In recent years, the incidence of adhesive intestinal obstruction has been increasing. In a national cohort study, the overall incidence increased by 50% over the past 30 years, placing a significant financial burden on patients and the healthcare system [26, 27]. Previous studies have shown that laparoscopic adhesiolysis has a lower mortality rate and a lower risk of surgical infection and cardiopulmonary complications than traditional open surgery [28, 29]. In addition, laparoscopic surgery has been found to reduce the incidence and severity of adhesion formation compared with open surgery due to the reduction of trauma and bleeding and the ability to maintain the humidity of the natural environment, thereby reducing the recurrence rate of adhesive intestinal obstruction [30, 31].
Although laparoscopic surgery is less invasive, some patients still experience significant pain and discomfort after surgery. Some scholars believe that this postoperative pain may be due to carbon dioxide retention in the abdominal cavity, which in turn stimulates the phrenic nerve and diaphragm, leading to referred pain in the shoulder and upper abdomen [32]. In addition, the high carbon dioxide pressure during laparoscopic surgery not only increases the risk of compression syndrome and subcutaneous emphysema, but also leads to peritoneal hypoperfusion, hypercapnia, and reduced clearance of reactive oxygen species, which can induce the formation of adhesions. A study published in The Lancet pointed out that as minimally invasive surgery continues to increase, it is expected to further reduce the incidence of adhesion-related diseases in the population [3]. As one of the super minimally invasive technologies, NOTES has become a research hotspot in recent years because of its advantages of less trauma, faster recovery, lower cost, and no new scars on the abdominal wall after surgery, which can bring many benefits to patients [33]. With the advancement in endoscopic technology, including inverted observation, closure, resection, and haemostasis in the abdominal cavity, endoscopy can be used for observation and a series of other operations as a laparoscopy [34]. On the other hand, since the photography and various operating instruments are integrated into the same tube, the surgeon can operate alone without the need for an assistant to use the lens, thus saving labor costs.
NOTES can be performed through different natural orifices, each with its own advantages and limitations. Transvaginal natural orifice transluminal endoscopic surgery is the earliest surgical method, but because the vagina is a female-specific organ, it can only be limited to female patients. Moreover, due to the influence of traditional culture and the fear that the surgery may affect sexual life, pregnancy and fertility, some people are resistant to it [35]. Although there is no gender restriction for transgastric or transrectal natural orifice transluminal endoscopic surgery, the mouth, stomach, and rectum are connected to the outside world, thus their microecological systems are very complex and contain a large number of bacteria, which increases the risk of infection [36]. Moreover, the incision is difficult to close and anastomotic leakage is prone to occur, which limits its further development.
TUES has no gender limitations and does not need to pass through the wall of the digestive tract, so there is no need for intestinal cleaning preparation. By using the natural fold of the umbilicus as an entrance, disinfection can be performed directly on the body surface, which can not only greatly reduce the incidence of infection, but also improve the field of view and maneuverability of the endoscopy. In addition, the umbilicus is the channel for the exchange of substances between the fetus and the mother during the embryonic period. Its wall is thin and there are fewer nerves and blood vessels. Therefore, puncture at this site will cause less stimulation and damage to the abdominal nerves and blood vessels, and the postoperative pain is less, making it an ideal approach. Moreover, since the incision at this site is small, sutures can be used directly, which is simpler than endoscopic wound closure and can effectively reduce the risk of anastomotic leakage. In terms of beauty, the postoperative scar can be hidden in the natural wrinkles of the umbilicus, which is extremely concealed. The incision is almost invisible on the body surface after surgery, which can achieve a “scarless” visual effect, which greatly satisfies people’s pursuit of minimally invasive beauty [19]. Therefore, TUES using a flexible endoscopy has its unique advantages compared with other approaches, which has shown benefit in the treatment of abdominal diseases such as pancreatitis [37].
Compared with traditional open adhesiolysis, TUES adhesiolysis only requires one incision during the entire surgical process, so the preoperative preparation procedures are simpler and the requirements for anesthesia are relatively low. At the same time, compared with single-port laparoscopy, gastric endoscopy, as an important tool for the diagnosis and treatment of digestive tract diseases, integrates light sources, water injection, air injection and other channels, so that operations such as lighting, observation and treatment can be performed simultaneously. During the operation, various treatment instruments can be inserted according to the needs of the operation, and operations such as separation and hemostasis can be performed safely. The endoscopy can magnify the lesion, and the front end of the mirror body can be freely turned. Compared with rigid laparoscopy, its angle is more flexible, and adhesions can be flexibly observed and loosened from multiple angles, thereby reducing damage to the intestines to a certain extent.
Many studies have also explored solutions to reduce adhesions from different directions. The risk factors for adhesion formation mainly include tissue damage caused by tissue exposure to the external environment, tissue dryness and ischemia during the surgery [38]. Moreover, the presence of reactive foreign bodies and contamination of surgical areas can also promote adhesion formation. In addition, regulating the pneumoabdominal parameters of carbon dioxide, to maintain a appropriate flow and pressure range, and preventing hypoxia, acidosis and intestinal dryness are also conducive to reducing the recurrence of adhesions.
