Common Inflammatory Disorders and Neoplasia of the Ileal Pouch: A Review of Histopathology

Abstract

Ileal pouch-anal anastomosis (IPAA) is the standard restorative procedure after proctocolectomy in patients with ulcerative colitis (UC) who require colectomy. The ileal pouch is susceptible to a variety of insults including mechanical injury, ischemia, fecal stasis, and infectious agents. In addition, the development of recurrent and idiopathic inflammatory bowel disease and neoplasia may occur in the ileal pouch. Although clinical, endoscopic, and radiographic examination can diagnose many ileal pouch diseases, histologic examination plays an essential role in diagnosis and management, particularly in cases with antibiotic refractory chronic pouchitis and pouch neoplasia.

Keywords: Diagnosis; Histopathology; Ileal pouch; Inflammatory disorder; Neoplasia; Pouchitis; Ulcerative colitis.

Figure 1

Histology of normal pouch (a) and pouchitis (b, c). (a) This pouch biopsy shows normal histology (H&E stain, × 20). The small bowel mucosa demonstrates preserved and slender villous projection into the lumen. There are a few mononuclear inflammatory cells in the lamina propria but without expansion of the lamina propria. There is no basal lymphoplasmacytosis, neutrophilic inflammation, epithelial injury, erosion or ulceration. (b, c) This pouch specimen shows small bowel mucosa with villous blunting, erosion, chronic and active inflammation (b, H&E, × 100; c, H&E stain, × 200), features of chronic pouchitis.

Figure 2

Crohn’s disease of the pouch. This biopsy shows small bowel mucosa with mononuclear inflammatory expansion of the lamina propria (not included in the photo) and one well-formed non-caseating epithelioid granuloma in one lymphoid aggregate (H&E stain, × 200). In the right clinical setting, this finding supports the diagnosis of Crohn’s disease of the pouch.

Figure 3

Pouch biopsy with epithelium negative for dysplasia. This biopsy shows small bowel mucosa with chronic active inflammation, architectural distortion, erosion, pyloric gland metaplasia, and regenerative epithelial changes (H&E stain, × 100). A few glands show slightly enlarged, hyperchromatic, pencil-shaped nuclei. However, the aforementioned findings are seen in proximity to an erosion and there is at least partial maturation, thus, these changes should be interpreted as negative for dysplasia.

Figure 4

Pouch biopsy with low-grade dysplasia. This pouch biopsy shows low-grade dysplasia which is characterized by epithelium containing enlarged, hyperchromatic, pencil-shaped nuclei without surface maturation (H&E stain, × 100). This lesion does not show obvious nuclear pleomorphism or architectural complexity, features of high-grade dysplasia.

Figure 5

Pouch biopsy with high-grade dysplasia. This pouch biopsy shows glands with enlarged, hyperchromatic nuclei without surface maturation (a, H&E stain, × 100). The glands show marked pleomorphism, high nuclear to cytoplasmic ratio, and abnormal mitotic figure (b, H&E stain, × 400).

Figure 6

Pouch adenocarcinoma. This adenocarcinoma is well differentiated, contains abundant extracellular mucin, and invades the muscularis propria (a, H&E stain, × 20; b, H&E stain, × 40).