Approach to the Patient with Anorectal Complaints
Paul C. Shellito
Anorectal complaints are common but often incompletely evaluated. The symptoms are usually the result of minor conditions such as hemorrhoids or anal fissures but can herald more important underlying pathology such as neoplasm, infection, or inflammatory bowel disease. Moreover, anorectal disease can lead to considerable discomfort and disability. As such, anorectal symptoms deserve attention and careful evaluation.
Anorectal Anatomy
An understanding of anorectal anatomy is important to proper assessment. The anal canal, the most distal portion of the gastrointestinal tract, is surrounded by sphincter musculature and extends 4 to 5 cm (a little longer in males than in females) from the anal verge inferiorly (the palpable and visible lower edge of the sphincter muscles) to the levators or pelvic floor superiorly. The anorectal ring corresponds to the palpable upper border of the sphincter muscles at the puborectalis. The anal verge corresponds to the lower border of the sphincters and the anal canal. The anal canal is bisected by the dentate line (the midpoint between the lower and upper borders of the anal canal), which serves as the demarcation between rectal mucosa superiorly and squamous epithelium inferiorly. Along the dentate line are small depressions or pockets called crypts. Some crypts have tiny vestigial glands at their base. Between the crypts are small protrusions called anal papillae.
Anoderm, the squamous epithelium between the dentate line and the anal verge, lines the lower half of the anal canal and appears similar to normal skin, except that it is thin and very sensitive and has no hair follicles or sweat glands. Skin caudal to or outside the anal verge is called perianal skin and is no different than skin elsewhere in the body. There are two distinct layers of sphincter muscle surrounding the anal canal. Internally, just under the mucosa or anoderm, lies the internal sphincter, which is a thickening of the normal circular smooth involuntary muscle of the intestine. Just outside the internal sphincter lies the external sphincter, which is striated voluntary muscle and is the most important structure for continence. Between the internal and external sphincter is the intersphincteric plane. Lateral to the external sphincter on each side is the subcutaneous fat of the ischiorectal fossa.
Hemorrhoids
Hemorrhoids are anal “cushions” or masses of connective tissue, arterioles, and venules within the submucosa under the low rectal mucosa, the anoderm, or perianal skin. Small anal cushions within the anal canal are normal structures and may assist with continence. These may enlarge with time, perhaps exacerbated by chronic straining or pregnancy, often becoming symptomatic and labeled as hemorrhoids. They are not varicose veins and have no relation to portal hypertension. Internal hemorrhoids lie above the dentate line and are covered with rectal mucosa. External hemorrhoids lie below the dentate line and are covered by squamous epithelium.
Internal hemorrhoids, if they cause symptoms, primarily cause intermittent bleeding and occasionally mucous discharge. The bleeding is typically fresh or bright red blood with bowel movements; blood may drip into the toilet or appear on the toilet paper afterward. If large and prolapsing, they may also cause a bothersome clear or brown mucous discharge. External hemorrhoids, if they cause symptoms, produce bothersome swellings and sometimes difficulties with anal hygiene. Many patients have both internal and external hemorrhoids.
Sometimes, the blood vessels in a small external hemorrhoid undergo thrombosis, often after a period of transient constipation or diarrhea, causing sudden appearance of a small painful firm mass at the anal verge. The original underlying hemorrhoid may have been so small that the patient never previously noticed it. The skin or anoderm over the apex of a thrombosed external hemorrhoid may ulcerate a bit, leading to a constant slight bloody discharge (not necessarily associated with bowel movements).
Anal Fissure
Anal fissures are small longitudinal tears, splits, or ulcerations in the anoderm (between the dentate line and the anal verge), often associated with chronic constipation and resulting in gradual narrowing of the anal canal and a tight internal sphincter. The split in the anoderm often first appears after a period of transient constipation (or diarrhea). Less often, the fissure is triggered by an unrelated painful anal condition (such as an abscess, childbirth, or anal surgery), which causes initial internal anal sphincter spasm. Fissures are most commonly located in the posterior midline, but they may also lie in the anterior midline, especially in females. The most prominent symptom is sharp and severe anal pain with bowel movements, sometimes lasting for hours afterward. Slight fresh bleeding with bowel movements may accompany the pain. Patients sometimes present with a prolapsing hypertrophic anal papillae without an active fissure (i.e., no pain).
Anal Abscess
Perianal or perirectal abscesses originate within the crypt glands of the dentate line. As the abscess enlarges, it extends laterally and inferiorly toward the perianal skin. The patient notices an acute painful swelling. On exam, there is usually a red tender fluctuant mass, typical for an abscess. With deeper abscesses, however (within the ischiorectal space), there may be only vague induration and tenderness and perhaps fever. Frequently, the abscess eventually breaks through the perianal skin spontaneously and drains pus and blood.
