Background: The development of noninvasive markers to assess mucosal healing in ulcerative colitis (UC) is essential in the treat-to-target era. The aim of this study was to evaluate the performance of intestinal ultrasound (IUS), fecal calprotectin (FC), and their combination to assess mucosal healing in UC patients.

Methods: All consecutive patients between January 2021 and September 2022 with UC who underwent a complete colonoscopy and IUS and/or an FC test within 4 weeks were included in a prospective cohort. Bowel wall thickness (BWT) and the color Doppler signal (CDS) were assessed for each segment. Endoscopic mucosal healing was defined by a Mayo score of 0 to 1.

Results: A total of 61 patients were included, of whom 79% showed endoscopic healing (26 Mayo 0 and 11 Mayo 1). Among the patients, 16 (27.6%) of 58 had a BWT <3 mm, and 41 (70.7%) of 58 had no CDS. The sensitivity, specificity, positive predictive value, and negative predictive value of a BWT <3 mm to predict endoscopic mucosal healing were 37%, 77%, 72%, and 44%, respectively. The association of FC <150 µg/g, a BWT <3 mm, and a CDS = 0 increased the specificity and positive predictive value (sensitivity 33%, specificity 94%, positive predictive value 89%, negative predictive value 48%). The combination of a normal IUS, no rectal bleeding, and an FC <172 µg/g identified all patients with mucosal healing.

Conclusions: The combination of IUS and FC is effective in identifying mucosal healing in UC. Noninvasive evaluation of mucosal healing is possible for most UC patients.