Bariatric Surgery: Endoluminal Techniques

Introduction

Obesity surgery is perhaps the most logical application for incisionless surgery as it is characterized by a high incidence of incisional hernias. Using a laparoscopic approach reduces the frequency of this complication, but does not render it absent. Only the use of natural orifices can eliminate the risk of incisional hernias.

Subcutaneous fat is a substantial hurdle in weight loss surgery. This thick, fatty layer significantly impedes swift manipulation of laparoscopic tools since it reduces the mobility of the trocars which harbour the instruments needed for dissection. This limitation is in addition to the already reduced number of degrees of freedom that characterize laparoscopy. Fat accumulation is also mainly located in the peritoneal cavity, the mesentery, and the omentum, but typically not inside the viscera. Therefore, an endoscopic approach very logically avoids the limitations caused by subcutaneous and intraperitoneal fat.

Several recent technological developments allow the application of endoscopic approaches to established procedures. Tools used for the endoscopic approach need to be long because of the natural distance between the mouth and the stomach, the most proximal target organ in obesity surgery. Since tool length is inversely related to the strength at the tip of effector tools, this long distance constitutes one of the most significant obstacles in the implementation of endoscopic surgery. In addition, for safety and practical reasons, it is essential to limit the motions within the afferent organ (esophagus) and to obtain maximum motility at the tip. This can be achieved by over-tubes (USGI) or by making the tools semi-rigid at the shaft and extremely mobile at the tip (Flexible Endostitch, Covidien). Ingenious sewing devices have also emerged (Eagle Claw, Olympus; Spiderman, Ethicon) to achieve this goal. To translate manipulations performed outside the body into efficient actions within the body, specific devices have been designed e.g. master-slave robotic systems (Intuitive) or computerized activators of specialized endoscopic tools (Rothstein, Marescaux, Swanstrom). Technological improvements like the ones mentioned above have enabled the modern endoscopist to perform advanced endogastric procedures, mimicking established procedures like vertical banded gastroplasty (VBG) or even sleeve gastrectomy, now more correctly named sleeve gastroplasty (TOGA). Preliminary results of the novel approach of “old” operations are promising.

Interestingly, advances in endoscopic techniques have also enabled surgeons to expand the field of operation beyond the stomach. Prosthetic devices have been developed for bypass of the duodenum and proximal jejunum (Endobarrier) or for bypass of the stomach and the proximal small bowel (ValenTx). Whereas the surgical community is very familiar with using foreign objects to obtain restriction (adjustable gastric band), these devices typically have been placed outside the viscus. The newer prosthetic devices are now located within the viscera. Anchoring systems for the prosthetic sleeves are various and safety remains an important issue (TERIS).

The wall of the viscera no longer constitutes an insurmountable limit for endoscopic surgery. The emergence of NOTES presently has all but revolutionized the practice of surgery for weight loss. Gastro-enterostomies can now be performed without skin incisions, opening an array of possible endoscopic procedures for the care of the obese patient. Working inside an organ does away with the single most important problem in redo surgery: adhesions. Redo surgery is performed on a regular basis in bariatric patients and some operations are even designed as staged procedures (Duodenal Switch). Patients who regain weight years after their initial operation can now be helped by strictly endoscopic means (ROSE procedure, StomaPhyx, EndoCinch). Existing pouches can be made smaller and anastomosis can be made tighter, thus approaching the initial postoperative conditions. In conclusion, endoscopic techniques are very helpful in the care of obese patients. Several existing procedures can be mimicked by strictly endoscopic means while new operations designed for this novel approach have emerged in recent years. Though it is too soon to correctly evaluate this approach, it appears that redo bariatric procedures constitute an obviously fertile field for incisionless surgery.

Endoluminal Gastric Bypass

Obesity is a major health problem and is the second most common preventable cause of death (after smoking) in the United States. Obesity is associated with a multitude of medical comorbidities that affect almost every human system and has been strongly associated with an increased incidence of diabetes, as well as cardiovascular disease and cancer. Diets and exercise programs are considered the pillars for the treatment of obesity but long-term studies have failed to show a sustained weight loss for the vast majority of patients. Currently, bariatric surgery procedures appear to be the only modality that results in sustained weight loss along with reversal of the comorbidities.

Among the available bariatric surgery procedures, Roux-en-Y gastric bypass (RYGB) is the most widely used in USA. Surgical reconstruction of the gastrointestinal tract during RYGB likely alters gastric volume and mucosal exposure to ingested macronutrients so as to differentially modulate efferent gut signals that govern energy regulation and metabolism. The result is weight loss and improved metabolic control.

