Laparoscopic Sigmoid Colectomy in a Patient With Congenital Left Renal Agenesis: A Case Report

Congenital renal agenesis is a rare anomaly that can alter retroperitoneal anatomy and affect the spatial relationships between adjacent organs, potentially complicating colorectal surgery. Here, we present the case of a 54-year-old woman with congenital left renal agenesis who was diagnosed with an obstructing sigmoid colon tumor. She initially underwent transanal decompression with an ileus tube and was referred to our institution for further management. Contrast-enhanced computed tomography revealed no distant metastasis and incidentally revealed the absence of the left kidney. After adequate decompression, a laparoscopic sigmoid colectomy with D3 lymph node dissection was performed. Preoperatively, we anticipated that identification of the retroperitoneal plane and mobilization of the splenic flexure would be technically challenging owing to the altered anatomy. However, intraoperatively, the retroperitoneal plane was identified without difficulty by maintaining continuity with the mesocolic plane and referring to consistent anatomical landmarks. By contrast, splenic flexure mobilization proved more technically demanding, as the colon was displaced into the left renal fossa, resulting in large distances from standard port positions, limited instrument reach, and suboptimal traction. Modification of port usage and the operator's position enabled safe completion of the procedure without conversion to open surgery. The patient's postoperative course was uneventful. Histopathological examination revealed a pT3N0M0 high-risk stage II adenocarcinoma, and adjuvant chemotherapy was administered. The patient remained alive without recurrence for 9.5 years after surgery. In patients with congenital renal agenesis, retroperitoneal dissection may be simple despite altered anatomy, whereas splenic flexure mobilization can be more technically demanding owing to changes in spatial relationships. Careful preoperative assessment and flexible intraoperative strategies are essential for safe laparoscopic surgery in such cases.