[A Case of a Congenital Right External Iliac Vein Defect Found after Robot-Assisted Radical Prostatectomy].

Congenital external iliac vein defects are extremely rare. A 56-year-old man underwent robotic prostatectomy (RARP) without pelvic lymph node dissection (PLND) for localized low-risk prostate cancer. Intraoperative findings revealed a markedly dilated vein on the dorsal side of the pubic bone,which was difficult to preserve and was therefore clipped. Sudden swelling and pain appeared in the right leg on day 2 after successful RARP. A contrast-enhanced computed tomography (CT) scan showed a deep vein thrombus (DVT) and lack of a right external iliac vein. Immediate heparinization improved the symptoms, and no other postoperative complications occurred. In the retrospective review,a large dilated vein lying transversely on the prostate surface was observed with a robotic scope,but no manipulation of the pelvic vessels was performed because PLND was not performed. Therefore,the dilated vein was not recognized as a shunt from the right femoral vein to the left external iliac vein. A preoperative staging CT scan,which faintly revealed the right external iliac vein,could be useful to identify this extremely rare deformity in advance of surgery. Although preoperative imaging examinations are often difficult to diagnose preoperatively,as in this case,we consider it important to use appropriate approaches and treatment when dealing with symptoms that arise during pelvic surgery in patients with many anatomical variations.