Data from Rex DK, Johnson DA, Anderson JC, Schoenfeld PS, Burke CA, Inadomi JM: American College of Gastroenterology Guidelines for Colorectal Cancer Screening 2008, Am J Gastroenterol 104:739, 2009.

The anatomy of the anorectal area is important in describing the occurrence of various disorders. The anus is the most distal portion of the gastrointestinal tract and is approximately 4 cm long. Its distal end is lined by stratified squamous epithelium, while the proximal component is lined by simple columnar epithelium. The two components are divided by the dentate line—the line where the distal end and the columns and crypts of Morgagni meet. The dentate line is also known as the anorectal junction, which also denotes the boundary between the somatic (sensory) and the visceral nerve supply. Above (proximal to) the dentate line, the rectum is supplied by stretch nerve fibers but not pain nerve fibers. Below the dentate line, the area is extremely sensitive. The columns of Morgagni are longitudinal columns of mucosa located in the proximal anus; they fuse in a ring distally to form the anal papillae at the level of the dentate line. The crypts are the invaginations of the columns of Morgagni. From four to eight anal glands drain into the crypts of Morgagni at the level of the dentate line. Most rectal abscesses and fistulas originate in these glands. Figure 26-1 shows the anatomy of the anus and rectum.

FIGURE 26-1 Anatomy of the anus and rectum.

(From Seidel HM, Ball JW, Dains JE, Flynn J, Solomon B, Stewart R: Mosby’s guide to physical examination, ed 7, St Louis, 2011, Elsevier.)

Diagnostic reasoning: focused history

Might this condition require immediate hospitalization or referral?

What do the presenting symptoms tell me?

Key questions

Have you had any bleeding? How much bleeding has there been? When does it bleed? Describe the color of the blood.

If a child: How old is this patient?

Have you had pain? When does it occur? Can you describe the pain?

Specifically, do you have pain on defecation? If a child: Does the child cry on defecation?

Have you had itching? When does it itch?

Can you feel a lump?

Have you had any stains on your underwear? Can you describe the stains (e.g., blood, stool, pus)?

Have you had diarrhea?

Have you been constipated?

Bleeding

A patient presenting with significant passage of clots, dark blood, and loose bloody stool needs an evaluation to rule out gastrointestinal (GI) bleeding. Blood that is black and tarry and has an aroma is from the upper GI tract and is called melena. Melena stool should be differentiated in patients who have dark stool. Stool with melena will test positive for blood. When blood is bright red, the source is usually in the more distal GI tract or the rectum. Melena is seen in children with Meckel diverticulum. Bleeding from the rectum is a red flag for colorectal cancer.

Anorectal bleeding usually comes from internal hemorrhoidal veins or from a tear in the anal canal. Excoriations of the perianal skin can also cause bleeding, as can eroded skin overlying a thrombosed external hemorrhoid. Bleeding associated with defecation is characteristic of hemorrhoids and fissures. Bleeding from hemorrhoids typically occurs after defecation and is noted on the toilet paper (“wipe hematochezia”) or coating the stool. The blood is bright red and may vary from a few spots on the toilet paper to a thin stream or coating on the stool. Bleeding with fissures occurs with defecation and is accompanied by pain. Spontaneous rectal bleeding can occur with proctitis. Condyloma acuminata may grow to a size sufficient to occlude the rectal opening and will bleed on defecation. Significant pathological conditions such as carcinomas and polyps can bleed intermittently.

Some foods, such as fruit juices and drinks, food coloring, and beets, affect the stool, making the stool appear reddish. Such foods as spinach, blueberries, and grape juice may cause the stool to be dark. Iron supplementation also may affect the color of the stool, making it appear dark.

A loose stool that has blood that is bright red and mixed with mucus may indicate chronic ulcerative colitis. Currant jelly–like coloring of the stool in young children often is a sign of intussusception, which is potentially life threatening.

Age of the child with bleeding

Premature infants.

All premature infants with lower GI bleeding must be referred and evaluated for NEC.

Newborns.

The most common cause of blood in the stool is from swallowing maternal blood during delivery. Newborns who have not received vitamin K and have a prolonged prothrombin time may have hemorrhagic disease of the newborn.

Neonatal stress can cause gastritis and gastroduodenal ulceration. Another cause of neonatal rectal bleeding is gastroduodenal ulceration from sepsis.

Infants younger than 6 months.

Nonspecific colitis or allergic colitis due to milk allergy can cause blood-streaked stool. Bleeding can also have a bacterial etiology (see Chapter 11).

Age 6 months to 5 years.

Intussusception is seen in children less than 1 year old and may cause currant jelly stool (see Chapter 2). Meckel diverticulum that ulcerates because of acid secretion onto the gastric mucosa can cause painless, sometimes significant, bleeding resulting in black or maroon stool. Henoch-Schönlein purpura may first manifest as lower GI bleeding (see Chapter 11).

Juvenile colonic polyps are seen in children ages 2 to 5 years. These are benign hamartomatous lesions. Bleeding occurs with defecation because of the sloughing of the polyps.

Anal tears resulting from constipation and stool holding can cause bleeding as well as pain. Blood may be visible on the stool or in the underwear (see Chapter 9).