Pilonidal disease is a type of skin infection that typically occurs as a cyst between the cheeks of the buttocks and often at the upper end. Symptoms may include pain, swelling, and redness. There may also be drainage of fluid, but rarely a fever. Risk factors include

obesity Obesity is a medical condition, considered by multiple organizations to be a disease, in which excess Adipose tissue, body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classifi ...

, family history, prolonged sitting, greater amounts of hair, and not enough exercise. The underlying mechanism is believed to involve a mechanical process where hair and skin debris get sucked into the subcutaneous tissues through skin openings called pits. Diagnosis is based on symptoms and examination. If there is an infection, treatment is generally by

incision and drainage Incision and drainage (I&D), also known as clinical lancing, are minor surgical procedures to release pus or pressure built up under the skin, such as from an abscess, boil, or infected paranasal sinus. It is performed by treating the area wit ...

just off the midline.

Shaving Shaving is the removal of hair, by using a razor or any other kind of bladed implement, to slice it down—to the level of the skin or otherwise. Shaving is most commonly practiced by men to remove their facial hair and by women to remove the ...

the area and laser hair removal may prevent recurrence. More extensive surgery may be required if the disease recurs.

Antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

are usually not needed. Without treatment, the condition may remain long-term. About 3 per 10,000 people per year are affected, and it occurs more often in males than females. Young adults are most commonly affected. The term ''pilonidal'' means 'nest of hair'. The condition was first described in 1833.

Signs and symptoms

Pilonidal cysts can be itchy and often very painful, and typically occur between the ages of 15 and 35. Although usually found near the

coccyx The coccyx (: coccyges or coccyxes), commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horse anatomy, horses. In tailless primates (e.g. hum ...

, the condition can also affect the

navel The navel (clinically known as the umbilicus; : umbilici or umbilicuses; also known as the belly button or tummy button) is a protruding, flat, or hollowed area on the abdomen at the attachment site of the umbilical cord. Structure The u ...

armpit The axilla (: axillae or axillas; also known as the armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm an ...

, the cheek, or the genital region, though these locations are much rarer. Signs and symptoms may include: *Intermittent pain/discomfort or swelling above the anus or near the tailbone *Opaque yellow (purulent) or bloody discharge from the tailbone area *Unexpected moisture in the tailbone region *Discomfort sitting on the tailbone, doing sit-ups, or riding a bicycle—any activities that roll over the tailbone area Some people with a pilonidal cyst will be

asymptomatic Asymptomatic (or clinically silent) is an adjective categorising the medical conditions (i.e., injuries or diseases) that patients carry but without experiencing their symptoms, despite an explicit diagnosis (e.g., a positive medical test). P ...

Pilonidal sinus

Pilonidal sinus (PNS): a

sinus Sinus may refer to: History * a sac in front of body worn into a toga, in the typical style of wearing it Anatomy * Sinus (anatomy), a sac or cavity in any organ or tissue ** Paranasal sinuses, air cavities in the cranial bones, especially those ...

tract, or small channel, that may originate from the source of infection and open to the surface of the skin. Material from the cyst drains through the pilonidal sinus. A pilonidal cyst is usually painful, but if it is a draining sinus, the pressure is relieved and the patient might not feel pain.

Causes

Hair insertion is the causative agent of pilonidal cysts. An analysis of 624 patients' cyst hair found that 74% of the hair was rootless, and resembled spiky, razor-cut hair rather than intact body hair. One proposed cause is

ingrown hair Ingrown hair is a condition where a hair curls back or grows sideways into the skin. The condition is most prevalent among people who have coarse or curly hair. It may or may not be accompanied by an infection of the hair follicle (folliculitis) o ...

, although hairs found in pilonidal sinus tracts have more often been found to originate from the head. Excessive sitting is thought to predispose people to the condition, as sitting increases pressure on the

coccygeal The coccyx (: coccyges or coccyxes), commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horses. In tailless primates (e.g. humans and other g ...

region. Trauma is not believed to cause a pilonidal cyst; however, such an event may result in inflammation of an existing cyst; there are cases where this can occur months after a localized injury to the area. Pilonidal cysts may be caused by a congenital pilonidal dimple. Excessive sweating can also contribute to the formation 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 An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenat ...

