GIS12 Contrast Imaging Of The Intestinal Tract

Question 1

Plain abdominal X-ray (AXR)

Answer 1

1. Able to visualise bony skeleton
2. Outlines of organs (due to density difference within/outside intestine)
3. Bowel gas
4. Faeces

Question 2

Plain AXR advantages and limitations

Answer 2

Advantages:

• easily accessible
• fast
• portable X-ray suitable for critically ill patient

Limitations:

• cannot evaluate ***mucosa
• cannot assess ***bowel motility (∵ only snapshot of moment)
• cannot evaluate ***level of obstruction accurately
• cannot see ***perforation / leaks (have to do chest X-ray to see air floats to thoracic area)

Question 3

Normal Gas pattern vs Normal Fluid level

Answer 3

Normal gas pattern:

• Stomach: always present
• Small bowel: not always visible, 2-3 loops of non-distended bowel (2.5cm diameter)
• Large bowel: Rectum and Sigmoid almost always present

Normal fluid level (only taken at erect position, nothing to see in supine position)
- Stomach: (fluid level) always present except supine film
- Small bowel: 2-3 levels possible
- Large bowel: ***None normally —> ∵ large bowel absorb water
—> too many fluid levels: obstruction

Question 4

Difference between small and large bowel on plain AXR

Answer 4

Small bowel:

• centrally located
• ***valvulae conniventes (valves of Kerckring: circular folds projecting into small bowel lumen, transverse whole thickness of lumen)
• ***no faeces
• 3-5cm diameter

Large bowel:

• peripheral
• ***haustra (do not transverse whole thickness of bowel)
• ***+/- faeces
• > 5cm diameter

Question 5

Signs of small bowel obstruction

Answer 5

1. ***Multiple fluid level
2. ***Dilated small bowel
3. ***Paucity (very little) large bowel gas

RMB:

• proximal to obstruction site: Dilation
• distal to obstruction site: Collapse

Question 6

Contrast imaging

Answer 6

• Coat and show mucosa
• Demonstrate ***bowel motility
• Demonstrate ***site of obstruction and leaks
• ***also use X-ray
• ***Fluoroscopy used to view contrast through the bowel in real-time
• Spot films: done intermittently throughout the examination, taken at specific time of specific area and images are shown

Contrast medium:
1. ***Barium sulphate (coats/stick to mucosa very well)

2. **Water soluble contrast media (with **Iodine)
   —> used in single bolus to opaquesify lumen
   —> used when barium is contraindicated (suspected perforation, check anastomosis post-surgery)
   —> used to show bowel in CT examination (oral / per rectum / rectal catheter)
3. Air (provide density difference)

Question 7

Barium and Iodine

Answer 7

• dense elements
• absorbs X-ray
• appear white on film

Question 8

Types of Barium studies and indications

Answer 8

1. Barium swallow (for Esophagus)
   - Indications: **dysphagia, suspected tumours, strictures, ulcers, oesophagitis (inflammation)
   - swallow **baking soda crystals to make gas (distend esophagus to produce double contrast effect / better definition of small mucosal abnormalities)
   —> drink barium liquid
   —> passage of barium is screened with X-ray with patient standing
   —> spot X-ray films taken
2. Barium meal (for Stomach)
   - Indications: **Dyspepsia, weight loss, upper abdominal mass, GIT haemorrhage, partial upper GIT obstruction
   - swallow **baking soda crystals to make gas
   —> drink the barium liquid lying down on X-ray couch
   —> patient **gently rolled around to coat wall of stomach and duodenum
   —> stomach is screened
   —> spot films taken with patient in different positions
   - patients need to **fast 6 hours before procedure
3. Barium follow through (for Small intestine)
   - Indications: abdominal pain, diarrhoea, GIT haemorrhage, partial obstruction
   - patients on laxative evening before (help flow of barium into colon), fast for 6 hours before
   —> performed at the end of barium meal / swallow examination
   —> drinks more barium until reaches colon
   —> X-ray taken every 20-30 minutes until barium seen in ***colon
4. Small bowel enema (for Small intestine)
   - Indications: abdominal pain, diarrhoea, GIT haemorrhage, partial obstruction
   - a tube inserted into the patients’ mouth / nose / negotiated through the stomach to reach **4th part of duodenum
   —> fill the entire small bowel with dilute barium / barium followed by methyl cellulose through the tube
   **- Better distension and delineation of small bowel
5. Barium enema (for Large intestine)
   - Indications: alteration in bowel habit, chronic diarrhoea / constipation, rectal bleeding, abdominal pain, suspected abdominal mass, obstruction
   - patients on **laxatives and clear fluid 1 day before examination
   —> colonic washout with tepid (lukewarm) water on day of examination
   —> cleanse the colon of any faecal material
   —> patient lies on X-ray couch with rectal tube inserted
   —> barium +/- air infused
   —> X-ray taken with patient in different positions
   - 2 types:
   —> **Single contrast:
   - entire colon filled with barium
   - shows LARGE surface abnormalities
   - performed to show site and extent of mucosal lesions urgently
   - in children whom it is not essential to see mucosal pattern
   —> ***Double contrast:
   - thicker barium fluid first followed by air
   - shows FINER surface abnormalities
   - method for seeing mucosal abnormalities

Question 9

Barium enema limitations

Answer 9

1. Uncomfortable procedure
2. Pain/discomfort due to bowel distension
3. ***Vasovagal attack in elderly
4. ***Incontinent during procedure
5. Preparation is uncomfortable and arduous

Question 10

Barium studies complications

Answer 10

1. Perforation (50% mortality if barium leaks into peritoneal cavity —> barium peritonitis, 30% develop peritoneal adhesions)
   —> do water-soluble contrast instead
2. Aspiration in patient with dysphagia
   —> physiotherapy (relatively harmless)
3. Side effects of drugs

Question 11

Barium studies contraindications

Answer 11

1. Complete colonic obstruction in upper GIT
2. Suspected perforation
3. Any condition that will lead to perforation:
   - Toxic megacolon
   - Pseudo-membranous colitis
   - within 7 days of rectal biopsy

Question 12

Computed tomography

Answer 12

• Cross-sectional imaging
• Follow-up on AXR / contrast studies: ***further evaluation of masses / abnormalities found
• use ***water / contrast to fill bowel
• give information outside of bowel but does ***not give good mucosal information

***- Indications:
—> bowel wall thickening (strictures seen)
—> further delineation of masses e.g. abscess, tumour
—> cancer staging (local spread / nodal / distant metastasis)

• Multi-detector CT (MDCT)
  —> fast imaging of large volume of tissues
  —> multi-planar reconstruction (3D)
  —> better anatomical correlation

Question 13

CT colonoscopy

Answer 13

• software to allow reconstruction of data to show endoluminal view
• inflate large bowel with ***AIR instead
• provide roadmap prior to actual endoscopy