We describe a case of a caecovesical fistula in a 60-year-old woman caused by an inflammatory tumour of a probably appendicular origin which mimicked cancer of the caecum. The patient, had a history of idiopathic peripheral polineuropathy and chronic constipation. Presented urinary tract infection and fecaluria, without symptoms of appendicitis. At operation, a solid mass including the caecum and the fundus of the bladder was found, and the appendix was not identified. In view of the neoplastic appearance and the impossibility of separating the caecum from the bladder, "en bloc" right hemicolectomy and partial cystectomy were performed. The pathologic study showed the inflammatory nature of the lesion.