| Pruritus ani | |
|---|---|
| Specialty | Dermatology  |
Pruritus ani is the irritation of the skin at the exit of therectum, known as theanus, causing the desire to scratch.[1] The intensity of analitching increases from moisture,[2] pressure, and rubbing caused by clothing and sitting. At worst, anal itching causes intolerable discomfort accompanied by burning and soreness. It is estimated that up to 5% of the population of the United States experiences this type of discomfort daily.
If a specific cause for pruritus ani is found it is classified as "secondary pruritus ani". If a specific cause isnot found it is classified as "idiopathic pruritus ani".[3] The irritation can be caused by intestinal parasites, analperspiration, frequent liquid stools,diarrhea, residual stool deposits, or the escape of small amounts of stool as a result ofincontinence orflatulence. Another cause isyeast infection orcandidiasis. Some diseases increase the possibility of yeast infections, such asdiabetes mellitus orHIV infection. Treatment withantibiotics can bring about a disturbance of the natural balance of intestinal flora, and lead to perianalthrush, ayeast infection affecting the anus.Psoriasis may also be present in the anal area and cause irritation.
Abnormal passageways (fistulas) from the small intestine or colon to the skin surrounding the anus can form as a result of disease (such asCrohn's disease), acting as channels which may allow leakage of irritating fluids to the anal area. Other problems that can contribute to anal itching includepinworms,hemorrhoids, tears of the anal skin near the mucocutaneous junction (fissures), andskin tags (abnormal local growth of anal skin). Aside from diseases relative to the condition, a common view suggests that the initial cause of the itch may have passed, and that the illness is in fact prolonged by what is known as anitch-scratch-itch cycle.[4][5] It states that scratching the itch encourages the release of inflammatory chemicals, which worsen redness, intensifies itchiness and increases the area covered by dry skin, thereby causing asnowball effect.
Some authorities describe “psychogenic pruritus” or "functional itch disorder",[6] where psychological factors may contribute to awareness of itching.
Ingestion ofpinworm eggs leads toenterobiasis, indicative of severe itching around the anus from migration of gravid females from the bowel. Severe cases of enterobiasis result inhemorrhage andeczema.
Diagnosis is usually done with a careful examination of the anus and the patient's history. If the presentation or physical findings are atypical, i.e. change in bowel habits or personal/family history of colorectal cancer/adenomas, acolonoscopy should be proposed.[7]
In case of long-lasting symptoms, above all in patients over 50 years of age, a colonoscopy is useful to rule out a colonic polyp or tumor, that can show pruritus ani as first symptom.[8]
The goal of treatment is asymptomatic, intact, dry, clean perianal skin with reversal of morphological changes. For pruritus ani of unknown cause (idiopathic pruritus ani)[3] treatment typically begins with measures to reduce irritation and trauma to the perianal area.[9]Stool softeners can help prevent constipation.[9] If this is not effective topicalsteroids or injectedmethylene blue may be tried. Another treatment option that has been met with success in small-scale trials is the application of a very mild (0.006%) topical capsaicin cream.[10] This strength cream is not typically commercially available and therefore must be diluted by a pharmacist or end-user. If the itchiness is secondary to another condition such as infection or psoriasis these are typically treated.[9]
A successful treatment option for chronic idiopathic pruritus ani has been documented using a clean, dry and apply (if necessary) method. The person is instructed to follow this procedure every time the urge to scratch occurs. The treatment makes the assumption that there is an unidentified bacteria in the feces that causes irritation and itching when the feces makes contact with the anal and perianal skin during defecation, flatulation or anal leakage (particularly during sleep).
For otherwise idiopathic, intractable cases, a double-blind trial with 44 patients found thatcapsaicin may be an effective treatment. By applying topical capsaicin mixed with paraffin wax (both available over the counter) with a concentration of 0.006% to the perianal area every 1-2 days, approximately three quarters of patients reported total (or near-total) relief of symptoms.[11]