55 ANORECTAL DISEASE
Eric L. Sarin M.D., John B. Moore M.D.

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

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Clinical history, including duration of complaints, exacerbating or alleviating issues, precipitating events, dietary and bowel habits, and current or previous treatments. This may not sound glamorous, but you will never encounter a more grateful patient than one whose rectal problem you have solved.

2. What is the most common cause of painless, bright red blood per rectum? Show answer
Internal hemorrhoids.

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

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The anal canal starts at the anorectal junction (which is the upper border of the internal sphincter muscle or puborectalis muscle) and ends at the anal verge. The average length is only 3-4 cm. The midpoint of the anal canal is called the dentate line.

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

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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), is covered by columnar epithelium, and is the origin of internal hemorrhoids. Below the dentate line, the anal canal receives somatic innervation (voluntary control), is lined with squamous epithelium, and is the location of external hemorrhoids.