|Classification and external resources|
Two pilonidal cysts that have formed in the gluteal cleft of an adult man.
A pilonidal cyst, also referred to as a pilonidal abscess, pilonidal sinus or sacrococcygeal fistula, is a cyst or abscess near or on the natal cleft of the buttocks that often contains hair and skin debris.
Pilonidal means nest of hair and is derived from the Latin words for hair (pilus) and nest (nidus). The condition was first described by Herbert Mayo in 1833. R.M. Hodges was the first to use the phrase pilonidal cyst to describe the condition in 1880.
Signs and symptoms
Pilonidal cysts are often very painful, and typically occur between the ages of 15 and 35. Although usually found near the coccyx, the condition can also affect the navel, armpit or genital region, though these locations are much rarer.
A sinus tract, or small channel, may originate from the source of infection and open to the surface of the skin. Material from the cyst may drain through the pilonidal sinus. A pilonidal cyst is usually painful, but with draining, the patient might not feel pain.
One proposed cause of pilonidal cysts is ingrown hair. Excessive sitting is thought to predispose people to the condition because they increase pressure on the coccyx region. Trauma is not believed to cause a pilonidal cyst; however, such an event may result in inflammation of an existing cyst. However there are cases where this can occur months after a localized injury to the area. Some researchers have proposed that pilonidal cysts may be the result of a congenital pilonidal dimple. Excessive sweating can also contribute to the cause of a pilonidal cyst. Moisture can fill a stretched hair follicle, which helps create a low-oxygen environment that promotes the growth of anaerobic bacteria, often found in pilonidal cysts. The presence of bacteria and low oxygen levels hamper wound healing and exacerbate a forming pilonidal cyst.
The condition was widespread in the United States Army during World War II. More than eighty thousand soldiers having the condition required hospitalization;  the average length of these wartime hospital stays was 55 days. The condition was termed "jeep seat" or "Jeep riders' disease", because a large portion of people who were being hospitalized for it rode in Jeeps, and prolonged rides in the bumpy vehicles were believed to have caused the condition due to irritation and pressure on the coccyx.
In more severe cases, the cyst may need to be lanced or surgically excised (along with pilonidal sinus tracts). Post-surgical wound packing may be necessary, and packing typically must be replaced twice daily for 4 to 8 weeks. In some cases, two years may be required for complete granulation to occur. Sometimes the cyst is resolved via surgical marsupialization.
Surgeons can also excise the sinus and repair with a reconstructive flap technique, such as a "cleft lift" procedure or Z-plasty, usually done under general anesthetic. This approach is especially useful for complicated or recurring pilonidal disease, leaves little scar tissue and flattens the region between the buttocks, reducing the risk of recurrence.
A novel and less destructive treatment is scraping the tract out and filling it with fibrin glue. This has the advantage of causing much less pain than traditional surgical treatments and allowing return to normal activities after 1–2 days in most cases.
Pilonidal cysts recur and do so more frequently if the surgical wound is sutured in the midline, as opposed to away from the midline, which obliterates the natal cleft and removes the focus of shearing stress. An incision lateral to the intergluteal cleft is therefore preferred, especially given the poor healing of midline incisions in this region.
A pilonidal cyst can resemble a dermoid cyst, a kind of teratoma (germ cell tumor). In particular, a pilonidal cyst in the gluteal cleft can resemble a sacrococcygeal teratoma. Correct diagnosis is important because all teratomas require complete surgical excision, if possible without any spillage, and consultation with an oncologist.
|Wikimedia Commons has media related to Sinus pilonidalis.|
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