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Pilonidal Sinus Disease

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Overview

Pilonidal sinus disease describes the inflammation of the skin in the midline above the natal cleft leading to the formation of sinuses and cysts. They may be asymptomatic or present as an acute abscess or a chronic cyst and/or sinus with persistent drainage.

Pathophysiology

Pilonidal sinus disease is thought to be due to hair being driven into the skin of the natal cleft, resulting in inflammation in the surrounding tissue, resulting in a small pit. The pit fills with dead skin and other debris, leading to chronic inflammation and the formation of a sinus. An associated abscess may form and drain into the sinus or become larger over time. 

Epidemiology

  • Pilonidal sinus disease is 2-4 times more common in men than in women
  • Most often presents at around 20 years old

Risk Factors

  • Male sex
  • Obesity
  • Poor hygiene
  • Prolonged sitting
  • Family history
  • Hirsutism
  • Coarse hair
  • Macerated/broken skin

Presentation

Overview

Patients may present with:

  • An asymptomatic pilonidal sinus:
    • A non-tender pit or lump in the natal cleft
  • An acute pilonidal abscess:
    • A painful lump (often severe) that may be fluctuant and have purulent discharge
    • There may be cellulitis of the surrounding skin (erythema, warmth, pain)
    • Some patients may have a fever 
  • A discharging pilonidal sinus:
    • Chronic intermittent pain
    • Discharging of pus and blood
    • Recurrent abscess formation and infection

Differential Diagnoses

Boil (furuncle)

  • Usually initially appear as a firm, tender, erythematous nodule before enlarging and becoming painful and fluctuant over several days
  • They occur due to an infection around hair follicles

Hidradenitis suppurativa

  • Recurrent, painful, and inflamed nodules usually on the intertriginous skin, most commonly the axillae
  • Open comedones are found in affected areas
  • Lesions are unilateral to begin with but as time goes on, features are seen bilaterally

Perianal fistula

  • An opening is seen in the perianal region and the skin of the natal cleft is normal
  • Patients may have recurrent episodes of passing mucus per rectum
  • Features of underlying causes (e.g. Crohn’s disease) may be present, such as bloody stools, abdominal pain, constitutional symptoms, perianal pain or tenderness, skin tags, fissures, and abscesses. 

Perianal abscess

  • The abscess is seen in the perianal region and the skin of the natal cleft is normal
  • Features of underlying causes (e.g. Crohn’s disease) may be present, such as bloody stools, abdominal pain, constitutional symptoms, perianal pain or tenderness, skin tags, fissures, and abscesses. 

Sacral osteomyelitis

  • This can also cause pain and tenderness in the same area, but the overlying skin should be normal as the underlying bone is what is infected and inflamed
  • This is much less common than pilonidal sinus disease

Diagnosis

Overview

Pilonidal sinus disease does not require specific investigations unless other differential diagnoses are suspected.

Management

Overview

  • Asymptomatic pilonidal sinus disease:
    • Conservative management and give advice on perianal hygiene
  • Acute pilonidal abscess:
    • Arrange urgent same-day hospital admission for incision and drainage
    • If associated cellulitis is present, consider prescribing an antibiotic
  • Discharging pilonidal sinus disease:
    • Refer to secondary care for surgery (urgency depending on clinical judgement)
    • Surgical excision of the infected tissue with primary closure or healing by secondary intention
  • For complex recurrent disease after definitive treatment, refer to a colorectal surgeon 

Patient Advice

Patients should be given advice on taking measures to reduce recurrence:

  • Regular baths and showers and good perianal hygiene
  • Buttock hair removal such as by shaving, waxing etc.
  • Avoiding sitting for prolonged periods

Complications

  • Chronic pain and discomfort – cause reduced productivity in otherwise healthy people
  • Cellulitis
  • Pilonidal abscess
  • Sepsis
  • Altered body image and self-esteem

Prognosis

  • Simple incision and drainage has a 15-40% recurrent rate
  • Recurrence is less likely to occur if the wound is left to heal by secondary intention after wide excisional surgery for extensive chronic disease

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