The anal canal has a cylindrical double-layered shape. The anorectal ring is easily identified on digital examination and on image studies such as transrectal ultrasound or rectal magnetic resonance imaging (MRI). The internal anal sphincter (IAS), external anal sphincter and puborectalis muscle constitute the surgical anal canal. The length of the surgical anal canal is 4.4 cm in men compared with 4.0 cm in women. The anorectal ring consists of the external anal sphincter and the puborectalis muscles and is a good landmark for locating the tumor or the level of the colorectal anastomosis. The anorectal ring is usually palpable as a tight ring-like structure, and when patients are asked to squeeze the anal sphincter, it moves anteriorly. On the other hand, the surgical anal canal is defined as the area between the anorectal ring and the anal verge. The anatomic anal canal is defined as beginning at the dentate line and ending at the anal verge. We will also describe the important structures and surgical strategies from the surgeon’s point of view. For those reason, we will discuss in this paper the basic anatomy of the anorectum and the latest knowledge on that subject.
Also, familiarity with the techniques used to treat patients with benign anorectal diseases, such as the hemorrhoidectomy or the fistulectomy, will be useful to surgeons performing coloanal or intersphincteric procedures for the surgical treatment of patients with distal rectal cancer.
#ESSENTIAL ANATOMY 3 VS 5 FULL#
Especially in rectal cancer surgery, an approach to the anus, such as the transanal total mesorectal excision, is attempted at a location different from that used in the conventional transabdominal approach, so a full understanding of the anatomy around the anus is now needed.
Both minor and major surgical procedures have real impacts on the quality of life of patients.īecause surgical techniques are based on an understanding of anatomy, accurate anatomical knowledge of the anorectum helps the surgeon to perform safe, high-quality surgery on patients with rectal diseases ranging from benign to malignant. As far as the field of anorectal surgery is concerned, not only the short-term outcome but also the long-term functional outcome is a very important issue, probably due to the complexity of the anorectal anatomy. Surgical procedures for both benign and malignant disease of the anorectum are known to be technically demanding procedures. However, because the anorectal anatomy is not yet fully understood, we hope that additional studies of anatomy will enable anorectal surgery to be performed based on complete anatomical knowledge. With the development of pelvic structure anatomy, we can understand better how we can remove the tumor and the surrounding metastatic lymph nodes without damaging the neural structure. Because the autonomic nerves also pass between the mesorectal fascia and the parietal fascia, a sharp pelvic dissection must be made along the anatomic fascial plane. The mesorectal fascia is a multi-layered membrane that surrounds the mesorectum. Preserving the rectourethralis muscle without damage to the carvernous nerve or veins passing through it when the abdominoperineal resection is implemented is important. The conjoined longitudinal muscle consists of smooth muscle from the longitudinal muscle of the rectum and the striate muscle from the levator ani and helps maintain continence the rectourethralis muscle is connected directly to the conjoined longitudinal muscle at the top of the external anal sphincter.
The anorectum is a region with a very complex structure, and surgery for benign or malignant disease of the anorectum is impossible without accurate anatomical knowledge.
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