Introduction

Achalasia is a neurodegenerative motility disorder of the esophagus that results in deranged peristalsis and loss of lower esophageal sphincter function, especially during swallowing [1,2,3,4]. The incidence is still rare, approximately 1.6 per 100,000 [5, 6]. It occurs equally in males and females, without racial predilection, and across all ages, with a peak incidence between the ages of 30 and 60 [7].

The disease manifests as symptoms of dysphagia, regurgitation of food and retrosternal chest pain [8]. Even with advancements in diagnostic tools and accurate screening methods, the etiology remains unclear. The general consensus of the literature suggests that achalasia represents a family of disorders rather than a single disease with a fixed pathophysiologic profile [9, 10]. The current understanding suggests that three factors determine the clinical phenotype including genetic predisposition, environmental triggers, and autoimmune myenteric plexitis [11,12,13,14]. The exact pathophysiology of the disease is not completely understood, and is beyond the scope of this review.

First-line treatment options have varied in the past, and well-established modalities such as pneumatic balloon dilation and surgical myotomy have been the mainstays over the past decade. Newer treatment options such as the peroral endoscopic myotomy (POEM) procedure have been practiced with increasing frequency in Asia and other parts of the world [15], but has yet to gain universal acceptance, though the data appears promising. POEM has the potential to be the preferred modality for achalasia and related esophageal motility disorders when personnel and logistics allow [16].

This review focuses on the diagnosis of achalasia based on the Chicago Classification ver. 3.0. A concise review of literature was conducted, focusing on the diagnosis and management of achalasia, and included papers discussing newer treatment modalities. We review the treatment options for achalasia and other motility disorders of the esophagus, and we draw special attention towards the POEM procedure as the primary management, and include our experience with its implementation.

Diagnosis

When approaching a patient with dysphagia as the chief complaint, a high index of suspicion for achalasia must be maintained. Evaluation must rule out common disorders, such as gastroesophageal reflux disease, mechanical obstruction, or malignancy [17]. Once such disorders are ruled out, work-up should then focus on motility disorders of the esophagus. A few technological advances have enhanced the diagnostic work-up for achalasia [18], but the modalities utilized most frequently include endoscopy, radiographic studies, and manometry. Esophagogastroduodenoscopy (EGD) is performed to rule out erosive gastroesophageal reflux disease, esophageal cancer, and structural lesions, such as strictures, webs, or rings. A normal EGD should not dissuade a clinician from making the diagnosis because up to 40% of patients with achalasia will have normal endoscopy [19]. Barium esophagogram may reveal a classic “bird’s beak” appearance, esophageal dilation, or a corkscrew appearance with aperistalsis. In our institution, esophagogastroduodenoscopy, high-resolution manometry, barium esophagogram, as well as CT scan imaging have become the routine for patients presenting with dysphagia and a clinical history suggestive of an esophageal motility disorder.

The gold standard for achalasia diagnosis is esophageal manometry, with findings of aperistalsis and failure of relaxation of the lower esophageal sphincter (LES) [20, 21]. With the incorporation of color pressure topography plots, we are provided with more information regarding the dynamics of the esophagus [22]. The Chicago Classification v3.0 categorizes esophageal motility disorders with high-resolution manometry (HRM), and presents a hierarchical approach to the interpretation. Motility disorders are divided into categories of esophagogastric junction outflow obstruction, major disorders of peristalsis, and minor disorders of peristalsis, as seen in Table 1 [23].

Table 1 Interpretation of HRM studies
Full size table

Another diagnostic modality that can determine the dynamic profile of the esophagus is the functional lumen imaging probe (FLIP), used mostly at the esophagogastric junction [24]. This device consists of a distensible bag surrounding a catheter with impedance electrodes that measures cross-sectional area and impedance patterns [25]. The advantage is that the results can be observed in real time, and therapy can be tailored appropriately to the findings [26]. Information regarding FLIP is still limited, and it is unknown whether its application will be valuable as an alternative or an adjunct to manometry.

