Discordance between endoscopic and histopathologic assessment in ileal Crohn's disease.

Background: Discordance between endoscopic and histologic assessments in Crohn's disease (CD) have been observed, however the prevalence and cause are unclear.

Aim: To assess if a protocolized approach to biopsy collection facilitates understanding of this discordance in patients with ileal CD.

Methods: Patients with known ileal CD underwent colonoscopy with endoscopic disease activity assessment. Three protocolized biopsies were taken respectively from an ulcer edge, 7-mm, and 14-mm away from the ulcer edge in patients with discrete ileal ulcer(s). In patients with no ulcers as controls, the same 3-site biopsy protocol was applied in a randomly selected area of endoscopically-unremarkable terminal ileal mucosa. A blinded pathologist assessed mucosal inflammation in each biopsy using 3 validated histologic indices.

Results: Twenty-four participants had visible ulcer(s) on endoscopy and 12 served as no-ulcer controls. Of biopsies taken from an ulcer edge, only 67% showed histologic evidence of active (neutrophilic) inflammation, and 33% showed histologic features of ulcer or erosion; all were from either large (n = 4) or very large (n = 4) ulcers. In the no-ulcer controls, no biopsies showed histologic features of ulcer or erosion, but 8% showed active inflammation.

Conclusion: A striking discordance exists between endoscopic and histologic assessments for mucosal inflammation in patients with active ileal CD, even in biopsies targeted at an ulcer edge, while a higher concordance is seen in patients with no endoscopic disease activity. It remains unclear how to incorporate histologic disease activity into the treatment paradigm. Further research is needed to optimize biopsy protocols and histologic assessments for CD.