Laparoscopic abdominal perineal rectal resection for rectal cancer with a horseshoe kidney using preoperative 3D-CT angiography: a case report.

BACKGROUND A horseshoe kidney is a congenital malformation involving the fusion of the bilateral kidneys and is often accompanied by anomalies of the ureteropelvic and vascular systems. When performing resection of colorectal cancer in a patient with horseshoe kidney, damage to the ureter or excessive renal arteries should be avoided. To achieve this purpose, comprehensive preoperative anatomical assessments and surgical planning are important. Here, we report a case of a laparoscopic abdominal perineal rectal resection for lower rectal cancer with a horseshoe kidney. CASE PRESENTATION A 79-year-old woman presented with bloody stool and was diagnosed with advanced lower rectal cancer, immediately above the rectal dentate line, without metastasis. A preoperative computed tomography (CT) scan revealed a horseshoe kidney, while a three-dimensional CT (3D-CT) angiography revealed aberrant excess renal artery from the aorta to the renal isthmus. The left ureter ran in front of the isthmus of the horseshoe kidney and presented calculus formation. Laparoscopic abdominal perineal rectal resection was performed with D3 lymph node dissection. During the operation, we mobilized the sigmoid colon mesentery via a medial approach and preserved the left ureter, the left gonadal vessels, and the hypogastric nerve plexus in the retroperitoneum in front of the horseshoe kidney. CONCLUSIONS We report a rare case of rectal cancer surgery in a patient with a horseshoe kidney. We discuss the anatomical peculiarities of a horseshoe kidney, such as excess renal arteries, inferior vena cava, ureter, gonadal vessels, and nerves, that should be preserved according to the literature. We suggest that preoperative 3D-CT angiography is both useful for revealing the relationship between the vascular system and a horseshoe kidney and helpful when performing laparoscopic surgery for a left-sided colon and rectal cancer to avoid intraoperative injury.