S483 Esophageal Circular Muscle Thickness with Endoscopic Ultrasound among Esophageal Motility Disorders

Introduction: Esophageal motility disorders comprise heterogeneous pathologies at the lower esophageal sphincter (LES) and/or esophageal body. As endoscopic ultrasound (EUS) can accurately measure muscle thickness, this study aimed to characterize and compare LES and esophageal body muscle thickness among patients with achalasia and normal motility on high-resolution manometry (HRM). Methods: This retrospective, single center study evaluated adult patients with achalasia or normal motility on HRM (Medtronic, Minneapolis, MN; interpreted per Chicago Classification v4.0) who underwent EUS from 01/2019-05/2021. On EUS, measurements of the circular muscle thickness were taken at the LES and every cm proximal until the muscle thickness reached 1mm or less. Mean distal esophageal thickness was calculated as an average of the muscle thickness 6cm proximal to the LES. Distal esophageal thickness was categorized as thickened if ≥ 1.5mm, or not thickened if < 1.5mm. Results: Of 41 patients [mean age 57 years and 47% male], 9 (22%) had normal motility on HRM and 32 (78%) had achalasia [3 (7%) type 1, 20 (49%) type 2, 9 (22%) type 3]. Mean LES muscle was significantly thicker in achalasia vs normal (1.8mm (SD 1.2) vs 0.9 (0.4), P=0.03). Specifically, mean LES muscle thickness was 1.6 (1.2) for type 1, 1.8 (1.4) for type 2, and 1.9 (0.8) for type 3. Mean distal esophageal muscle was significantly thicker in achalasia vs normal (1.9mm (SD 1.4) vs 0.9 (0.4), P=0.05). Specifically, mean distal esophageal muscle thickness was 1.2 (0.6) for type 1, 1.8 (1.4) for type 2, and 2.3 (1.5) for type 3. A thickened distal esophageal muscle was seen in 33% type 1, 50% type 2, and 78% type 3 achalasia patients (Figure 1). Ten of 20 type 2 achalasia patients had a thickened distal esophageal muscle. Of those who underwent barium esophagram, 5/5 (100%) with thickened distal esophageal muscle had tertiary contractions compared to 3/7 (43%) with non-thickened distal esophageal muscle (P=0.08). Conclusion: On EUS, type 1 achalasia exhibits a thickened LES with normalization of circular muscle proximally whereas type 3 achalasia exhibits a thickened LES and distal esophageal muscle, supporting the current paradigm of short myotomy for type 1 and extended myotomy for type 3. Interestingly, manometric type 2 achalasia may represent 2 physiologic phenotypes, one akin to type 1 that may respond well to short myotomy, and one with distal esophageal spasticity that may respond to tailored myotomy.Figure 1:: Figure legend: (A) boxplot depiction of esophageal circular muscle thickness (measured in cm along the x-axis) measured at each cm along the distal esophagus from the lower esophageal sphincter (location 0 on the y-axis) to 6 cm proximal for each achalasia sub-type. (B) proportion of subjects with a thickened esophageal muscle layer (blue) and not thickened muscle layer (orange).Table 1.: Title: Table. Cohort Demographics; Table Key: (a) P-value of comparison between achalasia vs normal (b) P-value of comparison between achalasia type 1, 2, and 3