Imaging and Diagnostic Testing

Diagnostic tests and imaging are vitally important for establishing the diagnosis and ruling out alternative causes of presenting symptoms such as severe gastroesophageal reflux, peptic stricture, an obstructing mass, or pseudo-achalasia. The first step in ruling out many of these alternative etiologies is performance of flexible endoscopy. Patients with a negative endoscopy should then undergo a high-resolution manometry (HRM) to diagnose achalasia or other esophageal motility disorders. The Chicago Classification v3.0 stratifies the types of achalasia based on results from HRM [13, 14]. Finally, a timed barium esophagram (TBE) is useful for anatomical evaluation preoperatively [15]. Significant dilation, tortuosity, and gastroesophageal junction angulation contribute to increased technical challenge of POEM. Additionally, detection of a hiatal hernia on endoscopy or esophagram would lead to reconsideration of the operative approach to a myotomy as this condition would predispose patients to increased risk of post-POEM reflux. A laparoscopic approach would allow for simultaneous hiatal hernia repair, myotomy, and anti-reflux procedure and would therefore be the preferred intervention for those patients found to have a concurrent hiatal hernia.

Operative Technique

POEM is an intervention in the submucosal space that uses a submucosal lift technique followed by endoscopic submucosal dissection (ESD) to create a submucosal flap or tunnel. The tunnel allows for the mucosal layer to remain intact over the area of muscular disruption, protecting the mediastinum and peritoneum from contact with gastrointestinal luminal contents. Following completion of the endoscopic submucosal myotomy, the tunnel entry point is closed, and the procedure is completed with no external incisions on the patient. Several technical variants to the performance of this procedure have been described, and this chapter will discuss our institutional practice, which is similar to Inoue and colleagues [3]. Complications are best avoided when practitioners employ methods most familiar to their practice in addition to strict adherence to the fundamental principles of surgery.

Submucosal Injection and Mucosotomy

The initial site for mucosotomy and tunneling is chosen based on the patient’s prior interventions. Our institution prefers to perform an anterior myotomy and reserves the posterior approach for those patients who have had a prior anterior myotomy. The position for initial submucosal dissection is therefore typically chosen on the anterior esophagus at a 12 to 1 o’clock position approximately 4–6 cm proximal to the planned starting point of the myotomy. An endoscopic injection needle is used to create a submucosal lift or bleb. This technique allows for hydro-dissection of the submucosal space by lifting the mucosa off of the underlying muscular layer. The solution used for injection is typically saline based but can also be a solution that is less easily absorbed such as hydroxypropyl methylcellulose or sodium hyaluronate. Next, a longitudinal mucosotomy is performed through the lifted mucosa with an endoscopic cautery knife on cut mode in order to reduce thermal spread (Fig. 5.1a). The endoscope is fitted with an angled, transparent dissecting cap and is then used to bluntly enter the submucosal space through the mucosotomy .

Complications

POEM, when performed by experienced practitioners, has low rates of associated complications [20]. However, there is a significant learning curve associated with performance of this procedure, even for advanced endoscopists, as operating in the submucosal space is still an emerging technique. Perioperative complications, such as mucosal perforations and increased operative time, have been shown to be associated with the operator learning curve [17, 21]. It is therefore recommended that the POEM novice first spend time observing an experienced practitioner, followed by deliberate practice in simulation, cadaveric, and live animal models, in order to ensure proficiency with each step of the operation [22]. Finally, they may graduate to supervised performance and, ultimately, independent performance of the POEM procedure. Only experienced interventional endoscopists who will have significant volume of cases should perform POEMs.

Bleeding is a common intraoperative complication that can make visualization in the small working space of the submucosal tunnel challenging. When bleeding is encountered, the operator must exercise control and diligence to achieve hemostasis. Mild bleeding can often be controlled with electrocautery, but when larger vessels are encountered, a coagulation grasper should be utilized. Bleeding that obscures visualization requires the use of irrigation through either an external system or one of the dual ESD /irrigation tools. The use of dilute epinephrine solution within the tunnel has also been described [23]. External pressure may also be applied requiring withdrawal of the endoscope from the submucosal tunnel and direct pressure to the tunnel from the intraluminal side. The use of intraluminal balloons such as those used for bleeding varices should be absolutely avoided given the risk of esophageal perforation in the setting of a new myotomy. Significant bleeding requiring conversion to a laparoscopic or open operation, or the transfusion of blood products is exceedingly rare. Close communication with anesthesia to ensure that the patient’s systolic blood pressure is maintained below 120 mmHg for the duration of the operation will help minimize engorgement of the delicate submucosal vessels.

Capnoperitoneum is a relatively common intraoperative event occurring in 20–40% of cases [21, 24]. However, it should not be considered a true complication unless it goes unrecognized and leads to abdominal compartment syndrome. Capnoperitoneum is diagnosed when progressive abdominal distension occurs despite adequate gastric decompression. A Veress needle should be used for abdominal decompression in these cases, which is a simple and effective treatment. Capnothorax is uncommon and when encountered, resulting hemodynamic compromise is extremely unlikely [25, 26]. However, we still recommend tools necessary for rapid decompression of the chest be readily available during performance of a POEM.

