General aspectsPatient positioning and system installation

Robotic colorectal surgery usually comprises almost half of the abdominal cavity and therefore fully exploits or even exceeds the limits of the robot’s range of motion. This can cause increasing interaction between the robotic arms in the peripheral areas of the system alignment, which leads to a significant impairment of manipulation and triangulation. To prevent repeated re-docking and to avoid arm–arm collisions, particular care must therefore be taken when aligning and positioning the system. Instead of strictly following the general recommendations, we advise surgeons to first carefully review the specific anatomical characteristics of the patient and the location of the disease and to adjust the angulation of the trocar line according to these. Questions to be answered here concern the exact tumor location; the required vascular dissection; the extent of intestinal mobilization; and patient-specific conditions such as prior surgeries, body mass index (BMI), or the size of the belly. More detailed recommendations on how to install the system are given below. The same applies to the positioning of the patient, which can only be corrected after undocking the system in case no table motion being available, and which should also consider the respective patient anatomy and the planned operation.

Surgical strategy

In RAS the four robotic arms must be seen as a functional unit that should be activated together and used in combination. Robotic systems are optimized for a clear proximity to the surgical site and for fine manipulation, i.e., the site is adjusted more directly and immediately than in laparoscopy. Arm–arm interactions (also outside the body) are best avoided by always converging all four arms to the surgical site, which further enhances exposure and alleviates traction–countertraction. As a basic principle, we therefore advise surgeons to divide the surgical area into numerous small regions and to adjust all four arms to these successively instead of adopting a distant position and divergent arm orientations. To facilitate true bimanual dissection, we recommend exposing the operating site with one passive retractor, while using the two remaining active instruments for dissection. In contrast to having two retractors, this principle not only speeds up the intervention but also adds safety and control, particularly in demanding parts of the procedure or in the case of bleeding (Fig. 1). As repositioning all four instruments and setting the system to a new surgical area (e.g., left flexure versus pelvic inlet) is complicated and time demanding, each step of an operation should be fully completed before the next step begins. Here too, the procedure must be strategically planned in alignment with the anatomy and the disease. We therefore recommend defining individually adapted target criteria for different surgical steps, analogous to the principle of nodal points according to Immenroth et al. [6].

Fig. 1

Two examples of bimanual dissection in colorectal robot-assisted surgery which show the importance of exposing the surgical site with the passive retractor alone: a dissection of the ileocolic trunk; b dissection of the inferior mesenteric artery

While RAS is characterized by significantly better fine manipulation and local dissection, many users report difficulties in manipulating larger tissue masses or controlling the mobile bowel. To overcome these issues, we recommend first completing the central and challenging aspects of a procedure before starting to detach larger organs that would otherwise also need to be controlled. Accordingly, adhesions and embryonic attachments should only be removed once central and critical dissections have been completed. Likewise, central and posterior dissection steps should be performed first before releasing superficial and ventral adhesions. Another robotic-specific aspect is the fact that the endoscope is not inserted medially in most cases but rather laterally, which causes a flatter sight of view. Accordingly, lateral dissection steps should first be prepared from the medial side and be postponed to the later course of the operation.

Component training

Robot-assisted colorectal surgery should be trained step by step, and appropriate skills should be acquired before complex procedures are performed [5]. This is often overlooked when starting a robotic program, as surgeons want to quickly transfer their existing expertise to RAS. In accordance with the principle of component training, where the training of complex surgeries is separated into defined substeps [6], we recommend selecting suitable interventions during the initial training that not only have an increasing degree of difficulty but which also specifically serve to achieve robotic expertise in key aspects of colorectal surgery. For right-sided interventions we propose starting with ileocolic resection before continuing with right hemicolectomy, while sigmoid resection and pelvic floor repair suit training prior to rectal resection (Fig. 2). In addition, patient-specific aspects such as BMI, gender, tumor location, and anatomical features should show an increasing complexity.

Fig. 2

Training in robot-assisted colorectal surgery should be step by step, aiming for the trainee to progressively learn the relevant aspects of challenging procedures

Procedure-specific aspects

This section will only deal with special recommendations for system installation and for the most common problem areas. For complete descriptions of the respective procedures and treatment of the transverse colon, we refer to the available literature (e.g., [7,8,9,10]).

