anal canal anatomy

Endoanal and Endorectal scanning

Endorectal/anal ultrasound scanning is an essential component of the service provided by a Specialist Colorectal unit.

This technique scans the anal canal and rectum detecting and staging cancers of both, using a rotating head scanner, which provides a 360-degree view of the entire anal canal and rectal wall and the adjacent structures. The scanning is performed by colorectal surgeon. has prepared for you information about the two methods for this type of scanning.

Benefits to Patients with Anal and Rectal pathologies:
a) Drastic reduction in waiting time – Patients with Rectal cancers need their tumour to be staged to plan appropriate treatment. Experience in Colorectal units would suggest that Endorectal ultrasound scanning of the rectum is the most accurate of current modalities of investigation and can be undertaken much more quickly than alternative methods of staging investigation. In the East Kent NHS Trust, the accuracy of ERUS is 82% for low rectal cancers as apposed to MRI which is 64%. Two thirds of rectal cancers are below the peritoneal reflection and well within reach of endo-rectal scanner. Many of these would then undergo curative resection of their rectal cancer. In the Pelvic floor clinic, one would expect these patients to have a USS of the liver in the same sitting. This would shorten the staging time significantly.
anal canal anatomy
b) Delineation of anatomy of anal sphincter damage and complex fistulae:
At the moment there are a number of patients with sphincter damage or with
complex fistulae. In the past, these patients have necessarily been referred to
St.Marks, London for evaluation, leading to inevitable delay in treatment.
Provision of local Endoanal ultrasound represents a cost-effective approach to
Patients with damaged sphincters and functional disorders of the anorectum. Here is a picture of an endoanal USS which shows the damaged anal external and internal sphincter. The dark line is the internal spincter and the white line is the external sphincter.