Session 10 - Imagine imaging of the GI tract Flashcards
Give five different types of imaging used to investigate the GI tract
- Plain x-rays
- Contrast studies
- Ultrasound
- Cross-sectional imaging
- Angiography
Give two types of x-rays
- Abdominal x-ray
* Erect cheat x-ray
Give four types of contrast studies
- Barium swallow
- Barium enema
- Barium meal/follow through
- Water soluble contrast studies
Give two types of cross sectional imaging
- Computed tomography
* Magnetic resonance imaging
What are the risks of imagine?
• Radiation
○ Carcinogenesis
○ Genetic
○ Developmental risk to foetus
What is a contrast study used for?
• Defining hollow viscera
Give a water soluble contrast
• Iodine used
What is a barium enema used for?
• Study where contrast medium is inserted rectally
What is ultrasound?
- Use of sound waves to generate an imahe
- Frequency above audible range of human hearing
Usually 2-18 MHz
What are the advantages of ultrasound?
- Cheap compared to CT and MRI
- Portable
- Highly user dependent
What can ultrasound be used for?
- To determine if patient has gall stones
- See if common bile duct inflated
- Liver, protal vein and appendix
What is GI angiography?
- Injection of radio-opaque contrast agent intravenously and then using various methods to capture the image
- Used for both bleeding and ischaemia to allow visualisation of the GI tract
Give four key features of an abdominal x-ray
- Stomach
- Small and large bowel
- Soft tissues
- Bones
Give 6 soft tissues that can be visualised on an abdominal x-ray
- Liver
- Spleen
- Kidneys
- Psoas major
- Bladder
- Lung bases
When are the intestines visible?
When filled with gas
When are the intestines not visible?
• When filled with fluid
Give four common reasons for requesting an abdominal x-ray
- Acute abdominal pain
- Small or large bowel obstruction
- Acute exacerbation of IBD
Renal colic
What are the circular folds of the small bowel called?
- Valvulae conniventes
* Appear as lines that appear to cross the whole of bowel lumen
Where is the large bowel seen on an abdominal x-ray?
- Periphery
* Possible to see haustra on the x-ray
What does faeces look like on an x-ray?
Clouds in the lumen
What is the rule of 3/6/9 in checking the small and large bowel for gas obstruction?
- Small bowel is said to be dilated when it is greater than 3cm
- Large bowel when it is greater than 6cm
- Caecum (when the ileocaecal valve is working) is said to be dilated when it is >9cm
What does small bowel obstruction usually present with?
- Vomiting
- Mild distension
- Absolute constipation is a late feature
Why may you vomit earlier in small bowel obstruction?
• Obstruction closer to mouth
Give four causes of small bowel obstruction
• Adhesions
• Hernias
○ Inguinal, femoral, incisional
• Tumours
Inflammation
What do people with large bowel obstruction present with?
- Abdominal pain and distension, with constipation as an early feature
- Vomiting and faeculance is a late feature
What is the abdominal pain like in large bowel obstruction?
• Colicky, but not as frequent as small bowel obstruction
Give five causes of large bowel obstruction
- Colorectal cacrinoma
- Diverticular stricture
- Hernia
- Volvulus
- Pseudo-obstruction
What is a volvulus?
• This is when a viscera twists around itself or the mesentery
Most common is a sigmoid/caecum volvulus
What happens when a volvulus occurs?
• Twisting occurs and the enclosed loop of bile dilates
Increases risk of perforating or cutting of its blood suppl
Name 6 abnormalities which can be visualised on an x-ray
- Pancreatitis
- Aneurysms
- Nodes
- Bones
- Artifacts
- Foreign body
- Kidney stones
What is an erect chest x-ray useful in diagnosing?
• A perforated bowel
Give 6 causes of a perforated bowel
- Peptic ulcer
- Diverticular disease
- Tumor
- Obstruction
- Trauma
- Iatrogenic
Why does the chest x-ray need to be erect for a perforated bowel?
• The diaphragm will only be separated from other viscera by the air rising to the top
What is normally found in the peritoneal cavity?
• Small amount of fluid
What is an abdominal CT?
- High dose radiation
- Good spatial resolution (Poor contrast compared to MRI)
Use of IV or oral.rectal contrast
What is MRI?
- No radiation
- Good spatial and contrast resolution
Time consuming
What is an MRI scan used to visualize the gall bladder and biliary tree?
• Magnetic resonance cholangio-pancreatogram
