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Approach to the patient with anal pruritus

Approach to the patient with anal pruritus
Literature review current through: Jan 2024.
This topic last updated: Mar 20, 2023.

INTRODUCTION — Itching of the anus or perianal skin is a common disorder usually arising from benign conditions. It may be transient or chronic and difficult to treat. This topic will review the etiology, diagnostic approach, and management of patients with anal pruritus.

EPIDEMIOLOGY — Anal pruritus is estimated to affect 1 to 5 percent of the general population [1]. However, most of these patients probably do not come to medical attention. Anal pruritus is more common in the fourth to sixth decades of life and has a higher prevalence in males [2].

ETIOLOGY — Approximately 75 percent of cases of anal pruritus are secondary to inflammatory, infectious, systemic, neoplastic, and anorectal disorders that contribute to or underlie the development of pruritus [2,3]. Idiopathic anal pruritus likely results from perianal fecal contamination and resultant trauma from wiping and scratching.

Anorectal diseases — Anorectal diseases associated with anal pruritus include prolapsed internal hemorrhoids, abscesses, fissures, and fistulas (picture 1 and picture 2 and picture 3) [2]. Skin tags do not contribute significantly to anal pruritus [4]. (See "Hemorrhoids: Clinical manifestations and diagnosis", section on 'Clinical manifestations' and "Perianal and perirectal abscess" and "Anal fissure: Clinical manifestations, diagnosis, prevention" and "Anorectal fistula: Clinical manifestations and diagnosis", section on 'Clinical features'.)

Dermatologic diseases — Anal pruritus can also result from a variety of inflammatory skin disorders [5].

Inverse psoriasis can involve the intertriginous areas, including the inguinal, perineal, genital, intergluteal, axillary, and inframammary regions, but unlike most cases of psoriasis, there is no visible scaling (picture 4). There tends to be a cyclical quality to the symptoms, with the majority of pruritus occurring at night.

Contact dermatitis is characterized by macular erythema, hyperkeratosis, or fissuring (picture 5 and picture 6). Irritant contact dermatitis results from exposure to substances that cause physical, mechanical, or chemical irritation of the skin. Irritant contact dermatitis can be caused by common exposures used repeatedly on a daily basis (eg, soapy water, cleansers, rubbing alcohol) and, in some cases, with one exposure (eg, bleach). Individuals with compromised skin (atopic dermatitis, dry skin) and with light-colored or "fair" skin are at a higher risk. (See "Irritant contact dermatitis in adults", section on 'Diagnosis'.)

Atopic dermatitis is characterized by thickened skin, increased skin markings (lichenification), and excoriated and fibrotic papules (picture 7). Most patients have manifestations of atopic dermatitis by five to seven years of age. In adults, the flexural areas (neck, antecubital fossae, and popliteal fossae) are most commonly involved and only in rare cases are lesions seen in the gluteal area. Pruritus, chronic and recurring dermatitis, a positive family history of allergic disease, and an early age of onset of symptoms suggest the diagnosis. (See "Atopic dermatitis (eczema): Pathogenesis, clinical manifestations, and diagnosis", section on 'Clinical manifestations'.)

Hidradenitis suppurativa (HS) is a debilitating, chronic, suppurative process involving the skin and subcutaneous tissue. The usual initial presentation of HS is of recurrent, painful, and inflamed nodules (picture 8). The nodules may rupture, discharging purulent, sometimes malodorous material. Persistent disease leads to the formation of sinus tracts, end-stage "tombstone" comedones, and scarring. (See "Hidradenitis suppurativa: Pathogenesis, clinical features, and diagnosis", section on 'Clinical manifestations'.)

Cutaneous squamous cell carcinoma in situ (Bowen’s disease) appears as a well-demarcated plaque with crusting and scaling. Perianal intraepithelial adenocarcinoma (Paget disease) usually occurs in the seventh decade of life and appears as a slowly expanding, sharply demarcated erythematous plaque that can be eczematous, crusting, scaling, or ulcerated. (See "Cutaneous squamous cell carcinoma (cSCC): Clinical features and diagnosis", section on 'Cutaneous squamous cell carcinoma in situ (Bowen's disease)'.)

