10a.) Imaging of GI Tract Flashcards
State 5 generic ways of imaging the GI tract; provide some examples for each
-
Plain x-rays
- Abdominal x-ray (AXR)
- Chest x-ray (CXR)
-
Contrast studies
- Barium swallow
- Barium enema
- Barium meal/follow through
- Water soluble contrast studies
- Ultrasound
-
Cross sectional imaging
- Computed tonography (CT)
- Magnetic resonance imaging (MRI)
- PET-CT
- Angiography
State 3 reasons why a doctor may request an AXR
- Acute abdo pain
- Small or large bowel obstruction
- Acute excerbation of IBD
NOTE: used to use for renal colic but now CT is first line
What projection do we use on an AXR?
Anterior-posterior
State what features you can see on AXR
Think ABCDE
- Bowel gas
- Soft tissue structures
- Bones
OR…
- A= air/gas
- B= bowel
- C= calcification & stones
- D= dem bones
- E= everything else
Or…. ABDOX
Describe the ABDOX mnemonic in full
Used as a checklist of thing to look for on an AXR:
- A= air: where it should and shouldn’t be
- B= bowel: size and wall thickness
- D= dense structures: calcification, bones
- O= organs & soft tissues: liver, spleen, kidneys
- X= eXternal: objects & artefacts
Describe whether the hollow part of GI tract would be visible if filled with:
- Gas
- Gas & fluid
- Fully fluid
- Gas= visible
- Gas & fluid= visible
- Fully fluid= not visible
State what each of the following contains in terms of solid, liquid and gas and also state whether transit time is slow, medium or fast?
- Stomach
- Small bowel
- Colon
- Stomach: fluid & lots of gas- medium
- Small bowel: fluid - fast
- Colon: faeces & gas - slow
Describe the appearance of small bowel on AXR
- Central position
- Valvulae conniventes (lines that cross entire bowel wall)
Describe the apperance of large bowel on AXR
- Peripheral position
- Haustra (seen as incomplete lines across bowel wall)
- Faeces & gas present dueto slow transit time of large bowel
Transverse colon can hang down into pelvis; true or false?
True
State the diameter of:
- Small bowel
- Large bowel
- Caecum
… if there is a bowel obsturction in each of these areas
- Small bowel obstruction: >3cm
- Large bowel obstruction (with incompetent ileocaecal valve): >6cm
- Large bowel obstruction (with competent ileocaecal valve): caecum >9cm
RULE OF 3’s: 3, 6, 9
What does this image show?
Small bowel >3cm therefore small bowel obstruction
Describe how someone with a small bowel obstruction may present
- Nausea & vomitting (EARLY)
- Distentsion (mild)
- Absolute constipation (LATE)
- Colicky pain
State some possible causes of smal bowel obstruction
- Adhesions
- Hernias (inguinal, femoral, incisional)
- Tumours
- Inflammation
What does this image show?
Large bowel obstruction
Describe how someone with a large bowel obstruction may present
- Vomitting (late, faeculant)
- Distensionn (significant)
- Pain
- Absolute constipation
State some possible causes of large bowel obstruction
- Colorectal cancers
- Diverticular stricture
- Hernia
- Volvulus
- Pseudo-obstruction
What is volvulus?
Which part of bowel is it common in?
Describe appearance on AXR
- Twisting of bowel its mesentery (the enclosed bowel loops then dilates which can lead to perforatin or ischaemia. Bowel proximal also dilates)
- Sigmoid colon
- Coffee bean sign that starts in left iliac fossa and goes towards right upper quadrant
What does this AXR show?
Sigmoid volvulus (coffee bean sign starting in LIF towards RUQ)
Is AXR the gold standard for infection and inflammation? Discuss
- Not the gold standard. But may see acute or chronic changes e.g.:
- Mucosal thickening
- Featureless colon
- Bowel wall thickening
What is toxic megacolon?
Who is it common in?
What are some complications of toxic megacolon?
- Abnormal dilation of colon (megacolon part) that is very serious/can be life threatening (toxic part)
- Common in IBD patients (more so in UC)
- Complications: sepsis, perforation,
State some features of toxic megacolon on AXR (3)
- Colonic dilation
- Oedema
- Pseudopolyps
What is meant by ‘lead pipe colon’ and who is it comon in?
- Featureless colon with lack of haustra
- Common in UC patients
What does this AXR show?
Lead pipe colon
What is meant by thumb printing and what does it suggest?
- Oedematous thickened haustra and bowel wall
- Suggests active inflammation (often in UC)
Where is the liver on this AXR?
State some of the organs you can see on AXR
State some of the bones you can see on AXR
Where is the spleen on this AXR?
Where are the kidneys on this AXR?
Where is the bladder on this AXR?
On AXR you can see 3 types of calcification; state these
- Renal canaliculi
- Vascular calcification
- Calcification of pancreas following chronic inflammation
What does this image show?
State some causes of perforation
- Peptic ulcer
- Diverticular
- Tumour
- Obstruction
- Trauma
- Iatrogenic
What is the imaging of choice for perforation?
Erect chest x-ray- see gas under diaphragm (pneumoperitoneum)
What does this abdominal CT show?
Pneumoperitoneum
Foreign bodies are also visible on AXR; true or false?
True
What two contrasts can be used to define hollow viscera?
- Water soluble
- Barium
Describe the difference between a barium swallow, meal, follow through
Drink barium then take x-rays:
- Swallow: looks at how it moves through oesophagus
- Meal: looks at stomach
- Follow through: looks at small intestine
Describe a barium enema
Barium liquid passed into large bowel through anus then x-rays taken
Discuss the advantages and disadvantages of an abodminal CT
Advantages
- High resolution
- Can add contrast to get btter image
Disadvantages
- High dose radiation
Individual images from a CT scan can be reformatted and combined to produce a 3D representatoin of the scanned anatomy e.g. a virtual colonscopy; true or false?
True
What is contrast induced nephropathy?
Impairment of renal function- measured as either a 25% increase in serum creatinine from baseline or a 0.5mg/dL increase in absolute SCr value within 38-72 hours after intravenous contrast administration
Does MRI use ionising radiation?
No
Discuss advantages and disadvantages of abdo CT
Advantages
- Detailed, high contrast image
- No radiation
Disadvantages
- Time consumiing
- Expensive
Discuss the advantages and disadvantages of abdominal ultrasound
Advantages
- Cheap
- Portable (fast)
- No radiation
Disadvantages
- Highly user dependent
What is abdominal ultrasound often used to visualise?
Biliary tree (for gallstones and dilated bile duct)
What are abodminal angiograms used for?
To detect:
- Aneuryseums
- Stenosis
- Blockage of vessel
Be able to label CT of abdo
Be able to label MRI of abdo
Be able to lable MRI of abdo
Be able to label MRI of abdo
(L1)
Be able to label CT of abdo
(T12)
Be able to label MRI of abdo
(L4)
What is paralytic ileus?
Intestinal blockage in the absence of an actual physical obstruction; due to malfunction in nerves and muscles that impairs digestive movements
What organ is this an AXR?
Stomach
