Four‐dimensional impedance manometry volume metrics for predicting abnormal bolus retention

BackgroundThe objective measurement for esophageal bolus volume and bolus clearance could classify abnormal high‐resolution manometry (HRM) beyond the current Chicago classification. We aimed to compare the novel four‐dimensional impedance manometry (4D HRM) volume metrics with timed barium esophagram (TBE).MethodsAdults with esophageal symptoms undergoing HRM and TBE were included. A custom‐built program for 4D HRM analysis measured esophageal luminal cross‐sectional area (CSA) from impedance and subsequently derived esophageal bolus volume and clearance. 4D HRM volume metrics included pre‐swallow residual volume, maximal volume, retention volume, and clearance ratio defined as 1.0—retention volume divided by the maximal volume. An abnormal TBE was defined as a column height >5 cm at 1 min or 5 min.Key ResultsA total of 95 patients (normal motility: 33%; ineffective esophageal motility: 12%; absent contractility: 10%; esophagogastric junction outflow obstruction: 30%; type I achalasia: 5%; type II achalasia: 12%) were categorized into normal TBE (58%), abnormal TBE at 1 min (17%), and abnormal TBE at 5 min (25%). The AUROC demonstrated that, among all 4D HRM volume metrics, the clearance ratio had the best performance in predicting abnormal TBE at 5 min (AUROC, 95% confidence interval: 0.89, 0.82–0.96), and exhibited a strong negative correlation with TBE at 5 min (r = −0.65; p < 0.001).Conclusions & InferencesNovel 4D HRM volume metrics provide objective measurement of esophageal bolus volume and bolus clearance. The clearance ratio has a strong correlation with TBE and could potentially serve as a substitute for TBE to measure esophageal retention.