Etiology of CD of the pouch

Etiology of CD of the pouch

November 27, 2023

Issue 23

Clinical Question

Is it Crohn’s disease of the pouch or a surgical sequela?

Editor’s Bottom Line

Cross-sectional imaging in patients with suspected Crohn’s disease of the pouch often suggests
an alternative cause such as a surgical complication. Clinicians should think carefully before
diagnosing Crohn’s disease in this situation.


Reijntjes M, de Jong D, Wessels E, et al. Crohn’s Disease of the Ileoanal Pouch: A High Rate of
Potential Overdiagnoses. Inflamm Bowel Dis. 2023 Oct 6, 2023. Online ahead of print.


Roughly 10% of ulcerative colitis (UC) patients with an ileal pouch-anal anastomosis (IPAA) are
diagnosed with Crohn’s disease (CD) of the pouch. To investigate the etiology of this diagnosis,
researchers in the Netherlands retrospectively reviewed medical records from 481
patients—nearly all of whom had UC—who had undergone IPAA between 1990 and 2017 at
Amsterdam University Medical Center. Patients were a median 36 years of age at the time of
IPAA construction and were split by sex roughly evenly.

After a median 6.2 years of postoperative follow-up (Interquartile Range: 2.3–13.5 years), 10%
of patients were diagnosed with CD of the pouch. Endoscopic and clinical records showed that
81% of these patients had inflammation of the pouch, 74% had prepouch ileitis, 36% had
strictures, and 32% had fistulae.

Magnetic resonance imaging (MRI) findings revealed that 43% of patients with CD of the pouch
had surgical sequelae (perianastomotic fistula or chronic sinus) and the imaging modality
identified several more fistulae not visible at endoscopy. MRI showed that 25% of patients with
CD of the pouch had a fistula originating from the pouch-anal anastomosis, and 18% had a
chronic presacral sinus. Fifteen percent of patients had non-anastomotic fistulas on MRI.

Pouch biopsies showed that all patients with CD of the pouch had chronically active
inflammation. Only one patient had granulomas, and this was in a pouch resection specimen.

Four of eight patients with CD of the pouch who had a colectomy specimen tested met
histopathological criteria for CD and also had surgical sequelae following initial IPAA surgery.

Patients diagnosed with CD of the pouch were diagnosed earlier if they had surgical sequalae
than those that did not have surgical sequelae (median 3.7 vs. 8.7 years).


Study Design: Retrospective cohort
Funding: Not stated
Allocation: Not applicable
Setting: Single center
Level of Evidence: 1b