Postoperative Care

Routine postoperative care following POEM may vary slightly depending on institution. Our institutional practice following POEM is to allow a clear liquid diet on the evening of postoperative day zero as long as the patient is not affected by postoperative nausea. All patients are discharged on a proton-pump inhibitor that continues until six months postoperatively at which time, formal pH testing is performed. Patients are typically discharged on postoperative day one; however, some patients may feel well enough to leave on the day of surgery. Some centers are moving toward outpatient, same-day discharge for POEMs due to the brief recovery period. We allow advancement to a mechanical soft diet 1 week following surgery and solid foods 3 to 4 weeks postoperatively. Routine outpatient follow-up commences at two to four weeks and subsequently six months at which time, in addition to pH testing, patients undergo symptom assessment, endoscopy, HRM , and a TBE . Due to the low specificity for clinically relevant complications, our institution no longer obtains an immediate postoperative esophagram; however, we would recommend routine use in the early POEM experiences for the novice practitioner [27].

Outcomes

POEM has been refined over the past decade since it was first used clinically in 2008. The procedure has been shown to be safe and effective with a perioperative complication profile similar to standard of care interventions [20, 28–31]. As previously discussed, the vast majority of perioperative complications arise while the endoscopist is in the early stages of the learning curve [17, 20, 23]. Major complications such as esophageal perforation, pneumothorax, or complications requiring reintervention occur in less than 1% of patients [32]. POEM has also been shown to have a significant reduction in convalescence period when compared to laparoscopic Heller myotomy that results in shorter hospital length of stay [20, 33–36]. As already mentioned, some centers have even transitioned to performing POEM as an outpatient procedure with same-day discharge .

Symptomatic improvement following POEM has been demonstrated as comparable to standard of care treatments with excellent improvement in dysphagia and regurgitation in the short- and moderate-term [30, 33, 37–39]. Follow-up at 1–2 years showed symptomatic success (Eckardt score ≤ 3) in 90–95% of patients. This success remained over 80% at five years, which is comparable to the five-year outcomes of laparoscopic Heller myotomy and pneumatic dilation [7, 24, 30, 40]. Several studies have shown that POEM may offer superior symptomatic outcomes for patients with Type III achalasia due to its ability to perform an extended proximal esophageal myotomy compared to LHM [18, 19].

Physiologic parameters have also been demonstrated to be improved following POEM. Basal EGJ pressure as measured on HRM was shown to be significantly reduced [40–42]. Postoperative impedance planimetry demonstrated sustained reductions in the EGJ distensibility index [43]. Timed barium esophagram revealed improvements in barium retention [44]. Monitoring of physiologic parameters by EGD, HRM, and TBE is encouraged at 2- to 3-year intervals postoperatively.

Post-myotomy gastroesophageal reflux disease (GERD) was an early concern for POEM. Heller myotomy employs a partial fundoplication following myotomy to minimize postoperative reflux, while POEM has no such anti-reflux component. However, a theorized advantage to POEM is the lack of surgical disruption of the body’s natural anti-reflux anatomy, namely, the angle of His and the phreno-esophageal ligament. GERD has multiple clinical assessment tools including subjective symptom questionnaires and objective measurements such as pH monitors and endoscopic evaluation. There is no standardization among centers regarding which evaluative measures to use, which limits comparative studies across institutions. An additional complicating factor remains the challenge of patient compliance with postoperative physiologic studies [20, 34, 40]. The most robust long-term outcomes data have estimated rates of GERD symptoms post-POEM at 20–30% [23]. The rates of endoscopic esophagitis and positive pH studies were higher at 30–56% and 40–60%, respectively [23]. These values are slightly higher compared to rates of reflux after LHM with partial fundoplication, which are reported at 21–42% in well-controlled studies [8, 45]. Fortunately, post-myotomy reflux is readily controlled on an anti-secretory medication and in long-term follow-up rarely requires intervention [28, 40].

Conclusion

POEM is a procedure that evolved from advances in endoscopic interventions and the advent of submucosal surgery. Over the past decade, POEM has been shown to be a safe and effective procedure for the treatment of achalasia. Due to the rarity of achalasia, POEM should remain a procedure performed at high-volume tertiary and quaternary care centers by advanced interventional endoscopists. Novice proceduralists who wish to perform this procedure should undergo graduated introduction to POEM to minimize learning curve-associated complications. Robust short- and moderate-term outcomes data rival current standard of care therapies. Long-term data is emerging from several centers of excellence with encouraging results. Patients have already begun to seek out POEM over Heller myotomy due to the advantages of a shorter convalescence period with preserved effectiveness and durability. As more long-term data is published, POEM might become the preferred initial treatment of achalasia and similar esophageal motility disorders.