Fig. 8.1
Uncomplicated pilonidal sinus disease with multiple midline pits
Work by Karydakis [3] with 6,000 patients suggests that loose hairs “impale” normal tissue inducing, a foreign body reaction. He devised a pathogenic formula involving three variables, namely, loose hair (H), force (F), and the vulnerability (V) of local skin and tissues. In this model the primary sinuses represent hair entry sites and secondary sinuses represent exit points, such that Pilonidal disease = H × F × V 2.
The most common site of occurrence is the sacrococcygeal region. Rarer sites include the interdigital cleft, the breast, and the umbilicus [4]. Not uncommonly (20 %), PD occurs with hidradenitis suppurativa (acne inversa) [5], sharing the same pathological process, that is, an occluding follicular hyperkeratosis followed by a dissecting cellulitis and the formation of draining sinuses (Fig. 8.2). In addition, friction between the buttocks may be responsible for sucking or sticking hairs into the pits. The stiffness of body hair and hair scales functioning as microbarbs facilitate the penetration of hair shafts deeper into the skin. Hair acts as a potent foreign body, causing a prolonged inflammatory reaction and the development of sinus tracts filled with granulated tissue and often with masses of hair shafts. By this time these tracts are always at least partially lined by epithelium.
Fig. 8.2
Pilonidal sinus and hidradenitis suppurativa (acne inversa)
The risk factors for the development of symptomatic PD are listed in Table 8.1.
8.3 Incidence
PD most commonly occurs in the second and third decades of life, and it is twice as common among men than women. The incidence is highest among Caucasians. An estimated 1.1 % of male students and 0.11 % of female students suffer from PD [8]. PD is rare after the age of 40 years, suggesting an association with sex hormones, which can affect pilosebaceous glands.
8.4 Clinical Presentation and Diagnosis
PD is clinically diagnosed by visible single or a series of midline pits in the natal cleft that have the microscopic appearance of enlarged hair openings. Often these pits are minute, whereas others may contain a tuft of hairs. The clinical picture of a developing acute abscess maybe inconspicuous, presenting as a slight bulging of the skin in the natal cleft. Recurrent painful indurations in this area with purulent secretion followed by silent periods are characteristic of PD. These often settle down with antibiotic treatment but almost always recur later.
Chronic PD may reveal a lateral track in the upper parts of the buttocks filled with granulation tissue resembling pyogenic granuloma. The differential diagnosis may include fistula in ano, hidradenitis, and, rarely, perforating diverticular disease [9].
In selected cases computed tomography or magnetic resonance imaging (MRI) may be indicated. The latter is particularly useful to exclude fistula in ano or to clarify obscure presentations [10] (Fig. 8.3).
Fig. 8.3
Magnetic resonance imaging of a pilonidal sinus and track (arrow) (Courtesy of Dr. D. Blunt)
8.5 Therapy
The management of PD is variable, debateable, and occasionally difficult. The principles of treatment are eradication of the sinus tract and complete healing of the epidermis with no recurrence. Ideal treatment should be quick, allowing these young patients to return early to normal activity and work, with minimal complication.
8.6 Nonoperative Treatment
Asymptomatic PD may be treated conservatively by meticulous hair control (shaving the natal cleft), improved hygiene, and mechanical removal of shed hairs [11]. Laser removal of hair in the natal cleft is increasingly popular [12]. Evidence that conservative treatment of symptomatic PD is effective is limited; therefore the mainstay of treatment is surgical. Antibiotics may be indicated in purulent stages of PD before surgery or in rare cases of systemic infection. Prophylactic use of antibiotics in the surgical treatment of PD remains unproven [13].
8.7 Surgical Treatment
Several techniques are described. Recurrence rates are variable with all procedures and may reach 20 % or more. Postoperative professional wound care and hair control are important for optimal wound healing and are likely to play an important role in avoiding complications and recurrences. The main therapeutic goals are set out in Table 8.2.
Table 8.2
Therapeutic goals
Flatten the natal grove |
Low rate of complications and recurrences |
Minimal discomfort for the patient |
Short healing and little time off work |
Good cosmetic results |
Suitable for a day-case operation |
8.8 Pilonidal Abscess
Pilonidal abscess (which occurs in half of all cases of PD) should be drained or deroofed to provide optimal drainage. This rapidly alleviates symptoms and can control PD in the outpatient setting. General anesthesia allows curettage of the sinus in the same session and, together with removal of the pits, occasionally may heal PD, but recurrences often occur [1, 14].
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