Correspondence: Antonio Alcaraz M.D., Ph.D., Department of Urology, Hospital Clinic, University of Barcelona, 170 Villarroel, Barcelona 08036, Spain. Email: email@example.com
Natural orifice transluminal endoscopic surgery designates a surgical procedure that utilizes one or more patent natural orifices of the body with the intention to puncture a hollow viscera in order to enter the abdominal cavity. First carried out at the beginning of the 2000s in experimental models, it can be considered the natural evolution of laparoscopy towards the ideal of scarless surgery, as the avoidance of a large abdominal scar is associated with better cosmetic results and better recovery. However, the technology currently available does not allow the performance of complete pure natural orifice transluminal endoscopic surgery procedures. The surgical tools used are not specially designed for this approach, so difficulties in retracting organs, bleeding control and clashing of instruments are the main obstacle surgeons face. For this reason, the current available technique is the so-called hybrid approach, where a natural orifice approach is combined with some abdominal trocars, using the natural orifice as the exit door for the specimen removal. As not many comparative studies have been published evaluating the advantages of natural orifice transluminal endoscopic surgery in front of traditional laparoscopic surgery, a review of the history of natural orifice transluminal endoscopic surgery, and an assessment of the available evidence of this technique regarding renal and urological pelvic surgery are performed in this article.
Urology is a surgical speciality that can be considered as a pioneer in using minimally invasive techniques. The development of minimally invasive surgeries over the past 20 years has led to the near extinction of several traditional open procedures. Laparoscopy is a minimally invasive surgery associated with many advantages, including small incisions, less postoperative pain and faster recovery compared with open surgery. Along the same line and as a step further in minimizing surgery's impact, the new concept of scarless surgery has emerged. The idea of this technique is to enter inside the peritoneal cavity of a patient without injuring the abdominal wall, which might result in a complete absence of visible scars. Overall, minimally invasive scarless surgery is a challenging technique, which might improve quality of life and offer an advantage over conventional laparoscopy.
NOTES is one of the most interesting recent developments in surgery.[1-3] It is an evolution of laparoscopy. NOTES designates a surgical procedure that utilizes one or more patent natural orifices of the body with the intention to puncture a hollow viscera in order to enter an otherwise inaccessible body cavity. These orifices include the mouth, anus, nares, vagina and urethra, and the hollow viscera that might be punctured include the bladder, vagina, colon, stomach and esophagus. By this way, the benefits obtained include an improvement in cosmesis owing to the lack of surgical incision in the abdominal wall (Fig. 1). This lack of incision can also potentially be translated into a lower risk of wound infection and less postoperative pain. The safe and successful development of NOTES has the potential to create a paradigm shift in urological surgery. Investigative research in this area of minimally invasive surgery has shown that rigorous laboratory work is still clearly imperative, as technical issues related to NOTES are yet to be addressed.
To date, NOTES has been successfully completed experimentally in the abdominal cavity using different methods. In 2002, Gettman et al. described the first experimental application of NOTES when transvaginal nephrectomy was carried out in a porcine model. Kalloo et al. later reported the first natural orifice endoscopic surgery using a transluminal gastric (transgastric) port also in a porcine model. During this period, Pai et al. described the use of a transluminal colonic (transcolonic) port, which was hindered by limitations related to the lack of sterility and an effective closure method. In addition, Lima et al. designed the transluminal vesical (transvesical) port for NOTES applications. Bazzi et al. described the feasibility of transluminal rectal (transrectal) NOTES nephrectomy in the cadaveric and porcine model (Table 1).[9, 10]
Table 1. NOTES surgical characteristics of each approach
Evidence of low side-effects
Laparoscopic tools useful
Only 50% of the population
Easy access to the kidney
Removal of specimen
Access to the pelvis
Characteristics of NOTES approach
The NOTES procedure might provide additional benefits when compared with current minimally invasive procedures. Potential advantages include lack of skin incisions, improved cosmetic result, reduced postoperative pain, diminished risks of postoperative hernias and earlier recovery. However, “pure” NOTES instruments have been criticized because of their flexibility, the impossibility to retract large organs such as the kidney, the incongruence of the flexible material to be used in the abdominal cavity and the limited port access to use good hemostatic devices. Another disadvantage is that the endoscope camera rotates with the rotation of the instruments, misleading the surgeon and moving the surgical field outside the visual space. In fact, ureteroscopes and gastroscopes were designed primarily as diagnostic tools, and they are far from being ideal for use in NOTES. Besides, the essential design for diagnostic maneuver involves the difficulty in using the instruments, not only for formal surgery, but especially when intraoperative complications arise, such as bleeding.
