According to Tonouchi et al., PSHs are classified into three types: the early-onset type, which often occurs within a few weeks after surgery and frequently leads to bowel obstruction; the late-onset type that develops several months after surgery; and the special type, indicating the protrusion of the intestine or omentum, or both [1]. In this case, the hernia developed 11 days postoperatively, presenting as the early-onset type with associated small bowel obstruction. During suturing under local anesthesia, the peritoneum was not identified as a hernia sac.

A PSH is a complication exclusive to laparoscopic surgery [4]. According to previous reports, its incidence ranges from 1.50% to 1.80% [5, 6]. Regarding the causes of PSHs, technical factors during port insertion, such as incisional length, the shape and angle of the trocar tip, unnecessary damage to the abdominal wall during port insertion, intraoperative weakening of the abdominal wall due to factors such as increased intraoperative pneumoperitoneal pressure and vigorous movement of the trocar, and decisions on whether to close the port site, all contribute. In addition, patient-related factors, such as a history of multiple pregnancies, advanced age, which represents a weakened abdominal wall, and medical conditions such as diabetes mellitus (a risk factor for delayed wound healing and postoperative infection), chronic respiratory diseases leading to chronically elevated intra-abdominal pressures, and obesity, have been reported [1, 7, 8]. Furthermore, new risk factors have emerged with the increasing prevalence of robotic-assisted surgeries, such as those involving the da Vinci® surgical system (Intuitive Surgical Inc.). During laparoscopic surgery, ports are fixed to the abdominal wall, and the pivot point of their movement is inevitably the abdominal wall. However, during robotic-assisted surgery, ports are attached to robotic arms, and the pivot point for port movement is always the remote center. Therefore, unless the ports are connected to the robotic arms in a natural position, with no three-dimensional pressure on the abdominal wall, there will be a constant load on the abdominal wall during surgery, leading to fascia damage. Depressurizing after adjusting the remote center to the appropriate depth and attaching the ports to the robotic arms are recommended [9]. However, as many have suggested, the hypothesis that the port size is a significant risk factor for PSHs is reasonable [10,11,12,13,14,15,16,17,18]. During laparoscopic surgery, suturing the fascia at port sites that are 10 mm or larger is generally recommended; however, closure of the fascia at 5-mm ports is not routinely performed [1]. There is uncertainty regarding the need to close the fascia at 8-mm ports. Some reviews have suggested that closure of the fascia at such port sites may not be necessary; in actual clinical practice, many facilities do not perform closure of the fascia at 8-mm port sites [2, 3]. However, data regarding hernias associated with 8-mm port sites are insufficient.

Diez-Barroso et al. reported 178 robotic-assisted digestive surgeries performed at a single institution and found that the fascia was not closed at all 8-mm port sites; furthermore, only three (1.7%) of the 178 patients developed PSHs at the 8-mm port sites, accounting for 0.3% of all 8-mm ports (433 ports) [19]. In addition, Damani et al. analyzed 11,566 various robotic-assisted surgeries, including general surgery, urological surgery, and gynecological surgery, and found that the incidence of PSHs at 8-mm port sites was 0.1% (11 cases) [3]. These findings suggest a very low frequency of PSHs at 8-mm port sites. However, it is noteworthy that 10 of the 11 PSHs occurred specifically at the lateral abdominal port sites [3]. The target organ during robotic-assisted colectomy is located in the mid-abdomen, and ports are mainly placed in the lower abdomen. Therefore, the abdominal wall at the port sites is more susceptible to the effects of gravity and intra-abdominal pressure. In addition, during robotic surgery, maintaining a certain distance between ports is recommended to prevent collisions of the robotic arms [9]. Consequently, ports are often positioned more laterally beyond the Spigelian fascia. The internal and external oblique muscles, as well as the transversus abdominis, have origins and insertions from the ribs to the iliac crest and inguinal ligament. Because of the different directions of their muscle fibers, they move in different directions during insufflation and desufflation. The sliding phenomenon walls off the tract made by the port and prevents herniation after desufflation. However, muscle fibers closer to their origins or insertions may have limited mobility, making it less likely for this sliding mechanism to occur. In other words, in the lower abdomen, on the lateral side near the iliac crest, the risk of a PSH may be higher because the sliding phenomenon is less likely to occur [19]. Our patient did not have the above-mentioned patient-related risk factors. While we cannot deny the possibility of excessive damage to the abdominal wall during port insertion or unnecessary damage to the abdominal wall during the operation, this case had difficulties in the functioning of the “shutter mechanism,” not only from the perspective of port configuration but also due to the patient’s relatively slender body mass index of 19.5 kg/m2. This could have resulted in less mesenteric and preperitoneal fat, making it easier for the bowel to get entrapped in the fascial layer. Regarding reports on PSHs after robotic surgery, a review of individual cases did not reveal any specific considerations other than the tendency to occur in the lateral port sites. However, it is noteworthy that the majority of reported cases of PSHs occurred after urological and gynecological surgeries, with only one case reported after digestive surgery [7, 20,21,22,23,24,25]. This discrepancy is likely not disease-specific but rather attributed to the timing of the widespread adoption of robotic surgery. It is important to note that in the field of digestive surgery, where the adoption of robotic surgery has been slightly delayed compared to urology, there could be an increase in the number of reports on PSHs in the future.

Closure of the fascia at 12-mm port sites significantly reduces the incidence of PSHs; therefore, closure of the fascia at 8-mm port sites may be beneficial for preventing PSHs [26]. Thus, even though closing all the layers at 8-mm port sites is complex and not practical, closing the fascia alone may lead to a Richter-type hernia, so it is preferable to close all the layers of the abdominal wall. Moreover, the closure of an 8-mm port site under direct visualization is challenging; therefore, the use of specialized instruments may be advisable [27]. In addition, there are potential disadvantages associated with closure at 8-mm port sites, such as the risks of intestinal injury and damage to the abdominal wall vessels and nerves, including the inferior epigastric vessels [28]. Therefore, guidelines should be established to determine which cases with specific risk factors warrant closure of the fascia. However, statistical evaluations remain challenging because of the low incidence of PSHs.