Assessing the impact of renal artery clamping during laparoscopic partial nephrectomy (LPN) for small renal masses: the rationale and design of the CLamp vs Off Clamp Kidney during LPN (CLOCK II) randomised phase III trial

Interplay between patient‐ and surgery‐related factors determines the functional recovery after partial nephrectomy (PN) 1. Ischaemic injury resulting from renal arterial clamping has historically been one of the major modifiable surgical factors responsible for the functional decline after PN. As such, several techniques for minimising or even eliminating hilar clamping have been described 2. Laparoscopic PN (LPN) with a pure off‐clamp technique has been described, but the debate is still ongoing as to whether it is appropriate and beneficial with respect to safety and renal function 3. The indication to perform an off‐clamp LPN has remained mostly subjective. When opted for, the off‐clamp resection is attempted to eventually clamp the artery ‘on demand’ in cases of bleeding. This behaviour has undoubtedly compromised the quality of the published data. With the aim of raising the level of evidence, the CLamp vs Off Clamp Kidney during LPN (CLOCK II) randomised clinical trial was conceived. The CLOCK II is a pre–postoperative, prospective, multicentre, parallel, superiority, randomised controlled trial (RCT), supported by the Italian Group for Advanced Laparo‐Endoscopic surgery