PHYSICAL EXAMINATION

LABORATORY STUDIES

DIAGNOSIS

Achalasia

PATHOPHYSIOLOGY OF KEY SYMPTOMS

Achalasia results from the failure to move food from the esophagus into the proximal portion of the stomach. Consequently, the food can accumulate in the esophagus, where it can putrefy, and possibly move from the esophagus back upward through the upper esophageal sphincter and be aspirated.

The esophagus connects the pharynx and the stomach. Entry into the esophagus from the pharynx is limited by the tonic contracture of the upper esophageal sphincter. Retrograde entry into the esophagus from the stomach is similarly limited by the tonic contraction of the lower esophageal sphincter.

The musculature of the esophagus is a mixture of skeletal muscle and smooth muscle innervated by the enteric nervous system. The upper portions of the esophagus are predominantly skeletal muscle, the middle third of the esophagus a mixture of skeletal and smooth muscle, and the lower portion of the esophagus predominantly smooth muscle.

Movement of swallowed food through the esophagus occurs by peristalsis and is coordinated by the enteric nervous system. The stimulation of stretch receptors in the pharynx initiates the reflex. During swallowing reflex, contraction of the vocal cords and the neck muscles position the epiglottis to prevent food entry into the respiratory passages.

The swallowing reflex begins as a voluntary action in the mouth and continues as an involuntary reflex through the pharynx and the esophagus (Fig. 52-1). Esophageal peristalsis results from two muscular actions: a contraction of the muscle proximal to the bolus of food and a relaxation of the muscle distal to the bolus of food. As the wave of relaxation progresses down the esophagus, the bolus of food is moved down the esophagus by the wave of contraction proximal to the bolus.

FIGURE 52–1 Swallowing mechanism.