Background and aims <p>After the introduction of POEM several years ago, the position of pneumatic dilation (PD) in the treatment of achalasia has been challenged. During PD, balloon pressure changes according to the volume of gas injected. This may reflect esophagogastric junction (EGJ) compliance, a parameter recently considered important by POEM operators. In this study, we aimed to assess whether the pneumatic dilation balloon catheter combined with a precise pressure sensor allows for the evaluation of EGJ compliance, and then, help predict the outcome of POEM in the treatment of achalasia.</p> Methods <p>In this retrospective study enrolled 82 achalasia patients and 10 healthy volunteers. Gas was injected into the balloon after placement of the pneumatic dilation catheter and the pressure was recorded. Biopsies of esophageal muscle and mucosal tissue were obtained during POEM to assess the infiltration degree of inflammation by hematoxylin and eosin staining (HE) and fibrosis status by Masson staining. Both clinical evaluation and data of high-resolution manometry were assessed before and 6&#xa0;months after POEM.</p> Results <p>EGJ compliance in 82 achalasia patients was significantly lower than controls (<i>P</i> &lt; 0.05). Achalasia with fibrosis was present in 74 patients (90.2%). The EGJ compliance was negatively correlated with fibrosis and inflammatory status, respectively (<i>P</i> &lt; 0.05), and a correlation between Eckardt score and EGJ compliance was also confirmed while resting esophageal body (<i>P</i> &lt; 0.05). Moreover, the EGJ was significantly more distensible in patients who have not received previous treatment for achalasia (<i>P</i> &lt; 0.05).</p> Conclusions <p>Assessment of EGJ compliance with the novel measurement of pneumatic dilation balloon catheter might be able to reflect the degree of inflammation and fibrosis in esophagus of achalasia patients and predict the outcome of POEM.</p>