Figure 70-8. Lymphatic drainage of the anal canal.

Defecation involves both voluntary and involuntary mechanisms. If the call to defecate is answered,

either the sitting or squatting position is assumed, thereby helping to straighten the anorectal angle.

Straining by increasing the intra-abdominal pressure leads to a reflex relaxation of the puborectal

muscle which further opens the anorectal angle and shortens the anal canal. Both the internal and

external anal sphincters relax, the pelvic floor descends, and a funneling occurs, allowing the rectal

contents to be expelled. After completion of rectal evacuation, a “closing reflex” occurs, where transient

contraction of the external anal sphincter and puborectalis help to restore tonic contracture of the IAS

(Fig. 70-10).

Diagnostic Evaluation of the Anus

Accurate diagnosis of anorectal disorders requires a detailed history and physical examination, and may

include both anatomical and functional testing. Underlying illness or mediation use may present with

symptoms in the anal area, and it is important to know about travel history and sexual activity. The

most common presenting symptoms of anorectal disease are pain, bleeding, discharge, and change in

bowel habits.

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Figure 70-9. Sympathetic and parasympathetic nerve supply of the rectum.

Bleeding may be seen as the result of an anal condition, or may represent bleeding from a more

proximal source in the gastrointestinal system. Obtaining a history of the type and frequency of

bleeding may help in making the diagnosis. Bleeding that is bright red and is not mixed with the stool

may indicate an anal source, while blood in the form of clots or melena is more indicative of a colonic

source. Even in patients with rectal bleeding in whom an anal disorder is found, it is important to

consider colonoscopic evaluation of the colon to exclude other sources, particularly in patients who are

at increased risk for cancer.

Anal pain associated with swelling that may or may not be related to defecation may be indicative of

a thrombosed external hemorrhoid or an abscess. Pain that occurs during or immediately after

defecation is often secondary to an anal fissure. Episodic pain (unrelated to bowel movements) that lasts

for a short duration may be due to a condition known as proctalgia fugax or levator ani syndrome.

Physical examination of the anus should include a visual inspection of the perianal area as well as a

digital examination (Table 70-1). Patients can be examined in either the left lateral decubitus or prone

jack-knife position. Simple explanation and reassurance about the planned examination helps to ensure

cooperation of the patient and minimize discomfort. Inspection of the anus may demonstrate skin tags

or external hemorrhoids, fissures, scars, or excoriation of the skin. Straining during inspection may help

to demonstrate rectal prolapse or perineal descent. Digital examination with a well-lubricated gloved

index finger will give information including the tone of the anal sphincters as well identification of any

rectal masses.

More detailed evaluation of the anus includes anoscopy, rigid or flexible proctosigmoidoscopy, and

ultrasonography, as well as physiologic tests such as anal manometry, electromyography, pudendal

nerve assessment, and defecography. Use of these tests for specific conditions will be discussed later in

the chapter.

BENIGN ANORECTAL DISEASE

Hemorrhoids

Hemorrhoids are cushions of vascular tissue found in the anal canal found from birth. Histologically,

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this tissue contains vascular structures whose walls do not contain muscle, and are therefore considered

sinusoids instead of veins. The number and location of hemorrhoids may vary, however most commonly

there are three pillars located in the left lateral, right anterior, and right posterior quadrants.

The term “hemorrhoids” typically refers to clinical situations where these vascular cushions are

abnormal and cause symptoms. External hemorrhoids are defined by their location distal to the dentate

line and are covered with squamous epithelium. Although these may swell and make anal hygiene

difficult, they may also cause pain secondary to formation of clot within the sinusoid (thrombosed

external hemorrhoids). Internal hemorrhoids are located proximal to the dentate line and are covered

by transitional epithelium. As there are no somatic nerve endings here, internal hemorrhoids do not

cause pain, but may present with bleeding or downward displacement of the cushion during defecation

(referred to as prolapse). Hemorrhoids are classified according to the degree of prolapse (Table 70-2).

Figure 70-10. Mechanics of defecation.

Clinical Manifestations

1 Although patients may present with complaints of “hemorrhoids,” many of the symptoms of pain,

itching, burning, and swelling may not be related to hemorrhoidal disease, instead being due to anal

fissure, prolapsed anal papilla, or pruritus ani. The most common symptoms of internal hemorrhoids are

bleeding with bowel movements and prolapse of tissue with defecation. Patients will often describe

blood dripping into the bowl and staining the toilet water bright red. After passing a firm stool or a

forceful straining, bleeding may continue with bowel movements for several days and then resolve for a

variable length of time. It is rare that hemorrhoidal bleeding is severe enough to result in anemia.

Patients may also complain of a sensation of incomplete evacuation of the rectum, and in chronic cases

of prolapse may complain of mucous drainage or incontinence.

Physical examination should include inspection both at rest and during straining, digital rectal

examination, and anoscopy. Evaluation may be performed in either the left lateral or prone jack-knife

position. Inspection will help to exclude other pathology, including anal fissure, external opening of an

anal fistula, and perianal excoriation, as well as to evaluate for the presence of skin tags, external

hemorrhoids, and prolapse. Internal hemorrhoids are soft and cannot be reliable diagnosed with the

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examining finger, however digital rectal examination may help to rule out a low rectal or anal

neoplasm. If prolapse is present, it is possible to reduce the hemorrhoidal tissue during the examination.

Anoscopy provides definitive examination of the anal canal, however this should be avoided in patients

with anal pain due to fissure or abscess. While anoscopy may provide the diagnosis of hemorrhoids or

other intra-anal pathology, patients presenting with rectal bleeding should also undergo assessment of

the large intestine. In young patients, a flexible sigmoidoscopy may be sufficient, however in patients

over the age of 50, those with significant risk factors for polyps or malignancy, or patients with

inflammatory bowel disease, a colonoscopy should be performed.

Table 70-1 The Complete Digital Rectal Examination

CLASSIFICATION

Table 70-2 Hemorrhoids Classification

Treatment

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