Minimally invasive is a consistent tenet of surgery and a realm pursued by the surgical community. The first laparoscopic cholecystectomy performed by Mouret in 1987 was a revolutionary advancement in minimally invasive surgery, turning the traditional “big scar surgery” into “small scar surgery”. Today, minimally invasive surgery has permeated all specialties in the field of surgery. However, reducing trauma and pain has always been the goal of surgeons, and the “natural orifice translumenal endoscopic surgery” (natural orifice endoscopy) has emerged.
However, reducing trauma and pain has always been the goal of surgeons, and the natural orifice translumenal endoscopic surgery (NOTES) has been developed to achieve “no scar surgery” in the true sense. 1. The concept and development of NOTES refers to the treatment method of examining, diagnosing and operating on organs outside the cavity through the natural orifices of human body such as stomach, vagina and colon without opening the abdomen. NOTES is a new highlight of minimally invasive surgery, because it has no scars on the body surface, compared with traditional open surgery and laparoscopic surgery, it can avoid complications caused by incision such as pain, incision infection and dehiscence, incisional hernia, adhesions, and reduction of body immune function. Complications caused by incisions, such as pain, incisional infections and fissures, incisional hernias, adhesions, reduced immune function, and more aesthetic results. The basic concept of NOTES was first proposed in 1998 [1], and in 2004 Kalloo et al. reported the first animal trial of NOTES, using a transoral transgastric approach to endoscopically incise the gastric wall into the abdominal cavity for peritoneal exploration and liver biopsy in pigs, with no postoperative complications of peritonitis or gastrointestinal leakage, confirming the feasibility of the technique [2]. Since then, studies about animal testing of NOTES have flourished and involved several specialties in the field of surgery, such as the application of NOTES by transesophageal route for diagnostic staging, tumor biopsy and treatment of mediastinal and thoracic tumors [3]; the application of NOTES by transvaginal route for nephrectomy [4]; and the application of NOTES by transgastric route for tubal ligation [5] and ovariectomy [6]. In 2007, Marescaux reported the first human gallbladder resection under NOTES by the transvaginal route, and the patient had basically no pain and good recovery. In 2008, Palanivelu reported the first case of human appendectomy under complete NOTES by transvaginal route with satisfactory results [13]. As a result, research on NOTES has gradually shifted from animal trials to clinical trials. in 2005 the American ASGE
(American Society of Gastroenterology) and SAGES ( Society of Gastrointestinal
Endoscopic Surgeons) established a special NOTES research working group, published a white paper on NOTES, and held regular international conferences on NOTES. With the development of NOTES research, there are various researches on the selection of surgical routes for different natural orifices, which have developed from the single transgastric route to transesophageal route, transgastric route, transcolonic route, transrectal route, transcystic route and transvaginal route. (1) Transgastric route: It is the earliest route used by NOTES and currently occupies the main position. The stomach is located in the upper abdomen with a large cavity, so it is relatively easy to cut into the abdominal cavity and provide a better view of the organs in the middle and lower abdomen; however, the stomach is an endoperitoneal organ, which provides poor stability for instrumentation, and the gastric cavity needs to be cleared and lavaged before cutting the gastric wall because the gastric fluid is a strongly acidic liquid. (2) Transvaginal route: This route is gradually gaining popularity among researchers and has become a hot spot. Unlike the transdigestive route, it is simple to incise and suture; it has few infections and other near and long-term complications; there is no risk of leakage; the distance from the vaginal entrance to the posterior vault is short, so access to the abdominal cavity is quick and easy; the vaginal wall is rich in elastic fibers, which are ductile and easily expandable, painless, and allows the removal of larger specimens. (3) Transrectal route: Since the rectum is located in the pelvic cavity and the lower section is more fixed, the transrectal route provides better exposure of the upper abdominal organs and more stable operation; however, the exposure of the pelvic organs is poor, and there are more bacteria in the rectum compared to the stomach, which is easy to contaminate. 3, technical difficulties and problems of NOTES Like the maturity of laparoscopic technology, there are still some bottlenecks in the clinical application of NOTES, both theoretically and technically. First of all, the closure of the incision of the natural orifice into the abdominal cavity is a crucial step and a problem that must be solved before entering the clinical application on a large scale. Various closure methods have been proposed, such as the use of anchored suture methods [15], suture systems with a combination of needle and forceps [16], endoscopic anastomoses [17], and continuous hair closure clips [18], but none of them can be proven to be absolutely safe and reliable when applied to humans. Secondly, NOTES has high requirements for operating instruments and endoscopy. The ability to insert the required endoscopic system and instruments through the small space between the natural orifice and the abdominal cavity and to maintain good visual exposure and operational stability requires the design and improvement of the instruments. Third, there is the issue of infection. The contents of the digestive tract are complex and have different components in different areas, which need to be adequately cleared and irrigated before entering the abdominal cavity to avoid contamination of the abdominal cavity and postoperative closure infection. 4, NOTES leads the development of minimally invasive surgery conceptually At present, scholars at home and abroad have done a lot of research work on the safety, feasibility, surgical indications and complications of NOTES technology, and the research enthusiasm even exceeds that of laparoscopic surgery, which was once called the “second French revolution” in 1987. However, the research work is still at the stage of animal testing, and the reports of successful clinical application are mostly individual cases, the number of clinical cases is small, and there is a lack of evidence-based medicine, and there are still ethical issues and technical bottlenecks that have not been completely solved, so it cannot be widely carried out in clinical practice at this stage. However, the concept of NOTES has pointed out the direction for the development of minimally invasive surgery in terms of surgical concept. Fewer incisions and smaller scars will definitely become the goal of minimally invasive surgery. Since the umbilical foramen is a natural orifice during the embryonic period, the emergence of transumbilical single-port laparoscopic surgery (E-NOTES) has to some extent compensated for the numerous problems that full NOTES failed to solve. E-NOTES concentrates multiple body puncture holes of traditional laparoscopy in the umbilicus, which reduces trauma and pain, and reduces surgical scars. Also, the NOTES concept has promoted the development of related surgical instruments, such as bendable operating instruments and magnetic retractors. In addition, the NOTES concept will certainly promote the integration of endoscopic and lumpectomy techniques. In conclusion, the emergence of NOTES has injected new vitality into minimally invasive surgery, representing a new concept and leading the future direction of minimally invasive surgery, i.e., scarless surgery, while giving surgeons more insight: in the future, the completion of NOTES requires multidisciplinary cooperation, including endoscopists, surgeons, gynecologists, and even instrument manufacturers and computer experts. The learning curve for NOTES is longer and requires mastery of both endoscopic and laparoscopic surgical techniques.