Clearance mechanisms of the aperistaltic esophagus. The pump-gun hypothesis.

Transcription

1 Gut Online First, published on December 14, 2005 as /gut Clearance mechanisms of the aperistaltic esophagus. The pump-gun hypothesis. Radu Tutuian 1, Daniel Pohl 1, Donald O Castell 2, Michael Fried 1 1 Clinic for Gastroenterology and Hepatology, Department of Internal Medicine, University Hospital Zurich, Zurich, Switzerland 2 Division of Gastroenterology - Hepatology, Medical University of South Carolina, Charleston SC, USA Keywords: - Achalasia - High resolution manometry - Esophageal clearance Corresponding author: Radu Tutuian, MD University Hospital Zurich Division of Gastroenterology and Hepatology Raemistrasse 100 CH-8091 Zurich Switzerland radu.tutuian@usz.ch License for publication: "The Corresponding Author has the right to grant on behalf of all authors and does grant on behalf of all authors, an exclusive licence (or non-exclusive for government employees) on a worldwide basis to the BMJ Publishing Group Ltd and its Licensees to permit this article to be published in Gut editions and any other BMJPGL products to exploit all subsidiary rights, as set out in our licence ( Competing Interests: none Sponsors / Acknowledgements: none Copyright Article author (or their employer) Produced by BMJ Publishing Group Ltd (& BSG) under licence.

2 Abstract We describe the pattern of esophageal pressure changes noted during high-resolution manometry in a patient with achalasia. Our data indicate that longitudinal muscle contraction of the esophagus is the major mechanism to empty esophageal contents against a poorly relaxing lower esophageal sphincter. This phenomenon may enable patients with achalasia to empty the esophagus and thus to relieve discomfort and maintain an adequate nutritional status. Achalasia (Greek for lack of relaxation ) is a primary esophageal motility disorder characterized by the absence of esophageal peristalsis due to damages of the myenteric plexus. Typically, patients with achalasia report difficulties swallowing of both liquids and solids (dysphagia) but young patients may initially complain of chest pain and regurgitation. These patients have mostly a normal endoscopy (i.e. no food retention) and initially do not loose weight which leads to a delay in establishing this diagnosis. Clearance of the aperistaltic esophagus of patients with achalasia is thought to occur passively as the hydrostatic pressure of the column built in the esophagus distends and opens the poorly relaxing lower esophageal sphincter (LES). However patients with achalasia often have a high lower esophageal sphincter pressure i.e. above 45mmHg. For a column of fluid to overcome hydrostatic pressures of this magnitude it would have to exceed 61 cm in height, i.e. almost 3 fold the length of a normal human esophagus. We hereby show a case which implies that another mechanism may be involved. Our observations are based on changes noted during highresolution manometry testing in a patient with achalasia. In a 45 year old Caucasian male who was complaining for the past 3 years of difficulty swallowing both liquids and solids and retrosternal chest pressure after meal intake a manometric examination was performed in order to prove the suspected diagnosis of achalasia. An upper endoscopy was normal and a barium esophagogram identified a normal-sized esophagus with the typical bird-beak appearance of at the gastroesophageal junction. A 32-channel esophageal manometry catheter was introduced transnasally and positioned in the esophagus such that it spanned the entire esophagus including both upper and lower esophageal sphincters. The diagnosis of achalasia was confirmed by the low-amplitude mirror-image intraesophageal pressure changes during the swallowing of 10ml of water in recumbent position, a high LES resting pressure of 50mmHg and LES residual pressures of 11mmHg during swallowing. The patient was then asked to sit up and to reproduce his symptoms of retrosternal pressure/pain by repeated swallowing of liquid. After 10 water swallows he stopped and reported a sensation of chest fullness. Approximately 10 seconds later he reported increasing discomfort of retrosternal chest pressure immediately followed by the sensation of bolus passage and pressure relief. The pressure recordings during this period are shown in figure 1 and represent the aperistaltic pressure changes during swallowing followed by a brief period of inactivity. After a dry swallow the pressure in the esophagus increases as the lower esophageal sphincter is moving upwards and the fluid column is pressed against the closed upper esophageal sphincter. Subsequently the pressure is declining and the lower esophageal sphincter returns to the initial position. 2

3 We interpret these changes as a reflex shortening of the longitudinal esophageal musculature against the closed upper esophageal sphincter resulting in the generation of sufficient pressures to evacuate esophageal contents into the stomach through the hypertensive and poorly relaxing lower esophageal sphincter. The presence of this esophageal propulsive force has been previously described by Winship and Zborlaske 1 as the esophageal response to acute obstruction. While the shortening of the esophagus during swallowing has been previously documented in normal subjects 2,3 this is the first report to describe it in a patient with achalasia. Our observation stimulates questions on the pathophysiology of achalasia and the role of esophageal longitudinal musculature contraction. This, as we call it pump-gun (after the classic side-action firearm first patented in Britain by Alexander Bain in 1854) esophageal emptying may enable patients with achalasia to clear the esophagus, relieve pain and maintain an adequate nutritional status. Figure 1: Topographic representation of a high-resolution (32-channel) manometric recording of the events of esophageal filling and emptying in a patient with achalasia. After 10 swallows the esophagus is filled with water. The elevation of the pressure transition zone corresponding to the lower esophageal sphincter is assumed to be the result of the reflex contraction of the longitudinal musculature of the esophagus. At the time of rise in intraesophageal pressure the patient reports an increase in chest pressure which improves once the esophageal pressure returns to baseline. During this time the upper esophageal sphincter (pressure band between cm from nares) remains closed. 3

4 References 1 Winship DH, Zboralske FF. The esophageal propulsive force: esophageal response to acute obstruction. J Clin Invest. 1967; 46: Pouderoux P, Lin S, Kahrilas PJ. Timing, propagation, coordination, and effect of esophageal shortening during peristalsis. Gastroenterology. 1997; 112: Edmundowicz SA, Clouse RE. Shortening of the esophagus in response to swallowing. Am J Physiol. 1991; 260:G

5 Water swallows cough Chest pressure starting ending -180 mmhg -150 mmhg -120 mmhg - 90 mmhg - 60 mmhg - 30 mmhg - 20 mmhg - 10 mmhg Ascent and descent of the LES and longitudinal muscle contraction Distance from nares (mm)