Motility changes in primary achalasia following pneumatic dilatation. The changes in esophageal motility after pneumatic dilatation were evaluated prospectively in 51 patients with achalasia. The patients were evaluated for a median of 14 months. Pneumatic dilatation led to a clinical improvement in 41 patients. On manometric evaluation, a significant decrease in lower esophageal sphincter pressure was observed (28.4 +/- 14.9 mmHg vs. 13.5 +/- 7.2 mmHg; p = 0.001); the resting pressure of the esophageal body dropped from 4.8 +/- 4.2 mmHg above gastric baseline to 0.1 +/- 3.9 mmHg below gastric baseline. After therapy, peristaltic activity was present in 10/51 (20%) patients; in 1 case, complete relaxation of the lower esophageal sphincter was recorded. Treatment-induced motility changes could not be predicted by clinical history or the lower esophageal sphincter pressure before or after therapy. However, the resting pressure of the esophageal body before and after therapy was significantly lower in these patients in whom peristalsis recurred after therapy than in patients with an unchanged motility pattern. The reappearance of peristaltic activity after pneumatic dilatation was unrelated to lower esophageal sphincter pressure. In conclusion, motility disturbances of the esophageal body in patients with achalasia do not simply reflect the functional obstruction of the lower esophageal sphincter. These findings support the hypothesis that achalasia is not a distinct motility disturbance but should be regarded as part of a broad spectrum of different interrelated esophageal motility disorders. 