Viscous impedance is an important indicator of abnormal esophageal motility.

Background: Non-obstructive Dysphagia (NOD) is one of the most common symptoms evaluated using esophageal manometry. Although manometry is considered the gold standard, many NOD patients have normal evaluations. Esophageal function testing with combined multichannel intraluminal impedance and esophageal manometry (MII-EM) is performed using ten 5-mL swallows of a liquid and a viscous material and provides supplemental information about bolus transit. The aim of this study was to evaluate esophageal function using combined MII-EM in patients with NOD who had normal evaluations with liquid manometry.

Methods: Multichannel intraluminal impedance and esophageal manometry was performed in consecutive patients presenting for evaluation of NOD. Patients were excluded if any abnormality was detected during liquid manometry. Viscous manometry and liquid and viscous impedance data were analyzed to detect manometric or bolus transit abnormalities. Patients referred for GERD evaluation without any swallowing complaints were used as patient controls and were subject to the same exclusion criteria as the NOD group. All swallow evaluations were performed with 10 liquid and 10 viscous swallows.

Key Results: Data from 240 patients were evaluated, 129 with NOD and 111 patient controls. In the NOD group, 9% (12/129) had abnormal liquid impedance and 29% (37/129) had abnormal viscous impedance. In the control group, 4% (4/111) had abnormal liquid impedance and 16% (18/111) had abnormal viscous impedance. Chi-square analysis showed a significant difference between the two study groups for viscous impedance (P = 0.02) but not for liquid impedance (P = 0.12).

Conclusions & Inferences: Our data support our belief that a normal liquid manometry with an abnormal viscous impedance analysis in a patient with NOD indicates abnormal esophageal motility. Therefore, viscous impedance should be performed on all patients during the evaluation of NOD.