Clinical Features and Natural History of Paediatric Patients with Ulcerative Proctitis: A Multicentre Study from the Paediatric IBD Porto Group of ESPGHAN

Background and aims: Ulcerative proctitis (UP) is an uncommon presentation in paediatric patients with ulcerative colitis. We aimed to characterize the clinical features and natural history of UP in children, and identify predictors of poor outcomes. Methods: Retrospective study involving 37 sites affiliated with the IBD Porto Group of ESPGHAN. Data were collected from patients aged<18 years diagnosed with UP between 01/01/2016-31/12/2020. Results: We identified 196 patients with UP (median age at diagnosis 14.6 [IQR 12.5-16.0] years), with a median follow-up of 2.7 (IQR 1.7-3.8) years. The most common presenting symptoms were bloody stools (95%), abdominal pain (61%) and diarrhea )47%). At diagnosis, the median paediatric ulcerative colitis activity index (PUCAI) score was 25 (IQR 20-35), but most patients exhibited moderate-severe endoscopic inflammation. By the end-of-induction, 5-aminosalicylic acid administration orally, topically or both resulted in clinical remission rates of 48%, 48% and 73%, respectively. The rates of treatment escalation to biologics at 1, 3 and 5 years were 10%, 22% and 43%, respectively. In multivariate analysis, the PUCAI score at diagnosis was significantly associated with initiation of systemic steroids, or biologics, and subsequent acute severe colitis events and IBD-associated admission, with a score≥35 providing increased risk for poor outcomes. By the end of follow-up, 3.1% of patients underwent colectomy. Patients with proximal disease progression (48%) had significantly higher rates of cecal patch at diagnosis and higher PUCAI score by end-of-induction, compared to those without progression. Conclusion: Paediatric patients with UP exhibit high rates of treatment escalation and proximal disease extension.