Management of Pruritus Ani

Introduction

Patients with pruritus ani experience symptoms of perianal itching, burning, or soreness. These symptoms may occur during the day or night, with higher intensity after bowel movements, and may even interfere with sleep. The prevalence may increase during the warm summer months with increased sweating and moisture. Pruritus ani afflicts 1% to 5% of the population, with men experiencing symptoms more often than women at a 4:1 ratio, possibly because men have a longer anal canal. The condition predominantly affects persons aged 20 to 40 years and is less common in elderly persons even though they have more frequent episodes of perianal soiling. Itching leads to scratching, which provides temporary relief. However, continued scratching damages the protective skin surface, causing further seepage, which in turn exacerbates the itching. In this manner a vicious cycle of itching and scratching can develop, and the scratching may lead to a secondary infection. Overuse of wipes, ointments, or other topical treatments that contain chemicals caustic to the skin may worsen the symptoms, and any ointment, although it provides temporary relief, ultimately prolongs symptoms because of its wetness.

Etiology

The causes of pruritus ani can be classified as primary (idiopathic) and secondary. Primary pruritus ani is most common, but secondary causes must be sought and ruled out before a diagnosis of primary pruritus ani can be made. Secondary causes (listed in Table 9-1 ) are dealt with initially because they are the easiest to treat once diagnosed. Diagnosis is determined on the basis of a thorough history and physical examination and a careful examination of the perianal skin.

TABLE 9-1

Secondary Causes of Pruritus Ani

	Cause	Mechanism
Anorectal conditions	Rectal prolapse Hemorrhoids Fistula-in-ano Anal fissure Skin tags, mucosal ectropion Villous adenoma Hidradenitis suppurativa	Seepage either of mucus or stool leading to inadequate cleanliness; prevention of the anus from closing effectively leads to seepage
Infectious	STD Viral: human papilloma virus, condyloma acuminatum, herpes II Bacterial: gonorrhea, syphilis Non-STD Bacterial: tuberculosis, Corynebacterium minutissimum (erythrasma) Fungal: Candida albicans and dermatophytes (e.g., Epidermophyton floccosum, Trichophyton mentagrophytes, and T. rubrum ) cause a characteristic unilateral ringworm appearance on the skin Parasites: pinworm ( Enterobius vermicularis ), pubic louse ( Pediculosis pubis ), and scabies ( Sarcoptes scabiei )	An underlying irritation or inability to maintain perianal hygiene
Alterations of fecal continence	Surgical: restorative proctocolectomy with ileoanal anastomosis; proctosigmoidectomy with coloanal anastomosis Trauma: anal sphincter damage; sexual practices causing chronic anal dilatation Medical: diseases that cause sphincter function loss or deterioration (neurologic: CVA, MS, and MND)	Increased exposure of perianal skin to fecal material as a result of a weakened sphincter and/or absent rectal vault
Primary skin disorders	Contact dermatitis Psoriasis Eczema, atopic dermatitis, and seborrheic dermatitis Lichen planus and lichen simplex Lichen sclerosus Leukoplakia Radiation dermatitis	Contact dermatitis due to allergens in soaps, detergents, bleaches, and even perfumes
Neoplastic	Extramammary Paget disease Bowen disease, anal intraepithelial neoplasia, perianal neoplasms
Drugs	Antidepressants (e.g., Prozac and Zoloft), ACE inhibitors (e.g., Captopril and Vasotec), antibiotics (e.g., ampicillin, amoxicillin, tetracycline, and cephalosporins), colchicine, digoxin, diuretics, laxatives, and many chemotherapeutic treatments	Diarrhea is the common denominator in most drugs related to pruritus ani
Systemic disorders	Diabetes mellitus Jaundice Uremia Leukemia, lymphoma	Diabetes mellitus causes pruritus as a result of internal sphincter weakening, decreased sensation, or fungal overgrowth

ACE, Angiotensin-converting enzyme; CVA, cerebrovascular accident; MND, motor neuron disease; MS, multiple sclerosis; STD, sexually transmitted disease.