Other skin disorders that may be associated with anal pruritus include scleroderma, erythema multiforme, dermatitis herpetiformis, lichen planus, radiation dermatitis, and Darier disease. (See "Erythema multiforme: Pathogenesis, clinical features, and diagnosis", section on 'Clinical manifestations' and "Lichen planus", section on 'Clinical features' and "Darier disease", section on 'Clinical features' and "Radiation dermatitis".)

Infections — Sexually transmitted diseases (eg, condyloma (picture 9), herpes, syphilis, gonorrhea) and Candida can cause anal pruritus in patients with risk factors. Parasitic infection with Enterobius vermicularis (pinworm) is associated with characteristic nocturnal anal pruritus and is more common in children as compared with adults. Anal pruritus has also been reported with Dientamoeba fragilis [6]. Perianal streptococcal dermatitis can cause anal pruritus in children and adults [7,8]. Erythrasma, an infection with Corynebacterium minutissimum, is more common in older adults and patients who are diabetic or immunocompromised. Other risk factors include obesity, hyperhidrosis, and living in tropical climates. Lesions are typically red-brown, sharply demarcated macules or patches that most commonly involve the pedal interdigital areas, followed by the groin and axilla. (See "Enterobiasis (pinworm) and trichuriasis (whipworm)", section on 'Clinical manifestations' and "Erythrasma", section on 'Clinical presentation' and "Clinical manifestations and diagnosis of Neisseria gonorrhoeae infection in adults and adolescents", section on 'Proctitis' and "Condylomata acuminata (anogenital warts) in adults: Epidemiology, pathogenesis, clinical features, and diagnosis", section on 'Clinical manifestations' and "Syphilis: Epidemiology, pathophysiology, and clinical manifestations in patients without HIV", section on 'Clinical manifestations' and "Intertrigo".)

Systemic diseases — Anal pruritus has been associated with diabetes, cholestasis, lymphoma, leukemia, pellagra, renal failure, thyrotoxicosis, hypothyroidism, human immunodeficiency virus (HIV) disease, and deficiencies in vitamin A, D, and iron. However, patients with systemic diseases usually have generalized pruritus. (See "Pruritus: Etiology and patient evaluation" and "Pruritus: Etiology and patient evaluation", section on 'Systemic disorders'.)

Dietary factors and medications — Specific foods (eg, coffee, tomatoes, beer, cola, tea, peanuts, milk produce, citrus, chocolate, grapes) and medications (eg, tetracycline, colchicine, quinidine, peppermint oil, local anesthetics, and neomycin) have been associated with anal pruritus. It is unclear if these medications and foods act as direct irritants or indirectly cause irritation by causing diarrhea or fecal seepage.

Fecal soilage — Idiopathic anal pruritus likely results from perianal fecal contamination and resultant trauma from wiping and scratching. Fecal soilage in patients with anal pruritus may be due to diarrhea or seepage due to an abnormality of the rectoanal inhibitory reflex and a lower threshold for internal anal sphincter relaxation, or transient internal anal sphincter relaxation [9]. In a case-control study that included 23 men with anal pruritus and 16 controls who underwent anorectal electromyography and manometry, patients with anal pruritus had a greater rise in rectal pressure during internal sphincter relaxation (29 versus 18 mmHg), a greater fall in anal pressure (39 versus 29 mmHg), and a longer duration of internal sphincter relaxation (29 versus 8 seconds) as compared with controls. Abnormal internal sphincter relaxation was associated with the development of anal pruritus within one hour in 17 (74 percent) patients.

DIAGNOSTIC APPROACH — The clinical assessment of a patient with anal pruritus begins with a history, physical examination, and anoscopy. The decision to perform laboratory testing and endoscopic evaluation should be guided by the clinical assessment and/or response to initial therapy. The evaluation of patients with generalized pruritus is discussed in detail, separately. (See "Pruritus: Etiology and patient evaluation", section on 'Evaluation'.)

