The minimally invasive approach for colorectal surgery, preferred for both oncological and benign cases, leads to fewer post-surgical complications, quicker recovery, less pain, and shorter hospital stays [1,2,3,4].

In right hemicolectomy, especially with a robotic approach, IA provides better short-term outcomes without adding risks [5, 6, 8, 44]. . However, anatomical complexities and anvil head insertion have limited IA use in left colon surgery.

Recently, TIA has been gradually incorporated into left colon surgery. Robotic approach has been a critical step in the evolution of TIA in recent years; it has helped to overcome the technical difficulties and has established a systematized and reproducible method for anastomosis.

Our comparative study did not show differences in patient demographic characteristics between groups.

In the preliminary analysis within the TIA group comparing the two approaches (laparoscopic and robotic), differences are only observed in terms of operative time, which is significantly longer in the robotic group. We interpret this result as both approaches being comparable in terms of outcomes, except for the operative time. The extended robotic surgery time is primarily due to technical factors like docking, instrument placement, and potential redocking as needed. The Propensity score matching analysis (PSM) demonstrate that laparoscopic EA and IA surgery is similar, implying that it doesn’t demand exceptional skills, and it suggest that the extended surgical time is primarily due to the robotic approach. For experienced colorectal surgeons, TIA isn’t a challenging procedure.

Regarding intraoperative variables, the operative time is not assessable, as we are aware that differences exist based on the approach. However, differences do appear in intraoperative complications and the conversion rate to open surgery. Based on this data, we can deduce that performing intracorporeal anastomosis reduces intraoperative negative events. However, the fact that patients with robotic approach are only in the TIA group and not in the EA group is an evident bias. When conducting the analysis exclusively with the laparoscopic approach, and thus eliminate the patients with robotic approach, the PSM shows us that there do not seem to be differences in any variables. This suggests that the robotic approach may be the key factor in reducing complications during the surgical process, but at the expense of a longer surgical time, which in communities with significant healthcare pressure is clinically relevant.

Concerning postoperative results, we observed a higher rate of anastomotic bleeding in the EA group compared to the TIA group. EA involves the extraction of the colon through the accessory incision, which increases mesenteric tension and may lead to ischemia, edema, delayed intestinal recovery or subsequent anastomotic bleeding. The rates of anastomotic dehiscence and adynamic ileus did not differ between the groups, but the rate of anastomotic bleeding was higher in the EA group. It results in a higher rate of visits to the emergency department, and it has an impact on health expenditure, and increases the overall healthcare costs per patient, which in turn influences clinical practice.

From a surgical perspective, there are no technical differences that could explain the variation in postoperative bleeding rates, aside from the need to extract tissue through an accessory incision to complete the resection and place the anvil head. In both the EA and TIA groups, using both approaches, the vascular division is performed at the same level (high ligation), and the colonic division is carried out mechanically with a linear stapler with the same caliber. Colorectal anastomosis is performed with the same circular stapler, also with the same caliber. No differences were observed in the number of linear stapler firings required for the colon resection.

Therefore, our hypothesis is that the tension exerted during the extraction of the sigmoid colon through the Pfannenstiel incision for resection and anvil placement can sufficiently damage the tissues, leading to a higher rate of postoperative bleeding at the anastomosis site compared to intracorporeal anastomosis, where such tension is absent. In addition, manipulation and exposure of the colon are reduced in the intracorporeal technique, minimizing tissue trauma and consequently, bleeding. Lastly, enhanced visualization and stability of the surgical field in intracorporeal laparoscopy may contribute to more effective hemostasis.

Eliminating the robotic factor in the PSM equalizes the outcomes, suggesting that the robotic approach plays a crucial role in minimizing unnecessary tissue manipulation, reducing anastomotic bleeding and consequently decreasing the rate of consultations to the emergency department.

If we review the literature on postoperative bleeding from the staple line, no differences are described between types of anastomosis (side-to-end or end-to-end) [18], nor in differences between robotic and laparoscopic approaches [19]. Regarding potential differences based on extracorporeal or intracorporeal anastomosis, most published comparative studies do not specifically describe this data [29, 30]. However, in studies that do describe it, no statistically significant differences are found [28, 32, 45]. It is noteworthy that these studies exclusively encompass patients treated with either laparoscopic or robotic approaches separately, thereby bolstering our hypothesis that the combined use of intracorporeal anastomosis and robotic approach constitutes a pivotal factor influencing the observed outcomes.

In relation to surgery-induced inflammation, limited literature explores the connection between CRP levels in laparoscopic and robotic approaches and their clinical relevance. In our study, the TIA group exhibited higher CRP levels on the first and third postoperative days. Within the laparoscopic approach group, the PSM analysis reveals higher levels of CRP on the first postoperative day, with no differences on the 3rd day.

