From the case:
Anal sphincter
{"current_user":null,"step_through_annotations":true,"access":{"can_edit":false,"can_download":true,"can_toggle_annotations":true,"can_feature":false,"can_examine_pipeline_reports":false,"can_pin":false},"extraPropsURL":"/studies/140604/annotated_viewer_json?lang=us"}
Internal anal sphincter is hypoechoic.
External anal sphincter is hyperechoic.
Levator ani muscle is hypoechoic.
Case Discussion
Annotated images of the anal sphincter by ultrasound.