pouchitis

WKP

Definition: Pouchitis is inflammation of the ileal pouch (an artificial rectum surgically created out of ileal gut tissue in patients who have undergone a colectomy), which is created in the management of patients with ulcerative colitis, indeterminate colitis, or, rarely, other colitides.

A variety of pathophysiological mechanisms have been proposed for pouchitis, but the precise pathogenesis (biological cause) remains unknown.

Total proctocolectomy with ileal pouch-anal anastomosis (IPAA) has become an established surgical procedure for ulcerative colitis. Occasional patients who have undergone IPAA develop persistent or recurrent episodes of pouchitis (chronic pouchitis), from which a subset also develop gastrointestinal and systemic complications that are identical to those seen in Crohn’s disease.

These complications include:
 enteric stenoses
 enteric fistulas in the pouch or pouch inlet segment
 perianal fistulas or perianal abscesses
 pouch fistulas
 Crohn-like systemic anomalies

• arthritis
• iridocyclitis
• pyoderma gangrenosum.

The development of Crohn’s-like gastrointestinal complications in a patient with chronic pouchitis frequently engenders concern that the pathologist misinterpreted the proctocolectomy specimen as Crohn’s disease.

Crohn’s-like complications are most likely related to chronic pouchitis, which probably is a form of recrudescent ulcerative colitis within the novel environment of the pouch.

A diagnosis of Crohn’s disease after IPAA surgery should only be made:
 if reexamination of the original proctocolectomy specimen shows typical pathologic features of Crohn’s disease,
 if Crohn’s disease arises in parts of the gastrointestinal tract distant from the pouch,
 if pouch biopsies contain active enteritis with granulomas,
 or if excised pouches show the characteristic features of Crohn’s disease, including granulomas.

Clinical synopsis

The incidence of a first episode of pouchitis at 1, 5 and 10 years post-operatively is 15%, 33% and 45% respectively.

Patients with pouchitis typically present with bloody diarrhea, urgency in passing stools, or discomfort while passing stools. The loss of blood and/or dehydration resulting from the frequent stools will frequently result in nausea. In fewer cases, pain can occur with pouchitis.

Endoscopy in patients with pouchitis usually reveals erythematous pouch mucosa, loss of pseudocolonic vaculature or other architecture, and friability of the mucosa. Biopsies show evidence of inflammatory cells or red blood cells in the lamina propria.

Predictive factors

Inflammation of ileal reservoir mucosa ("pouchitis") is a common sequelae in ulcerative colitis (UC) patients who have had a colectomy with ileal pouch anal-anastomosis (IPAA).

Pathologic features that are associated with the subsequent development of pouchitis include:
 the presence of severe colitis that extended into the cecum (severe pancolitis)
 early fissuring ulcers
 active inflammation of the appendix
 appendiceal ulceration.

No significant differences in patient gender or age, depth or extent of ulceration, or the presence or absence of "backwash ileitis" were identified between the 2 groups.

There are several histologic features in colectomy specimens from UC patients who have undergone an IPAA procedure that may help predict the subsequent development of pouchitis.

Of these features, appendiceal ulceration is highly associated with pouchitis.

References

 Histomorphologic and molecular features of pouch and peripouch adenocarcinoma: a comparison with ulcerative colitis-associated adenocarcinoma. Jiang W, Shadrach B, Carver P, Goldblum JR, Shen B, Liu X. Am J Surg Pathol. 2012 Sep;36(9):1385-94. PMID: 22895272

 Histologic predictors of pouchitis in patients with chronic ulcerative colitis. Yantiss RK, Sapp HL, Farraye FA, El-Zammar O, O’Brien MJ, Fruin AB, Stucchi AF, Brien TP, Becker JM, Odze RD. Am J Surg Pathol. 2004 Aug;28(8):999-1006. PMID: 15252305

 Crohn’s-like complications in patients with ulcerative colitis after total proctocolectomy and ileal pouch-anal anastomosis. Goldstein NS, Sanford WW, Bodzin JH. Am J Surg Pathol. 1997 Nov;21(11):1343-53. PMID: 9351572