BACKGROUNDManometric pressure asymmetry of the anal sphincter exists in the anal canal. There are reports about the anatomy of the anal sphincter, but the relationship between the configuration and the pressure asymmetry of the anal sphincter is not clear. This study is to investigate the anatomic evidence and clinical application of anal sphincter pressure asymmetry.

METHODSPC polygram HR at the state of relaxing and squeezing was used in 27 normal children and 12 abnormal ones with fecal incontinence.

RESULTSIn normal children, longitudinal pressure gradients existed at eight channels in the anal canal, and the maximal pressure 1 cm from the anal verge. Longitudinal pressure asymmetry changes of eight channels also existed in the anal canal, from 3 cm to 2 cm to 1 cm from the anal verge. The high pressure distribution changed from the posterior to the anterior anal canal. Anteriorly, 1 cm from the anal verge, the maximal pressure was formed in the anal canal. However, neither longitudinal pressure gradients nor longitudinal pressure asymmetry changes were seen in patients with fecal incontinence.

CONCLUSIONThe configuration and function of the striated muscle complex possibly contribute to the formation of the pressure asymmetry of the anal sphincter, which is essential to anal control.