Pruritus Ani, Pilonidal Sinus and Hidradenitis Suppurativa

Bradley R. Davis, MD, FACS, FASCRS

Assistant Professor of Surgery

University of Cincinnati, Cincinnati, OH

Pruritus Ani

Pruritus is defined as an unpleasant cutaneous sensation that produces the desire to scratch.  Acutely it may be protective but chronically it causes distress and is maladaptive.  Pruritus is further subdivided into primary or idiopathic, with no identifiable cause, and secondary, with an identifiable and often treatable cause.

Pathogenesis

The symptom of pruritus is common to many anorectal conditions but the pathogenesis of idiopathic pruritus often of long standing duration is not entirely understood.  The unifying theory is the presence of an irritative secretion emanating from the anal canal causing itching. This is also referred to as (1) pruritoceptive itching meaning that the sensation is transmitted by C nerve fibers in the dermis that may become chronically active with the repetitive trauma of scratching over months to years.  Itching can also be (2) neuropathic, due to disorders of the afferent pathways (e.g. post herpetic neuralgia) (3) neurogenic as a result of centrally mediated stimuli (e.g. morphine induced itching) and (4) psychogenic. 

Potential causes of irritation include moisture from sweat, stool and mucus; fecal factors such as bile salts and stool pH; inadequate hygiene, as well as overzealous hygiene with introduction of irritating soaps, lotions, and scents; certain food products; as well as topical compounds used by the patient to obtain relief. Patient’s often attribute the symptom to being dirty and will justify this by the fact that they use excessive amounts of toilet paper and feel moist following bowel movements a symptom of incomplete evacuation.  As a result they often shower, bath or perform elaborate cleansing routines after every bowel movement or when symptoms occur.  This, in addition to the use of topical steroids, can destroy the natural barriers and traumatize the anoderm and anal margin skin and exacerbate the problem.  Diagnosis, patient education, and treatment often proceed simultaneously.

Differential Diagnosis

The differential diagnosis of pruritus ani is listed in Table One.  When no known cause can be elicited it is considered idiopathic. 

Table One:  Differential Diagnosis of Pruritus Ani

Evaluation

The history must focus on the timing and duration of the pruritus as well as any accompanying symptoms.  The patient’s toileting behaviors’ and post defecation cleansing should be ascertained as well as the presence of mucous leakage, perianal moisture, or incomplete evacuation. Travel history and current medications (including topical agents) must be detailed.  A detailed diet history specific to pruritogenic foods and drinks should be obtained.  Often a heavy consumption of caffeine can be elicited in beverage choices such as colas and energy drinks.  Adults rarely harbor pinworms, but infected children must be inquired about.  Exposed adults should be evaluated with a scotch tape test.

The goal of the physical examination is to identify a possible cause of the patient’s symptoms beginning with a thorough inspection of the anal margin skin and anoderm. The skin may appear normal but often will have characteristic changes of lichenification and erythema due to persistent scratching and irritation.  An office biopsy with a 3 or 4 mm punch can assist in determining if these skin changes are pathologic or reactive aiding in the decision regarding treatment.

Treatment

The rationale for treatment of pruritus ani hinges on the fact that most cases are idiopathic.  It is the judgment of the surgeon to determine if a large anal tag that may interfere with hygiene or hemorrhoidal disease contributes to the symptom complex, but there is nothing lost to initially treating the problem non-operatively.  The goal then should be to achieve clean, dry, and intact skin.  Bowel medications should be tailored to achieve a formed bowel movement not loose stools in an effort to minimize seepage and effect a complete evacuation. Counseling and behavior modification are often necessary.  In some instances a short course of topical steroids such as betamethasone (a long acting glucocorticoid) or hydrocortisone may be used in conjunction with dietary and behavioral modification.  An inert skin barrier such as zinc oxide can also be effective as an adjunct or alternative.  Patient’s who scratch during their sleep should be counseled to cut their nails or wear cotton gloves to avoid excessive trauma.  Keeping the skin dry with cornstarch or a cotton ball over the anus can also be prescribed. 

