www.kjurology.org DOI:10.4111/kju.2010.51.7.501 Case Report Mesenteric Fibromatosis Causing Ureteral Stenosis Jae Young Choi, Kyung Mo Kang, Bum Soo Kim, Tae-Hwan Kim Department of Urology, School of Medicine, Kyungpook National University, Daegu, Korea Mesenteric fibromatosis is a rare benign disease characterized by proliferating fibrous tissue in the bowel mesentery. We report a case of aggressive mesenteric fibromatosis with ureteral stenosis arising in a 46-year-old woman who suffered from intermittent right abdominal pain. Computed tomography revealed a right retroperitoneal mass with right ureteral stenosis at the level of the right common iliac vessel. The mass was excised with resection of the affected segment of the ileum, ascending colon, and ureter, and end-to-end ureter anastomosis was performed. Pathological examination con- firmed mesenteric fibromatosis. Key Words: Aggressive fibromatosis; Retroperitoneal neoplasms This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Article History: received 18 February, 2010 accepted 18 March, 2010 Corresponding Author: Tae-Hwan Kim Department of Urology, School of Medicine, Kyungpook National University, 200, Dongduk-ro, Jung-gu, Daegu 700-721, Korea TEL: +82-53-420-5841 FAX: +82-53-421-9618 E-mail: peak@urology.or.kr Mesenteric fibromatosis (MF) is a rare, benign, intra-ab- dominal tumor. MF is characterized by proliferating fi- brous tissue in the bowel mesentery. Although MF occa- sionally invades the bowel or adjacent tissues with ag- gressive myofibroblastic proliferation, MF lacks the ca- pacity of malignant tumorigenesis with distant metastasis [1]. MF is frequently associated with Gardner’s syndrome, previous trauma, prolonged estrogen intake, and preg- nancy, but MF can occur as a primary condition in the ab- sence of predisposing factors [2]. MF-induced ureteral stenosis is a very rare urological problem. We present a case of primary MF causing ureteral stenosis with a review of the relevant literature. CASE REPORT A 46-year-old woman presented with intermittent right flank pain she had experienced for a year. The patient had previously been healthy and had no history of disease. Physical examination revealed no significant findings such as tenderness at the costovertebral angle area, a pal- pable mass, or peripheral lymphadenopathy. Urinalysis, a complete blood count, and routine blood biochemistry tests showed no abnormal findings. Plain abdominal radio- graphs were normal. There were no abnormal findings in urine cytology or cystoscopic examination. Computed to- mography (CT) showed a 2.7x1.5 cm diffuse, noncalcified, moderately infiltrating mass with ill-defined lobulated Korean Journal of Urology Ⓒ The Korean Urological Association, 2010 walls located at the right common iliac vessel level (Fig. 1). The mass was located in the right ureter anteriorly, and mild focal enhancement, wall thickening, and luminal nar- rowing were found in the ureter (Fig. 1). The mass looked as if it compressed the right ureter, resulting in moderate hydroureteronephrosis above the affected level (Fig. 1). Retroperitoneal lymphadenopathy was not observed. 　In a ureterorenoscopic examination, there was no in- trinsic obstructive lesion such as a ureteral tumor causing ipsilateral hydronephrosis. A laparoscopic exploration was undertaken to debulk the tumor due to the patient’s increasing symptoms. At the time of surgery, due to ex- tensive adhesion of the ileocecal valve area and mass, the laparoscopic exploration was converted to open surgery to safely perform the tumor resection. We could not rule out the possibility of a malignant tumor before final histo- pathological confirmation of the affected lesion. The pa- tient underwent extensive debulking of the mass including bowel segmentectomy with anastomosis and excision of the affected ureter. Then, end-to-end ureter anastomosis was performed, and a ureteral stent was deployed in the right urinary tract for decompression. A white wedge of tissue was obtained for pathological evaluation. 　The specimen except of resected bowel segment was a 5.5x3x3 cm firm, poorly circumscribed mass. Upon section- ing, the cut surface of the mass revealed a white, whorled fibrous and trabecular appearance and ill-defined margins with the surrounding fat tissue (Fig. 2). Microscopically, 501 Korean J Urol 2010;51:501-504