In 2002, Hashizume and Weber et al. first reported robotic colectomy [16] [17]. Since then, more and more studies have shown that robotic colorectal surgery has similar oncological results compared with laparoscopic or open surgery [18] [19], the application of robotic surgery in the field of general surgery has increased year by year. Although laparoscopy has now become the gold standard for a variety of relatively easy general surgery. However, laparoscopic ergonomics and technical limitations, the loss of anatomical orientation due to two-dimensional views make the identification of important structures a problem. The extraordinary visual and ergonomic advantages of the Da Vinci system were presumed to overcome the limitations of laparoscopy and improve the results of minimally invasive colon surgery[20]. Although the application of the Da Vinci system in the general field has increased year by year, due to the lack of effective tactile feedback assistance, intraoperative exploration is often difficult when the tumor is small or does not invade the serosa. It has been reported that the wrong colon segment is removed during laparoscopic surgery, which requires conversion to open surgery and resection of longer intestine segments[21] [22].
For colon tumors, colonoscopy is still the most sensitive diagnostic tool, but due to the lack of obvious anatomical landmarks in the colon, inaccurate tumor localization may lead to longer lengths of resection, and even the removal of normal intestinal segments leaving the tumor. 16.7% of cases will have different procedures from the original plan due to inaccurate preoperative colonoscopy, especially for transverse colon tumors [23]. So the 2013 Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) and the 2004 European Association of Endoscopic Surgery (EAES) clinical practice guidelines for laparoscopic resection of colon cancer recommend colonoscopic tattooing of small lesions[24] [25]. But until now there were no evidence that suggest that colonoscopic tattooing should be used only for small lesions. Moreover, tumors localized in the transverse colon are commonly considered challenging, and routine tattooing of these tumors is recommended. Because the tumor is located close to the liver curvature, spleen curvature and the middle part of the transverse colon, the resection range is very different, so the surgical approach is divided into left hemicolectomy, right colon colectomy and transverse colon resection. In the Da Vinci surgical system, the three surgical methods, the placement of the robot and the port are different. If the surgical plan is changed during the operation, it will not only directly increase the cost of surgery, but also lead to prolonged operation time and increased risks of surgery. Therefore, how to achieve accurate preoperative and intraoperative positioning determines the premise of the success of robotic surgery.
There are a number of techniques currently used for the localization of colonic lesions, including double-contrast barium enema, computed tomography colonography, titanium clip positioning, intraoperative colonoscopy, and preoperative injection stain positioning. But each method has its shortcomings and limitations. Double-contrast barium enema and computed tomography colonography are easy to miss smaller lesions [12] [26]. Titanium clip positioning is a short-term solution, costly, often shifts or falls off after 2–3 weeks of implantation; and the titanium clip is small, the clip cannot be seen from the serosal side, and it cannot be touched during laparoscopic surgery [27]. Intraoperative colonoscopy can also be used for positioning, but it is a more complex method that requires experienced endoscopists and specific equipment in the operating room, which can increase the time of surgery and increase the risk of anesthesia and the probability of infection [7]. In addition, colonoscopy will inflate the intestines, increasing the difficulty of surgery [13]. In recent years, the most common method of positioning has been to inject a stain into the intestinal wall. Commonly used dyes such as methylene blue, indigo carmine, and phthalocyanine green have relatively short dyeing times, which tend to spread over time and contaminate the surgical field of view and cause inaccurate positioning [28] [29]. Although Indian inks have a long time at the marked parts, some studys reported Indian ink can cause peritonitis, cellulitis, gastritis, colonic abscesses and inflammatory pseudotumors. [30] [31] [32]
The nano-carbon used in this study, Askin M P et al., evaluated the safety and efficacy of colon labeling using nano-carbon in a study of 113 patients [33]. In the study, no patients developed fever, abdominal pain or symptoms of inflammation, and nano-carbons existed for 1 year, confirming that nano-carbon is a long-term safe and effective marker. In this study, we also did not find any discomfort after the patient received nano-carbon injection. In addition, we use the "four quadrant" method[15] (ie, four points are selected centered on the tumor, each point is 90° apart) injection labeling is performed around the tumor to avoid staining of the intestinal wall when the tumor is on the mesenteric side. Moreover, the marker points are 1 cm away from the tumor and avoid direct injection into the tumor. Secondly, the needle is at an angle of 45° to the wall of the intestine when the needle is inserted, because the vertical needle easily penetrates the intestinal wall, causing the dye to enter the mesentery or the abdominal cavity to contaminate the surgical field of view. The diffusion of nano-carbon can also be reduced by the "three-step injection method" of J. W. Park et al[34]. The final intraoperative findings showed that all 16 patients were able to find nano-carbon labeled sites, confirming that our approach worked. In this study, we placed a titanium clip on each of the anal side and the mouth side, and then immediately examined the radiation. The titanium clip showed a high signal in the X-ray, and the tumor was located between the two titanium clips. Studies have shown that two titanium clips are used to prevent displacement or shedding when using titanium clips for colon marking[27]. In general, the peak period of shedding is 2–3 weeks after placement, the longer the time, the greater the probability of shedding. Radiation inspection immediately after the titanium clip is placed can reduce errors caused by displacement or shedding of the titanium clip. Moreover, all patients underwent surgery within 1 week after receiving the marker, thereby avoiding the peak of titanium clip detachment.
Nano-carbon labeling helps us to quickly find tumors during surgery, avoid excision of the wrong bowel segment, and ensure a sufficient safety margin. Titanium clip marking allows us to obtain a more accurate positioning before surgery, which helps to develop a surgical plan and avoid the cost associated with robotic surgery and additional operative time due to changes to the surgical plan. Accurate preoperative positioning can provide a reliable basis for the selection of Trocar position and surgical incision for laparoscopic surgery, to avoid surgical errors due to poor exposure of the surgical field caused by incorrect selection of Trocar position. In general, robotic surgery has a longer operation time than laparoscopic surgery. Although long operation time may be related to high postoperative morbidity, operative time is not the only parameter showing the quality of surgery and it is obvious that the operation time may decrease as the experience of robotic surgery increases. And our method can significantly reduce the exploration time.
In conclusion, the findings of this study have shown that the preoperative colonoscopy nano-carbon and titanium clip combined labeling method is safe and effective in robot-assisted transverse colon cancer surgery. At the same time, the labeling method shows potential in shortening the operation time, ensuring sufficient safety margin and reducing complications.