Bolus pressure and bolus mismatch in patients with dysphagia and preserved esophageal peristalsis.

Dysphagia is common in patients with preserved contraction phase of esophageal peristalsis, such as those diagnosed with functional dysphagia (FD) or esophagogastric junction outflow obstruction (EGJOO); it amounts to ≥50% patients undergoing high-resolution manometry impedance (HRMZ) study. We aimed to characterize the distension phase of esophageal peristalsis (bolus domain) and identify abnormalities that may contribute to dysphagia in these patients. HRMZ recordings from 35 healthy controls, 35 patients with FD, and 35 patients with EGJOO were analyzed. Distension-contraction plots were used to assess the luminal cross-sectional area, bolus pressure, and regions without bolus ("no-bolus areas") within the bolus domain of peristalsis. The proportion of no-bolus area was compared among groups, and receiver operating characteristic (ROC) analysis evaluated diagnostic performance. Esophageal wall compliance during the distension phase was also determined. Both FD and EGJOO groups exhibited a significantly greater proportion of no-bolus area within the bolus domain compared with controls, particularly in the distal esophagus (P < 0.001). Pressure peaks frequently occurred in the absence of bolus, indicating pseudo-bolus pressures. Ultrasound imaging revealed transient luminal collapse against the manometry catheter in the "pseudo-bolus" zone. Esophageal wall compliance was reduced in both patient groups. ROC analysis demonstrated that the percentage of no-bolus area discriminated patients from controls with high accuracy (area under the curve 0.83 for FD, 0.88 for EGJOO). We propose that impaired esophageal distensibility and transient luminal collapse within the bolus domain cause functional obstruction and possibly dysphagia.NEW & NOTEWORTHY This study introduces a novel impedance-based method to analyze the bolus domain of esophageal peristalsis, emphasizing bolus pressure and bolus mismatch. Patients with functional dysphagia and EGJOO demonstrated impaired esophageal distension, reduced wall compliance, and frequent pseudo-bolus pressures from transient luminal collapse during peristalsis. These findings suggest that dysphagia may result from dynamic obstruction due to esophageal collapse during peristalsis rather than fixed outflow obstruction, highlighting bolus domain mechanics as a complementary diagnostic tool.