Renal Masses Herniating into the Hilum: Technical Considerations of the “Ball-Valve Phenomenon” During Nephron-sparing Surgery

To describe our technique to recognize and resect renal tumors "ball-valving" into the sinus. Partial nephrectomy (PN) offers a functional advantage over radical nephrectomy for many cases of localized renal cell carcinoma. However, PN is underutilized particularly in anatomically challenging cases. Often unrecognized is the tendency for central renal tumors to herniate into the renal sinus.From our prospective kidney cancer database, we identified 36 patients who underwent open, laparoscopic, or robotic PN for solitary localized renal cell carcinoma herniating into the renal sinus.Axial and reformatted radiographs were reviewed for all renal hilar lesions. Intraoperative techniques include hilar dissection, establishment of a sinus plane allowing tumor and parenchymal retraction, reduction of the tumor out of the sinus, resection, and repair. Mean preoperative lesion size was 3.8 cm. Indications for PN included 15 of 36 (42%) absolute, 13 of 36 (36%) relative, and 2 of 36 (6%) reoperative PN. No procedure was converted to radical nephrectomy. Of the 36 PN, 5 (14%) were performed using a minimally invasive approach and no minimally invasive surgery procedures were converted to open. No patient required renal replacement.Recognition of the tendency for hilar masses to herniate or "ball-valve" into the renal sinus is essential for effective PN of central tumors. By using our technique, we have demonstrated success in nephron-sparing surgery with minimal intraoperative complications and favorable postoperative outcomes in patients with central tumors herniating into the renal sinus.