Intraoperative mapping of renal lymphatic drainage: technique and application in a porcine model

The use of lymphadenectomy in renal-cell carcinoma (RCC) is controversial. Proponents argue that lymphadenectomy improves survival, whereas opponents challenge the procedure on the basis of its morbidity and the variable lymphatic drainage of the kidney. Intraoperative gamma probes have been used to guide resection of radiolabeled sentinel nodes in cancers of the breast, penis, and head and neck and in melanoma. Our goal in applying this technique to RCC is to improve detection and to limit sampling of lymph nodes during lymphadenectomy. This preliminary study in a porcine model evaluated the feasibility and transit time of radiolabeled tracer injected into the kidney.

Data were collected on four 40-kg Yorkshire pigs. The right kidney was exposed through a flank incision. Using both blue dye and technetium-99m, mapping and resection of the sentinel lymph nodes was performed with the assistance of an intraoperative gamma probe (Neoprobe). Remote cervical lymph nodes were utilized as controls. Vascular counts along the carotid vessels were obtained to confirm that the radioisotope was not being dispersed systemically.

Within 10 minutes of renal injection of the tracer, excised sentinel lymph nodes demonstrated significant radioactive counts compared with controls. Vascular counts confirmed that radioisotope tracer did not enter the venous circulation.

Sentinel lymph node sampling using a gamma probe and blue dye appears to be feasible in the porcine kidney. Further studies using this technique in humans will evaluate the impact of selective lymphadenectomy on survival in RCC.