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Pilonidal Cyst and Sinus

Author: Michael D Lanigan, MD, Attending Physician, Department of Emergency Medicine, Administrative Section, State University of New York Downstate, Brooklyn
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Updated: Aug 6, 2009

Introduction

Background

Historical

Pilonidal disease is described back as far as 1833, when Mayo described a hair-containing cyst located just below the coccyx. Hodge coined the term "pilonidal" from its Latin origins in 1880, and, today, pilonidal disease describes a spectrum of clinical presentations, ranging from asymptomatic hair-containing cysts and sinuses to large symptomatic abscesses of the sacrococcygeal region that have some tendency to recur.¹

In the 19^th and early 20^th centuries, pilonidal disease was studied on an embryologic basis by many authors who considered it to be of congenital origin. Excision of the lesion was thought to be fundamental to removing all embryologic remnants. This was the prevailing thought process well into the 20^th century, when pilonidal disease gained prominence and practical importance amongst World War II soldiers with a high incidence of the disease, so much so it came to be known as Jeep disease. According to US Army publications, nearly 80,000 US soldiers were admitted and treated at US Army Hospitals between the years 1941-1945. Prompt return of soldiers to the field was important, and, during that time, several articles proposed a variety of surgical treatments aimed at this goal. After the war, Patey and Scarf hypothesized the origin of pilonidal disease was acquired by penetration of hair into the subcutaneous tissue with consequent granulomatous reaction, basing this theory on the high incidence of recurrence, as well as occurrence of disease in other areas of the body, such as the hands of a barber or sheep shearer. Other authors have followed this emphasis of hair as disease origin, and, in fact, an acquired etiology of the disease is now the prevailing theory in the medical world.²

Epidemiology

Incidence of pilonidal disease is about 26 per 100,000 population. Pilonidal disease occurs predominantly in males, at a ratio of about 3-4:1. It occurs predominantly in white patients, typically in the late teens to early twenties, decreasing after age 25 and rarely occurs after age 45.^1,2 One publication listed local irritation to the SC site, positive family history of pilonidal disease (PD), sedentary life style, and obesity as occurring in notable percentages of patients with PD (all factors between 34-50% occurrence in PD).³

Pathophysiology

It has been postulated that hair penetrates into the subcutaneous tissues through dilated hair follicles, which is thought to occur particularly in late adolescence, though follicles are not found in the walls of cysts. A sinus develops with a short tract, with a not clearly understood suction mechanism involving local anatomy, eventually leading to further penetration of the hair into the subcutaneous tissue. A foreign body-type reaction may then lead to formation of an abscess. If given the opportunity to drain spontaneously, this may act as a portal of further invasion and eventually formation of a foreign body granuloma.

Microscopically, the sinus where the hair enters is lined with stratified squamous epithelium with slight cornification. Additional sinuses are frequent. Cyst cavities are lined with chronic granulation tissue and may contain hair, epithelial debris, and young granulation tissue. Cutaneous appendages are not seen in the wall of cysts. Cellular infiltration consists of PMNs, lymphocytes, and plasma cells in varying proportions. Foreign body giant cells in association with dead hairs are a frequent finding. 

In summary, 3 pieces are instrumental in this process: (1) the invader, hair; (2) the force, causing hair penetration; and (3) the vulnerability of the skin.^1,2 This process has been well characterized by Patey and Scarff as well as a number of other authors from the second half of the 20^th century through today.

Frequency

United States

Pilonidal disease affects approximately 26 per 100,000 people.

International

In England in 2000-2001, a total of 11,534 admissions were recorded for pilonidal disease. The mean hospital stay was 4.3 days.

Sex

Pilonidal disease in the general population has a male preponderance. It occurs in the ratio of 3 or 4:1. In children, however, the ratio is the opposite occurring in 4 females for each male it afflicts.

Age

Pilonidal disease commonly affects adults in the second to third decade of life. Pilonidal cysts are extremely uncommon after age 40 years, and the incidence usually decreases by age 25 years. The average age of presentation is 21 years for men and 19 years for women.

Clinical

History

Pilonidal disease can present in a couple of different disease states, but the most common seen in the ED is a painful, swollen lesion in the sacrococcygeal region about 4-5 cm posterior to the anal orifice. At times, spontaneous drainage may have occurred prior to presentation to the clinician.

Occasionally, a history of trauma is recalled, and the patient may state that a similar lesion occurred in that area before, for which the patient may have had a primary incision and drainage or other definitive care prior to this presentation.⁴  Given most patients are young and healthy, other comorbidities are not common, and review of systems is often negative, including fever and chills.

There is no known preponderance of this disease in smokers or alcohol or drug abusers.   

Physical

Usually, the patient is afebrile and nontoxic. Local examination may show a relatively unremarkable sinus tract in the sacrococcygeal region, but, usually at ED presentation, the patient has typical findings of an abscess, including redness, warmth, local tenderness, and fluctuance with or without induration. Loose hair may be seen projecting from the site.^5,3

Causes

• Pilonidal disease involves loose hair and skin and perineal flora.
  • Risk factors for pilonidal disease include male gender, hirsute individuals, Caucasians, sitting occupations, existence of a deep natal cleft, and presence of hair within the natal cleft. Family history is seen in 38% of patients with pilonidal disease. Obesity is a risk factor for recurrent disease.
  • The most commonly reported bacteria cultured from pilonidal abscesses differ by author. In one study, anaerobic cocci were present 77% of the time; aerobic, 4%; and mixed aerobic and anaerobic, 17%. Other studies quote Staphylococcus aureus, an aerobe, as being the most common bacterial pathogen.

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