, often found in pilonidal cysts. The presence of bacteria and low oxygen levels hamper wound healing and exacerbate a developing pilonidal cyst.

Differential diagnosis

A pilonidal cyst can resemble a

dermoid cyst A dermoid cyst is a teratoma of a cystic nature that contains an array of developmentally mature, solid tissues. It frequently consists of skin, hair follicles, and sweat glands, while other commonly found components include clumps of long hair ...

, a kind of

teratoma A teratoma is a neoplasia, tumor made up of several types of biological tissue, tissue, such as hair, muscle, Human tooth, teeth, or bone. Teratomata typically form in the tailbone (where it is known as a sacrococcygeal teratoma), ovary, or test ...

(

germ cell tumor A germ cell tumor (GCT) is a neoplasm derived from primordial germ cells. Germ-cell tumors can be cancerous or benign. Germ cell tumors typically originate from the gonads (ovary and testis), but can arise in other areas of the body. Extragon ...

). In particular, a pilonidal cyst in the

gluteal cleft The intergluteal cleft or just gluteal cleft, also known by a number of synonyms, including natal cleft and cluneal cleft, is the groove between the buttocks that runs from just below the sacrum to the perineum, so named because it forms the vis ...

can resemble a

sacrococcygeal teratoma Sacrococcygeal teratoma (SCT) is a type of tumor known as a teratoma that develops at the base of the coccyx (tailbone) and is thought to be primarily derived from remnants of the primitive streak. Sacrococcygeal teratomas are Benign tumor, benign ...

. Correct diagnosis is important because all

s require consultation with an

oncologist Oncology is a branch of medicine that deals with the study, treatment, diagnosis, and prevention of cancer. A medical professional who practices oncology is an ''oncologist''. The name's etymological origin is the Greek word ὄγκος (''� ...

and complete surgical excision, if possible without any spillage.

Treatment

If there is an infection, treatment is generally by

just off the midline because incisions in the midline have a hard time healing well. Following five simple rules has been known to prevent recurring inflammations for some people and avoid surgery: 1. Avoiding chairs and car seats that put pressure on the coccyx; 2. Being of average weight, preferably with low BMI; 3. Keeping the area clean; 4. Keeping the area dry by wearing exclusively cotton garments; 5. Keeping the area completely hair-free, for example, by regularly using an IPL hair removal device. The evidence for elective treatment of pilonidal sinus disease is poor. The most commonly performed surgery is for the pilonidal sinus complex to be surgically excised with the wound often left open to heal. Post-surgical wound packing may be necessary, and packing typically must be replaced daily for four to eight weeks. In some cases, two years may be required for complete

granulation Granulation is the process of forming grains or granules from a powdery or solid substance, producing a granular material. It is applied in several technological processes in the chemical and pharmaceutical industries. Typically, granulation inv ...

to occur. Sometimes the cyst is resolved via surgical

marsupialization 400px, Marsupialization Marsupialization is the surgical technique of cutting a slit into an abscess or cyst and suturing the edges of the slit to form a continuous surface from the exterior surface to the interior surface of the cyst or abscess. ...

. A 2018 literature review of 740 records of surgeries that included recurrence rates found that primary midline closure surgeries resulted in a 67.9% recurrence rate within 20 years, and recommended that they should be discontinued due to the high recurrence rate. Incision and drainage had a recurrence rate of 25.9% within 2 years, up to 40.2% in 5 years. Phenol treatment has a recurrence rate of 14.1% at 2 years and 40.4% at 5 years. A 2024 study involving 667 people found that, compared with tissue-removing surgery, minor procedures (such as draining and pit-picking) were associated with less pain, fewer complications and a faster recovery. However, minor surgeries were less likely to resolve the condition. Surgeons can also excise the sinus and repair it with a reconstructive flap technique, such as a "cleft lift" procedure or Z-plasty, usually done under

general anesthetic General anaesthetics (or anesthetics) are often defined as compounds that induce a loss of consciousness in humans or loss of righting reflex in animals. Clinical definitions are also extended to include an induced coma that causes lack of aware ...

