Sonography of the anal canal, anorectal junction and distal rectal wall was performed in 20 normal patients and in 3 resected specimens of human anorectal segment. Sonographic images were compared with histologic specimen section. Sonography of
the
anal
canal revealed hypoechoic interanl sphincter and broader continued to the muscularis propria of the rectal wall. Sonographically the rectal wall was composed of inner hyperechoic layer, inner hypoechoic layer, middle hyperechoic layer, outer
hypoechoic
layer, and outer hyperechoic layer. Sonographic examination of the resected specimen showed 7 layers of the rectal wall components : the muscle layer was divided by inner circular, intermuscular plane and outer longitudinal muscle layers and
these
muscular layers continued as internal sphincter and intersphincteric plane respectively.
In conclusion, longitudinal endosonography provides a precise anatomic detail in anorectal wall including internal and external sphincters.
Index terms : Rectum, anus normal anatomy 757.1 Rectum, anus, US studies 757.12989 Gastrointestinal tract, US studies 70.12989
Journal of Korean Society of Medical Ultrasound 1992 ; 11 : 36~42
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