However, patients’ symptoms following POEM may not necessarily be a reliable indicator of functional improvement after treatment as symptom resolution can occur without a significant improvement in esophageal emptying, which can place the patient at risk for developing long-term complications of achalasia such as mega-esophagus [4]. As such, patients should also undergo objective testing following POEM to demonstrate clinical response, such as high-resolution manometry and timed barium esophagram. Multiple studies have demonstrated that upright timed barium esophagram can predict treatment success and requirement for future intervention. Vaezi et al. demonstrated that there was an approximate 73% concordance between the degree of symptom improvement and degree of esophageal emptying by barium esophagram in patients with achalasia treated with pneumatic dilation. Furthermore, there was an association and predictive value seen in patients with poor esophageal emptying on barium esophagram in the context of complete symptom resolution and symptom relapse at 1 year. Patients in this treatment group were found to benefit from more intensive follow-up regardless of symptoms due to the risk of relapse and, as such, it was found to be reasonable to repeat barium esophagram annually to assess for esophageal emptying [9].

Esophageal manometry has also been cited as an indicator for treatment outcome, given that the diagnosis of achalasia is dependent on the manometric description of LES function. Numerous studies have supported that an LES pressure of 10 mmHg can be correlated with and can predict clinical response as well as remission in patients treated with pneumatic dilatation [10]. Despite this, manometry is not routinely used in this manner because it is more invasive and less widely available than barium esophagram. Although both timed barium esophagram and manometry can be used to assess short-term treatment success and predict long-term outcomes after pneumatic dilation, further studies are needed to infer its utility and predictability for treatment effects post-POEM.

There has also been particular interest in the extent of gastroesophageal reflux (GERD) following POEM, given that there is no combined anti-reflux procedure in contrast to Heller myotomy. The rate of postoperative reflux has been found to vary widely in numerous published studies, ranging from 0 to 53% [11–13]. Given this variability, there has been debate whether all patients following POEM should be treated with acid suppression. Standardized symptom scales, such as the gastroesophageal reflux disease health-related quality of life (GERD-HRQL) (Fig. 12.2) and GERD symptom scale (GERDSS) (Fig. 12.3), have been used to attempt to quantify gastroesophageal reflux disease health-related quality of life. Objectively, 24 h or 48 h pH monitoring, typically performed 6 months following POEM, has been utilized to determine evidence of pathologic acid reflux defined as a DeMeester score greater than 14.72 in a 24 h period. Jones et al. demonstrated that there was no correlation between subjective symptoms of GERD and objective pH testing for pathologic acid reflux following POEM, with 58% of patients with documented abnormal distal esophageal acid exposure not experiencing clinical symptoms of reflux, which is consistent with results in achalasia patients treated with Heller myotomy [14, 15]. Given the lack of correlation, we recommended that all patients following POEM undergo routine postoperative pH monitoring and esophagogastroduodenoscopy to identify and treat patients at risk of long-term complications of uncontrolled acid reflux, such as esophagitis, stricture, and recurrent dysphagia, and to avoid unnecessary long-term proton pump inhibitor therapy in patients with normal esophageal acid exposure.

Patients with achalasia are also at a substantially increased risk of developing esophageal squamous cell carcinoma and adenocarcinoma theoretically due to poor esophageal emptying and increased acid exposure leading to dysplasia and, eventually, carcinoma. However, at this time, there is insufficient data to support the routine endoscopic surveillance for esophageal cancer, given the low incidence and poor outcomes once the diagnosis is made [16].