Outcomes of oral vancomycin therapy in children with atypical ulcerative colitis with or without confirmed primary sclerosing cholangitis: a real-world observational study.

Objective: Atypical ulcerative colitis (UC) presenting reverse gradient colitis, backwash ileitis, or rectal sparing and/or positive atypical antineutrophil cytoplasmic antibody serology is often associated with primary sclerosing cholangitis (PSC) and can be resistant to conventional medical therapies (CMT) for inflammatory bowel diseases. We report short-term and long-term outcomes of oral vancomycin therapy (OVT) in children with atypical UC and confirmed PSC in imaging/biopsy (PSC-UC) or treatment-resistant atypical UC without detectable PSC (aUC-non-PSC).

Methods: In this retrospective real-world observational study from a tertiary paediatric centre in Brisbane, Australia, 44 children with aUC (29 PSC-UC, 15 aUC-non-PSC) received 79 OVT courses between 2014 and 2023. Pre-post-OVT characteristics were compared and relapses/repeated courses were recorded.

Results: Pre-OVT, all had active colitis by Paediatric Ulcerative Colitis Activity Index (PUCAI), Feacal Calprotectin (FC) and/or colonoscopy. Post-OVT, PUCAI reduced from 15 (IQR 5-33) to 0 (IQR 0-5); 85% of children with pre-OVT PUCAI ≥10 achieved clinical remission (100% PSC-UC vs 64% aUC-non-PSC, p=0.019). FC reduced from 995 (IQR 319-1825) to 44 (IQR 16-79) µg/g; 83% of children with pre-OVT FC ≥100 µg/g achieved biochemical remission (92% PSC-UC vs 64% aUC-non-PSC, p=0.063). Colonoscopy confirmed Mayo 0 healing in 62% (67% PSC-UC vs 54% aUC-non-PSC, p=0.443) and 46% achieved pan-colonic histological remission (54% PSC-UC vs 31% aUC-non-PSC, p=0.173). All pre-post-OVT changes in these four markers were significant in both groups. After ceasing first OVT, 25/44 relapsed within 8.2 (IQR 1.9-14.5) months. Recommencing OVT regained biomarker remission in 13/25. During 3.8 (IQR 2.0-5.3) years of follow-up, 79 OVT courses in conjunction with CMT maintained deep remission in 67%. Routine stool testing (n=138) detected no vancomycin-resistant Enterococcus (VRE).

Conclusions: OVT induced and reinduced remission in children with atypical UC. Relapse often followed ceasing vancomycin, half responded to reinduction. No VRE was developed.