Cross- sectional imaging
- Computed tomography
- Magnetic resonance imaging (MRI)
- Angiography
AXR is …….. utilised as a first line investigation
less
when is AXR used vs CT scan in relation to small or large bowel obstruction
- CT scan is first for small bowel obstruction
- Abdo x-ray may show volvulus in large bowel obstruction
first line investigation for renal colic
CT
- abdo Xray can be done to check stone ahs passed
AXR and Acute exacerbation of IBD?
Potentially useful for toxic megacolon with perforation
presentation of small bowel obstriction on X-ray
- Central position
- Often don’t see (need gas in the bowel to see)
- Plica/circulares/ permanent folds/ Valvulae conniventes
- Cross the entire wall
- Thin
which rule applies for large boewl obstruction
369
The 3-6-9 rule is a simple aide-memoire describing the normal bowel calibre:
small bowel: <3 cm
large bowel: <6 cm
appendix: <6 mm
caecum: <9 cm
presentation of large bpewl obstruction
- Peripheral position
- Haustra- sacculation’s formed by outer longitudinal muscles
- Lines only extend partially along the bowel wall
- Remember
- Transverse colon hands down to the pelvic
- Sigmoid colon can loop and be long
example cause: diverticular stricture
Ct and small bowel obstruction
- CT = first line of imaging
- Can identify the level and cause of obstruction
- Also good helping to determine whether bowel is strangulated
- Do not use plain abdominal radiographs unless CT unavailable
why is CT most widley used method in large bowel obstruction
- Localise location of obstruction but in most instances also identify causes
sigmoidal volvulus is said to look like a
coffee bean
- Due to a twist at the base of the sigmoid mesentery which is in a fixed position (*) in the left iliac fossa
- This results in the appearance of a giant coffee bean, the typical sign of sigmoid volvulus
toxic megacolon can be caused by
- Acute deterioration with UC or colitis
- patient will be unwell
Toxic megacolon- X-ray
- Colonic dilatation
- Oedema
- Pseudopolyps
erect CXr will be in
AP
- cant get accurate reading o heart side
what may you need an erect chest X-ray for inr regards to the GI system
Pneumoperitoneum
- An erect chest x-ray can show even a very small volume of abdominal gas
- Reference to the clinical setting is required to determine if this a life threating perforation
- A careful check should be made for free gas under the diaphragm on every chest X-ray
iatrogenic causes of penumoperitoneum
- Patient might have undergone laparoscopic surgery earlier in the day free gas under diaphragm is insufflated CO2- an acceptable post surgery finding
- Causes of pneumoperitoneum
perforation due to
- Peptic ulcer
- Diverticular
- Tumour
- Obstruction
- Trauma
- Iatrogenic
x-rays are also useful in looking for
- stones and calcificatione e.g. in chronic pancreatitis
- foregein bodies
barium swallow is a dedicated test of the
pharynx, oesophagus and proximal stomach
- You give pt barium to swallow then use video fluoroscopy (which is a continuous X-ray which is view in Realtime on a screen)
what has largely replaced barium swallow for the assessemnt of peptic ulcer disease and elevation haematemesis
Upper GI endoscopy has largely replaced barium swallow for the assessment of peptic ulcer disease and elevation of haematemesis
Barium follow-through
- Following a barium swallow, we can wait for the barium to reach the small intestine
- Therefore can be used to image small intestine (endoscopy cannot reach here)
barium enema
- Tube inserted into rectum
- Administered and results monitored by fluoroscopy
- If mucosal problems are suspected then adding another contrast medium (air or CO2) will help
- Largely superseded by CT
- Used to visualise:
- Strictures
- Mucosal problems (with air or CO2)
CT shows UC
abdominal ultrasound uses
- Use of sound waves to generate image
- Frequency above audible range of human hearing (20 KHz)
- Usually 2-18 MHz)