There are at least six common foods believed to precipitate pruritus ani although the evidence is generally lacking and is mostly anecdotal.  Never the less in cases in which excessive consumption of these so-called pruritogenic foods (coffee, colas, chocolate, tea, tomatoes and beer) occur, patients can be counseled to completely avoid their use. Gradual reintroduction of the offending foods can then help the patient identify both the food group and the threshold for tolerance. The excessive consumption of liquids may also predispose to seepage.

Treatments of secondary causes of pruritus ani are directed towards the specific pathology and are reviewed elsewhere. 

Intractable Pruritus Ani

The natural history of pruritus ani seems to be repeated response and relapse. Once educated regarding the benign nature of the problem, most patients can cope with this.  There are however a subset of patients who will continue to seek treatment and can be very difficult to manage.  In these patient topical capsaicin or injection of methylene blue can be considered although studies are very small and efficacy dubious.   Capsaicin, a derivative of Capsicum chili peppers, appears to exert a depressive effect, probably by desensitizing the C neurons.  A randomized, placebo controlled, crossover study using topical capsaicin and topical menthol showed that 31 of 44 patients with intractable pruritus ani experienced relief with capsaicin. Relief was maintained during the follow-up period (mean 10.9 months) with a single daily application of capsaicin in 29 patients.  Injection of 10-15 ml of a 1% methylene blue solution (sometimes mixed with a local anesthetic and a steroid) intracutaneously and subcutaneously has been reported to relieve pruritus in as high as 83% of patients at 12 months.

Pilonidal Cyst

The description of a coccygeal fistula was first described in the middle of the 19^th Century and was later given the name of Pilonidal sinus – ‘nest of hair’ in the late 1800’s.  The initial belief as proposed by Warren in 1867 was that the sinus was the result of a reversed hair follicle.  This later gave way to the concept that they were congenital with a host of theories as to the etiology of the deformity.  Scrutiny of such theories and the consistent finding that the hair does not arise from within the sinus but is extraneous has led to the modern belief that pilonidal sinuses are acquired.  Two popular theories maintain that either 1) the infection is the inciting event followed by hair penetration into the resulting sinus (secondary to negative pressure or a vacuum); or 2) the growth of an errant hair strand burrowing into the skin results in the infection with further accumulation of hair in the sinus.  The direction of hair growth in the natal cleft would support this hypothesis.  In either case, a subcutaneous cavity or sinus is created, not uncommonly with a surprisingly large amount of hair present in the space. This may smolder for months or years before becoming secondarily infected and creating fistulas surrounding the sinus.

Diagnosis

Pilonidal disease predominates in men in their second and third decade.  While some amount of drainage may be present, treatment is usually sought due to an abscess and cellulitis at the level of the sacrococcygeal area.  Secondary sinuses or granulation-lined fistulas may ensue. The majority of secondary sinuses track cephalad, but some may track toward the anus, potentially being confused with fistula-in-ano or hidradenitis suppurativa.

The diagnosis is most often readily apparent, with an area of swelling and fluctuance over the sacrum characterizing the acute presentation of a pilonidal abscess, and one or multiple sinus opening in the midline over the sacrum in the chronic state. Midline pits are almost always identifiable inferior to the sinus. Differential diagnosis includes furuncle, anal disease and sacral osteomyelitis.

Treatment

The treatment of a pilonidal sinus depends on the presentation – acute, chronic or recurrent/refractory.  An acute pilonidal abscess should be treated immediately and can often be drained in the office.  Incisions off the midline are preferable as is debridement of the hair within the sinus.  If adequate, such treated abscesses will often heal without sequelae.