Left-sided interventions System installation

System installation for left-sided colorectal procedures depends on how extensively the left colonic flexure must be mobilized, how far the pelvic dissection must be guided, and how demanding the pelvic anatomy appears to be (Fig. 3). We recommend placing the trocars more to the right side of the body to cover the left side well, whereby the spacing of the arms in relation to each other and the relationship to the pelvic inlet must account for the requirements of the lower pelvic dissection. The trocar furthest to the right should not be placed too deeply or too laterally to prevent the pelvic inlet becoming a hypomochlion for this instrument. The height of installation of the second arm (left to the camera) should not, or only slightly, exceed the origin of the inferior mesenteric vein to ensure efficient exposure of this region from medial.

Fig. 3

The angulation of the trocars must be adapted to the patient’s individual anatomy (a) but should also consider how well access to the left flexure is given (b). Secondary repositioning of the left outer trocar to a lower left lateral position can facilitate exposure of the pelvic floor (c)

Dissection of the left-sided colon

In our experience, dissection of the left colonic flexure initially poses a problem for many RAS surgeons. To overcome this problem, we recommend consistent median-to-lateral guided dissection of the pancreatic tail and left flexure with suprapancreatic opening of the omental bursa and preservation of the splenic adhesions until last (Fig. 4). For this, we first expose the pancreatic tail from the mesocolic side to subsequently open the omental bursa above it and left of the mesenteric vein. This step exposes the transverse mesocolon, which we then dissect towards the spleen, always staying close to the pancreas, reaching as far as possible toward the splenic hilum. A compress on the lateral aspect of the pancreas serves to protect the organ during the subsequent lateral release and shows the correct path for dissection. While we prefer to preserve the inferior mesenteric vein until the suprapancreatic opening of the bursa, others aim for early dissection of this vessel to prevent inadvertent tearing during retraction. Regardless of when the vein was transected, this step allows the left mesocolon to be stretched open with more tension. With this retraction, the left-sided mesocolic dissection is now easily achieved and should be continued as far lateral as possible and up to Toldt’s line. Only after having completed this step of the procedure is the left colon and flexure released from the lateral side.

Fig. 4

Suprapancreatic dissection of the transverse mesocolon to facilitate later mobilization of the splenic flexure

If a wider mobilization including the left transverse colon is necessary, the bursa should first be opened supracolically before the lateral adhesions are detached, as these adhesions help with controlling the left flexure and prevent it from falling toward medial.

Right-sided interventions System installation

Many recommendations exist for installing the system for right-sided interventions [11]. In our own experience, the suprapubic technique with horizontal alignment of the trocars is, in principle, the best [12], but it can cause difficulties in case of a low ileocecal junction and at the right flexure, which is why we sometimes prefer a slightly ascending line instead. The camera trocar (second) should be placed in the longitudinal axis of the superior mesenteric vessels to achieve perfect exposure of the central vasculature. We advise taking the third trocar for insertion of the stapler, not only as it facilitates dissection of the intestine and formation of the anastomosis but also because it eases instrument exchange while restoring intestinal continuity. If one aims for an intracorporeal anastomosis, the positioning of the patient should avoid excessive lateral tilt in order to not shift the remaining transverse colon too far towards the left flexure.

Dissection of the right hemicolon

Right-sided resections start with exposure and subsequent dissection of the mesocolic plane, which we enter via a transmesenteric infra-ileocolic approach. For better control and to facilitate exposure of the central vessels, we maintain the lateral adhesions of the ascending colon until the central vascular dissection is completed. The dissection of the mesocolon is continued to the pancreatic head and duodenum and until behind the mesenteric axis, which significantly facilitates the subsequent ileocolic dissection and increases radicality. We continue the dissection from left of the mesenteric axis, which is now carefully exposed from anterior and starting from below the ileocolic vessels. This sequence perfectly exposes the mesenteric vessels and the ileocolic axis so that the latter can be transsected very centrally. Now the preparation is continued until the central infrapancreatic region. To achieve control of the complex and highly variable anatomy here, we recommend early visualization and dissection of the middle colic artery. For this, the transverse mesocolon is spanned at the height of the middle colic artery towards the abdominal wall, which exposes the course of this artery and allows for dissection of the mesocolon right of it (Fig. 5). Opening of the omental bursa is usually easy and safe at the level of the middle mesocolon and makes the further central dissection much easier and can help separation of the mesogastric body. In the case of an obese mesentery, we advise the use of indocyanine (ICG) intraoperatively to further explore the vascular anatomy. With this two-sided exposure of the central anatomy, the further dissection along the trunk of Henle is generally achieved easily. Insertion of a compress below the separated mesogastrium facilitates completion of the central dissection, which is why some groups generally place this step at the beginning of the operation [13]. As the retroperitoneal dissection of the mesocolon is much more easily achieved from medial to lateral, we recommend continuing the dissection over the remaining parts of the pancreas and duodenum towards the lateral deflection before it is released at the very end and from lateral, if necessary.

