AUA 2018: Surgical Techniques: Tips & Tricks: Dissection of the Renal Mass with Hilar Fat Invasion

San Francisco, CA USA ( Dr. Monish Aron discussed tips and tricks for resecting renal masses with Hilar fat invasion. Dr. Aron states that being prepared for these tumors is important, considering that they may be difficult to predict on preoperative imaging. Not recognizing these tumors may lead to tumor violation or positive surgical margins, leading to potential implications for prognosis. The incidence of upstaging a tumor to pT3a is certainly not uncommon. A recent report from the SEER database found that upstaging from cT1a to pT3a occurs in 4.2% of cases, for cT1b in 9.5%, and cT2 in 19.5% of cases [1]. Patients that were upstaged to pT3a had worse CSS compared to similar stage patients that were not upstaged, and there was no difference in survival amongst upstaged patients whether a partial or radical nephrectomy was performed.

Preoperative planning for these patients is crucial and should include a high-quality multiphase CT scan (2mm cuts) and read by an experienced radiologist. 3D reconstruction may be helpful and there should always be a high index of suspicion for the possibility of pT3a disease. Imaging indicators for possible pT3a tumors include a high nephrometry score, increasing tumor diameter, and a hilar located tumor. Additionally, tumors >7.5 cm with irregular tumor margins are more likely to be pT3a.

Dr. Aron then proceeded to cover some operative tips when he’s performing a partial nephrectomy for suspected pT3a lesions. For the robotic approach, he always goes transperitoneal, uses a 4-arm approach and uses two assistant ports for optimal access. Complete and adequate mobilization of the kidney is key, with “more than you think necessary” kidney defatting. It is important to retain strategic ‘handles’ of fat to allow for kidney manipulation with the robotic arms. Intraoperative ultrasound is also important as it minimizes the chances of positive margins and allows the surgeon to be meticulous. Marking the resection lines also allows the surgeon to have a clear idea of where the resection is headed during the extirpation, and Dr. Aron notes that one should always give yourself a few extra millimeters than you think necessary. Dr. Aron is a proponent of robust hilar clamping and uses surgeon applied bulldog clamps, usually just the renal artery. For larger and deeper tumors, he is prepared to clamp the renal vein, but cautions that one must be sure all arteries are clamped prior to clamping the renal vein.

During the tumor dissection, there are several tips and tricks that Dr. Aron highlights:

• Ensure a bloodless field
• Circumferentially excise the tumor
• Retraction/counter traction is key with the 4th arm
• Approach the deepest portion of the tumor late/last
• Adjusting the robot light intensity can assist with visualization
• Be able to differentiate the tumor from the sinus fat
• Bag the specimen immediately after excision to prevent tumor spillage

Dr. Aron concluded with highlights from his institution’s experience of 530 cT1 tumors, of which 6.2% were upstaged to pT3a. For these patients, this was associated with a 2.9% positive margin rate and significantly longer warm ischemia time (20 min vs 14 min, p=0.01) compared to patients who were not upstaged.

Presented by: Monish Aron, University of Southern California, Los Angeles, CA

Written by: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre, Twitter: @zklaassen_md, at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA

1. Srivastava A, Patel HD, Joice GA, et al. Incidence of T3a up-staging and survival after partial nephrectomy: Size-stratified rates and implications for prognosis. Urol Oncol 2018;36(1):12.e7-e12.e13.
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