Following the onset of puberty, sex hormones affect the pilosebaceous glands, and subsequently, hair follicles can become distended with keratin. A folliculitis can result producing edema and follicle occlusion. If the infected follicle extends and ruptures into the subcutaneous tissue, a pilonidal abscess forms.
This results in a sinus tract leading to a deep, subcutaneous cavity. In the majority of cases, this tract follows a cephalad direction (as this is the directional growth of the hair follicle). Rarely, sinus tracts can communicate caudally or laterally. Loose hairs become entrapped within the sinus by friction and movement of the patients buttocks (when sitting or standing), inciting a foreign body reaction and infection.
The incidence of pilonidal disease is about 2-4 times more likely in men than in women. Hair characteristics such as kinking, coarseness, and growth rate have been studied in their relation to incidence. Other factors including increased sweating, poor personal hygiene, and obesity have been linked to an increased risk. Additionally, the disease is more common in younger age groups (15-30), and is rare is persons over 40.
A pilonidal dimple is a small pit or sinus in the sacral area just at the top of the crease between the buttocks. The pilonidal dimple may also be a deep tract, rather than a shallow depression, leading to a sinus that may contain hair. During adolescence the pilonidal dimple or tract may become infected forming a cyst-like structure called a pilonidal cyst. Although pilonidal disease may manifest as an abscess, sinus, or cyst, most cases present as a painful, fluctuant mass in the sacrococcygeal region. Pain and purulent discharge are present in the majority of cases and are the most frequently described symptoms.
The diagnosis is made by inspection of the area and identification of the epithelialized, follicle opening. A deep area of induration can most often be palpated.
Most often, pilonidal disease can be managed surgically in the ambulatory setting. Although more popular in Europe, medical therapy with phenol has been used before attempting surgery. Phenol is injected into the site, which sterilizes the sinus tract and removes embedded hair. Its use in the U.S. is limited, because of the toxicity of phenol.
Surgically, a pilonidal abscess is treated as any type of abscess. Incision, drainage, and curettage of the abscess cavity is the primary management goal. The patient should then be instructed to cleanse the wound daily or take warm, Sitz baths. Good personal hygiene and close hair shaving in the area will help prevent contamination of the healing wound. Most wounds heal within 1 month, although the meticulous cleansing process should be done for at least 3 months.
For patients with pilonidal disease which persists despite minimal surgery, the surgical options for management include excision with primary closure, excision and laying open of the tract to heal by secondary intention, wide and deep excision to the sacrum, and incision with marsupialization. Each has their own advantages and disadvantages and should be tailored to the patient.