Identification of Achalasia Within Absent Contractility Phenotypes on High-Resolution Manometry: Prevalence, Predictive Factors, and Treatment Outcome

INTRODUCTION: Absent contractility on high-resolution manometry (HRM) defines severe hypomotility but needs distinction from achalasia. We retrospectively identified achalasia within absent contractility using HRM provocative maneuvers, barium esophagography, and functional lumen imaging probe (FLIP). METHODS: Adult patients with absent contractility on HRM during the 4-year study period were eligible for inclusion. Inadequate studies, achalasia after therapy, or prior foregut surgery were exclusions. Upright integrated relaxation pressure (IRP) >12 mm Hg, panesophageal pressurization, and/or elevated IRP on multiple rapid swallows and rapid drink challenge (RDC) were considered abnormal. Esophageal barium retention and abnormal esophagogastric junction distensibility index (<2.0 mm²/mm Hg) on FLIP defined achalasia. Clinical, endoscopic, and motor characteristics of patients with achalasia were compared with absent contractility without obstruction. RESULTS: Of 164 patients, 20 (12.2%) had achalasia (17.9% of 112 patients with adjunctive testing), while 92 did not, and 52 did not undergo adjunctive tests. Achalasia was diagnosed regardless of IRP value, but the median supine IRP was higher (odds ratio 1.196, 95% confidence interval 1.041–1.375, P 5 0.012). Patients with achalasia were more likely to present with dysphagia (80.0% vs 35.9%, P < 0.001), with obstructive features on HRM maneuvers (83.3% vs 48.9%, P 5 0.039), but lower likelihood of GERD evidence (20.0% vs 47.3%, P 5 0.027) or large hiatus hernia (15.0% vs 43.8%, P 5 0.002). On multivariable analysis, dysphagia presentation (P 5 0.006) and pressurization on RDC (P 5 0.027) predicted achalasia, while reflux and presurgical evaluations and lack of RDC obstruction predicted absent contractility without obstruction. DISCUSSION: Despite HRM diagnosis of absent contractility, achalasia is identified in more than 1 in 10 patients regardless of IRP value.