Histological features in colectomy specimens and their importance
| Histological feature | Definition | Importance |
|---|---|---|
| CD, Crohn’s disease; LP, lamina propria; IBD, inflammatory bowel disease; IC, indeterminate colitis; UC, ulcerative colitis. | ||
| Focal LP inflammation | Patchy increase of mononuclear cells in LP separated by areas of normal LP cellularity | In UC can be seen after treatment, may be seen in infection; characteristic of CD especially if intense; may be seen in infection but tends to affect mid and upper crypts and surface epithelium; not helpful in fulminant colitis |
| Diffuse cryptitis | Evenly distributed inflammation of crypts, involving most crypts | Characteristic of UC, seen in pretreatment material and flares of disease. Avidity of neutrophils for crypts, unlike CD in biopsies and fulminant colectomy specimens |
| Idiopathic granulomas | Discrete aggregate of macrophages, more than 5 histiocytes | Against a diagnosis of UC unless crypt related; characteristic of CD, but seen in some infections (TB, yersinia, others); in fulminant colitis against a diagnosis of UC, favours CD |
| Microgranulomas (small aggregates) | A granuloma is defined as 5 histiocytes or more and everything else is not a granuloma, so microgranuloma probably does not exist | Some believe carries weight in favour of CD |
| Crypt related granulomas or giant cells/mucin granulomas | Giant cells or granulomatous reaction adjacent to a ruptured or injured crypt | No special importance |
| Muscularis mucosa duplication/hyperplasia | Splaying, thickening, and disorganisation of smooth muscle, sometimes blending with submucosa | Indicates previous ulceration; usually seen in CD; may be seen in UC after immunosuppressive treatment for temporisation of severe disease, not helpful in fulminant colitis |
| Narrow fissures | Cleft-like fissure extending into submucosa | Characteristic of CD, but are tracts—usually histiocytes—at periphery and neutrophils centrally (different from fissures seen in IC); may occur in IC and occasionally in UC |
| Wide fissures, deep undermining ulcers (fig 7A) | V shaped clefts that may extend into submucosa or muscularis propria with overhanging edges | Typical for any form of fulminant colitis; typical of all severe IBD and some infections. When undermining ulcers are tangentially cut, they may give the false impression of linear fissures seen in CD (fig 7B) |