The last disadvantage to comment on is the need for internal organ closure after any NOTES procedure. Once the surgery is completed, the hole in the viscera has to be closed, and this is of the outmost importance in the stomach, bladder or colon, where an intraperitoneal contamination could occur if closure is not appropriately carried out. Some devices are currently being developed with promising results.[12, 13]
In order to overcome current technical limitations, investigators have combined NOTES with the conventional laparoscopic approach. The different techniques that should derive from this combination and the multiple names for them required a standardization of the nomenclature. For this reason, a consensus was reached in 2008, and the different definitions of what can be considered NOTES and which techniques do not correspond to this definition are included. In this sense, if any instruments or ports are passed transabdominally, but the majority (>75%) of the procedure is carried out by the instrumentation inserted through the natural orifice, this should then be designated as a hybrid NOTES procedure. The hybrid NOTES allows perforation of the organ under direct vision, minimizing the possibility of injury to adjacent tissues. Furthermore, the hybrid approach dramatically improves the spatial orientation to allow attendance of laparoscopic cameras specially designed to overcome the limitations of endoscopic material. The retraction and tissue dissection improves with the assistance of transabdominal port for instrumentation, and allows triangulation. Some authors, among them us, are defending the current minimally invasive hybrid approach over pure NOTES without laparoscopic assistance. The main argument is that the hybrid technique improves the security of the pure NOTES procedure while minimizing the invasiveness of the laparoscopic approach.
The use of a natural orifice as an additional port for insertion of an instrument or an endoscope for visualization during laparoscopic surgery should be designated as NOTES-assisted surgery, describing the portal used.
In our opinion, the most important advantage of NOTES is to avoid an abdominal scar for the specimen extraction, which might result in an obvious cosmetic improvement and probably a better postoperative recovery. We do not see any point in determining which percentage of the surgery is carried out through the transvaginal approach, nor do we see any advantage in increasing the risk of a difficult surgery by limiting the number of transabdominal trocars. The current available tools do not allow the possibility to carry out safe procedures by a pure NOTES approach, as is evidenced by the 7-h surgery required in the first “pure” NOTES transvaginal nephrectomy carried out by Kaouk et al. In that case, a very experienced team with worldwide known surgeons experienced very important difficulties in finishing a selected case for a nephrectomy, and the authors concluded that despite their success, ports and instrumentation require further modification for NOTES urological surgery to be pragmatic. Despite that, we still think that avoiding a 5–6 cm incision in the abdomen decreases patient morbidity substantially. For these reason, we consider all these “hybrid” techniques as NOTES, as they avoid the abdominal incision, although discrimination between “pure” and “hybrid” NOTES should be made in order to reach the ideal of scarless surgery.
NOTES in renal surgery
Non-oncological radical nephrectomy
Hybrid NOTES nephrectomy in humans was first described by Branco et al. Since then, other investigators reported their clinical experience with hybrid NOTES nephrectomy.[15, 17-19] More recently, Kaouk et al. at the Cleveland Clinic successfully carried out the world's first transvaginal “pure” NOTES nephrectomy in a 58-year-old woman who presented with an atrophic right kidney. Later, Castillo et al. reported two cases of transvaginal hybrid NOTES simple nephrectomy with standard laparoscopic instruments.
The vagina has been considered a viable route for kidney retrieval after laparoscopic nephrectomy since a landmark report by Breda et al. In 2002, Gill et al. reported an initial series using this natural orifice for intact specimen extraction. Transvaginal access closure is considered superior to transgastric or transcolonic, as it can be made by a conventional open surgical technique. In the gynecological literature, countless patients have undergone transvaginal access to the peritoneal cavity for a wide variety of procedures with a low complication rate. Furthermore, of all the accesses, the vagina is the one that allows easier retrieval of the specimen, especially large pieces, as in the case of nephrectomy. It also enables the use of rigid instruments and maintenance of the target organ directly in line with the access point to improve the issues related to spatial orientation. However despite the low infection rate reported in the gynecological literature, the transvaginal technique involves manipulation of the peritoneal cavity through the vagina, which could mean more contamination and subsequent increased peritoneal infection rate.
For these reasons, the transvaginal approach seems to fit perfectly with the wish of cosmetic improvement allowing a channel for removal of surgical specimens of considerable size. Despite all its advantages, transvaginal access is only possible for 50% of the population to be treated, as a matter of sex, and even within the female population, conditions such as previous gynecological pelvic surgery might contraindicate this approach, which possibly means that it could only be feasible for less than half of the population to be treated.
Oncological radical nephrectomy
Our group presented their early experience with transvaginal NOTES-assisted laparoscopic simple and radical nephrectomy. We were the first group that reported the possibility of carrying out the procedure in oncological cases.
