Background and aims: Neoangiogenesis and increased endothelial permeability are observed as results of chronic intestinal inflammation. However, limited data on microvascular and crypt architecture during remission phases is available. The aim of this prospective investigator blinded cohort study was to assess crypt and microvascular architecture and function in ulcerative colitis by probe based confocal laser endomicroscopy; we also evaluated whether these findings may have the potential to predict disease relapse.

Methods: 19 ulcerative colitis patients in clinical and endoscopic remission and 19 controls were studied. A computer based image processing technique was applied to construct 20 mosaicing image sets from each subject. Remitting patients were sub-grouped into either inactive or quiescent disease according to histology.

Results: Pericrypt fluorescence (p < 0.01), crypt diameter (p < 0.05) but not intercrypt distance (p = 0.07) were significantly increased in ulcerative colitis patients compared to controls. Patients with inactive disease showed a significant increase in fluorescence leakage (median fluorescence (IQR), 3888 (3560–4240) vs. 2696 (2502–3390), p < 0.01), crypt diameter (median diameter (IQR), 92.5 (85.5–101) vs. 73 (70–77), p < 0.05) and intercrypt distance (median distance (IQR), 82.5 (70.5–91.2) vs. 66 (59.5–73.5), p < 0.05) compared to those with quiescent disease. A composite outcome score combining fluorescence leakage and crypt diameter was able to predict a disease flare during a 12 month follow-up period (p < 0.01).

Conclusions: In vivo intramucosal changes detected by confocal endomicroscopy in ulcerative colitis remittent patients can predict disease relapse. This observation may have further implications for disease management and medical treatment.