Esophageal manometry is the gold standard diagnostic method for achalasia. Esophagography (barium swallow) and endoscopy are also used in the diagnosis of achalasia. Esophagography shows the upper esophagus dilated and narrowing progressively downwards; this is known as the "bird's beak" sign. Endoscopy shows narrowing of the esophagus downwards and fungal esophagitis at the lower end. The gold standard, manometry, shows high lower esophageal sphincter pressure and the absence or minimal relaxation of the lower esophageal sphincter upon swallowing, thus confirming the diagnosis of achalasia.