Achalasia is a disease characterized by lack of peristalsis and lower esophageal sphincter failing to relax. Longitudinal muscle, outer layer of esophageal smooth muscle, is recently found to be responsible for emptying of esophagus for achalasia patients, especially for those type Ⅱcases. Clinical observations also conclude that type Ⅱ achalasia which still preserve longitudinal muscle response best to treatment, among the 3 types. Thus, with high frequent intraluminal ultrasound, clinically applied as endoscopic ultrasound, to measure the function of longitudinal muscle in achalasia patients, the current research aims to explore the influence of longitudinal muscle on the prognosis of achalasia patients after peroral endoscopic myotomy, a routine treatment.

Inclusion Criteria:

• Diagnosed of esophageal achalasia
• Patients or legal surrogates willing and competent to give informed consent

Exclusion Criteria:

• postoperative or post-POEM
• post-pneumatic dilation or post-stenting
• fail to go through high frequency intraluminal ultrasound （HFIUS)
• Patients with American Society of Anesthesiologists （ASA） score ≥3