Fig. 5

After exposure of the superior mesenteric vessels, the middle colic artery (MCA) serves as an additional guiding structure for further dissection of the central vasculature. SMV superior mesenteric vein, SMA superior mesenteric artery

Pelvic cavity System installation

For dissection of the pelvic floor, a trocar line that is as horizontal as possible is facilitating but must also take into account any necessary mobilization of the splenic flexure (see above). We recommend tilting the patient as far as possible to the right and placing them in a Trendelenburg position so that the small bowel loops do not cover the promontory.

Pelvic dissection

While the upper mesorectum and dissection around the promontory pose no relevant difficulties and are easily achieved in general, some recommendations might be given for the continuation of the procedure. Before continuing the posterior mesorectal excision, we recommend first cutting the lateral mesorectal suspensions above the peritoneal deflection, which is best done from ventrally. The ventral adhesions to the vagina or seminal vesicles, however, must remain untouched until the muscular pelvic floor or the posterior level of deposition is reached, as they hold the mesorectal body ventrally and allow for better exposure of the posterior mesorectum via the robotic retractor. It is important that this retractor not be inserted too high into the abdominal cavity, as it would otherwise be at too shallow an angle, allowing only minimal movement in relation to the symphysis; if necessary, it must be repositioned according to Fig. 1. After the lateral mesorectum has been divided up to the level of the peritoneal deflection, the posterior mesorectum (Waldeyer’s fascia) is dissected until reaching the muscular pelvic floor. For the deeper posterior dissection, it is important to guide the dissection completely to both sides laterally and then distally in stages. Using the additional degrees of freedom and the possibility of anatomically appropriate angulation of the instrument using the additional joints of the end effector is particularly helpful here, which becomes even more important in a narrow pelvis and for the low ventral aspects. To cope with the sometimes-observed constant contamination of the camera or the collection of secretions in the small pelvis, it is possible to insert a gravity drain via a small abdominal incision, which is positioned at the lowest point of the pelvis. With the positive abdominal pressure, this leads to continuous evacuation of pelvic secretions. To support exposure in the very low pelvis, additional traction to the posterior mesorectum by means of a laparoscopic grasper is recommend. Only after having reached the muscular pelvic floor and completed the posterior mesorectal excision until the height of the later anastomosis should one continue with ventral dissection of Denovillier’s layer. Dissection here is best achieved when the assistant tightens the rectum from ventrally while the dissection line is perfectly exposed via the two retractors and according to the principle of traction and countertraction (Fig. 6).

Fig. 6

The concept of traction and countertraction can be used perfectly for ventral dissection of the mesorectum and for exposure of the correct dissection line

Indocyanine application

While ICG fluorescence angiography for assessing anastomotic and intestinal perfusion has become a routine application in RAS, it can also be used for intraoperative navigation and vessel demarcation (as described above) and for detection of draining lymph nodes. As preoperative injection via endoscopy is sometimes difficult to organize, we recommend use of an endoscopic scleral needle for this purpose. The needle can be easily inserted via the assistant trocar and used to mark the tumor area (Fig. 7). Spillage of ICG should be avoided. The fluorescent dye diffuses into the adjacent lymph nodes within a few minutes and allows for their visualization. Even if the sentinel lymph node concept has not yet been proven in colorectal cancer, fluorescent staining can help with additional information in borderline areas and to exclude atypical lymph drainage pathways.

Fig. 7

Intraoperative injection of indocyanine green at the tumor site via a transabdominally placed endoscopic scleroneedle (left) and visualization of the stained lymph nodes (right)