| Objective:This study was designed to investigate the safety, efficacy and feasibility of using focused ultrasound surgical clamp (FUSC) for bloodless partial nephrectomy, and to provide significant data for this novel surgical instrument in kidney resection and its clinical application.Methods:(1) A focused ultrasound surgical clamp consisted of two transducers fixed on a forceps-like handle. The directions of focused ultrasound beams were opposite with the same central axes, and ultrasound energy was continuously delivered by the transducers to ablate targeted tissue located between both transducers. Eighty fresh porcine kidneys were divided into 4 groups and each group had 20 kidneys. With a 1.6MHz of frequency and 150W of acoustic power, the kidneys in each group were ablated by FUSC with 30s, 60s, 90s and 120s of exposure time. Using a needle thermocouple, temperatures were measured in the centre of targeted kidneys immediately after ablative procedure. The size and shape of coagulation necrosis were measured after FUSC exposure, and pathological changes in both treated and untreated kidneys were observed. (2) Ten healthy goats were randomly divided into a FUSC group (n =5) and renal hilum clamping+FUSC group (n =5).After anesthesia, the right kidney of each goat was totally exposed with surgical procedure in both groups. Using the same acoustic power and frequency, FUSC was only performed in the FUSC group for ablating the low pole of targeted kidneys; while in the combined group FUSC ablation was performed immediately after renal hillar vascular clamping. FUSC exposure time and the characteristics of coagulation necrosis were recorded in both groups. Histological changes of the treated kidney were observed immediately after FUSC exposure. (3) After surgical exposure, FUSC was performed directly to ablate the predetermined renal tissue of the low pole of the right kidney along with a resection line in 10 goats, followed by partial nephrectomy. FUSC exposure time, blood loss, and the time for the nephrectomy were recorded. Blood routine examination and renal function were measured after surgical procedure. Survival and complications were observed in all goats during followed-up period.Results:(1) FUSC could induce complete coagulation necrosis of in vitro porcine kidneys, and the margin was clear between the treated and untreated kidney. There was a close relationship between coagulation necrosis and temperature rise in the centre of targeted kidneys. With an increase of FUSC exposure time, the extent of coagulation necrosis was significantly enlarged, and a 60s-exposure was the optimal ablation time for the complete necrosis. (2) FUSC could induce complete coagulation necrosis of ex vitro goat kidneys in both groups. The length, width and thickness of the necrosis were 3.6±0.2cm, 1.0±0.2cm and 2.6±0.3cm in the FUSC group, and 3.7±0.3cm, 1.1±0.2cm and 2.6±0.3cm in the renal hilum clamping + FUSC group, respectively. There were no statistical differences of these data between the FUSC and combined groups. FUSC exposure time was 330±20s in the FUSC group and 270±15s in the combined group.A significant difference was observed between two groups (P<0.05). Immediately after ultrasound exposure, the treated kidneys became grey and harder. Under light microscopy there was obviously thermal damage on normal renal tissues which presented coagulation necrosis on macroscopic examination. Electron microscopy showed typical characteristics of coagulation necrosis in the renal corpuscles and tubules. (3)Partial nephrectomy was successfully performed in all goats immediately after FUSC exposure, which could induce complete coagulation necrosis of predetermined kidney tissues along with the resection line. Average FUSC exposure time was 330±20s (range, 300 to 360 seconds),average time for partial nephrectomy including FUSC exposure was 12±3min (range, 8-17min), and mean blood loss was 57±7ml (range, 25-160ml) during surgical resection. Compared to the values before surgery, no significant changes were observed in renal functions after partial nephrectomy. During follow-up period all animals survived well, with no complications. Conclusion:(1) FUSC can induce complete coagulation necrosis of in vitro porcine kidneys. With an increase of FUSC exposure time, the extent of coagulation necrosis was significantly enlarged. (2) Both FUSC alone and FUSC combined with renal hilum clamping can induce complete coagulation necrosis of ex vitro goat kidneys. After hilar vascular clamping, FUSC exposure time is significantly shorter for thermal ablation. (3)FUSC is safe, effective and feasible in the assistance to partial nephrectomy. It can significantly decrease operation time, reduce blood loss, and be easy to perform during interventional procedure. It will provide a novel surgical instrument for bloodless kidney resection. |
