Probe-based confocal laser endomicroscopy: a new method for quantitative analysis of pit structure in healthy and Crohn's disease patients

Background: Probe-based confocal laser endomicroscopy enables microscopic examination of the digestive mucosa.

Aims: (1) To identify and validate quantitative endomicroscopic criteria for evaluation of the colonic mucosa and (2) to compare these criteria between healthy and Crohn's disease patients in clinical remission.

Methods: Six healthy controls and ten Crohn's disease patients in clinical remission were included in this prospective study. Methylene blue-stained biopsies of the right colon and corresponding endomicroscopic images were analyzed. Major axis, minor axis, and major axis/minor axis ratio of crypt lumens were quantified.

Results: Quantitative assessment was performed on 21 ± 4 crypt lumens per patient. Major axis/minor axis ratio values measured with endomicroscopy or methylene blue-stained biopsies were linearly correlated (r=0.63, p=0.01). All macroscopically inflamed mucosa had values of major axis/minor axis ratio higher than the median of controls. Interestingly, 50% (3/6) of Crohn's disease patients with macroscopically normal mucosa had also a higher ratio than pooled controls. Histological analysis showed that 6/7 patients with major axis/minor axis ratio superior to 1.7 had microscopic inflammation.

Conclusion: Probe-based confocal laser endomicroscopy allows quantitative analysis of colonic pit structure. Endomicroscopic analysis of major axis/minor axis ratio allows the detection of microscopic residual inflammation with greater accuracy than standard endoscopy in Crohn's disease patients in clinical remission.