Diarrhoea – Approach to the Colonic Biopsy

Approach:

  • 1) Crypt Architecture – budding, crypt fission, mucin depletion
  • 2) Inflammatory cell gradient
  • 3) Increased inflammatory cells in the lamina propria
  • 4) Evidence of active inflammation – Cryptitis, Crypt abscesses
  • 5) Specific features – granulomas
  • 6) Evidence of dysplasia or malignancy

Specific Conditions:

Crohn’s disease – Bx – Patchy active chronic inflammation with cryptitis, crypt abscesses and granulomas. Resections – Transmural inflammation with fissuring ulceration and fistulae. Thickening of the muscularis mucosae. Narrow fibrotic submucosa. Ulcer associated cell lineage (Pseudopyloric metaplasia). Neural hyperplasia. Crohn’s rosary pattern lymphoid aggregates. On macro – prominent fat wrapping, thickened bowel wall, skip lesions, stricture formation, cobblestoned mucosa, ulceration.

Ulcerative colitis – Bx diffuse active chronic inflammation with cryptitis & crypt abscesses typically confluent continuous disease extending proximally. Crypt distortion, paneth cell metaplasia (paneth cells are normally present only in the caecum & proximal right colon), diffuse mucosal inflammation, crypt abscesses, mucin depletion, mucosal ulceration. There may be rectal sparing with those treated with steroids. Resections – Diffuse mucosal ulceration with pseudopolyps. Sometimes toxic megacolon. Normal serosa & normal bowel thickness. Isolated appendiceal involvement & caecal patch are well described in UC.

Infectious colitis: Focal active chronic inflammation with cryptitis & crypt abscesses. Acute on set & short duration (although TB, yersinia & salmonella can occur for months). Classically differentiating factors from IBD include – preserved crypt architecture, no paneth cell metaplasia, flat surface epithelium, predominantly superficial inflammation, no basal lymphoid aggregates, no granulomas

Lymphocytic colitis: Shows an increase in the chronic inflammatory cells of the lamina propria and intraepithelial lymphocytosis. > 15/100 epithelial cells.

Collagenous colitis: Increased subepithelial collagen plate (>15 microm thick), subepithelial vacuoles, and surface epithelial sloughing. Picrosirius red stain for collagen.

Pseudomembranous colitis: Classically eruptive acute inflammatory exudate is seen on surface of intact inflamed mucosa. Paint splatter like macro.

Ischaemic colitis: showing coagulative necrosis, mild acute inflammation, and karyorrhectic debris involving the surface with relative preservation of the deep crypt. Especially in the watershed area between supply of the superior mesenteric to midgut and inferior mesenteric to the hind gut in splenic flexure area.

CMV infection: Infected stromal cells with cytomegaly, cytoplasmic inclusions, and prominent intranuclear inclusions with surrounding halo (Cowdry type A). Immunocomprimised. Variable, often discrete, ulcers affecting the esophagus, stomach, or intestines. CMV stain.

Mucosal Prolapse Syndromes (solitary rectal ulcer) : History of constipation, passage of blood or mucus per rectum. There is architectural distortion accompanied by fibromuscular obliteration of the lamina propria with capillary ectasia.

Radiation Colitis: Atypical fibroblasts.

Graft vs Host Disease: Numerous apoptotic bodies. Diarrhoea and abdo pain post bone marrow transplant.

Organisms: Amaebiasis, Enterobius, Microsporidia

References:

Differential diagnosis in Surgical Pathology. Gattuso et al.

Morson & Dawson’s Gastrointestinal Pathology. 4th ed.

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