In Hospital Clinic in Barcelona, Spain, we have carried out a total of 17 transvaginal NOTES-assisted laparoscopic nephrectomy for T1–T3a N0M0 renal cancer. The mean age of the women was 53.9 years (range 34–78 years). A total of 10 left and seven right nephrectomies were carried out. The mean operative time was 122 min (range 80–270 min) and the mean estimated blood loss was 167.5 mL (range 30–400 mL). One patient required a blood transfusion after surgery. The mean hospital stay was 4.1 days. Major complications occurred in two patients; in one patient, who had previous abdominal and pelvic surgery, a colon injury occurred. This patient underwent surgery and a temporary colostomy was carried out. The patient has already undergone reconstruction.
Living donor nephrectomy
During the past two decades, kidney surgery has undergone a radical transformation. Improvements in patient recovery after laparoscopic surgery were the main reason for rapidly promoting its use in living kidney donation. Minimizing morbidity in the donor population while maintaining graft outcomes is a challenge for surgeons. Indeed, any new harvesting technique should be shown to be at least as safe for the donor and to produce grafts with functional characteristics as good as those obtained with current techniques.
The use of NOTES within living donor nephrectomy is currently limited to transvaginal extraction of the specimen,[23, 24] and instrumentation through the transvaginal port. This is intended to further reduce the trauma of living donation, but it is obviously applicable only to a subset of donors. As experience with these techniques develops and further technological advances arrive, NOTES might become the next major advance in living kidney donation.
Allaf et al. described a successful laparoscopic living donor nephrectomy with vaginal extraction in March 2009. Our group published the first paper in the literature about 20 NOTES-assisted living donor nephrectomy series. By July 2012, a total of 50 women were submitted to a transvaginally NOTES-assisted living donor nephrectomy in our center. The mean age was 56.65 years (range 54–69 years). A total of 78% of the series had previous vaginal deliveries. The ratio of left : right kidneys removed was 41:9. The mean operative time and mean warm ischemia time were 119.4 min (range 75–260 min) and 274 s (range 256–292 s), respectively. The hospital stay was 4.07 days. Regarding the intraoperative complications, one case of bladder injury and one case of bleeding occurred. During the postoperative period, one patient presented an ileus.
We concluded that transvaginal NOTES-assisted nephrectomy appears to be a feasible and reproducible surgical technique. Despite the longer warm ischemia time (although less than 5 min) in comparison with conventional laparoscopic nephrectomy, there was no effect on graft function, so it might be considered a good alternative procedure that might increase the living donor rate in the female population. However, proper selection of donors is warranted, and larger series and longer follow up are required to establish its future role in kidney living donation surgery.
NOTES in pelvic surgery
The pelvic cavity hosts a number of important organs that are suitable to receive surgical treatment for both benign and malignant diseases. Laparoscopic surgery is increasingly used as an alternative to laparotomy, and more recently the evolution of surgery has brought up the concept of LESS. No papers are published in the literature about pelvic NOTES urological surgery.[28, 29]
The surgical procedures carried out in the pelvic cavity, from the sacral promontory to the insertion of the levator ani muscle, are challenging operations, where both experience and surgical skill play an important role. Experience in rectal oncological surgery has validated the relationship between the difficulty of surgical performance and pelvis space. Besides, in classic laparoscopy or LESS, there is a restriction imposed by the two-dimensional view of the endoscopic field. The presence of multiple factors, such as a large prostate or uterus, narrow pelvis and shallow sacral angle, will definitively impact surgical therapeutics, as these will translate into lack of maneuvering space and inefficient count traction turns. Unsatisfactory surgical outcomes might naturally occur under such conditions.[30, 31]
In urology, these extreme conditions could become even more difficult because, as shown by Targarona et al., male patients tend to have deep, narrow, shallow pelvis angles. They reported males to have a significantly narrow bony pelvis compared with female patients, from various points of pelvic measurement. Countertraction is important for successful surgery, as adequate traction of the structures provides better visibility, with surgical exposure of the anatomical structures involved in the operation, such as the so-called neurovascular bundles in the case of radical prostatectomy. Another factor is surgical space. In a shallow concave sacrum or with a narrow intertuberous diameter, it is very difficult to expose adequate planes and perhaps even more difficult to carry out intracorporeal suturing, which is an essential part of reconstructive pelvic procedure. The latter explains the low percentage (7.8%) of pelvic LESS procedures, coined worldwide, between 2007 and 2010, as urological LESS. In this sense, LESS surgery is in its infancy and there is a lot of work pending in order to further develop the technique.
The only literature about NOTES pelvic surgery comes from the general surgeons. Recent publications using the transanal resection of colorectal tumors approach in pigs and cadavers for colon resections have shown that this could be a valid option, but there is still no clinical evidence of its feasibility.[35, 36]
NOTES surgery is the surgical technique that is the closest to the ideal of scarless surgery. Although pure NOTES is not feasible yet, the so-called “hybrid” approaches are the current valid options to improve surgical morbidity, as a large scar in the abdominal wall for the specimen extraction is avoided. Despite the use of additional abdominal trocars, these techniques must be considered as NOTES.