History — A history should include the following:

Duration of anal pruritus and the presence of generalized pruritus

Association of pruritus with bowel movements

Fecal seepage, diarrhea, constipation, or a change in bowel habits

Systemic symptoms including fever, night sweats, fatigue, change in appetite or weight, heat/cold intolerance, decrease in urine output, change in the color of stool or urine, jaundice

A history of diabetes, dermatological, gastrointestinal, renal, or sexually transmitted diseases, radiation, and food allergies

Changes in diet to include foods associated with anal pruritus

Use of topical or systemic medications

Anal hygiene practices including the use of soaps, detergents, perfumes, and the frequency of cleansing

Use of tight-fitting undergarments

Physical examination — A physical examination including a digital examination of the anorectum should be performed to identify anorectal and dermatological diseases that are associated with anal pruritus (picture 10). In patients with an anorectal fistula, the external opening may be visualized or palpated as induration just below the skin if the external opening is incomplete or blind. The external opening may be inflamed, tender, and/or draining purulent fluid, and the perianal skin may be excoriated and inflamed. (See "Anorectal fistula: Clinical manifestations and diagnosis", section on 'Physical examination'.)

Perianal plaques with a distinct boundary are suggestive of psoriasis, erythrasma, or neoplasia. Perianal erythema may be seen in patients with chronic steroid use and candidiasis. Hyperpigmentation of the skin may result from chronic inflammation due to an infection or chronic discharge. The presence of palpable inguinal lymph nodes is suggestive of a neoplasia or sexually transmitted disease. A biopsy of the skin should be performed when a neoplasia is suspected or if the diagnosis is unclear. (See "Skin biopsy techniques", section on 'Biopsy techniques'.)

Anoscopy — An anoscopy should be performed to evaluate the anal canal and the distal rectum. Anoscopy has the advantage of being a quick, relatively painless, inexpensive procedure that can be performed in an unprepped patient to exclude distal anorectal disorders.

Internal hemorrhoidal bundles appear as bulging, purplish-blue veins. Prolapsed internal hemorrhoids appear as dark pink, glistening, and sometimes tender masses at the anal margin. Thrombosed external hemorrhoids are acutely tender and have a purplish hue. An anal fissure can be visualized as a superficial linear tear in the anodermal lining of the anal canal distal to the dentate line and most commonly occurs in the posterior midline. (See "Anal fissure: Clinical manifestations, diagnosis, prevention", section on 'Physical examination' and "Hemorrhoids: Clinical manifestations and diagnosis", section on 'Digital rectal examination'.)

Laboratory testing — In patients with systemic symptoms or those with refractory symptoms despite initial therapy, we perform the following laboratory tests to rule out systemic diseases associated with anal pruritus (see 'History' above and 'Systemic diseases' above):

Complete blood count with differential to evaluate for evidence of malignancy, myeloproliferative disease, or iron deficiency

Serum bilirubin, transaminases, and alkaline phosphatase to evaluate for evidence of liver disease

Thyroid-stimulating hormone to evaluate for evidence of a thyroid disorder

Blood urea nitrogen (BUN) and creatinine to evaluate for renal disease

Human immunodeficiency virus (HIV) antibody test in patients with risk factors for HIV infection

Endoscopy — In patients with systemic or refractory symptoms or a change in bowel habits, diarrhea, abdominal pain, or hematochezia, we perform endoscopic evaluation with a colonoscopy. While performing a colonoscopy, the distal rectum and anal verge should be inspected in retroflexion, with the rectum partially insufflated. Complete insufflation should be avoided as this causes the rectal vault to distend and stretch, thereby flattening internal hemorrhoids.

MANAGEMENT

Initial management — In patients with anal pruritus, initial management consists of improving anal hygiene, avoiding moisture in the anal area, removing offending agents, dietary modification, and protection of skin. Reassurance and conservative treatment are successful in approximately 90 percent of patients with idiopathic anal pruritus [3].

In patients with inflammatory, infectious, systemic, neoplastic, and anorectal disorders contributing to anal pruritus, it is important to treat the underlying etiology. (See 'Etiology' above and "Anal fissure: Medical management" and "Perianal and perirectal abscess", section on 'Management' and "Treatment of atopic dermatitis (eczema)" and "Hidradenitis suppurativa: Management" and "Treatment of psoriasis in adults".)