Primary Causes of Pruritus Ani

After secondary causes have been ruled out, the remaining cases are the result of idiopathic or primary disease. Perianal skin contact with feces has been established as a cause of pruritus ani, and thus any fecal contamination of perianal skin may be related to the condition. Food may cause the stool to become excessively liquid and acidic. Types of food that may contribute to pruritus ani are listed in Box 9-1 . Each of these foods has an intake threshold above which susceptible patients will have pruritus ani and below which they will not have it. These thresholds vary among individuals.

BOX 9-1

Foods Possibly Causing Pruritus Ani

Coffee
Beer
Tea
Milk
Colas
Tomatoes
Chocolate
Citrus fruits, vitamin C
Hot spices and associated foods

Compulsive anal cleaning can lead to pruritus ani. Frequent wiping with continuous and excessive cleaning can damage the skin and sometimes leads to a secondary bacterial infection that perpetuates and intensifies the problem. In the absence of an identifiable underlying cause, these patients are often misdiagnosed and mistreated and have persistent symptoms.

Pathophysiology

Pathophysiologic research has helped us understand the underlying disorder. Eyres and Thompson noted that symptomatic patients had an exaggerated rectal anal inhibitory reflex with rectal distention, leading to subsequent soiling. Allan and coworkers compared symptomatic patients with control subjects, and in patients with pruritus, earlier leakage from the anal canal was noted when the rectum was filled with saline solution. Smith et al used anal manometry to demonstrate diminished sphincter tone after ingestion of coffee. Farouk et al made three important observations: first, an internal sphincter pressure decrease that was greater in pruritic subjects than in control subjects; second, a prolonged duration of internal sphincter relaxation after rectal distention; and third, symptoms of seepage that correlated with abnormal sphincter relaxation. All these observations describe an abnormality in internal sphincter function, either as a primary defect or after ingestion of coffee.

History

The investigation of pruritus ani is centered on possible causes. Obtaining a complete history is important in narrowing down the possible cause ( Box 9-2 ).

BOX 9-2

Pruritus Ani History

1.
Duration and timing of symptoms
2.
Obvious precipitating factors: exposure to other people with intense itching, pets, strange environments, chemicals, use of soaps, tissue paper, and even the type of underclothes worn
3.
Contact allergens are ruled out by addressing the aforementioned agents; in addition, investigate use of creams and ointments (including those prescribed to treat pruritus)
4.
Hygiene habits are noted
5.
Chronic diarrhea: primary or secondary
6.
Drug history: rule out a possible pharmaceutical cause, such as use of antibiotics
7.
Dermatologic conditions of a systemic nature
8.
Prior sexually transmitted disease diagnoses and treatment
9.
Systemic conditions that may be related, such as diabetes mellitus, biliary disease, and uremia
10.
Dietary habits, especially use of coffee, tea, colas, chocolate, beer, milk, tomatoes, citrus fruits, and vitamin C, even in amounts not expected to cause symptoms, such as in multivitamins; excessive fluid intake is also noted, along with food allergies, which may necessitate keeping a food and liquid intake diary
11.
Presence of soiling, seepage, or full fecal incontinence

Examination

Examination involves careful inspection of the perianal skin for the presence of any seepage or soiling. The appearance of the skin changes may be classified as follows, although it is of limited clinical significance:

Stage 0: Normal skin
Stage 1: Red and inflamed skin
Stage 2: White, lichenified skin
Stage 3: Coarse ridging of the skin with ulceration superimposed on lichenification

Distribution of the rash is important in that diet-induced pruritus ani is centered symmetrically around the anus, whereas an infection is located asymmetrically at the anal orifice. This asymmetric, infected rash may occur as a result of scratching during sleep and usually corresponds to the side of the patient’s dominant hand. The diagnosis of specific infections, including scabies and the dermatophytoses, is sometimes possible with a discerning eye. Upon further inspection one should note the presence of anal disease, including prolapsing hemorrhoids, an anal fissure or fistula, skin tags, rectal prolapse, or mucosal ectropion ( Box 9-3 ). Suspicion of any dermatologic condition mandates examination of the entire body. Anoscopy may reveal redundant internal hemorrhoids or possibly prolapsing rectal mucosa, both of which allow mucus to leak from the anus. In these cases, elastic band ligation may be beneficial.

BOX 9-3

Examination and Further Diagnostic Testing

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