Differential Diagnosis of Erosive Rectosigmoiditis

Primary Inflammatory Bowel Disease Considerations

The European Crohn's and Colitis Organisation recommends that ulcerative colitis is the most likely diagnosis when inflammation is continuous and confluent, extending proximally from the rectum with clear demarcation 1, 2
Rectal involvement is present in more than 97% of untreated ulcerative colitis cases, according to the American Gastroenterological Association 3
Mucosal-only inflammation with diffuse basal plasmacytosis on histology is characteristic of ulcerative colitis, as stated by the European Society of Gastrointestinal Endoscopy 4
Crypt architectural distortion and mucosal atrophy develop after 4 weeks of symptoms in ulcerative colitis patients, according to the American College of Gastroenterology 4

The Centers for Disease Control and Prevention recommends obtaining stool cultures and C. difficile toxin assay before diagnosing IBD, as Salmonella, Shigella, and Campylobacter can produce endoscopic features similar to ulcerative colitis 5, 1, 2
Yersinia and cytomegalovirus enterocolitis resemble Crohn's disease, as stated by the World Gastroenterology Organisation 5, 1
Infectious colitis typically shows preserved crypt architecture with acute inflammation only, according to the Infectious Diseases Society of America 4

The American College of Radiology recommends that ischemic colitis is a common differential diagnosis, particularly in older patients with vascular risk factors, and typically affects watershed areas 5, 1
The National Institute of Diabetes and Digestive and Kidney Diseases states that NSAIDs, immunosuppressants, and chemotherapy agents can cause erosive colitis, and history of medication use is critical 5, 1

The American Society for Gastrointestinal Endoscopy recommends performing complete ileocolonoscopy with biopsies from at least five sites, taking at least two biopsies per site, even from normal-appearing mucosa 2, 3
The European Society of Gastrointestinal Endoscopy states that documenting lesion distribution, rectal involvement, and presence of skip lesions is essential for diagnosis 1, 2, 3
The American College of Gastroenterology recommends that biopsies from both inflamed and uninflamed segments are essential, and looking for granulomas, basal plasmacytosis, preserved crypt architecture, or eosinophilic infiltration is crucial for diagnosis 2, 4

The American Gastroenterological Association recommends obtaining complete blood count, CRP, albumin, liver function, iron studies, and renal function, and performing cross-sectional imaging to evaluate small bowel involvement and complications 2, 3, 4
The European Crohn's and Colitis Organisation states that fecal calprotectin >100 μg/g supports IBD diagnosis, with sensitivity 93% and specificity 96% 3

Crohn's disease should be considered when skip lesions, transmural inflammation, or perianal disease are present, characterized by patchy, transmural inflammation that may affect any part of the gastrointestinal tract, according to the European Crohn’s and Colitis Organisation 6