Colon

• Subgroup of idiopathic ulcerative colitis wherein the extent of disease is anatomically limited to the rectum (i.e., distal to the rectosigmoid junction)
• Corresponds to E1 in the Montreal classification of ulcerative colitis by extent of disease (Can J Gastroenterol 2005;19:5A)
• Comprises approximately 30% of patients with ulcerative colitis (Clin Gastroenterol Hepatol 2018;16:343)

• Same as ulcerative colitis

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• Factors associated with poor outcomes (i.e., complicated or aggressive disease requiring immunosuppressants, biologics [e.g., antibody based drugs]) in adults include (Clin Gastroenterol Hepatol 2015;13:635):
  • Young age of onset (< 40 years)
  • Nonsmokers and ex smokers
  • Deep ulcerations
• Extent of disease (ulcerative proctitis is more associated with lower risk of colectomy than left sided and extensive colitis):
  • Disease can extend proximally in up to 19% of patients after 5 years and up to 28% of patients after 10 years (Inflamm Bowel Dis 2012;18:573)
  • Progression to left sided colitis in 28 - 30% of patients and to extensive colitis in 14 - 16% (Clin Gastroenterol Hepatol 2018;16:343)
• Colitis related dysplasia and carcinoma:
  • When disease is limited to the rectum (i.e., ulcerative proctitis), patients have not been shown to be at increased risk for colorectal neoplasia (N Engl J Med 1990;323:1228, Gastroenterology 2006;130:1039)

Contributed by John D. Paulsen, M.D. and Alexandros D. Polydorides, M.D., Ph.D.

Contributed by John D. Paulsen, M.D. and Alexandros D. Polydorides, M.D., Ph.D.

• Crohn's disease:
  • Nonnecrotizing epithelioid cell granulomas (not associated with ruptured crypts)
  • Transmural lymphoid aggregates in areas of intact (nonulcerated) mucosa
  • Fistulas or strictures
  • Perianal disease
• Sexually transmitted proctitis (i.e., syphilis and lymphogranuloma venereum):
  • Mucosal expansion by plasma cells and histiocytes
  • Granulomas (rare)
  • Relatively less crypt architecture distortion and Paneth cell metaplasia when compared to ulcerative proctitis (Am J Clin Pathol 2015;144:771)
  • Positive spirochete immunohistochemical stain in cases of syphilis proctitis
  • Correlation with gold standard clinical tests (rapid plasma reagin [RPR], Treponema specific serology, nucleic acid amplification [NAAT] using rectal swabs)
  • Clinical history of receptive anal intercourse
• Acute infectious (self limited) proctitis:
  • Neutrophils predominate in lamina propria
  • Lack of crypt architecture distortion
  • Lack of basal plasmacytosis
  • Lack of Paneth cell metaplasia
  • Correlation with clinical tests on stool samples (such as multiplex PCR panels)
• CMV proctitis:
  • May complicate ulcerative proctitis in patients on immunosuppressive treatment
  • Endothelial cells, mesenchymal stromal cells or glandular epithelial cells may show viral cytopathic effect, including enlargement (cytomegaly) and inclusions (owl eye intranuclear inclusions or pink cytoplasmic inclusions)
  • CMV immunohistochemical stain is an extremely useful adjunct
• Diversion proctitis:
  • Prominent mucosal / submucosal lymphoid hyperplasia
  • History of fecal stream diversion (i.e., ileostomy or colostomy proximal to the rectum)
  • Often seen in completion proctectomy specimens in patients with idiopathic inflammatory bowel disease undergoing multistage ileal pouch anal anastomosis (IPAA) procedures
• Immune checkpoint inhibitor associated proctitis:
  • Several patterns of injury have been described, including active colitis, lymphocytic colitis, collagenous colitis and apoptosis with increased intraepithelial apoptosis, apoptotic crypt abscesses and multifocal crypt injury (withered / shrunken crypts) (Am J Surg Pathol 2022;46:e15)
  • Mucosal expansion, crypt distortion, cryptitis and crypt abscesses may also be seen, mimicking idiopathic ulcerative proctitis
  • Clinical history of immune checkpoint inhibitor use
• Ischemic proctitis:
  • Uncommon in rectum due to dual blood supply from inferior mesenteric and iliac arteries
  • Surface active inflammation / necrosis
  • Hyalinized lamina propria
  • Withered / shrunken crypts
  • Ischemic type changes may be seen in stercoral ulceration, trauma and solitary rectal ulcer syndrome
• Solitary rectal ulcer syndrome (SRUS):
  • Microscopic changes imparted by rectal prolapse: fibromuscular hyperplasia of lamina propria splaying basal crypts (resulting in angulated or diamond shaped crypts), ectatic and congested subepithelial capillaries, surface ulceration, pseudomembranes
• Stercoral ulcer:
  • Ulceration secondary to impacted fecal material
  • Microscopically shows ulcer and focal ischemic changes variable embedded fecal material
  • Background mucosa should be relatively uninflamed

A 63 year old woman presents to her primary care physician with a 3 month history of bloody diarrhea and tenesmus. She is referred for a colonoscopy, which demonstrates an erythematous friable mucosa with erosions in the rectum, as demonstrated in the figure above. Biopsies are performed. Which of the following histologic findings would most suggest idiopathic ulcerative proctitis in this case?

1. Follicular lymphoid hyperplasia and cryptitis
2. Increased intraepithelial apoptosis and multifocal crypt injury
3. Lamina propria hyalinization and withered / shrunken crypts
4. Mucosal expansion, crypt architecture distortion and crypt abscesses
5. Prominent lamina neutrophils and preserved crypt architecture

D. Mucosal expansion, crypt architecture distortion and crypt abscesses are all features characteristic of idiopathic ulcerative proctitis. Answer A describes diversion proctitis. Answer B describes histology that can be seen in immune checkpoint inhibitor associated colitis. Answer C describes ischemic proctitis. Answer E describes acute infectious (self limited) proctitis.

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Reference: Ulcerative proctitis

A 22 year old man with a history of ulcerative proctitis undergoes surveillance colonoscopy. The rectum appears erythematous and granular. Biopsies are taken of the rectal mucosa and are sent for histopathologic evaluation. Which of the following, if found in the biopsy, would provide the best histologic evidence of active disease?

1. Basal plasmacytosis (crypt shortfall)
2. Crypt architecture distortion
3. Cryptitis
4. Mucosal expansion
5. Paneth cell metaplasia

C. Cryptitis (neutrophilic infiltration of the crypt epithelium) is a form of active mucosal inflammation and is evidence of active disease. The other forms of injury listed (basal plasmacytosis, crypt architecture distortion, mucosal expansion and Paneth cell metaplasia) are evidence of chronicity in ulcerative proctitis.

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Reference: Ulcerative proctitis