Although the efficacy of diets eliminating foods associated with anal pruritus have not been well studied, we suggest avoidance of foods and beverages known or suspected to exacerbate symptoms (table 1). In addition, foods (eg, lactose in patients with lactose intolerance) or drugs that could be contributing to diarrhea or loose bowel movements should also be avoided or substituted.

In patients with fecal seepage or partially formed stools, we suggest fiber supplementation to increase stool bulk and, if necessary, antidiarrheals to prevent fecal leakage. The optimal consistency of stool should be soft, but well formed, and easy to clean with one wipe. (See "Fecal incontinence in adults: Management", section on 'Medical therapy'.)

Tight-fitting clothing should be avoided as these trap moisture in the anal area. Patients should be advised to wear cotton undergarments.

The anoderm should be kept clean and dry without excessive wiping or use of astringent cleaners [10]. In severe cases, patients should be instructed to bathe following defecation. The area should be dried using a soft towel with a dabbing motion, or with a hair dryer on the cool setting. Alternatively, a premoistened pad or tissue can be used for wiping.

We also suggest a barrier cream containing zinc oxide be applied to the anal area. In patients with significant pruritus, we suggest 1 percent hydrocortisone cream twice daily for one to two weeks to be used in conjunction with the barrier cream. However, topical hydrocortisone should not be used for more than two weeks to avoid skin atrophy.

For patients whose symptoms are worse at night, an antihistamine (eg, diphenhydramine) may be helpful until local measures take effect.

Refractory symptoms — Patients with continued symptoms should be carefully reassessed, paying specific attention to the type of ongoing symptoms, the degree to which symptoms have improved or worsened, and compliance with initial management. In addition, we perform laboratory testing and, if not already performed, a colonoscopy. (See 'Laboratory testing' above and 'Endoscopy' above.)

Finally, a full thickness "punch" biopsy should be considered in cases that are not responsive to any treatment or that have suspicious clinical findings consistent with Bowen’s or Paget’s disease.

If no etiology is found after this additional testing, we suggest a trial of topical capsaicin. We reserve anal tattooing with methylene blue for patients refractory to capsaicin. (See 'Laboratory testing' above and 'Endoscopy' above.)

Capsaicin — Topical capsaicin is believed to deplete substance P, a neurotransmitter involved in pain sensitization. In a randomized crossover trial, 44 patients with idiopathic intractable anal pruritus were assigned to topical capsaicin (0.006 percent) or placebo (1 percent menthol) three times daily for four weeks. Treatment with topical capsaicin resulted in an improvement in symptoms in 31 of 44 patients (70 percent) [11]. Among responders to capsaicin, the benefit was either immediate or was evident within three days. The main side effect was a burning sensation upon application, which tended to decrease over time, but caused four patients to drop out of the study. Patients were followed for up to eight months, during which they required approximately one application every other day to minimize or eliminate symptoms.

Other — Other agents have been evaluated in patients with refractory symptoms, but evidence to support their use is limited.

Anal tattooing – Anal tattooing with intradermal injection of methylene blue has been used to treat patients with refractory symptoms with the rationale that it destroys dermal nerve endings [12-15]. However, there are no randomized trials to support its use, and small prospective studies have demonstrated low long-term success rates. In one prospective study that included 10 patients with idiopathic anal pruritus, all patients had symptom resolution in four weeks [16]. However, during a median follow-up of 47 months, anal pruritus recurred in eight patients, although it was less severe as compared with the initial presentation in four patients.

Tacrolimus – In a small, randomized crossover trial in which 21 patients were assigned to topical tacrolimus (0.1 percent ointment) or placebo for four weeks, there was no significant improvement in Dermatology Life Quality Index scores with topical tacrolimus as compared with placebo [17].

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, “The Basics” and “Beyond the Basics.” The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on “patient info” and the keyword(s) of interest.)

Basics topic (see "Patient education: Anal pruritus (anal itching) (The Basics)")

SUMMARY AND RECOMMENDATIONS

Anal pruritus is estimated to affect 1 to 5 percent of the general population. However, most of these patients probably do not come to medical attention. Anal pruritus is more common in the fourth to sixth decades of life and has a higher prevalence in males.

