title: High prevalence of undetected ulcerative colitis: data from the Nottingham fecal occult blood screening trial.
abstract: OBJECTIVE
  Inflammatory bowel disease (IBD) is usually diagnosed as a result of symptoms but occasionally is found during investigation for other conditions. An earlier report from Nottingham had found a high prevalence of previously undetected "asymptomatic" IBD detected as a result of colorectal cancer screening, and the aim of this study was to reassess the prevalence, symptoms, and outcome in these patients.
  
  
  METHODS
  We investigated subjects found to be fecal occult blood (FOB) positive in a randomized trial of FOB screening for colorectal cancer. All FOB-positive subjects were investigated by colonoscopy or flexible sigmoidoscopy and barium enema. Subjects with IBD were referred back to their general practitioner for any further investigation and treatment.
  
  
  RESULTS
  Seventy-five thousand two hundred fifty-three subjects (aged 45-74) were sent FOB tests and 44,838 (60%) completed a series of tests on one or more occasions. Of 133,000 test series, 1.5% were positive. During investigation 53 cases of previously undetected IBD (52 of ulcerative colitis) were found; 52% (27/52) had proctosigmoiditis only, whereas 25% (13/52) had pancolitis. Only 17% (9/52) were completely asymptomatic, with a half or more reporting some rectal bleeding (54%) or diarrhea (50%). The overall prevalence of undetected ulcerative colitis was 69/10(5) (95% CI = 50-88/10(5)) in people offered screening and 116/10(5) (95% CI = 85-147/10(5)) in people accepting screening and was higher in men. Of 32 subjects followed up 2-12 yr after diagnosis, 91% (29) continued to have few or no symptoms, with only 12 currently receiving any treatment for their colitis.
  
  
  CONCLUSIONS
  In comparison with detected disease, undetected ulcerative colitis is relatively common but does usually cause some symptoms. It generally appears to follow a benign course, but a significant proportion have extensive colitis and may therefore be at an increased risk of colorectal cancer.
authors.affiliation: Department of Surgery, University Hospital, Nottingham, United Kingdom.
authors.forename: G F
authors.initials: GF
authors.lastname: Howarth
authors.forename: M H E
authors.initials: MH
authors.lastname: Robinson
authors.forename: D
authors.initials: D
authors.lastname: Jenkins
authors.forename: J D
authors.initials: JD
authors.lastname: Hardcastle
authors.forename: R F A
authors.initials: RF
authors.lastname: Logan
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D003093:Colitis, Ulcerative / Q000175:diagnosis* / Q000453:epidemiology* / Q000628:therapy; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology* / Q000628:therapy; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D009780:Occult Blood; D017063:Outcome Assessment, Health Care; D015995:Prevalence; D016032:Randomized Controlled Trials as Topic; D017678:Sex Distribution; D006113:United Kingdom / Q000453:epidemiology