Anal Fistula
Anal fistulas originate as anal abscesses. After abscess drainage, the path that the evolving infection created between the anal canal (at the dentate line) and the perianal skin usually persists as an anal fistula. Typically, it causes only intermittent bloody or purulent drainage and intermittent mild pain. The patient may also notice a nodule of scar and granulation tissue at the external fistula orifice on the perianal skin. Sometimes after abscess
drainage, the perianal skin temporarily heals, and the discharge ceases, but there are subsequent periodic cycles of intermittent swelling, pain, and discharge when the underlying fistula erupts again.
drainage, the perianal skin temporarily heals, and the discharge ceases, but there are subsequent periodic cycles of intermittent swelling, pain, and discharge when the underlying fistula erupts again.
Pilonidal Sinus
This condition affects the skin over the coccyx or lower sacrum, in the cleft between the buttocks. It is not related to the anal canal. It is most common in patients in their teens and 20s and in hirsute patients. Hair follicles or skin pores in this region gradually enlarge, perhaps due to pressure from sitting, leading to a small chronic sinus. Body hairs work their way into the sinus over time (from the outside inward), which in turn causes formation of a larger chronic infected cavity (pilonidal cyst). The pilonidal sinus most often extends superiorly from its point of origin and to slightly one side of the midline. At this point, it may appear as a frank abscess, requiring incision and drainage. Often, this secondary site breaks open and drains spontaneously. The enlarged and chronically infected cavity then persists as a slightly swollen and sore area, which intermittently drains pus or bloody fluid through one or more small openings.
Rectal Cancer
The most common symptom of rectal cancer (adenocarcinoma) is bleeding with bowel movements. As the cancer enlarges, it can also cause tenesmus and frequent small bowel movements due to stimulation of evacuation by the neoplastic mass within the rectum; sometimes, there is only passage of mucus. The patient may report “diarrhea,” because of frequent trips to the bathroom, or “constipation,” because of tenesmus and inability to have a single large stool. Rectal cancer can sometimes be diagnosed when digital rectal exam reveals a firm mass (the examiner should be sure to palpate as high as possible in the rectum and to consciously palpate each quadrant of the rectum). Rarely, a low rectal adenocarcinoma can invade the anal canal below the dentate line and, therefore, cause pain. Most rectal cancers, however, are diagnosed by sigmoidoscopy or colonoscopy.
Condylomata Acuminatum (Anal Warts)
Condylomata acuminatum are caused by human papillomavirus (HPV). HPV infects the skin and mucous membranes of the anal and genital area. Fleshy exophytic or sessile verrucous growths of variable size ensue, which may be gray, pink, or skin colored. Size ranges from less than 1 mm in diameter to several centimeters and may be nearly flat or quite exophytic. Only a few may be present, or they may be innumerable. Locations include the perianal skin, anal canal (but only at or below the level of the dentate line), penis, vulva, vagina, cervix, and, occasionally, the groins. Most cause no symptoms other than bothersome growths, although they may cause considerable psychological distress. Anogenital HPV is strongly associated with anal intraepithelial neoplasia (AIN) and squamous cell carcinoma (SCC) of the anus (see below), which may coexist with condyloma acuminatum. HPV transmission is usually by genital contact with infected individuals (who may be asymptomatic). Condyloma acuminatum is the most common sexually transmitted disease, and its incidence is increasing. Anal warts may be acquired without anoreceptive intercourse. Digital contact or fomites might also spread HPV. Risk factors include a higher number of sexual partners, the presence of other sexually transmitted diseases, human immunodeficiency virus infection, and immunosuppression.
Anal Cancer and Anal Intraepithelial Neoplasia
AIN is probably the precursor to invasive anal SCC. Numerous other terms have been used to refer to AIN, which can be a source of confusion: carcinoma in situ, anal dysplasia, anal squamous intraepithelial lesion, and Bowen disease. These terms all refer to dysplasia in the squamous epithelium of the anus, which has a spectrum of severity from low-grade dysplasia to invasive cancer.
As noted, HPV infection strongly correlates with AIN and is the purported causative agent. AIN can affect the perianal skin and anal canal, causing macroscopic lesions such as warts, tumors, ulcers, or eczematous plaques. Alternatively, there may be only microscopic changes in grossly normal-appearing epithelium, and the patient may be asymptomatic. It tends to be multifocal. Although most cases of SCC are probably preceded by AIN, only a small fraction of patients with AIN progress to cancer (for high-grade AIN, the risk of invasive carcinoma is on the order of 5% to 10% in immunocompetent patients). The risk factors for AIN are men who have sex with men, anoreceptive intercourse, other sexually transmitted diseases, cervical dysplasia or cancer, smoking, immunosuppression (such as transplant patients), and HIV infection.