Treatment

The pathophysiology of the disease is not fully understood, therefore treatment modalities can neither reverse nor prevent the neurodegeneration of the myenteric plexus [8]. The primary goal of management should focus on early diagnosis and prevention of late complications, in order to preserve esophageal structure and function [17]. Available treatments aim to relieve esophageal outflow obstruction by lowering LES tone, or disrupting the LES, to facilitate passage of food across the LES. Available methods have used pharmacologic or interventional means. O’Neill et al. mentioned that patient preference, patient symptoms, and local expertise should guide the choice as to which modality to utilize [5].

Medical management has been used to relax smooth muscles, reduce LES pressure, and provide symptom relief, however the effects are limited clinically, and produce side effects. These therapies are now reserved for short-term treatment in patients who cannot tolerate invasive methods, or as a bridge to more definitive treatment [27]. Endoscopic botulinum toxin injection is still an accepted method for symptom relief, however the effects are often short lived [28, 29]. As with oral pharmacologic agents, Botox injection should be reserved for patients who cannot tolerate more invasive methods.

The mainstay of recent achalasia management focuses on the disruption of the LES by interventional means. Endoscopic pneumatic balloon dilatation (PD) positions a balloon across the LES and inflates it, effectively rupturing the muscle of the affected segment. Graded PD is performed by an initial dilation of 3.0 cm, progressing slowly at 0.5-cm intervals to reach a target of 4.0 cm. This is performed periodically with 4–6 weeks between each dilation. This modality is stated to have fewer major complications and deaths as compared to surgical myotomy [30]. Surgical LES myotomy also disrupts the LES fibers with a longitudinal incision. The preferred method has been the laparoscopic approach, or laparoscopic Heller myotomy (LHM), due to decreased morbidity and faster recovery [31, 32]. Though this method effectively relieves the obstruction, it also increases the risk of gastroesophageal reflux, and most surgeons incorporate an anti-reflux procedure by way of a partial fundoplication [33, 34]. Studies initially showed superiority of surgical myotomy in terms of efficiency and durability compared to single balloon dilatation [35, 36]. Further comparison of these two modalities has shown similar outcomes in treatment success rates after 2-year follow-up when a graded approach to PD has been used [32, 37, 38]. Pneumatic balloon dilatation and surgical myotomy therefore remain the universally accepted treatments for achalasia presently, and patients should be followed up long term [39].

The advent of the peroral endoscopic myotomy (POEM) procedure by Inoue et al. in 2008 provided another means of treatment that has been presented worldwide [40]. Initially described by Pasricha et al. [41], this form of natural orifice transluminal endoscopic surgery (NOTES) has provided adequate symptom relief, shown similar short-term results, and is less invasive as compared to laparoscopic Heller myotomy [42]. Short-term results have proven that POEM is a safe and effective approach for esophageal achalasia [43,44,45]. The patient is placed in a supine position under general anesthesia [46]. An endoscopic submucosal injection of dyed saline is followed by a mucosal incision, and subsequent creation of a submucosal tunnel to expose the circular muscle fibers at a length 2–3 cm beyond the LES. Selective circular muscle myotomy is then carried out under direct visualization, and the mucosa is closed with clips [47]. Advancements in technology as well as refinements in technique have led to safer procedures, as well as decreased operative time. The water-jet assisted triangle knife (Olympus, Tokyo, Japan) used in the creation of the submucosal plane, as well as the selective myotomy, provides a reduction of procedure time [48]. The use of the double-scope POEM technique provides a safe and reliable method for ensuring adequate gastric myotomy length during POEM, and may help to ensure proper outcomes [49]. These advancements along with the increase in operator expertise are what drive the use of POEM to be more widespread.

