The aetiology of pouchitis in patients with inflammatory bowel disease

Abstract

Restorative proctocolectomy with ileal pouch-anal anastomosis is a treatment option for patients with refractory ulcerative colitis. Pouchitis is the most common complication, representing a spectrum of diseases ranging from acute antibiotic-responsive type to chronic antibiotic-refractory. Early accurate diagnosis using a combined assessment of symptoms, endoscopy and histology is important for both treatment and prognostication. Most patients respond well to antibiotic therapy; however, management of chronic antibiotic-refractory pouchitis remains a challenge, and treatment options are based on small studies. Pouchitis is thought to be driven by the interaction between genetics, the immune system and the environment but as yet a causal relationship has yet to be identified. Further longitudinal assessment of the pouch integrating new technologies may help us understand the factors driving pouchitis. This review outlines the currently understood risk factors and aetiology of pouchitis.

Keywords: IBD; pouchitis; ulcerative colitis.

Figure 1.

A stepwise approach to the management of both acute and chronic pouchitis. Acute pouchitis is typically managed with antibiotics. A prolonged course of symptoms despite antibiotics suggests chronic pouchitis, which may require treatment with steroids or a biological agent.

Figure 2.

Summary of genetic, immune and microbiome factors involved in the aetiology of pouchitis. The altered pouch microbiome leads to increased activity of sulphate-reducing bacteria; which convert sulphomucin to hydrogen sulphide within the pouch. This, along with reduced levels of anti-inflammatory substances such as short-chain fatty acids and secondary bile acids, causes oxidative damage as well as increased epithelial permeability, leading to an increased immune response with subsequent inflammatory change. Processed foods rich in sulphite preservatives may contribute to this process by increasing the amount of sulphomucin substrate. Also illustrated is the effect of inflammatory bowel disease-related genetic polymorphisms as well as altered gene expression within the colonic mucosa, which may result in a proinflammatory state that then contributes to pouchitis development.