Is bilateral extended pelvic lymphadenectomy necessary for strictly unilateral invasive bladder cancer?

We determined the necessary extent of pelvic lymph node dissection in patients with strictly unilateral bladder cancer. A total of 40 patients with cystectomy and unilateral bladder cancer preoperatively underwent flexible cystoscopy guided injection of radioactive technetium into the contralateral bladder wall. Preoperatively single photon emission computerized tomography was done in all cases to detect and localize radioactive lymph nodes. Radioactive lymph nodes were confirmed intraoperatively by a γ probe and removed separately. Backup extended pelvic lymph node dissection and ex vivo examination of the whole specimen with a γ camera were done to preclude missed radioactive lymph nodes. Single photon emission computerized tomography and intraoperative findings were used to generate a 3-dimensional projection model of each lymph node site. A total of 228 radioactive lymph nodes (median 6, range 1 to 17) were detected, including 193 (85%) on the ipsilateral side of injection and 35 (15%) on the contralateral side. Of the contralateral lymph nodes 6%, 5% and 4% were in the external iliac, obturator fossa and common iliac region, respectively, but none were in the contralateral internal iliac region. At least 1 radioactive lymph node per patient was detected on the ipsilateral side. Additional lymphatic drainage to the contralateral side was found in 40% of patients. Crossover lymphatic drainage is a common phenomenon and unilateral pelvic lymph node dissection would have missed radioactive lymph nodes in 40% of patients. However, we noted no lymphatic drainage to the contralateral internal iliac region. Thus, when bladder tumors are strictly unilateral, contralateral pelvic lymph node dissection can be limited to the obturator fossa, and the external and common iliac regions. Consequently preserving the contralateral autonomic nerves situated close to the internal iliac vessels does not compromise surgical radicality