Intramural and Transmural Endoscopy

Introduction

Natural orifice transluminal endoscopic surgery (NOTES) is an evolving concept, combining minimally invasive surgery with flexible endoscopy, potentially representing a major paradigm shift to scarless surgery. Recently, NOTES went from few experimental reports to clinical series and multicentric studies. Since the early concept, from pioneers such as Kalloo and Kantsevoy in the United States, and Rao and Reddy in India, NOTES has emerged as a promising new alternative to open and laparoscopic surgery for abdominal access. Potential benefits include decreasing surgical incision complications, such as incisional hernias, adhesions, intestinal obstruction, scars, and wound infection, together with better aesthetics. This evolution led to the first successful series of clinical applications in the literature for transvaginal (TV) and transgastric (TG) NOTES.

Intramural surgery is an exciting new technical possibility, allowing for unimagined therapy for submucosal tumors, access for endoscopic techniques, and submucosal myotomy for achalasia. New tools and evolution of these techniques are changing the way many problems in gastroenterology are resolved. This chapter reviews early procedures and current clinical applications of intramural and transmural endoscopy.

Intramural Endoscopy Techniques

Techniques for Creation of a Submucosal Working Space

Submucosal Endoscopy With Mucosal Safety Valve Technique

The submucosal endoscopy with mucosal flap (SEMF) technique may offer safe access to the peritoneal cavity for NOTES surgery. The submucosal space functions as a tunneled portal and the free overlying mucosa as a protective sealant flap, minimizing contamination of the extraluminal peritoneal cavity.

In the original SEMF technique, balloon dissection combined with high-pressure carbon dioxide (CO ₂ ) is used to dissect the submucosa. A submucosal injection of saline is used to identify the submucosal tissue plane, then bursts of CO ₂ are injected to create a gas-filled submucosal bleb, followed by injection of hydroxypropyl methylcellulose, which prevents gas escape. A mucosal incision is made with a needle-knife at one margin of the bleb/fluid cushion to allow entry below the mucosa. Balloon dissection can be performed to transform the submucosa into an intramural free space. Blunt dissection with grasping forceps can also be used ( Fig. 45.1 ).

FIG 45.1, Submucosal flap construction. A, A small submucosal saline bleb is made to identify the submucosal tissue plane. B, After pretreatment of the submucosa with high-pressure carbon dioxide (CO 2 ) or mesna, balloon dissection is performed to create an open space within the submucosal tissue plane. C, The submucosal space is used as a working space for interventions such as inside-out submucosal endoscopy with mucosal resection, intramural myotomy, and offset access for natural orifice transluminal endoscopic surgery (NOTES) procedures. D, The muscular defect after myotomy is sealed with an overlying mucosal flap, and the submucosal tunnel is closed with mucosal clip apposition. EMR , endoscopy with mucosal resection.

Chemically Assisted Submucosal Dissection Technique

Aiming to minimize mechanical trauma to the mucosal flap, mesna was discovered as a useful adjuvant to the blunt dissection, acting by chemically softening the submucosa. In this technique, mesna solution is injected into the saline submucosal bleb before initiating balloon dissection.

Peroral Endoscopic Myotomy

Achalasia is an esophageal motility disorder for which treatment, until recently, was restricted to pharmacotherapy, balloon dilatation, botulinum toxin injection, and surgical intervention (e.g., Heller myotomy) with the aim to reduce lower esophageal sphincter pressure. Conservative treatment has limited efficacy, frequently needing repeated procedures, whereas surgical treatment requires additional fundoplication to prevent gastroesophageal reflux. Due to this, novel technologies have been explored to treat this pathology. Peroral endoscopic myotomy (POEM) is a novel procedure, first performed in humans by Inoue et al (2010), that has been established as safe, minimally invasive, and with expected long-lasting symptom control.

The technique involves four major consecutive steps: esophageal mucosal incision and entry into the submucosal space; creation of a submucosal tunnel; incision of the esophageal muscles (myotomy); and closure of the mucosal incision. It can also be used in patients with recurrence after other treatments have been performed.

Technique

The procedure is carried out with the patient under general anesthesia, with positive pressure ventilation, using higher pressures than those generated by endoscopic CO ₂ insufflation. A submucosal injection is administered at the level of the mid esophagus, 13 cm proximal to the gastroesophageal junction (GEJ), followed by injection of saline with 0.3% indigo carmine. A 2-cm longitudinal mucosal incision is made on the mucosal surface to create an entry to the submucosal space. A long submucosal tunnel is then created, of approximately half the circumference of the tubular esophagus. Dissection of the circular muscle bundle is subsequently initiated. When the tip of the endoscope reaches the stomach region, the submucosal space becomes wider, and muscle layer cutting is continued for approximately 2 cm distal to the GEJ. Complete division of the circular muscle bundle is confirmed by endoscopic appearance. The mucosal entry is closed with hemostatic clips.

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