Approximately 75 percent of cases of anal pruritus are secondary to inflammatory, infectious, systemic, neoplastic, and anorectal disorders that contribute to or underlie the development of pruritus. Idiopathic anal pruritus likely results from perianal fecal contamination and resultant trauma from wiping and scratching. (See 'Etiology' above.)

The clinical assessment of a patient with anal pruritus begins with a history, physical examination, and anoscopy. In patients with systemic symptoms or a change in bowel habits, diarrhea, abdominal pain, or hematochezia, we perform laboratory testing and endoscopic evaluation with a colonoscopy. (See 'Diagnostic approach' above.)

We suggest initial management of anal pruritus with conservative treatment and reassurance (Grade 2C). This includes improving anal hygiene, avoiding moisture in the anal area, removing offending agents, dietary modification, and protection of the perianal skin with the use of a protective ointment containing zinc oxide. In patients with severe pruritus, 1 percent hydrocortisone cream applied twice daily for one to two weeks can relieve symptoms. Hydrocortisone should not be used for more than two weeks to avoid skin atrophy. For patients whose symptoms are worse at night, an antihistamine (eg, diphenhydramine) may be helpful until local measures take effect. In addition, in patients with inflammatory, infectious, systemic, neoplastic, and anorectal disorders contributing to anal pruritus, it is important to treat the underlying etiology. (See 'Diagnostic approach' above.)

Patients with continued symptoms should be carefully reassessed, paying specific attention to the type of ongoing symptoms, the degree to which symptoms have improved or worsened, and compliance with initial management. In addition, we perform laboratory testing and, if not already performed, a colonoscopy. In patients with idiopathic anal pruritus and refractory symptoms, we suggest a trial of topical capsaicin (Grade 2C). We reserve anal tattooing with methylene blue injection for patients who do not respond to topical capsaicin. (See 'Diagnostic approach' above.)

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  3. Smith LE, Henrichs D, McCullah RD. Prospective studies on the etiology and treatment of pruritus ani. Dis Colon Rectum 1982; 25:358.
  4. Jensen SL. A randomised trial of simple excision of non-specific hypertrophied anal papillae versus expectant management in patients with chronic pruritus ani. Ann R Coll Surg Engl 1988; 70:348.
  5. Kränke B, Trummer M, Brabek E, et al. Etiologic and causative factors in perianal dermatitis: results of a prospective study in 126 patients. Wien Klin Wochenschr 2006; 118:90.
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  10. Oztaş MO, Oztaş P, Onder M. Idiopathic perianal pruritus: washing compared with topical corticosteroids. Postgrad Med J 2004; 80:295.
  11. Lysy J, Sistiery-Ittah M, Israelit Y, et al. Topical capsaicin--a novel and effective treatment for idiopathic intractable pruritus ani: a randomised, placebo controlled, crossover study. Gut 2003; 52:1323.
  12. Eusebio EB, Graham J, Mody N. Treatment of intractable pruritus ani. Dis Colon Rectum 1990; 33:770.
  13. Farouk R, Lee PW. Intradermal methylene blue injection for the treatment of intractable idiopathic pruritus ani. Br J Surg 1997; 84:670.
  14. Mentes BB, Akin M, Leventoglu S, et al. Intradermal methylene blue injection for the treatment of intractable idiopathic pruritus ani: results of 30 cases. Tech Coloproctol 2004; 8:11.
  15. Sutherland AD, Faragher IG, Frizelle FA. Intradermal injection of methylene blue for the treatment of refractory pruritus ani. Colorectal Dis 2009; 11:282.
  16. Samalavicius NE, Poskus T, Gupta RK, Lunevicius R. Long-term results of single intradermal 1 % methylene blue injection for intractable idiopathic pruritus ani: a prospective study. Tech Coloproctol 2012; 16:295.
  17. Suys E. Randomized study of topical tacrolimus ointment as possible treatment for resistant idiopathic pruritus ani. J Am Acad Dermatol 2012; 66:327.
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