8.1: Imaging of the GI tract Flashcards
List the two plain X-rays, four contrast studies, three forms of cross-sectional imaging and one more imaging modality of the GIT
Plain X rays: abdominal or chest (AXR or CXR)
Contrast Studies: Preformed after an overnight fast
- Barium swallow (endoscopy); can identify motility and anatomical lesions
- Barium enema: up the bum
* small bowel follow through with MRI
* normal enema follow through with CT - Mariam meal/follow it all the way through the GIT (endoscopy); examines stomach and DD
- Water soluble contrast studies
Cross-sectional imaging:
- Computed tomography (CT)
- Magnetic resonance imaging (MRI)
- Angiography
Or ultrasound!
What structures represent the dark parts, darker grey parts, light grey, white and bright white parts on an x-ray?
Dark: gas or air Darker grey: fat Light grey: soft tissue/fluid White: bone or calcified structures Bright white parts: metal
List the 6 components of the AXR and contrast studies checklist
- Patient identification
- Clinical status: how well they are
- Patient mobility
- Patient location and travel details
- Indications: Why do we need an AXR
- Contraindications
List the 6 reasons you might request an AXR
- Acute abdominal pain - although its debatable
- Small or large bowel obstruction
- Acute exacerbation of IBD
- Foreign body detection
- Small print indications
- Renal colic; may indicate stones - but CT now the first line of investigation
Name four clinical signs of a small or large bowel obstruction.
What features of a history could help you distinguish between a small or large bowel obstruction? define any differences depending on which obstruction it is
- Absence of bowel sounds
- Vomiting
- Constipation
- Distension
- Colicky pain (comes and goes in waves)
In LB obstruction
- vomiting will be feculant
- constipation will be early and absolute
- distension will be significant
- less frequent colicky pain
In SB obstruction
- vomiting first, constipation later
- more frequent colicky pain
Name 8 things you may look at on an X ray
- Where it was taken
- Identity of the patient
- Technical adequacy: is it a good quality X ray; orientation (L and R), field (both hemidiaphragms, hip joints) and penetration (outline of bone or vertebral body)
- Artefacts and foreign bodies
- External, surgical, foreign: up the oral/nasal, rectal, urethra or vaginal route - GI tract and bowel gas patterns: is there a normal looking gas pattern (all normal bowels should have some gas)
- Solid patterns: Should be able to see kidneys near the lateral psoas muscle margins
- Aorta and vessels: looking for any calcification of the vessels
- Muscles and bone
When will fluid and gas level not be shown on an X ray?
If the patient is lying down, (fully fluid filled will not be visible)
What is the small bowel’s position on an X-ray? Name one feature of the small bowel that is characteristic on an X-ray, do you always see the small bowel?
Central position but often don’t see the small bowel
Characteristic feature: valvulae conniventes: mucosal folds (that increase the SA!) appearing as long thin lines throughout the whole small bowel’s diameter
What is the larger bowel’s position on an X-ray and what features would you expect to see?
Peripheral position (like a picture frame around the small bowel)
Should see: Haustra (mucosal folds but don’t cover the whole diameter, appear as black areas surrounded by grey areas), feces and gas
Name five abnormal gas patterns that are important to recognize on an X-ray
- Small bowel obstruction: diameter has swelled to >3cm
- Large bowel obstruction: diameter has swelled to >6cm
- Paralytic ileus: obstruction due to paralysis, swelling
- Volvulus: twists and swelling
- Toxic megacolon (megacolon)
Discuss causes of a small bowel obstruction using the headings below
A) extrinsic
B) bowel wall lesions
C) intra-luminal
a) adhesions, hernias and volvulus
B) tumours, inflammation i.e; Crohn’s disease
C) foreign bodies, food bolus and meconium (CF), gallstones and intussusception
Name five causes of a large bowel obstruction
- Colorectal carcinoma
- Diverticula stricture
- Hernia
- Volvulus
- Pseudo-obstruction
What are some likely investigations to be performed following an X ray?
CT of the abdomen and pelvis with contrast
What is volvulus? Where does it commonly occur (including which population group) and why is it a surgical emergency?
*what does it look like?
Torsion of the bowel so it twists around the mesentery. Occurs commonly in the sigmoid colon (or caecum, just very rare) of constipated elderly patients.
The enclosed bowel loop dilates and there is high risk of perforation and ischemia
Looks like a coffee bean :)
What are two common causes of toxic megacolon? How does it appear on an x-ray?
Commonly due to ulcerative colitis or colitis. There is colonic dilation and the ‘thumb printing’ sign
