Background: "Indefinite for dysplasia" (IND) on pouch mucosal biopsy is occasionally reported during routine histopathological evaluation. The natural history and implication of this histologic entity in ileal pouch-anal anastomosis (IPAA) has not been studied.
Aim: The aim of this study is to characterize cumulative probability, natural history, and clinical outcome of pouch IND in a cohort of patients with inflammatory bowel disease (IBD).
Methods: All 932 patients with restorative proctocolectomy and IPAA for IBD were included. Patients with or without IND were classified into the study and control groups. Demographic, clinical, endoscopic, and histologic variables were analyzed.
Results: The mean duration from IBD diagnosis to colectomy and from pouch construction to data entry was 8.4 ± 8.5 and 9.7 ± 6.2 years, respectively. A total of 2,250 surveillance or diagnostic pouchoscopies with biopsies were performed for the cohort. Twenty-one patients (2.3%) were diagnosed with anal transitional zone and/or pouch IND, for whom subsequent pouchoscopies were performed with the mean procedure number being 3.4 ± 2.2 per patient during a mean of follow-up of 19.3 ± 16.1 months. One patient with IND developed low-grade dysplasia and one had high-grade dysplasia in a separate endoscopy. Cox model showed the presence of primary sclerosing cholangitis was an independent risk factor for pouch IND [hazard ratio = 6.76 (95% CI 2.56-17.88)]. Interobserver agreement (kappa score) for diagnosing pouch IND between GI pathologists ranged from 0.67 to 0.76.
Conclusions: Subsequent dysplasia was uncommon in pouch patients with IND. Natural history of pouch IND warrants further long-term investigation.