Imaging Of GIT Flashcards
What to look for in abdominal X-Ray?
Gas, soft tissue, calcium, foreign object.
What does normal gas distribution in an abdominal X-Ray look like?
Air is dark areas.
- gas bubble in stomach
- small intestine - 2/3 gas filled loops none larger than 2.5cm centrally
- large intestine - mostly in distal region e.g. sigmoid colon and rectum. Peripherally and in pelvis. Max diameter 5.5cm, caecum and beginning of colon can be up to 8cm.
How do you tell the difference between the small and large intestine?
- SI - central, thin folds going across entire circumference (valvulae conniventis/plica circulares)
- LI - periphery thicker and incomplete folds.
What does a small intestine obstruction look like in an abdominal x-ray?
- Distended (>2.5cm to 3cm).
- Multiple central fluid levels.
- Less gas or no gas in large intestine.
What does a large intestine obstruction look like in an abdominal x-ray?
- Distended gas filled loop or air fluid levels at the periphery.
- Caecum over 9cm, rest over 5/6cm.
- Look for haustra3 to differentiate.
- Less or no gas beyond level of obstruction.
Why would gas be in the wrong place in an X-Ray? And where do you look for gas in the wrong place?
- Due to intestinal perforation or could have been introduced from outside by injury or operation.
- wrong places include underneath diaphragm in erect film, surrounding the intesting (Riglers Sign: gas within and outside of intesting outlining the intestinal wall), gas outlining the ligaments and muscles, and gas collections which look like a different shape e.g. triangle or football-shaped.
What abnormal calcifications can be spotted on the X-Ray?
- stones: gall/renal/ureteric/bladder
- calcification in vessel wall (age-related atherosclerosis, diabetes, aneurysm)
- calcification in organs (pancreas, renal cyst, uterine fibroids).
What fluoroscopy can be used?
- Contrast (barium or thin water soluble contrast) swallow - oesophagus
- Barium meal
- Follow through
- Enema
- Limited use after advent of CT and MRI/ easy availability of endoscopy.
Why use ultrasound?
- No radiation (children and pregnant women)
- Easy availability
- Can be done bedside
- Blood supply can also be assessed.
- Quick
- Best to find gall stones and gall bladder inflammation.
- Foetal assessment and pregnancy complications.
- Best 1st line to assess uterus and ovaries, acute abdo in children (intussusception, congenital hypertrophic pyloric stenosis, intestinal obstruction, testicular infection and torsion), and in dynamic assessment (abdo and inguinal hernia).
What do we use CT scans for?
- Usually 2nd line after Ultrasound or X-Ray to further clarify findings.
- Sometimes 1st line if clinical suspicion is high (cases of trauma and appendicitis).
- Can pick up cancer early (e.g. colon cancer)
- Allows cross-sectional evaluation unlike X-Ray.
- Cons: Radiation. Avoid unless very essential in children and pregnant women.
- Gives definitive diagnosis in most cases wirh positive findings on x-ray and/or ultrasound.
Pros and Cons of using MRI for abdomen?
- Pros - no radiation, cross-sectional imaging, better soft tissue resolution than CT, can be done in children and pregnant women after 1st trimester.
- Cons - availability, takes time, not safe for patients with metal in body, difficult for some patients (body habitus or claustrophobia), safety in pregnancy not proven (noise/heat deposition) so to be avoided for first 3 months.
Why would we use Nuclear Medicine?
Tc pertechnatate scan (Meckel’s Scan) - To identify Meckel’s diverticulum which can cause bleeding and obstruction, particularly in children.
Aunt Minnie
A collection of findings which immediately raise a specific diagnosis