The symptoms of anal SCC are usually a noticeable mass, anal pain, and rectal bleeding. Inspection usually shows a mass at or near the anal verge. But, occasionally, the lesion may lie within the anal canal, such that it is only palpable on digital rectal exam and visible only on anoscopy or sigmoidoscopy.
Proctalgia Fugax
This condition may be due to pelvic muscle spasm. It typically causes intermittent rectal pain, which often awakens the patient at night. Sometimes, there is levator muscle tenderness on digital rectal exam. More broadly, this term encompasses all patients with idiopathic rectal pain who have an unremarkable anorectal exam.
Proctitis
Inflammation of the rectum, or proctitis, can be caused by a host of conditions. Ulcerative colitis and Crohn disease are important etiologies; abdominal or systemic symptoms may be absent if the inflammatory bowel disease is limited to the rectum. Transient proctitis may occur with pelvic radiation therapy given for cervical or prostate cancer. Another cause, gonococcal infection, is most prevalent in men who have sex with men. Amebic infection, Chlamydia, Campylobacter, and herpes simplex are other sexually transmitted causes. Typically, proctitis produces urgency, sometimes diarrhea, rectal bleeding, and mucopurulent discharge. The most important physical findings are on sigmoidoscopy, which shows diffuse mucosal erythema, edema, friability, and sometimes ulcerations.
Rectal Prolapse
This idiopathic condition is an intussusception of the rectum, which begins about 8 cm above the anal verge. It is more common in women, although it does not correlate with parity. It is sometimes associated with chronic constipation and straining and frequently associated with weak sphincter muscles and fecal incontinence, although it is unknown whether this muscle weakness is primary or secondary. It may produce only a small transient protruding anal mass at the time of bowel
movements (which then spontaneously reduces) or present as a nearly constant pink moist mass that the patient must repeatedly manually reduce. A bloody mucous discharge and occasionally some minor pain may ensue as may fecal incontinence.
movements (which then spontaneously reduces) or present as a nearly constant pink moist mass that the patient must repeatedly manually reduce. A bloody mucous discharge and occasionally some minor pain may ensue as may fecal incontinence.
Pruritus Ani
Anal irritation and itching are common, bothersome symptoms. In most instances, there is no identified underlying disorder (hemorrhoids are usually not responsible). The problem derives from the anus being both a sensitive and soiled area. The accumulation of moisture (perhaps from mucus or perspiration) and the normal rubbing together of the buttocks during walking or exercise combine to produce irritation and/or itching. Scratching the area, especially over a prolonged period, adds to the irritation and makes the problem worse. Chronic itching and scratching can lead to thickening, lichenification, edema, fissuring, and excoriation of the perianal skin.
In a minority of instances, pruritus ani is a consequence of pinworm infestation, fungal infection, or a specific dermatosis such as psoriasis. Pinworm infestation (Enterobius vermicularis) most commonly affects children aged 5 to 10 years and can spread to other household members. Typically, there is nocturnal anal itching, caused by the outward migration of the female pinworm each night to deposit eggs on the perianal skin.
Fecal Impaction
Fecal impaction most often affects elderly, frail, or bedridden patients. Chronic incomplete evacuation leads to the formation of an obstructing bolus of desiccated hard stool in the rectum. This causes constipation, urgency, and rectal discomfort; rectal pain may be the chief complaint. It may also cause paradoxical diarrhea and perhaps incontinence, caused by liquid stool collecting in the proximal colon and overflowing around the obstructing bolus.
Fecal Incontinence
There are multiple possible etiologies for fecal incontinence. A weak anal sphincter is most often responsible, which may in turn be due to traumatic childbirth, previous rectal surgery, or impalement injury. Alternatively, a weak anal sphincter may arise from neurologic problems or simply aging. Sometimes, a subclinical sphincter injury early in life may be asymptomatic until the patient reaches old age, when the effect of aging combines to produce incontinence. Loss of rectal compliance from rectal surgery or radiation can also promote incontinence. Chronic diarrhea may contribute to incontinence, since it is more difficult to control liquid stool than solid stool.
The most common causes of anal pain are an anal fissure, anal abscess, and acutely thrombosed external hemorrhoid. In general, hemorrhoids do not cause pain, unless they are acutely thrombosed and almost never an explanation for chronic anal pain. Rarely, pain can be from anal cancer, a foreign body (including fecal impaction), or herpes virus infection. Anorectal bleeding most often arises from hemorrhoids, an anal fissure, or less commonly anal or rectal cancer or proctitis. The source may also be more proximal from a colonic source (see Chapter 63).
TABLE 66-1 Important Causes of Anorectal Complaints | ||||||||||||||||||
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