Anorectal Disease

1

What aspect of the initial patient encounter is most important in the diagnosis of anorectal disease?

A careful history of anal complaints can point to the correct diagnosis even before completion of a physical exam. It is important to ask about the timeline of symptoms, characteristic of the discomfort, associated masses, bowel characteristics, sexual history, treatments attempted in the past, history of colonoscopy, and anal surgeries.

2

What is the most common cause of painless, bright red blood per rectum?

Internal hemorrhoids.

3

What are the proximal and distal anatomic landmarks of the anal canal? What is its average length?

Anatomists and surgeons differ on the definition of the anal canal. Anatomists consider the anal canal to be from the dentate line to the anal opening. Surgeons think bigger, and consider the anal canal to be from the anal opening to the anorectal ring, which is the most proximal portion of the external sphincter and puborectalis complex. The average length is about 3–4 cm.

4

What is the anatomic and surgical significance of the dentate line?

The dentate line is the location of the anal crypts that drain the intramuscular and intersphincteric anal glands, which are the site of anorectal abscesses and fistulas-in-ano. Above the dentate line, the anal canal receives visceral innervation (involuntary control and insensate), is covered by columnar epithelium, and is the origin of internal hemorrhoids. Below the dentate line, the anal canal receives somatic innervation (voluntary control and sensate), is lined with squamous epithelium, and is the location of external hemorrhoids.

5

What is the most common cause of anorectal abscess?

Ninety percent of anorectal abscesses result from infection of the anal glands that drain at the dentate line. This is often referred to as cryptoglandular disease .

6

What are the four potential anorectal spaces used to classify anorectal abscesses?

• a.

  Perianal (area of the anal verge)

• b.

  Ischiorectal (area lateral to the external sphincter muscles, extending from the levator ani muscles to the perineum)

• c.

  Intersphincteric (area between the internal and external sphincter muscles, continuous inferiorly with the perianal space and superiorly with the rectal wall)

• d.

  Supralevator (area superior to the levator ani muscles, inferior to the peritoneum, and lateral to the rectal wall)

7

Define fistula-in-ano

A fistula is an abnormal communication between any two epithelial lined surfaces. A fistula-in-ano is an abnormal communication between the anal canal and the skin of the perineum. The internal opening of the fistula-in-ano involves the anoderm, most commonly in the region of the dentate line, whereas the external orifice is located most commonly at the anal margin.

8

What is the incidence of fistula-in-ano after appropriate surgical incision and drainage of acute anorectal abscesses?

It is 50%.

9

What is the most important factor leading to the successful surgical eradication of anorectal abscesses and fistulae?

It is important to completely drain anorectal abscesses, thus knowledge of the perianal spaces is critical. In order to successfully treat fistula-in-ano, the course of the fistula and any of its side branches must be identified.

10

What is Goodsall’s rule?

Goodsall’s rule is used to predict the location of the internal opening of an anorectal fistula based on the position of the external opening. An opening posterior to a line drawn transversely across the perineum originates from an internal opening in the posterior midline. An external opening, anterior to this line, originates from the nearest anal crypt in a radial direction. While this is often referred to as a rule, it is not always correct; it is more reliable for fistulas in the posterior location compared with those that have an anterior external opening.