Title : Boari flap urinary tract reconstruction for rectosigmoid cancer with ureteral invasion : Report of a case Short running headline : Boari flap technique for rectosigmoid cancer case with ureteral invasion

Introduction: The Boari flap technique is a unique urinary tract reconstruction procedure performed after resection of the urinary tract. However, few previous reports have described the application of this technique to gastrointestinal cancer. Moreover, we have not found any papers describing the long-term prognosis. We report a case of right ureteral tract resection followed by Boari flap reconstruction for rectosigmoid carcinoma, with survival for 108 months without any urological complications. Case presentation: A woman in her 50s was diagnosed with rectosigmoid caner by local physician and referred to our institution. Computed tomography revealed right hydronephrosis due to rectosigmoid cancer invasion at the lower two-thirds of the right ureter. During laparotomy, massive lymphatic infiltration from the primary lesion to right ureter was observed. After primary tumor resection with lower ureter excision, the Boari flap procedure was performed to reconstruct the ureteral deficit. Postoperative course was uneventful, and she was discharged on postoperative day 20. The patient has been followed every 4 months for 9 years with no recurrence or unpleasant