Challenges in the swallowing mechanism: nonobstructive dysphagia in the era of high-resolution manometry and impedance.

Esophageal high-resolution manometry (HRM) improves the management of patients with nonobstructive dysphagia. It has increased the diagnostic yield for detecting achalasia and defined three clinically relevant achalasia subtypes. Esophagogastric junction (EGJ) outflow obstruction, defined as an impaired EGJ relaxation in association with some preserved peristalsis, might also represent an achalasia variant in some cases. Using the concept of distal latency, the criteria for defining distal esophageal spasm, have been revised as the occurrence of premature distal contractions. Finally, the combination of HRM and impedance monitoring allows for a functional definition of weak peristalsis associated with incomplete bolus transit.