Despite the low rate of complications related to laparoscopic bariatric surgery, there is a growing interest in endoluminal devices and techniques for stand-alone weight loss procedures. Endoluminal surgery, performed entirely through the GI tract by using flexible endoscopy, offers the potential for an ambulatory weight loss procedure that may be safer and more cost-effective compared with current laparoscopic approaches. If such an approach is developed, endoluminal therapy may extend the current indications for intervention to those with multiple comorbidities, older age, and those with class I obesity (BMI 30-35).

Endoscopic technologies that attempt to mimic the anatomic features and clinical efficacy of bariatric surgery are currently being developed and evaluated.

Many manufacturers have attempted to develop endoscopic suturing and stapling devices to promote volume reduction as well as add possible elements of malabsorption. Concepts have included endoluminal gastroplasties, restrictive valves, and combined approaches to restriction and malabsorption. However, to date, none of these endoluminal/endoscopic techniques have completely reproduced the changes in gastrointestinal anatomy that are created by the RYGB procedure.

There are 5 “components” of RYGB that are responsible for the unique subsets of the profound weight loss and metabolic effects of this procedure:

• Gastric restriction
• Exclusion of the stomach remnant from alimentary flow
• Exclusion of the proximal intestine from alimentary flow
• Exposure of the jejunum to partially digested nutrients
• Delivery of partially digested nutrients to the distal intestine

The RYGB components currently reproduced by endoscopic means are summarized In the following table.

Endoscopic Malabsorptive Procedures

The Endobarrier developed by GI Dynamics (GI Dynamics, Newton, Massachusetts) is an endoscopically placed sleeve positioned in the duodenum past the ligament of Trietz. The sleeve allows food to pass while preventing duodenal mixing of chyme with biliary and pancreatic secretions. This is intended

to mimic the duodenal and proximal jejunal bypass impact of a Roux-en-Y gastric bypass. The device is anchored past the duodenal bulb and can be endoscopically removed. The endoluminal sleeve has been tested in clinical trials with 10 successfully placed sleeves in 12 patients. Average percent of excess weight loss (%EWL) at 12 weeks was 23.6 percent. Diabetes remission was observed in all the diabetic patients.

Endoscopic Gastric Restriction Procedures

Multiple endoscopic suturing and stapling devices have been developed for creating tissue plication by apposition of adjacent tissue folds. Although their long-term effectiveness in gastroesophageal reflux disease (GERD) has been debated, extension of their therapeutic potential to obesity has been suggested. The Endo-Cinch device (C.R. Bard Inc, Murray Hill, New Jersey, USA) has been used for an experimental vertical banded gastroplasty (VBG) procedure. The device is mounted on an endoscope and fires a straight threaded needle through a tissue fold formed by suction. A proximal gastric pouch with an outlet ring was created by using the device to suture a flexible plastic ring along the lesser curvature and to suture together the anterior and posterior gastric walls. However, this device frequently delivers submucosal stitches resulting in early suture loss.

Another experimental gastric partitioning procedure that used a prototype suturing device (Eagle Claw VII; Apollo Group and Olympus Corporation) has been described. Under direct visualization a curved needle is driven into tissue, allowing intracorporeal knotting and the formation of a gastric partition. No clinical data are available for this procedure.

A transoral sleeve gastroplasty (TSG) is performed using a transoral gastroplasty stapling system (TOGA; Satiety Inc., Palo Alto, California, USA) under direct retroflexed visualization A septum with a retraction wire is deployed to orientate tissue for capture and 11 titanium staples were delivered in three rows by aspirating anterior and posterior gastric tissues. In the most recent study

employing this device, 11 patients received two sleeves with only two early midstoma gaps with a %EWL of 46.0.

Although these transoral gastroplasty has yielded promising short-term results, the long-term effects are yet to be seen. So far, the endoscopic restriction procedures have not shown an advantage over surgery in eliminating general anesthesia. There is in any case some skepticism about efficacy and indications, as several surgical gastric partitioning procedures have been abandoned as failures.

Conclusion

There is a growing demand for less-invasive approaches to the treatment of obesity. Endoluminal approaches including implants, suturing, and stapling have shown some promise. However, endoluminal therapies will need to be held to the same standards of current surgical treatments in terms of inducing meaningful and sustained reductions in body weight and rate of obesity-related comorbidities. To date, no endoscopic/endoluminal technique can reproduce all the components that are responsible for the unique subsets of the profound weight loss and metabolic effects of the RYGB. In particular, there are no endoscopic stapling devices that can provide complete exclusion of the stomach and the proximal intestine remnant from the alimentary flow. Therefore, the idea of a completely endoscopic RYGB is currently premature. However, this very exciting goal should be pursued again once new technologies (i.e. endoscopic stapling) will be available.