Relationship between anal canal diameter and pressure evaluated simultaneously by endosonography and manometry in...

The study investigated the relationship between anal canal size and anal canal pressure measured simultaneously by anal endosonography and an electronic pressure probe. Twelve normal subjects were studied. Anal endosonography was performed using a 7.5-Mhz rotating transducer of 2-5 cm focal length covered with a sylastic balloon filled with degassed water (25 ml). During anal endosonography an electronic manometric probe was passed along the side of the probe and positioned in the anal canal. The ultrasonic image was frozen when maximal anal pressure was seen at basal, squeeze, and minimal pressure during straining. An image was also obtained at maximal anal relaxation after rectal distension with a balloon filled with 150 ml air. The results showed that anal canal pressure was significantly and linearly correlated with anal canal diameter (P < 0.001).