Imaging Of The GI System Flashcards
What is the ABDO X approach to an abdominal x ray?
ABDO X
- Air
- Bowel
- Dense structures + calcifications
- Organs + soft tissues
- external objects, lines + tubes
How do you differentiate between the small + large bowel on an abdominal x ray?
small bowel: central | valvulae conniventes | contains air or fluid
large bowel: peripheral | haustral folds | contains air or faeces
Reasons for requesting abdominal x ray
- position of iatrogenic items
- forgein objects
- confirm ureteric stone identified on CT
- specialist cases
US or CT preferred as first line
Where should you see air in an abdominal x ray?
- should only be within the bowel (intramural)
- not within the perioneal space (extramural) | pneumoperitoneum
What is pneumoperitoneum?
Air within the peritoneal cavity
abnormal
What is Rigler’s sign?
- Bowel wall crisply + clearly defined due to gas on both sides
- Seen in pneumoperitoneum on AXR
What imaging is best to detect pneumoperitoneum?
CT
Features of small bowel on AXR
- Central
- Valvulae conniventes (lines across whole diameter)
- Contains air or fluid
Features of large bowel on AXR
- peripheral
- haustral folds
- contains air or faeces
What is seen in sigmoid volvulus on AXR?
- coffee bean sign
- large gas filled viscus from pelvis + epigastrium
- normal positioned caecum
What is seen in caecal volvulus on AXR?
- Reverse C shaped viscus on right side ‘fetal appearance’
- Normal sigmoid
What does oedematous bowel wall indicate on AXR?
What sign shows this?
Inflammatory bowel disease
e.g. crohn’s, ulcerative colitis
Thumb printing
What is seen in inflammatory bowel disease on AXR?
- thumb printing sign: mucosa thickening of haustra due to inflammation + oedema
- lead pipe colon: loss of haustral markings
- toxic megacolon: colonic dilation, oedema + pseudopolyps
What does a coffee bean sign on AXR indicate?
Sigmoid voluvus
What does thumb printing sign on AXR indicate?
Irritable bowel disease
Bowel wall oedema
What do you look for for A on ADBO X?
air
- pneumoperitoneum
- rigler sign: bowel wall crisply + cleared defined
What do you look for on B of ABDO X?
Bowel
- sigmoid volvulus: coffee bean sign
- caecal volvulus: fetal
What is achalasia?
Impaired relaxation of lower oesophageal sphincter
Symptoms of achalasia
- weight loss
- halitosis (bad breath)
What is used to investigate + image achalasia?
What sign is seen?
- X ray
- Barium swallow + fluoroscopy
. - Bird beak structure of distal oesophagus
What are the upper limits for the normal diameter of:
- small bowel
- colon
- caecum
- small bowel: 3cm
- colon: 6cm
- caecum 9cm
3/6/9 rule
What is seen on a AXR in small bowel obstruction?
- dilatation of small bowel >3cm
- coiled spring appearance
- inspect inguinal region for hernias
Causes of pneumoperitoneum
Bowel perforation
Perforated duodenal ulcer
Recent abdominal surgery
Standard imaging for colon cancer if patient has been diagnosed already
CT
Standard diagnostic imaging for colon cancer
CT colonogram
Imaging of rectal cancer
MRI
for staging + follow up
Imaging for Crohn’s disease
CT for acute abdomen
MRI for diagnosis + follow up
What does pneumoperitoneum look liked on erect chest X ray?
Free gas under diaphragm
Space between liver + diaphragm
What is a barium swallow used to test?
Pharynx
Oesophagus
Proximal stomach
Outline a barium enema
- tube is inserted into rectum to visualise large intestines
- barium administered
- results are monitored using fluoroscopy
How can you visualise the vasculature associated with the GI system?
Angiogram
Methods of imaging the GI tract
X rays
Contrast studies
Ultrasound
CT
MRI
Angiography
How can bowel perforation be determined using imaging?
Erect CXR
Free gas under diaphragm
Features of toxic mega colon on AXR
colonic dilation
oedema
pseudopolyps
Pros and cons of abdominal ultrasound
Cheap
Portable
No radiation
.
User dependant
Pros and cons of abdominal MRI
Detailed
No radiation
High contrast image
.
Time consuming
Issue with claustrophobia
GI features at T12 in CT scan
Liver
Stomach
Spleen
IVC
Aorta + coeliac trunk
T12 vertebra
(Kidneys?)
GI features at L1 in CT scan
Liver
Stomach
Spleen
Pancreas
IVC
Aorta + SMA
Both kidneys
L1 vertebra
GI features at L3 on CT scan
Liver
Aorta + IMA
IVC
Colon
Small intestines
Psoas major muscles
L3 vertebra
GI features at L4 on CT scan
Iliac crest
Bifurcation of abdominal aorta
