IOD GI Imaging

Question 1

IBD?

Answer 1

Autoimmune conditions
Ulcerative colitis: Inflammation confined to mucosal and submucosal layer of colon that extends from rectum proximally in continuous fashion
Crohn’s disease: Transmural inflammation involving any part of the GI tract, from mouth to anus, with skip lesions

Question 2

Ulcerative colitis?

Answer 2

Rectum is almost always involved (95%) and various amounts of more proximal colon, in continuity
Imaging features:
Bowel wall thickening (‘thumbprinting’ on AXR which is thickened mucosal folds due to bowel wall oedema)
In chronic cases, the bowel becomes featureless with loss of normal haustral markings, luminal narrowing and bowel shortening (‘lead pipe’)

Question 3

Ulcerative colitis complications?

Answer 3

Complications: 
toxic megacolon
perforation
stricture 
bowel cancer
‘Toxic megacolon’: atonic colon with progressive dilatation; risk of perforation
Serial AXRs to assess
Definitive management is surgical

Question 4

normal diameter of colon?

Answer 4

6cm

Question 5

Chorns disease?

Answer 5

Transmural inflammation involving any part of the GI tract, from mouth to anus:
Terminal Ileitis – 80%
Ileocolic – 50%
Colitis – 20% {Differentiate from UC - Crohn’s patients tend to have rectal sparing}
Perianal Disease – 30%
Oral and Esophagus – small percentage

Question 6

Crohns disease

Answer 6

Complications: 
Abscess
Fistula
Obstruction
Cancer

Question 7

imaging in CD?

Answer 7

These patients are often young (15-40yrs) and may have repeated disease flare ups
CT is a helpful imaging modality to assess the bowel and look for complications, however it exposes patients to ionising radiation
Ultrasound and MRI are important radiation-sparing alternatives

Question 8

findings on CT?

Answer 8

Findings on cross-sectional imaging (CT/MRI)
bowel wall thickening (most frequently seen in the terminal ileum)
bowel wall increased enhancement
comb sign (hypervascular appearance of the mesentery)
strictures and fistulae
abscesses (eventually seen in 15-20% of patients)

Question 9

Findings in CD on US?

Answer 9

Findings on ultrasound:
bowel wall thickening
Increased vascularity of the bowel wall
‘fat wrapping’ of the mesentery

Question 10

Appendicitis CP?

Answer 10

Inflammation of the appendix- short vestigial organ arising from the caecum
Peak incidence in teenagers and young adults
Pain which may migrate from umbilicus to right iliac fossa
Fever
Nausea and vomiting
Raised inflammatory markers

Question 11

Appendicitis imaging?

Answer 11

CT is the most sensitive and specific imaging modality
However these patients are usually young and CT uses ionising radiation
Ultrasound is an alternative modality that can detect appendicitis; if an inflamed appendix is visualised, the diagnosis is confirmed
The appendix can be difficult to visualise on US, especially if retrocaecally positioned; if the appendix is not seen, appendicitis is not excluded and the patient may then need CT
CT if US unavailable

Question 12

Appendicitis features?

Answer 12

Mural thickening (wall thickness >3mm)
Dilated appendix (lumen >6mm)
Surrounding inflammatory change
Abscess associated with the appendix
In severe cases, there may be perforation- free fluid/gas in the abdominal cavity
A focus of calcification may be seen in the appendix- appendicolith

Question 13

Diverticulitis CP?

Answer 13

Acute diverticulitis= inflammation of colonic diverticula
Sigmoid colon is the commonest site
Incidence increases with age- commonest in older patients
Lower abdominal pain
Fever
Change in bowel habit
Raised WCC

Question 14

Diverticulitis imaging

Answer 14

Colonic diverticula are small outpouchings of the bowel wall, which are visible on CT
They may be uncomplicated- ‘colonic diverticulosis’
They can become inflamed in acute diverticulitis:
Bowel wall thickening
Surrounding inflammatory change
Free fluid in the abdomen

Question 15

Complications diverticulitis?

Answer 15

_perforation, abscess formation, fistulation

Question 16

Bowel cancer?

Answer 16

Colorectal carcinoma is the most common cancer of the gastrointestinal tract and the fourth most frequently diagnosed malignancy in adults
Localisation
recto-sigmoid: 55%
caecum and ascending colon: ~20%
ileocaecal valve: 2%
transverse colon: ~10%
descending colon: ~5%

CT and MRI are most frequent modalities used for assessment
FL colonoscopy or CTC

Question 17

Imaging colorectal features?

Answer 17

Focal irregular mural thickening
If locally advanced, may invade through bowel wall into surrounding fat or nearby structures
There may be locally enlarged lymph nodes
Metastatic disease to other organs, eg liver, in advanced disease

Question 18

Complications of colorectal cancer?

Answer 18

Obstruction, perforation

Question 19

Barium enema?

Answer 19

showing a colonic tumour as an ‘apple core’ lesion in the ascending colon

This was previously a common radiologic investigation to assess for a colonic tumour but is no longer routinely performed

Question 20

CT colonography?

Answer 20

‘Virtual colonoscopy’
Patient has to undergo bowel prep in advance
Air is insufflated via a rectal tube
CT images are obtained with patient lying supine and prone
Images are analysed with the aid of special software to detect any lesions (polyps/tumours)

Question 21

Rectal cancer?

Answer 21

In recent years, MRI has become the mainstay for local staging of rectal cancer
As well as demonstrating the location and size of the primary tumour, it can assess for local spread through the bowel wall into the surrounding fat and other structures
It can also demonstrate locally enlarged lymph nodes

Question 22

biliary pathology?

Answer 22

Gallstones are the commonest cause of biliary pathology
They may cause
intermittent bouts of RUQ pain typically related to eating- biliary colic
acute gallbladder infection- cholecystitis
blockage of the biliary tree (biliary obstruction), most commonly due to a gallstone in the CBD

Question 23

Biliary imaging and complications?

Answer 23

Gallstones are often not visible on CT (may be visible if calcified)
Ultrasound is therefore the preferred modality for detecting gallstones
Ultrasound can also assess for features of cholecystitis, which can also often be seen on CT and include:
Mural thickening
Gallbladder distension
Pericholecystic fluid
Complications of cholecystitis include gallbladder perforation and liver abscess
The biliary tree can be evaluated with ultrasound or magnetic resonance cholangiopancreatography (MRCP) (a type of MRI)