title: Contemporary morphologic definition of backwash ileitis in ulcerative colitis and features that distinguish it from Crohn disease.
abstract: Terminal ileum (TI) sections from 250 ulcerative colitis (UC) total colectomy specimens resected during 3 periods and endoscopic TI biopsy specimens from 100 contemporary chronic UC and 100 Crohn disease (CD) patients were reviewed. The respective proportions of cases resected during the 3 periods with moderately or markedly active cecal UC were 72%, 34%, and 2% and with moderate or marked backwash ileitis (BWI), 21%, 18%, and 0%. The activity level of BWI correlated with level of cecal UC. In contemporary initial endoscopic TI biopsy specimens, 6% of chronic UC patients had BWI, all with moderately to markedly active cecal chronic UC. In CD cases, 75% had chronic or active enteritis, consisting of patchy lamina propria edema containing mildly active inflammation, crypt disarray, and focally blunted or flattened villi. Mucous gland metaplasia was present in 27% of CD biopsy specimens. BWI should be restricted to active enteritis that involves the ileum in a contiguous pattern from the cecum that has a similar or greater degree of active inflammation. Mild BWI predominantly involves the superficial mucosa in a contiguous pattern. Focal isolated ileal erosions, mucous gland metaplasia, or patchy edema with mild active inflammation are features of CD.
authors.affiliation: Department of Anatomic Pathology, William Beaumont Hospital, Royal Oak, MI 48073, USA.
authors.forename: Neal
authors.initials: N
authors.lastname: Goldstein
authors.forename: Mohanpal
authors.initials: M
authors.lastname: Dulai
mesh_terms: D001706:Biopsy; D002908:Chronic Disease; D003082:Colectomy; D003093:Colitis, Ulcerative / Q000473:pathology*; D003424:Crohn Disease / Q000473:pathology*; D006801:Humans; D007079:Ileitis / Q000473:pathology*; D007082:Ileum / Q000473:pathology; D007413:Intestinal Mucosa / Q000473:pathology