There is limited literature describing the differences in surgical stress between different approaches and types of anastomosis in left colectomy. In the case of right colectomy, the results of the RCT conducted by Milone et al. comparing intracorporeal anastomosis (IA) with extracorporeal anastomosis (EA) show a reduced pattern of pro-inflammatory mediators (IL-6, CRP, TNF, and IL-1β) in patients with IA compared to those with EA, along with higher levels of anti-inflammatory cytokines. The results of the RCT conducted by Mari et al. showed similar findings, with lower levels of IL-6 and CRP in the IA group [46, 47].

For left colectomy, our results differ from those published by Widder et al. According to their findings, the levels of pro-inflammatory factors (leukocytes and CRP) are lower with the robotic approach [21].

These differences with the literature, with an increase in the inflammatory response in the TIA group, may be due to the longer operative time associated with the robotic approach. Nevertheless, this data does not correlate with an increase in postoperative complications or clinical impact, making it not clinically relevant.

In terms of oncological results, no differences are seen between both techniques. We only notice a higher number of nodes collected in the EA group (22) compared to the TIA group (18). However, both groups have a median greater than 12, with a percentage of patients having more than 12 nodes collected without differences, it does not seem to be clinically relevant. From an oncological perspective, it will remain pending to determine whether both techniques yield similar long-term oncological outcomes in terms of recurrence and survival.

Our findings align with other studies in literature. In the laparoscopic approach, recent retrospectives reveal IA’s advantages over EA, including reduced post-op complications, faster recovery, and shorter hospital stays. However, IA linked to longer operation times [27, 30]. In terms of surgical site infection, a multicenter propensity score-matched study found IA lowers the risk of both superficial and deep SSI [31].

IA has been associated with shortened hospital stay in some studies [30, 33], though others have not found significant differences. The same applies to operating time: IA is associated with a longer surgical time in most comparative studies, though the difference is not always significant [32].

Comparing laparoscopic and robotic approaches, recent studies show the robotic approach entails extended surgery time and higher costs [20,21,22]. However, systematic reviews and meta-analyses reveal lower rates of overall morbidity, anastomotic dehiscence, and SSIs (superficial and deep) in robotic surgery [19, 20].

The literature presents conflicting findings regarding the length of hospital stay. Some studies demonstrate a shorter hospital stay for robot-assisted surgery, while others indicate a longer stay, and the majority do not show any significant differences [21, 22].

In reference to oncological outcomes, our findings corroborate those of previous reports as far as the approaches were not associated with any significant differences. Only one multicenter study found robotic surgery to be associated with a higher number of harvested lymph nodes, but this increase did not affect recurrence, persistence, or 3- and 5-year survival rates [22].

IA takes longer with the robotic approach, but the rate of postoperative complications is lower [11, 19, 20]. IA appears to be associated with longer operative time, especially in patients with a BMI greater than 30. It also shows a lower conversion rate to open surgery and long-term hernias. However, no clear differences are evident regarding short-term postoperative complications (e.g., anastomotic dehiscence and surgical site infections), time to first meal, hospital stay, reoperation rate, or hospital readmission, although there was a slight trend towards improved surgical morbidity [26,27,28].

In general, the results obtained in our study are similar to those found elsewhere in the literature. They demonstrate a trend towards better postoperative outcomes with the creation of IA, especially using the robotic approach.

A debated concern is the possible rise in intra-abdominal infections from IA, linked to colotomy within the cavity and potential intestinal content spillage. In our study, all patients had antegrade colon preparation, mitigating contamination risk. Existing literature does not show elevated superficial or deep SSIs in IA for both right and left colectomies [6, 31].

Another matter of concern is the possibility of tumor dissemination due to colonic opening in oncological patients. To date, there are no reports of local or distant spread due to the creation of IA. However, since few studies on left colectomy have been performed, longer-term assessments are now needed to determine possible late complications.

This study has several limitations that should be discussed. The main limitation is the study design. It has been designed with a sample size calculation based on non-inferiority criteria, so the results may demonstrate its non-inferiority but not the superiority of the intracorporeal technique. Therefore, we can say that the results suggest better outcomes in some variables, but we cannot assert it statistically. This is a prospective (but not randomized) cohort study with a retrospective or historical control group, a factor that might cause some selection bias, which we have tried to mitigate by performing the propensity score matching analysis. Second, all surgeries were performed by a team of five surgeons, experts in both laparoscopic and robotic colorectal surgery. This limits its replication by non-expert teams. Third, the study has restrictive inclusion and exclusion criteria, which may affect the standardization of the technique: only cancer patients are included, excluding other pathologies such as diverticular disease or colon volvulus. The reason for this is to minimize the confounding effects of different pathologies on the results of the study. Patients with splenic flexure neoplasia were excluded since they may present different evolutions and complications compared to other locations in the left-sided colon, sigma, and upper rectum, and require different surgical procedures involving sectioning of other vascular branches, which might have affected the results.

Finally, our current goal is identifying subgroups that can maximize technique benefits based on anatomy or underlying factors (vascular issues, tumor location, nutrition, tumor size, surgical technique, etc.). Prospective controlled studies should now be carried out as the assessment phase (Stage III) in the IDEAL framework of surgical innovation.