GI: Imaging Flashcards
Why would you request an abdominal xray?
- acute abdominal pain
- small or large bowel obstruction
- acute exacerbation of IBD
- renal colic (although CT now first in line)
What is a systematic approach to assessing an abdo xray?
A - air/gas
B - bowel
C - calcification (bones and stones)
How do you differentiate the small bowel from the large bowel on an abdo xray?
The small bowel has a central position whereas the large bowel is at the periphery
The small bowel has valvulae conniventes that cross the entire wall whereas the large bowel just has haustra
What is the 3 6 9 rule of identifying bowel obstruction?
Small bowel dilation is >3cm
Large bowel dilation is >6cm
Caecum is max 9 cm
How does small bowel obstruction present?
Vomiting (early)
Mild distension
Absolute constipation (late)
Colicky pain
What can cause small bowel obstruction?
Adhesions following surgery
Hernias
Tumours
Inflammation
How does large bowel obstruction present?
Vomiting (late and faeculant)
Significant distension
Colicky pain
Absolute constipation
What can cause large bowel obstruction?
Colorectal carcinoma Diverticular stricture Hernia Volvulus Pseudo-obstruction
What is a volvulus?
Twisting of the bowel around its mesentery - encloses the bowel loop which can become ischaemic or perforate
Sigmoid volvulus is common
What is toxic megacolon?
Acute severe colonic distension
It is usually a result of acute deterioration of UC (sometimes crohns)
There is also oedema and pseudopolyps
What is thumb printing?
(google a picture)
Due to oedematous thickened haustra caused by acute inflammation (often UC)
What is pneumoperitoneum and what are the causes?
Abnormal presence of gas in the peritoneum
Caused by a perforated peptic/duodenal ulcer, tumour, perforated bowel from obstruction or trauma
What are contrast studies used for? eg barium meal
Contrast is used to define hollow viscera
What are the advantages and disadvantages of CT, MRI and USS?
CT: good spatial resolution but high dose radiation
MRI: no radiation, good resolution but time consuming
USS: no radiation, portable, cheap but highly user dependent
