Distinguishing IBS from Inflammatory Bowel Disease

Endoscopic Features of IBD

Granularity is a macroscopic endoscopic feature of ulcerative colitis, characterized by loss of vascular pattern, friability, and ulceration of the rectal mucosa, according to the British Society of Gastroenterology 1
Patchy distribution with skip lesions is the endoscopic hallmark of Crohn's disease, where areas of inflammation are interposed between normal-appearing mucosa, as noted by the Journal of Crohn's and Colitis 2
The British Society of Gastroenterology (2025) emphasizes that IBD typically shows chronic histological changes including architectural distortion, crypt atrophy, increased lamina propria chronic inflammatory cells, and Paneth cell metaplasia—none of which occur in IBS 3

When patchy granularity is observed endoscopically, multiple biopsies from at least six segments (terminal ileum, ascending, transverse, descending, sigmoid, and rectum) should be obtained to confirm IBD and exclude IBS, as recommended by the Journal of Crohn's and Colitis and Gut 2, 3
Histological features that distinguish IBD from IBS include crypt architectural disturbances, basal plasmacytosis, non-cryptolytic granulomas (in Crohn's disease), and chronic inflammatory changes, according to Gut 3

Up to 16.3% of IBD patients in remission with mucosal healing report persistent IBS-like symptoms (diarrhea and abdominal pain), but this represents functional symptoms overlapping with IBD, not IBS causing the mucosal changes, as noted by the American Gastroenterological Association and Clinical Gastroenterology and Hepatology 6, 7
The American Gastroenterological Association (2019) notes that functional GI symptoms and mild residual inflammation can coexist in IBD patients, but the structural changes remain attributable to IBD, not IBS 6

Obtain comprehensive biopsies from multiple segments including terminal ileum to establish IBD diagnosis and subtype, as recommended by the Journal of Crohn's and Colitis and Gut 2, 3
Assess for histological features of IBD: architectural distortion, crypt atrophy, basal plasmacytosis, granulomas, and chronic inflammatory changes, according to Gut 3
Evaluate distribution pattern: continuous inflammation from rectum suggests ulcerative colitis; skip lesions with rectal sparing suggest Crohn's disease, as noted by the Journal of Crohn's and Colitis and Gut 2, 3