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 to identify predictors of poor outcomes. Methods: This was a 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 January 1, 2016 and December 31, 2020. Results: We identified 196 patients with UP (median age at diagnosis 14.6 years [interquartile range, IQR 12.5-16.0]), with a median follow-up of 2.7 years [IQR 1.7-3.8]. The most common presenting symptoms were bloody stools [95%], abdominal pain [61%] and diarrhoea [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 inflammatory bowel disease-associated admission, with a score ≥35 providing an increased risk for poor outcomes. By the end of follow-up, 3.1% of patients underwent colectomy. Patients with UP that experienced proximal disease progression during follow-up [48%] had significantly higher rates of a caecal patch at diagnosis and higher PUCAI score by the end of induction, compared to those without progression. Conclusion: Paediatric patients with UP exhibit high rates of treatment escalation and proximal disease extension.