Imaging of GI tract Flashcards
Identify examples of imaging methods.
- Conventional: X- ray, fluoroscopy
- Ultrasound
- CT
- MRI
Which investigation is initially performed in an acute abdominal pain ?
First line: X-ray and ultrasound
What position is abdominal X-ray done in ?
Erect (Air/ fluid levels seen), or
Supine (gas seen as blobs of dark or lucent areas)
What is the normal gas distribution in the abdomen ?
- Stomach (Left upper portion).
- Small intestine- 2/3 gas filled loops none larger than 2.5 cm centrally
- Large intestine mostly in distal portion i.e sigmoid colon and rectum. Peripherally and in lower portion (pelvis). Max. diameter 5.5 cm, caecum the beginning of colon can be up to 8 cm.
How may we distinguish between gas in the large, and small intestine ?
- Small intestine: central, thin folds going across entire circumference (valvulae conniventis)
- Large intestine: periphery, thicker and incomplete folds
Describe the X-ray appearance of a small intestine obstruction.
- Distended (>2.5 to 3 cm)
- Multiple central fluid levels
- Less gas or no gas in large intestine
Describe the X-ray appearance of a large intestine obstruction.
- Distended gas filled loop or air fluid levels at the periphery
- Caecum over 9 cm, rest over 5/6 cm.
- Look for haustrae to differentiate.
- Less or no gas beyond the level of obstruction.
Identify possible reasons for finding gas outside the stomach/intestine in an abdominal X-ray.
- Due to intestinal perforation
* Introduced from outside by injury, operation
Identify locations on an abdominal X-ray where we may look for gas (in the wrong place).
- Below the diaphragm in erect film.
- Surrounding the intestine (riglers sign: gas within and outside intestine outlining the intestinal wall).
- Gas collection which looks of different shape (triangle, football).
- Gas outlining the ligaments and muscles.
Define sigmoid volvulus. Describe the X-ray findings for sigmoid volvulus.
Major cause of large intestine obstruction.
Findings:
- large, dilated loop of the colon, often with a few air-fluid levels
- absent rectal gas
- coffee bean sign (the involved bowel wall is oedematous, and the contiguous walls form a dense white line on plain films of the abdomen. This line is surrounded by the curved and dilated gas-filled lumen, resulting in a coffee bean-shaped structure)
Identify possible causes of abnormal calcifications in the abdomen.
- Stones: gall, renal/ ureteric/ bladder
- Calcification in vessel wall (age related atherosclerosis, diabetes, aneurysm)
- Calcification in organs (pancreas, renal cyst, uterine fibroids)
Describe the X-ray appearance of calcification.
Well defined radiodensities
Identify the main pros of ultrasound as an imaging technique.
- No radiation. particularly good for children and pregnant women.
- Easy availability
- Can be done at bedside
- With help of color Doppler blood supply to organ can also be assessed.
Identify some indications for abdominal ultrasound.
- Can be used for quick assessment of abdomen in trauma cases( FAST scan)
- Only 15% of gall stones are calcified enough to be seen on plain x-ray. Ultrasound is the best test to assess for gall stones and gall bladder inflammation
- Utility of ultrasound in serial assessment of foetal well being throughout pregnancy is well known
- Also useful in assessing complications related to pregnancy( bleeding during pregnancy-placental rupture, low lying placenta, ectopic pregnancy)
- Best 1 st line test to assess uterus and ovaries
- In acute abdomen in children (Intussusception, Congenital hypertrophic pyloric stenosis, intestinal obstruction, testicular infection and torsion)
- In dynamic assessment (abdominal and inguinal hernia)
What are the main indications for abdominal CT scan use ?
- Usually a 2nd line imaging investigation after x-ray and ultrasound to clarify the findings further.
- Some times 1st line if the clinical suspicion is high( cases of trauma, appendicitis).
- Can pick up cancer early( e.g colon cancer).
