Bladder urothelial carcinoma rarely spreads to the gastrointestinal tract, and its presentation in the rectum varies. We report a case of a patient who presented with an annular constriction of the rectum.
A 60-year-old man was referred to our hospital with chief complaints of anal stricture and partial obstruction for about 1 month. Computed tomography and magnetic resonance imaging revealed diffuse wall thickening of the rectum, possible high cellularity in the lower portion of urinary bladder, and lesions in the visible pelvic bony structure. A colonoscopy showed a contiguous annular constriction from 5 to 15 cm above the anal verge. Carcinoembryonic antigen and carbohydrate antigen 19-9 levels were 39.75 ng/mL and 139.2 U/mL, respectively. A transurethral bladder biopsy revealed high-grade urothelial cell carcinoma, and anal biopsy showed a poorly differentiated carcinoma arranged in a small nested pattern within the subepithelial area of the anorectal tissue. A colostomy was performed, and the patient was transferred to another hospital for further treatment after series of survey with lung metastasis.
Invasive bladder cancers rarely infiltrates into the rectum and is known with the difficulty diagnosis by colonoscopy. Furthermore, the secondary rectum tumor due to bladder cancer had poor record for survival in the literature review.
This case of bladder urothelial carcinoma penetrating to the rectum was interesting because it mimicked proctitis with diffuse annular swelling observed in the colonoscopy.

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