Pilonidal Cyst and Sinus

Updated: Nov 14, 2022
Author: Alex Koyfman, MD; Chief Editor: Gil Z Shlamovitz, MD, FACEP 




Pilonidal disease is described back as far as 1833, when Mayo described a hair-containing cyst located just below the coccyx (see the image below). 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, 2, 3]

Pilonidal cyst. Pilonidal cyst.

In the 19th and early 20th 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 20th 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.[4]


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, decreases after age 25, and rarely occurs after age 45.[2, 4] One publication listed local irritation to the SC site, positive family history of pilonidal disease, sedentary life style, and obesity as occurring in notable percentages of patients with pilonidal disease (all factors between 34-50% occurrence in pilonidal disease).[5]



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. Upon sitting or bending, hair follicles can break and open a pit. Debris may collect in this pit, followed by development of a sinus 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.[4, 6]  This sinus tends to extend cephalad, likely owing to mechanical forces involved in sitting or bending.[6] 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. Infection may result in abscess formation.

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, meaning the cysts lack epithelial lining, unlike the sinus.[6] 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.[2, 4, 7] This process has been well characterized by Patey and Scarff as well as a number of other authors from the second half of the 20th century through today.



United States

Pilonidal disease affects approximately 26 per 100,000 people.


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


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.


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.


Long-term prognosis for pilonidal disease is excellent and mortality is practically nil, unless squamous cell carcinoma develops, though abscess recurrence is common as described above.

Patient Education

See the articles Pilonidal Cyst, Boils, and Abscess. Also, see the Skin, Hair, and Nails Center.

Pilonidal Support Alliance is a web-based support group and information for patients with pilonidal disease, particularly of a recurrent nature.




Pilonidal disease can present in a couple of different disease states and may be asymptomatic, but the most common form 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. Patients may present with intermittent swelling and drainage, including purulent, mucoid, or bloody fluid from the area. Chronic pilonidal disease often manifests as recurrent or persistent drainage and pain.

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.[8] 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.


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. A tender mass with sinus drainage may be present.[6] Loose hair may be seen projecting from the site.[5, 9]


Pilonidal disease is acquired, not congenital, and 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.


Recurrence of the abscess is by far the most common complication. Most literature reviewed quote a rate between 40% and 50%, although 58% will heal primarily by 5 weeks.

Primary incision and drainage seems to clearly be the primary mode of treatment; for recurrent disease presentations, a multitude of surgical techniques, from incision and curettage and marsupialization to wide excision with flap procedures, have been described throughout the years. A continuum seems to exist, from fairly simple to more complex procedures that should be offered to patients as needed given their particular needs; obviously, the surgeon's own training and experience will factor into the operative decision.[2, 4]

A Cochrane Database of Systematic Reviews article published in 2007 showed no significant difference in outcomes between techniques involving primary closure versus healing by secondary intention, though the review did recommend off-line closure when primary closure is performed.[10]  A series of treatments of the local region with phenol have also been described, with a low incidence of recurrence reported.[2]

Wound infection after primary incision and drainage is rare but described. At least one article suggests broad-spectrum antibiotics should be administered given the possibility of both aerobic and anaerobic infection at the incision site.[5]

Squamous cell carcinoma after recurrence of pilonidal disease has been described; it is rare in incidence but, when diagnosed, requires en bloc surgical resection and appropriate oncologic care with local radiation and possibly chemotherapy.[2]



Diagnostic Considerations

Location of the disease process is the best way to confirm the diagnosis of pilonidal disease, although several other disease entities should be considered:

Anal fistula and hidradenitis suppurativa: Several surgical studies mention the difficulty in differentiating pilonidal disease from anal fistula and hidradenitis suppurativa.[11] Pilonidal disease may result in sinuses that reach the perianal region and simulate an anal fistula. A valuable clinical observation in establishing diagnosis of anal fistula is palpation of the tract leading to the secondary opening to the anus. When no primary opening is observed and no tract is palpable, the possibility of an extra-anal source of the infection must be considered.[12] Consider hidradenitis suppurativa, a chronic inflammatory disease of the apocrine sweat glands in which folliculitis and local friction also play a role, in patients aged 30 years or older, especially with comorbidities such as diabetes and obesity. This disease often affects the groin, axillary, perianal, perineal, and inframammary regions. These patients need surgical referral because this condition is likely to be a long-term concern.[13]

Congenital abnormalities: In some congenital lesions, a continuous tract with the central cord of the spinal cord may occur, and discharge of CSF fluid may be present. It is likely that diagnosis of this variant will have occurred before an ED presentation.[4]

Inclusion dermoid/teratoma: Differentiation and post-primary presentation referral to a surgeon are critical, as treatment of a sacrococcygeal teratoma is en bloc excision and appropriate oncologic care.