In our study, TUES adhesiolysis was successfully completed with no serious complications and the vomiting symptoms of the beagles were relieved after surgery. TUES adhesiolysis has been proved to be safe and feasible. All beagles were generally in good condition and no new adhesions were observed 3 months after surgery, which we believe is related to the unique advantages of this procedure. The main advantage of TUES over traditional laparoscopic adhesiolysis is that the umbilical cord is the weakest part of the abdominal wall, and transumbilical puncture is less invasive and almost no bleeding, which can reduce damage to the abdominal wall. Secondly, the 2–4 incisions in the abdomen of traditional laparoscopic surgery can be converted into a small incision of 10 mm in the umbilical cord, reducing the pain of the surgical wound and the body’s stress response. In addition, the whole process of adhesiolysis is completed within the abdominal cavity, ensuring the normal humidity and temperature of the intestines. Moreover, there is no contact with gloves, talcum powder or other foreign objects during the operation, which reduces the reaction of foreign objects in the abdominal cavity. Finally, compared with laparoscopic adhesiolysis, the abdominal pressure during TUES adhesiolysis is smaller, which reduces the impact on peritoneal perfusion and reactive oxygen species clearance, thereby reducing the formation of adhesions to a certain extent.
Although compared with laparoscopy, gastric endoscopy lacks sufficient rigidity and may not be accurately positioned due to insufficient support after entering the abdominal cavity, we have successfully overcome this problem by cleverly combining the use of Trocar. Trocar can not only guide and assist the endoscopy to reach the designated operating position but also fix the endoscopy body, making the operation more convenient. It should be noted that the Trocar should be inserted gently and slowly to avoid iatrogenic damage caused by excessive force, which may damage the intestines or other abdominal organs and blood vessels adhered to the abdominal wall. In addition, the operation is relatively complicated, requiring the operator to be familiar with the abdominal anatomical structure and the methods of using endoscopic instruments. Therefore, doctors with rich endoscopic operation experience and a solid surgical foundation can better perform this type of operation.
There are also some limitations to our study. First of all, as an exploratory study of new technology, this study focuses on feasibility and preliminary safety. This study is not compared with traditional open adhesiolysis or laparoscopic adhesiolysis, which limits the meaningful statistical comparison of key outcome indicators, including operation time, blood loss and incidence of complications. Comparing the key outcome indicators of different surgical procedures in a larger sample is the focus of further research. Secondly, the interval between postoperative re-exploration of the abdominal cavity and adhesiolysis is relatively short. Although no significant recurrent adhesions were observed at 3 months after adhesiolysis, it may have been documented if the follow-up period had been extended. In addition, gastrointestinal transit time, feeding tolerance and behavioral indicators of chronic pain should be increased to comprehensively measure the effect of the technology on physiological function. Thirdly, the models prepared in this study are most commonly caused by adhesions between the intestine and the abdominal wall, and the degree of adhesions is relatively mild, ranging from grade 1 to 3, which may not fully reflect the clinical cases caused by surgery, infection, inflammation and other factors. They Therefore, it is necessary to further study the pathophysiological process of simulating chronic adhesion to confirm whether this method is also feasible for adhesive intestinal obstruction with more severe adhesions or obstruction located in deeper areas. Finally, since the sample size of this study is small, this result represents only preliminary safety and feasibility, and subsequent confirmatory studies will expand the sample based on power analysis calculation. And its clinical application value needs to be further explored in multi-institutional clinical randomized controlled trial studies with larger sample sizes. The initial clinical application should be limited to localized mild adhesion and exclude multiple organ involvement and dense adhesion. Subsequent clinical transformation requires the establishment of complete inclusion and exclusion standards, and a careful surgical plan and early warning scheme are formulated to systematically verify the universal value of this technology.
Minimally invasive and refined procedures will be an inevitable trend in the future development of medicine. NOTES has made an outstanding contribution to modern medicine entering the era of super minimally invasive surgery. It has the potential to bring another major shift in surgical practice, just as laparoscopic surgery has developed faster than many experts expected in the past three decades. However, there are still great challenges to overcome in the clinical application, including incision closure, device optimization, multidisciplinary training, indication selection, etc. [39, 40]. As for TUES adhesiolysis, the operation is difficult, covering internal medicine and surgical majors. The operator needs to be familiar with abdominal anatomy and operating equipment, and should have rich clinical experience. As a new technology, it needs to be reviewed for ethical support before it is officially launched, and active surgical preparation and preoperative training should also be carried out. Secondly, the choice of patients is crucial, and the initial clinical application should be limited to patients with localized mild adhesions. A thorough surgical plan and alternative plan need to be formulated, and should be performed under the guidance of an operators with rich experience in laparoscopic and open adhesiolysis. If there are problems that cannot be solved during the operation, the surgical plan should be replaced in time. We believe that appropriate patient selection, professional experience of doctors, and rigorous training in minimally invasive surgery are key factors in promoting TUES.