Diagnostic evaluation of achalasia: from the whalebone to the Chicago classification

From the earliest description of dysphagia relieved by dilatation with a whalebone in 1674 we have witnessed the evolution of esophageal function testing from the conventional manometry to the high-resolution manometry (HRM) and esophageal topography pressure plotting that have led to the revised Chicago classification for esophageal motility disorders in 2014. The goals of this paper are, therefore, (1) to highlight the historical milestones that have led to the diagnostic definition of achalasia, as we know it today; (2) to describe the evaluation process of patients with suspected achalasia; (3) to describe the diagnostic value of the HRM and the usefulness of the Chicago classification in predicting treatment outcomes. The value of Chicago classification is linked to the ability of the clinician to perform a thorough clinical evaluation to identify and correlate specific clinical phenotypes to specific manometric subtypes and predict treatment outcomes. Chicago classification, however, cannot predict which treatment, pneumatic dilatation, or Heller myotomy, should be selected for those with a specific subtype of achalasia.