Perirectal abscess: Location of the lesion is the best means to differentiate this entity from pilonidal disease. Perirectal abscesses frequently require surgical consultation in the ED for formal drainage in the operating room.

Pyoderma gangrenosum: Pyoderma gangrenosum is an ulcerative lesion also generally seen in the fourth decade of life with other comorbidities.

The following are other problems to consider:

  • Primary presacral or sacrococcygeal sinus
  • Furuncle or carbuncle
  • Syphilitic granuloma
  • Tuberculous granuloma

All of the above are rarely seen but should be considered in the face of atypical or variant history or physical examination findings. Readers are left to explore all these topics in further detail as indicated.

Differential Diagnoses



Laboratory Studies

No specific laboratory studies or tests are needed to diagnose pilonidal disease and its sequelae or differentiate it from other disease entities; it is a clinical diagnosis best elicited by history and physical examination findings.

Imaging Studies

Imaging is typically unnecessary for diagnosis; however, bedside ultrasound may be utilized to optimize incision and drainage.


If skin lesions are suspicious or consistent with malignant degeneration, skin biopsy is recommended in the outpatient setting. 



Emergency Department Care

Patients with pilonidal disease without abscess or other significant symptoms should be discharged from the ED with reassurance and instructions to return if signs of an abscess develop. Patients should maintain adequate hygiene of the area and closely observe for infection. Current literature review by this author failed to note an indication for surgical intervention at this stage.[14] However, if clinical signs of a pilonidal abscess are noted, primary incision and drainage should be performed in the ED for symptomatic relief, as follows[3, 15, 16] :

  • Place the patient in the prone position as comfortably as possible and have them undress adequately to expose the region in question. Rarely, a patient may require a small amount of sedative to tolerate the procedure, though reassurance by medical personnel is usually adequate.
  • Using sterile technique and instrumentation, prepare the region for incision with povidone-iodine (Betadine) or other suitable skin cleansing agent. Local anesthetic should be infiltrated generously with a small-gauge needle along the planned incision site (use of local vasoconstrictor such as epinephrine is acceptable).
  • The primary incision is longitudinal and should be made off the midline into skin, subsequently carrying it down to the level of subcutaneous tissue to open up the abscess cavity. As much purulent drainage and debris should be removed from the site as possible; blunt dissection may assist with this process as the patient can tolerate.
  • Once the space is evacuated adequately, ribbon wound packing should be placed to occupy the space and allow further passive drainage. The space should not be packed tightly, and there is no known advantage to using medicated ribbon gauze. Cover dressing can be with 4 X 4 gauze or an ABD pad secured with surgical tape. The patient may require brief amounts of nonopioid analgesia post procedure. [9]


A surgical consultation is only needed if the diagnosis and management are unclear from the patient presentation. The presence of chronic disease with recurrent painful episodes may warrant surgical consultation for surgical excision of all sinus tracts. If there is a question of whether a true pilonidal abscess has formed, ultrasound can be used to identify the abscess prior to definitive incision and drainage. The practice of exploratory needle aspiration in these instances seems to have gone by the wayside.

Medical Care

The overall goal of nonoperative medical therapy is to remove hair and debris that may contribute to a chronic inflammatory state that keeps any potential skin tracts open. Shaving or laser epilation therapy may be used as an adjunctive therapy if an abscess is not present to remove hair from the gluteal cleft and surrounding skin. After hair removal, patients without abscess may also be treated with phenol or fibrin glue applied to the affected area to remove granulation tissue and prevent further formation of debris, which can assist with sinus closure.[17]  

Surgical Care

Outside of standard incision and drainage, patients with chronic pilonidal disease may require excision with primary repair, excision and healing by seondary intention, or excision with marsupialization. The decision to place a drain is based on patient factors and surgeon preference. In the setting of complex, recurrent pilonidal disease, flap-based procedures may be performed if other techniques have not been successful.[17]


Routine physical activity may be helpful for prevention, as a sedentary lifestyle is a risk factor for developing pilonidal disease.

Long-Term Monitoring

First, packing removal needs to be performed. Generally, a formal wound check should be offered to the patient in the ED or office in 1-2 days, with removal of the packing at that time and redressing of the wound. However, if the patient is reliable and unwilling to return to the ED, he or she can remove the packing at home as long as care is taken to ensure that the ribbon is completely intact when removed. Once packing is removed, site cleansing with warm shower water or sitz baths should begin right away and be taken 2-3 times per day. A clean dressing should be applied after cleansing and continued until the abscess cavity has closed primarily.

Surgical follow-up is recommended in about 1-2 weeks. This allows the surgeon to examine the wound for healing, assess for potential recurrence, ensure that no other diagnosis and therapy should be considered, and arrange for definitive care of the sacrococcygeal region if necessary.[5, 9]  At least some literature suggests that conservative therapy with good local hygiene and site shaving every 1-3 weeks have been shown to be as effective in preventing recurrence as a secondary surgical procedure.[2]



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