lower GI Tract pathology and imaging Flashcards
what is the lower GI tract
starts with the caecum, ascending colon, transverse colon, descending colon and sigmoid colon
primary functions of GI tract
- absorption of water
- waste products from digestion
- waste removal
the appendix
a small, thin pouch about 5-10cm long
appendicitis
- inflammation of the appendix
- occurs when the appendix becomes infected or blocked by stool, FB or tumour
clinical indication of appendicitis
- central abdomen pain
- pain travels to rt hand side and becomes constant and severe
- loss of appetite, nausea, vomiting, diarrhoea and fever
ultrasound abdo/pelvis appendicitis
- transabdominal approach
- faecal matter and air-filled bowel may prohibit visualisation
- obese and bariatric patients are harder to visualise
CT adbo/pelvis with contrast appendicitis
- iv contrast - 3mls/s , delay 20 seconds
- breathing instructions
- patient is supine with arms above head
- venous phase - above diaphragm to symphysis pubis
clinical indications of large bowel pathologies
- mass
- obstruction
- weight loss
- anaemia
abdominal x-ray
- patient lies supine
- MSP perpendicular to table
- ASIS equidistant from table top - no rotation
AXR centring point
- level of the iliac crests
- arrested respiration
AXR collimation
sup - diaphragm
inf - symphysis pubis
lat - skin margins
abdo/pelvis CT with contrast
the contrast identifies presences of mass, signs of inflammation and bowel wall ischemia.
3mls/s delay 70 seconds
CT colonoscopy
- rectal catheter is inserted and large bowel is inflated, to get a detailed view of the lining of the bowel
MR colonoscopy
similar to CT colonoscopy
- non ionising radiation
- however Mr risks still apply
patient prep to clear bowel (2 days b4 procedure)
- patient drinks as much fluid as possible
- 7-9am given a list of foods allowed for breakfast
- 12 noon - given a list of foods allowed for lunch
- after this no solid food is eaten
- 7pm - gastrographin (50 mls) mixed with squash
patient prep to clear bowel ( 1 day before procedure)
- no solid food
- drink as much clear fluid as possible (150 mls every hour)
- 7pm 50 mls gastrographin with squash
patient prep to clear bowel (day of procedure)
- do not eat any food
- drink as much water as you like
- after procedure, eat normally
prior to scanning bowel (colonoscopy)
- catheter inserted into rectum
- wash hands
- ppe
- patient lays lateral, with knees bent
- buscopan is used
- catheter is lubricated
colonoscopy CT scan protocol
- inflate colon with air
- perform supine and prone views
- iv contrast if carcinoma is suspected
- single breath-hold aquisition
MR protocol - bright lumen technique
- water and gadolinium enema
- t1 weighted imaging
- ## lumen appears bright because of the presence of gadolinium and polyps are visible as filling defects
MR protocol - bright lumen technique
- water and gadolinium enema
- t1 weighted imaging
- ## lumen appears bright because of the presence of gadolinium and polyps are visible as filling defects
MR protocol - black lumen technique
- water enema for luminal distention and intravenous infusion of gadolinium for enhancement of colonic wall
- after complete filling, a 3D T1-weighted sequence is performed before and after iv administration
- lumen appears dark on t1 sequence, enhancement of colonic wall and inflammatory changes can be seen.
- a 2d/3d sequence is used before administration - T2/T1 Weighted- allows to see filling defects - lumen appears bright
Bowel obstruction
- A mechanical blockage of the bowel
- where a structural pathology physically blocks the passage
- dilated bowel (>6cm, or >9cm at caecum
Diverticular disease
- a condition that occurs when small puches, or sacs, form and push outward through weak spots in the wall of colon
- Contrast enhanced CT shows multiple gas filled outpouchings from the sigmoid colon - indicating diverticular disease
ulcerative colitis
- inflammation occurs in the colon (large intestines) and rectum
- development of small ulcers on the colon;s inner lining, which produce pus and mucus
- causes abdominal discomfort and frequent emtying of colon
ulcerative colitis ct
contrast enhanced CT sdcan shows minimal diffuse thickening of the sigmoid colon - small strands of inflammatory stranding
ulcerative colitis MR
- thickening of mucosal lining
- my show inflamed transverse colon
Crohn’s disease
- inflammation occurs in the colon and rectum
- can affect thickness of the digestive tract wall
- spreads through all wall in the interstines- causing small tears to the lining
crohn’s disease CT
- thickened bowel wall, narrowing of lumen
MR crohn’s disease
- shows marked bowel wall thickening and luminal narrowing of the terminal ileum
pathologies associated with bowel motility
- chronic functional constipation indications
- infrequent bowel movements/ difficult passage stools that persists for several weeks
- colonic inertia
- delayed transit
colonic transit test/ sitzmark study
- time taken for food residues to move through colon
- severity of constipation
- helps diagnose primary cause of constipation
colonic transit test/ sitzmark study procedure
- patient swallows capsules containing 10-24 soft rubber shapes
(radio-opaque markers) - 1 capsule followed by abdomen x-ray 5 days later
- oir 1 capsule at the same time each day for 3-5 days with abdo x-rays taken on day 5-7
outcomes on day 5 abdo x-ray colonic transit test/ sitzmark study
- fewer than 25% of markers left, suggests normal transit constipation
- more than 25% of markers left and evenly spread throughout colon is consistent with slow transit constipation
- more than 25% of markers left congregated in the recto-sigmoid are indicative of an outlet obstruction
clinical indications defacting issues
- pelvic floor pain
- evacuatory difficulty
- bulging or prolapsed rectum
defacting proctogram usingf fluoro or mri
- image of the rectum as it passes stool
- investigation gives morphological and functional information
defacting proctogram - fluoroscopy procedure
- patient changes into gown
- barium paste is made in the consistency of soft srool and is injected into the rectum
- patient sits laterally on a radiolucent commode - in front of fluoro unit
- both videofluoroscopy and spot images captured while patient is asked to rest, squeeze, cough, strain, defecate and strain
defacting proctogram MRI procedure
- patient changes into gown and completes questionnaire
- patient lays supine
- disposable endorectal coil is used to image anal sphincters - t1 and t2 spin echo
- coil is removed and a paste mixture of gadolinium is put into the patient
- images are acquired whilst the patient is resting, squeezing, defacating in supine. images are acquired every 1-1.4 secs.
rectocele
- end of large intestine pushes against and moves the back wall of the vagina
- may be a bulging in rectal floor
rectal prolapse
- bowel moves moves out of the rectum and back in again, or remaining outside the body, producing a prolapse appearance after defaction
