Background: Extension of the inflammatory process into the terminal ileum in ulcerative colitis is termed backwash ileitis. Ulcerative colitis patients with pancolitis and backwash ileitis may be at increased risk of colorectal carcinoma. A case of ulcerative colitis-associated cancer with backwash ileitis, which extended proximally over time, is described.
Case Report: A 67-year-old man was diagnosed with pancolitis; despite prednisolone and mesalazine treatment, he showed no improvement. Although initial endoscopic examination showed no abnormalities in the terminal ileum, a repeat colonoscopy 4 months later revealed erythema, absence of the vascular pattern, mucosal friability, and erosions within 30 cm of the terminal ileum in a continuous fashion from the cecum, and a flat, elevated lesion was found in the transverse colon. On histopathologic examination, the patient had nonspecific, active, chronic inflammation of the ileal mucosa, consistent with backwash ileitis, and colonic adenocarcinoma. Despite additional treatment with leukocytapheresis, the backwash ileitis progressed, with increased severity of mucosal inflammation and extensive erosions, 20 cm proximal to the primarily affected site of the ileum on repeat colonoscopy 2 months later. The patient underwent a proctocolectomy and excision of the terminal ileum with an ileostomy.
Conclusions: Histopathology of the surgical specimen revealed marked backwash ileitis and submucosal, well-differentiated adenocarcinoma. The patient has remained well for 5 years after surgery.

Keywords: Ileitis - radiography, Ileum - surgery, Follow-Up Studies, Colonoscopy, Colonic Neoplasms - radiography, Colitis, Ulcerative - radiography, Radiography, Abdominal