Background: The normal esophagus has not been manometrically mapped. The transition zone between esophageal smooth and skeletal muscles has also not been defined manometrically.
Aims: To manometrically map the normal esophagus and to define the transition zone.
Methods: Thirty normal adults [23 men; mean age 34.8 (10.4) years] underwent manometry using a water-perfused system. The lower esophageal sphincter (LES) was studied by station pull-through, and esophageal body musculature was evaluated at 1-cm intervals with five wet swallows at each level. The transition zone was identified as an area where the wave-forms did not resemble typical skeletal or smooth muscle wave-forms.
Results: The basal mid-expiratory LES pressure was 18.7 (7.2) mmHg, and its length was 3.6 (1.2) cm. Based on our findings, we defined the transition zone as an area where either the amplitude of contraction was < 40 mmHg or, if the amplitude was 40-50 mmHg, the rate of change of pressure from baseline to peak of the wave was < 50 mmHg/s. The lengths of the skeletal, transition and smooth muscle zones were 2.8 (1.2), 4.0 (1.7) and 12.5 (2.7) cm, respectively. The amplitude and dp/dt of contraction and transmission velocity were lowest in the transition zone (p < 0.05).
Conclusions: We have manometrically mapped the normal esophageal muscle zones; the parameters obtained may be used as reference values. The manometric criteria for the transition zone have also been defined.