Table 11

A summary of the distinguishing features of the three IBDs: ileal/ileocolonic CD, isolated colonic CD, UC

Ileal/ileocolonic CDIsolated colonic CDUC
SexSlightly commoner in females (55%)Commoner in females (65%)Equal or slight male predominance
GeneticsCrohn's-associated genotype including NOD2/CARD15Genotype midway between CD and UC
Associated with HLA-DRB1*01:03 but not NOD2/CARD15
UC-associated genotype including HLA-DRB1*01:03
SmokingMarked association
Worsens prognosis
Weak association
Possibly worsens prognosis
Marked negative association
Oral contraceptionPositively associatedPositively associatedPositively associated (mainly in smokers)
SerologyASCA commonly positive
pANCA usually negative
ASCA less commonly positive than ileal/ileocolonic CD
pANCA positive in minority
ASCA usually negative
pANCA commonly positive
Mucosa-associated microbiotaMarked changes commonly including increased Proteobacteria (eg, Escherichia coli) and Fusobacteria, reduced Firmicutes (eg, F. prausnitzii)Intermediate changes similar to ileal/ileocolonic CD but less consistentModest changes, including slight increase in E. coli but no reduction in F. prausnitzii
Response to mesalazineNo efficacyNo efficacyGood efficacy
Response to anti-TNFGood efficacyGood efficacy—probably better than for ileal/ileocolonic

Good efficacy
Response to exclusive enteral nutritionGood efficacyProbably good efficacy but mixed reportsNo efficacy
Surgery rate and typeRequired in majorityRequired in minority
Segmental colectomy effective
High failure for pouch-anal reconstruction
Required in minority
Segmental colectomy not effective
Low failure for pouch-anal reconstruction
  • CD, Crohn's disease; ASCA, anti-Saccharomyces cerevisiae; HLA, human leucocyte antigen; pANCA, perinuclear antineutrophil cytoplasmic antibodies; TNF, tumour necrosis factor.