Radiology Flashcards
main indications for an AXR?
acute abdominal pain- although shouldn’t often be performed in this situation
bowel obstruction-MAIN indication
acute flare of IBD, ?toxic megacolon
renal calculi- 70% will be seen on AXR, but low dose CT is better
foreign bodies
investigation of choice for gallstones?
US scan
adequate exposure for AXR?
from xiphisternum to PS
ABCs for AXR presentation?
air/gas- air normally present in stomach and large bowel, should not be present in small bowel
bones
calcification/artefacts
soft tissue structures
why should gas NOT normally be present in small bowel on AXR?
small bowel= transit organ, rapid movement through bowel so shouldn’t be stasis-segmentation.
3 most common causes of SBO?
adhesions
hernias
strictures e.g. Crohn’s disease
3 most common causes of LBO?
colorectal cancer
strictures e.g. diverticular disease, Crohn’s
volvulus
where would renal calculi be visible on an AXR?
along line of transverse processes of lumbar vertebrae as this is the course of the ureters
what may cause LNs to be calcified and visible on AXR?
TB
sarcoid
post lymhoma tment
upper limit of normal diameter of small bowel, large bowel and caecum?
small= 3cm
large (TC)= 6cm
caecum= 9cm
why can the caecum have a relatively larger diameter than small bowel or transverse colon before abnormal?
thin wall more distensible
BUT this means if abnormal, becomes ischaemic very quickly as high pressure exceeds venous pressure and arterial pressure insufficient, and high risk of perforation
initial investigation in suspected bowel perforation?
erect CXR
AXR shows gross dilation of large bowel (peripheral position, teniae coli) and no small bowel present, LBO suspected, is urgent surgery required?
YES
if no small bowel present, then ileo-caecal valve must be competent, and so decompression of large bowel unable to take place, so high risk of perforation.
why can caecal volvulus occur in some patients and not in others?
occurs in pts in whom caecum not attached to posterior abdominal wall.
AXR of a sigmoid volvulus characteristically shows a coffee bean sign, originating in LLQ. other than location, how can this be distinguished from a caecal volvulus?
in sigmoid, large bowel prox to volvulus will be dilated, whereas in caecal, no other large bowel will be seen due to distal bowel collapse.
AXR appearance of toxic megacolon?
grossly dilated large bowel to >6cm, large bowel pseudopolyps- areas of normal mucosa when bowel wall inflammation
clinically, ptnt systemically unwell (toxic)-SIRS
what is ‘thumb printing’ on an AXR, and in what conditions is it seen?
thickened haustra
occurs in IBD, and when colon oedematous for other reasons e.g. in LBO with high pressure exceeding venous pressure.
what must always be considered if unable to see psoas muscle on AXR?
AAA
what condition is associated with lead pipe sign on AXR?
UC
give 3 features on AXR indicating perforation?
falciform ligament visible
triangle of black between bowel loops
rigler’s sign- well defined bowel wall (both sides) due to gas either side(in bowel and free intra-abdominal gas).
predisposing factors to sigmoid volvulus?
excessively mobile colon
mega-colon
chronic constipation
sigmoid volvulus tment?
flatus tube insertion
endoscopic decompression
surgical resection if ischaemic bowel, or recurrent sigmoid volvulus
standard AXR projection?
supine
