Achalasia occurs due to problems with the muscles in your esophagus:

• The muscular contractions of the esophagus are affected and weaken over time, so that the esophagus loses its strength to propel food down to the stomach.
• On top of that, the ring-shaped muscle at the lower end of the esophagus usually stays closed to prevent stomach acid from backing up into the esophagus (reflux).
• In achalasia, the muscle fails to relax.

It's not clear why some people develop achalasia. Doctors think it might be caused by a viral infection. Another theory is that your immune system attacks the nerves that control muscle function in your esophagus.

In some cases, achalasia is secondary to other conditions, such as stomach cancer, Chagas disease, and certain neurodegenerative disorders.

Symptoms of achalasia include:

• Difficulty swallowing (dysphagia)
• Regurgitation of food back into your mouth
• Chest pain
• Heartburn
• Weight loss

Achalasia develops slowly, and you may not realize something is wrong right away. Over time, symptoms become more noticeable. 

When severe, achalasia can cause malnutrition and dehydration requiring hospital care. Pneumonia is also a risk if you aspirate food into your lungs. 

Tests your doctor may use to diagnose achalasia include:

• Barium swallow (esophagram): An X-ray procedure in which you drink a contrast liquid containing barium, which coats the esophagus and stomach, in order to look for abnormalities.
• Esophageal manometry: A thin tube is inserted through your mouth and throat into your esophagus. As you sip water, the tube measures pressure and muscle contractions.
• Upper endoscopy: A thin tube with a camera (endoscope) is inserted through your mouth and throat to examine the inside of your esophagus.

Gastroenterologists treat achalasia using a range of non-surgical approaches, including:

• Medications: Medications are available to ease symptoms, but they don't address the underlying cause of achalasia.
• Botulinum toxin injections: This procedure involves passing a thin tube equipped with a camera and tiny tools (endoscope) into your throat. Your doctor injects botulinum toxin (Botox) into the lower esophageal sphincter, relaxing the muscle so food can pass. Since there is paralysis of the lower esophageal sphincter to allow food to pass, there is a high risk of reflux. The effects typically last from three to six months.
• Balloon dilation: In this treatment, an endoscope is used to insert a deflated balloon inside the lower esophageal sphincter. As they inflate the balloon, the muscle opens. The effects may last up to a year, but symptoms often return. There is also a risk of perforation of the esophagus, especially with repeated procedures.
• Peroral endoscopic myotomy: In this endoscopic procedure, your doctor cuts through the lower esophageal sphincter from inside the esophagus. This treatment effectively opens the sphincter but has a high risk of reflux.