This site is targeted at medical and radiology professionals, contains user contributed content, and material that may be confusing to a lay audience. Use of this site implies acceptance of our Terms of Use.

Crohn's disease vs. ulcerative colitis

Dr Yuranga Weerakkody and Dr Frank Gaillard et al.

Due to the overlap in clinical presentation of Crohn's disease (CD) and ulcerative colitis (UC), imaging often has a role to play in distinguishing the two. Distinguishing features include:

bowel involved
- CD : small bowel 70 - 80%, only 15 - 20% have only colonic involvement
- UC : rectal involvement 95%, with terminal ileum only involved in pancolitis (backwash ileitis)
distribution
- CD : skip lesions typical
- UC : continuous disease from rectum up
gender
- CD : no gender preference
- UC : male predilection
colonic wall
- fat halo sign seen in 61% of chronic UC cases, but only in 8% of CD ²
- bowel wall is thicker in CD than in UC (when colon involved) ²
- serosal surface smooth in UC (95%), irregular in CD (80%) ²
perianal involvement
- UC : although rectal involvement is very common, perianal complication are not as frequently seen
- CD : common, seen in 82% of patients ²
  - stranding of ischiorectal fossa / perirectal fat (73%)
  - fistulas / sinus tracts (22%)
mesenteric creeping fat
- CD : common in chronic cases
- UD : not seen, as small bowel not involved
abscess formation
- CD : common, eventually seen in 15 -20% of patients
- UC : uncommon
extraintestinal complications
- gallstones, seen in 30 - 50% of CD patients ²
- primary sclerosing cholangitis more common in UC
- hepatic abscess seen in CD
- pancreatitis more common in CD