Per-Oral Endoscopic Pyloromyotomy

Marc A. Ward, MD and Lee L. Swanström, MD, FACS, FASGE, FRCSEng

Introduction

Flexible endoscopy has made incisionless treatment of a variety of diseases possible. Although traditionally limited by their endoluminal nature, these operations result in less postoperative pain and shorter convalesce compared to traditional surgeries that access the abdomen and thorax by violating skin and muscle. An extension of surgical endoscopic procedures has been developed over the last decade that utilizes flexible endoscopy to access the submucosa of the gastrointestinal tract. These procedures utilize this space for a variety of therapeutic purposes such as resecting tumors, cutting hypertrophied muscle, and dividing diverticula. This chapter will discuss how per-oral endoscopic pyloromyotomy (POP) takes advantage of this submucosal space in the treatment of gastroparesis.

Background

Gastroparesis is a debilitating disease defined by symptomatic delayed gastric emptying in the absence of mechanical obstruction.¹ Patients who have symptoms from gastroparesis can experience postprandial bloating, nausea, and vomiting, which in severe cases can progress to complete food intolerance and malnutrition. This disease can sometimes be attributed to complications of diabetes or iatrogenic vagal injury from surgery or radiation therapy; however, in most cases the etiology of the disease is unknown. The treatment of gastroparesis is frequently difficult because of the broad spectrum of symptoms, their often subjective nature, and underlying etiologies that contribute to its pathophysiology.^2,3

Medical treatment of these patients consists of dietary modification, tight glycemic control, and promotility medications (eg, erythromycin/metoclopramide). These measures should be tried first before considering more invasive measures. Often, however, patients do not respond to or develop tolerance to these therapies.4 Patients who have failed medical therapy are often referred for surgical or endoscopic interventions. Intervention options include pyloric dilation, pyloric botulinum toxin injections, gastric electrical stimulation, surgical pyloromyotomy or pyloroplasty, partial or total gastrectomy, and most recently, POP. Gastric stimulation has perhaps been the most rigorously studied. This procedure involves a submucosal-implanted generator with bipolar leads implanted in the gastric wall at the antral/body junction. These leads are usually implanted laparoscopically. A randomized, double-blinded cross-over study in which patients were not aware whether their device was turned on or off after implantation demonstrated significant improvement in symptoms with gastric stimulation.⁵ However, this effect appears to be most significant in patients with diabetic gastroparesis. Patients with idiopathic or postsurgical disease appear to benefit more from pyloric-focused interventions, such as laparoscopic pyloroplasty, endoscopic transpyloric stenting, or botulinum toxin injection of the pylorus.^6–9 All of these interventions have shown to provide some symptom relief; however, these therapies are not without their disadvantages. Botulinum toxin has questionable long-term efficacy, transpyloric stents have a tendency to migrate into the small bowel, and laparoscopic pyloroplasty requires general anesthesia and a surgical operation.

Recently, therapeutic endoscopy has emerged as a safe and effective approach in the management of achalasia with the development of per-oral endoscopic myotomy (POEM).^10,11 The submucosal tunneling techniques used in POEM have recently been adapted to performing pyloromyotomy. The POP is considered a less-invasive alternative to laparoscopic pyloroplasty. The safety and feasibility of this procedure has been described in several small, single-center case series and it seems to indicate that an effective incisionless procedure for patients with gastroparesis is possible.

Indications and Preoperative Evaluation

Evaluating symptoms of a patient suspected of gastroparesis requires both subjective and objective testing. After completing a thorough history and physical, an upper endoscopy is required to rule out a mechanical obstruction such as a malignancy or stricture. Once obstruction is ruled out, gastroparesis can be confirmed with a radionucleotide gastric-emptying study based on a 4-hour emptying time. This test measures gastric retention of an ingested radiolabeled tracer, in which greater than 10% retention at 4 hours confirms an abnormal study. In patients with symptoms of gastroesophageal reflux in addition to gastroparesis, one should also consider a 24-hour pH study. If objective reflux is present, consideration should be given to combining an antireflux procedure with a gastric-emptying procedure since fundoplication itself has been shown to improve gastric emptying at the same time as treating reflux.¹²

Patients confirmed with impaired gastric emptying and no mechanical outlet obstruction are first treated with diet modification and medical therapy. POP is offered only to patients with gastroparesis whose symptoms are refractory to these initial treatments. Since POP is a novel procedure with limited outcomes data, its use should be restricted to centers with substantial therapeutic endoscopy experience and patients should be enrolled in an institutional review board-approved study.

Operative Technique

POP should be performed in the operating room or endoscopy suite under general anesthesia. A high-definition, standard-length upper endoscope is required and carbon dioxide insufflation is absolutely necessary. A full diagnostic endoscopic gastroduodenoscopy is conducted prior to the operation. This is to ensure that no anatomical abnormalities exist and it also enables the surgeon to remove any retained food that might be present. An extra-long esophageal overtube is placed and the gastroscope is fitted with a transparent dissecting cap to enable tissue retraction while operating within the submucosal space.

Figure 33-1. POP, sagittal view. (A) Submucosal injection of methylene blue. (B) Submucosal tunnel creation. (C) Extension of the submucosal tunnel to the first part of the duodenum. (D) Pyloromyotomy, beginning 2 cm proximal to the pylorus. (E) Closure of mucosotomy with endoscopic clips. (Reprinted with permission from the Cleveland Clinic Center for Medical Art & Photography ©2018. All rights reserved.)

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