POEM has been used for all types of esophageal motility disorders, including, but not restricted to, advanced sigmoid achalasia and spastic motility disorders of the esophagus [50, 51]. POEM has even been performed successfully on refractory cases of achalasia following previous balloon dilation or laparoscopic Heller myotomy [52,53,54,55]. These cases should only be treated by highly experienced operators [47]. The advantage of POEM over surgical myotomy is that the length of the myotomy from the esophageal to gastric side can be adjusted freely to suit the individual case. This may make POEM a more appropriate, safe, and effective option for patients with sigmoid esophagus or history of surgical myotomy [56]. POEM has proven to be similar to LHM in terms of Eckardt score reduction, complications, operative time, and length of hospital stay [57,58,59]. POEM has also proven to be equally effective to pneumatic dilatation [60]. It is important to note, however, that data regarding the long-term effects of POEM are still limited, and randomized controlled trials comparing POEM with other treatment modalities are needed. This has been the barrier to the worldwide acceptance of the procedure, and its use has been confined to high-volume centers, though it is still believed that POEM represents a paradigm shift in the treatment of achalasia [61]. Post-procedure complications still arise, as with the other treatment modalities. On objective testing, the rate of gastroesophageal reflux disease (GERD) after POEM is 20–46%, which may not be significantly different from that observed after LHM with Dor fundoplication [62, 63].

At our institution, we have performed over 1200 cases of POEM since the innovation of the procedure, and this has become our treatment modality of choice for all motility disorders of the esophagus. Opinions have differed with regard to the length of the myotomy. Inoue et al. previously used a questionnaire regarding patients’ dysphagia symptoms to determine the length of the myotomy [56]. The current practice in our institution has evolved over the years. We determine the length of the myotomy based on the patient symptoms, the results of the diagnostic evaluation, and the endoscopic findings. From a decision-making standpoint, we present our treatment algorithm with POEM as the first-line therapy seen in Fig. 1.

Fig. 1
figure 1

Treatment algorithm for POEM. EGJOO Esophagogastric junction outlet obstruction, LES lower esophageal sphincter

Full size image

The different motility disorders of the esophagus are based on manometric study, barium esophagogram, and endoscopic findings and are further subdivided into categories depending on the area of involvement of each disease entity. It then follows that a standard-length myotomy through the LES is adequate treatment for classic achalasia (type I), achalasia with pan pressurization (type II), and esophagogastric junction outlet obstruction. An extended myotomy of the esophageal body and the LES should be considered for vigorous achalasia (type III) with premature contractions. Diffuse spasm and jackhammer esophagus cases can be managed with a focused myotomy of the esophageal body, and the LES may be preserved. In some cases, the specific motility disorder may not be clearly identified at the time of the procedure. It is important to note the presence of spastic simultaneous contractions, or non-peristaltic contractions, as these intraoperative findings may also affect the length of the myotomy. Previous interventional procedures, as well as anatomy of the esophagus itself will also affect the decision on myotomy length as well as placement. Further long-term studies are needed to properly evaluate the outcomes of cases that follow this algorithm and more studies are needed in order to determine what constitutes an adequate myotomy, whether that be measurable by pressurization studies (EndoFLIP) or subjective symptom relief based on the Eckardt score. The purpose of this algorithm is not to create a guideline for clinical practice, but to assist the decision-making process, and clarify the primary focus of the intervention.

Conclusions

Achalasia remains a difficult to diagnose condition and a high index of suspicion must be maintained when patients present with dysphagia. Other causes of mechanical obstruction must be ruled out, and proper diagnostics must confirm a motility disorder of the esophagus. Treatment focused on disrupting the LES and lowering LES tone has been the mainstay of management, and has traditionally utilized pneumatic balloon dilatation and surgical myotomy. Peroral endoscopic myotomy is an effective treatment option for all types of motility disorders of the esophagus. With time and physician experience, POEM may become the ideal management for achalasia and its use may change the way we approach this rare disorder.