5. Imaging of the GI tract

Question 1

What are the primary and secondary GIT imaging tools used?

Answer 1

Primary: X-ray, CT and USS

Secondary: MRI, Fluoroscopy (e.g. Barium meals, barium enemas)

Question 2

What types of x-ray are used to examine the GIT?

Excludes what pathology?

Answer 2

Types: Spine AXR, Crest CXR

Excludes bowel obstruction perforation

Question 3

The normal portal venous pressure is 5 - 10mm Hg

If elevated above this the term ‘____ _______’
is used

Answer 3

The normal portal venous pressure is 5 - 10mm Hg

If elevated above this the term ‘portal hypertension’
is used

Question 4

Which is more accurate, CT or USS?

Answer 4

Sensitivity of CT vs USS- 89% vs 70%

CT results in 46%-60% change in management :)

Question 5

Cons of CT scans?

Answer 5

Radiation exposure

Renal impairment

Question 6

Pros/ cons of MRI scan?

Answer 6

Pros:
No radiation
Good soft tissue delineation esp in pelvis

Con’s:
Long examination time
Not 24/7 in Fife
Contraindications/ claustrophobia

Question 7

Acute appendicitis:
Symptoms?
Localises at?
Scans used?

Answer 7

Symptoms: Periumbilical pain, nausea & vomiting

Localises at RIF

USS first, then CT

Question 8

Acute divericulitis:
Main age group affected by diverticulosis?
1/3+ are misdiagnosed as?
Complications?
Scans used?

Answer 8

80yrs +

Misdiagnosis: Appendicitis, colorectal Ca

Complications: Abscess, obstruction, perforation, fistulae

Scans: Plain x-ray, CT

Question 9

Acute cholecystitis:
Normally secondary?
Diagnosis basis?
Scans?

Answer 9

Almost always secondary gallstones

Diagnosis based on:
• One local sign of inflammation (RUQ pain etc)
• One sign of inflammation (fever ,WCC, CRP)
• Confirmatory imaging

Scans:
USS: Reveals gallstones, GB wall thickening, local fluid
CT: Can be false -ve
MRI: If biliary tree dilatation

Question 10

What is an MRCP?

Answer 10

MR cholangiopancreatography

Question 11

What is Emphysematous cholecystitis?

Treatment options?

Answer 11

Air in gallbladder wall.
Common in diabetics

Treatment: Medical, interventional radiology, surgery

Question 12

Small bowel obstruction:
Common in?
Symptoms?
Signs?
Imaginig defines?
Scans?

Answer 12

• Common – adhesions, cancer, herniae and gallstone ileus
• Symptoms: vomiting, pain and distension
• Signs: Increased bowel sounds, tenderness, palpable loops
• Imaging defines: site, cause, severity and detects complications (eg perforation, ischaemia)

Scans:
X-ray: For initial inspection. Can miss fluid filled loops.
CT: Transition point revealed, key. Adhesions not seen.

Question 13

Large bowel obstruction:
Causes?
Consistency of clinical presentation?
Surgeon wants to know?
Scan used?

Answer 13

Causes:
• Colorectal cancer 60% • Volvulus 15%
• Diverticulitis 10%

Clinical presentation often variable

Surgeon wants to know: Site, cause, distant disease

Scan used:CT
• sens/. Spec >93% 
• Transition point
• Underlying mass • State of caecum
• Distant disease

Question 14

Different forms of perforation in GIT?

Answer 14

Perforated ulcer
Diverticular **

(Less common: 2ndary to cancer, ischaemia)

Question 15

Scan used to identify perforation?

Answer 15

CT:
• High sens and spec 
• Shows free fluid
• Will often show clues to site of origin (86%)
-Distribution gas
-Defect in wall
-Localised inflammatory change

Question 16

Bowel ischaemia:
What % of CO = ishaemia?
Causes?
Signs/symptoms?
Scan chosen?

Answer 16

If <10% CO to GI, then ischaemia develops

Cause:
• Arterial occlusion – 60-70%
• Venous occlusion – 5-10%
• Non-occlusive hypoperfusion – 20-30%

S/S:
• Severe abdominal pain
• Vomiting, diarrhoea, distension inconsistent
• Borderline amylase, raised WCC, acidotic

Scan: Biphasic CT
-Shows site of occlusion, length of affected bowel

Question 17

In summary, the following scans are used for:

• Plain film?
• USS? Hint: RHS
• CT?

Answer 17

Role of plain film: obstruction orperforation

Role of USS – RUQ/ RIF pain

Role CT – Primary imaging technique for acute abdominal pain except for acute cholecystitis/ appendicitis