When a chronic sinus has developed, multiple options are available for definitive treatment.  General considerations include 1) excision of the entire sinus and associated fistulas 2) healing of the overlying skin 3) prevention of recurrence.  To accomplish this a number of different techniques have been described from radical excision and closure to selective debridement and packing.  In addition controversy exists as to whether these wounds should be closed or left open to heal by secondary intention. Wound closure can be accomplished with either midline or off midline (e.g. Z-plasty, VY plasty, rhomboid) techniques.  A 2008 meta-analysis of 18 trials selected from 1,346 eligible studies attempted to answer this question.  The authors looked at recurrence, infection and time to healing as primary outcome measures.  They noted a 58% reduction (5% vs. 15%) in recurrence when the wounds were left open versus closed.  In the group that was closed midline approaches fared worse than off midline.  Time to healing and return to work favored closure while infectious complications were equivalent.  The study design was imperfect but certainly aids in the decision regarding treatment options.  Surgeons should clearly identify the patient’s goals noting that in general wounds heal more quickly and return to work is sooner with closure at the expense of higher recurrence rates.  If closure is pursued off midline techniques can mitigate this higher recurrence rate but these techniques require more experience and expertise to perform. 

Several studies have advocated a more limited open approach with a lay open and curettage technique followed by meticulous wound care and close follow up.  This technique appears to maintain the benefit of low recurrence while decreasing the time to healing.  Closure techniques with off midline approaches can then be reserved for patients with persistent disease or chronic wounds that resist healing. 

Depilation of the hair of the natal cleft can be considered as an adjunct to surgery once the wounds have healed.  There is inconclusive evidence to recommend such treatments to patients with known pilonidal disease who are asymptomatic. 

Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) or acne inversa is a chronic, recurrent, inflammatory disease, initially presenting as tender subcutaneous nodules.  These lesions may spontaneously rupture or coalesce to form deep dermal, exquisitely painful abscesses. The inflammatory abscesses ultimately heal; producing fibrosis, dermal contractures, and induration of the skin.  The disease is insidious, typically developing in otherwise healthy postpubertal males and females.  It is most often seen in the second or third decade of life with a prevalence of 1-4%.   The most common location of disease is the axilla (70%) followed by the perineum and groin.  Patient may experience symptoms in more than one location.  Once believed to be the result of apocrine gland infection it is now considered a disease of follicular occlusion. Factors implicated in the development of HS include 1) host defenses, 2) genetics, 3) endocrine abnormalities, 4) obesity, 5) smoking and 6) environmental. 

Patients often present with multiple painful, swollen nodules, generally with little purulent discharge. The inflammatory process may resolve without treatment, but often waxes and wanes over many weeks to years.  Chronic skin changes and discharge may develop that is both painful and socially limiting.

The differential diagnosis in the perineal or genital area is primarily between HS and other subcutaneous tunneling diseases and if uncertain a biopsy should be considered. The absence of midline pits over the sacrum helps distinguish HS from pilonidal disease; the absence of involvement of the anal canal helps distinguish HS from Crohn's disease and benign anal fistula.

Treatment

Treatment of HS is multidisciplinary as there are a host of medical therapies from topical clindamycin to infliximab.  Surgery of HS lesions is reserved for intractability and acute abscess formation but is one of the most successful treatments available. 

Patients with HS may present with a subcutaneous abscess. These patients are treated with incision and drainage of the abscess. Then, depending on the individual circumstances, the patient is allocated to one of the multiple forms of nonsurgical management or to further surgery with curative intent once local inflammatory changes subside. On occasion, patients may present with an infected sinus tract and surrounding cellulitis. These patients may benefit from unroofing and of the tract and subsequent allocation to other forms of therapy if needed.

For patients who desire cure on an elective basis the entire affected area must be excised down to the subcutaneous fat.  Once the area has been excised, the resulting wound may be approached in different ways. If the wound is small, it can be closed primarily without tension. For larger wounds, the defect may be left open to close by secondary intention.  Perineal and perianal wounds so treated rarely require a colostomy.  Large wounds may also be treated by immediate or delayed split thickness skin graft. The recurrence rate after wide surgical excision has been reported at 0% for perianal disease, 3% for axillary disease and 37% for inguinoperineal disease

References

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