. 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. This approach typically results in a more rapid recovery than traditional surgery; however, there are fewer surgeons trained in the cleft lift procedure, and it consequently may not be as accessible to patients, depending on their location. Meta-analysis shows recurrence rates were lower in open healing than with primary closure (RR 0.60, 95% CI 0.42 to 0.87), at the expense of healing time. Pilonidal cysts can 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. Minimally invasive techniques with no wound and rapid return to full activities have been reported but await double-blind randomized trials. Another technique is to treat the pilonidal sinus with

fibrin glue Fibrin glue (also called fibrin sealant) is a surgical formulation used to create a fibrin clot for hemostasis, cartilage repair surgeries or wound healing. It contains separately packaged human fibrinogen and human thrombin. Medical uses This ...

. This technique is of unclear benefit as of 2017 due to insufficient research. The evidence for any treatment is of low quality, and care must be taken not to overinterpret any study in this field. Since the 2010s, several minimally invasive techniques have been developed to minimize the impact of surgery on patients and achieve less pain and shorter recovery times. In some cases, the wounds are left open after surgery to heal naturally instead of being closed with stitches. There are a lot of different dressings and topical agents (creams or lotions) that are available to help these open wounds heal. A 2022 systematic review brought together evidence from 11 studies that compared dressings and topical agents for treating open wounds after surgical treatment for pilonidal sinus of the buttocks. The authors concluded that: platelet rich plasma may help wounds to heal quicker compared to sterile gauze; Lietofix skin repair cream may help wounds to heal by 30 days compared to

iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...

(which helps to reduce bacteria in the wound); but it is not clear whether

hydrogel dressing Hydrogel dressing is a medical dressing based on hydrogels, three-dimensional hydrophilic structure. The insoluble hydrophilic structures absorb polar wound exudates and allow oxygen diffusion at the wound bed to accelerate healing. Hydrogel dre ...

s (designed to keep the wound moist) reduce the time it takes wounds to heal compared with cleaning the wound with iodine.

Endoscopic An endoscopy is a procedure used in medicine to look inside the body. The endoscopy procedure uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are insert ...

pilonidal treatment, which uses a small camera to guide the surgeon in removing hair, is a newer method of treatment that has minimal pain and quick healing compared to surgery. A literature review of 497 patients found that the average endoscopic operation time was 34.7 minutes, and the average healing time was 32.9 days. Failure occurred in 8% of patients, who had persistent disease or recurrence. File:Pilonidal Cyst.png, Excised pilonidal cyst File:Trephine surgery 1.png, Trephine/biopsy punch minimally invasive surgery for pilonidal disease (1) File:Trephine surgery 2.png, Trephine/biopsy punch minimally invasive surgery for pilonidal disease (2) File:Pilonidal cyst 2 days after surgery.jpg, Pilonidal cyst two days after traditional closed surgery File:Pilonidal cyst and fistula.jpg, alt=Pilonidal disease removed, Anatomy of pilonidal disease removed after trephine or biopsy punch surgery: pilonidal fistula (top) and pilonidal cyst (bottom)

Etymology

Pilonidal means 'nest of hair' and is derived from the Latin words for 'hair' () and 'nest' (). The condition was first described by

Herbert Mayo Herbert Mayo, M.D. (3 April 1796 – 28 June 1852), was a British physiologist, anatomist and medical writer. Biography Mayo was born in Queen Anne Street, London, the third son of John Mayo. He entered Middlesex Hospital as a surgical pup ...

in 1833. R. M. Hodges was the first to use the phrase ''pilonidal cyst'' to describe the condition in 1880. The condition was widespread in the

United States Army The United States Army (USA) is the primary Land warfare, land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of th ...

during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

. The condition was termed "Jeep seat" or "

Jeep Jeep is an American automobile brand, now owned by multi-national corporation Stellantis. Jeep has been part of Chrysler since 1987, when Chrysler acquired the Jeep brand, along with other assets, from its previous owner, American Motors Co ...

riders' disease", because a large portion of people who were being hospitalized for it rode in Jeeps, and prolonged bumpy rides in the vehicles were believed to have caused the condition due to irritation and pressure on the coccyx.

References

External links

NHS Choices for pilonidal sinus treatment
{{Bacterial cutaneous infections Buttocks Cysts Wikipedia medicine articles ready to translate