A closed, sac-like pocket of tissue that can form anywhere in the body. It may be filled with fluid, air, pus, or other material. Most cysts are benign (not cancer).

Summary

• Cysts are abnormal sacs of fluid that can form anywhere in the body.
• If left untreated, benign cysts can lead to a range of serious complications, including blood poisoning.
• Surgical removal is the most common treatment.

A cyst is an abnormal pocket of fluid, like a blister, that can form in many different areas of the body including the skin, genitals and internal organs. A cyst can vary in size from a tiny sac right up to a heavy bag containing litres of fluid. The common symptom is swelling around the area, but a cyst may or may not be painful. Sometimes, depending on the cause and location, a cyst contains semi-solid or solid material.

The typical treatment for any cyst is removal by surgery and a routine test for cancer, even though most cysts are benign. All unusual lumps need to be investigated by a qualified health professional.

Most cysts form for no apparent reason. Some of the known causes of cysts include:

• Blocked ducts, which cause a build-up of fluid
• A defect in the cells
• An impact injury that pops a blood vessel
• A parasite.

Some of the different types of cysts include:

• Arachnoid cyst – the arachnoid membrane covers the brain. A baby may be born with an arachnoid cyst. It is caused by the arachnoid membrane doubling up or splitting to form an abnormal pocket of cerebrospinal fluid. This can be treated by surgical drainage if necessary.
• Bartholin’s cyst – the Bartholin glands are situated inside the vagina. A cyst occurs if the ducts become blocked. Treatment includes surgery and antibiotics.
• Breast cyst – these cysts are usually painful and need to be drained with a needle. There is some evidence that breast cysts might indicate an increased risk of breast cancer.
• Cystic hygroma – occasionally, a baby is born with a small cyst or bursa. This birth defect can be corrected with surgery.
• Hydatid disease – a small tapeworm forms cysts in the liver or lungs. The tapeworm eggs are spread by contact with infected dogs, their faeces (poo) or anything contaminated with faeces such as soil. Treatment includes surgery and drugs.
• Ovarian cyst – most are benign, but can grow to such a size that the woman looks pregnant. Cysts less than 5cm are a common part of normal egg formation in the reproductive years. Sometimes, bleeding occurs into these cysts (this is called a haemorrhagic cyst). In some cases, the cysts are cancerous. Treatment includes surgery.
• Pilonidal disease – a cyst forms in the skin of the lower back, sometimes containing an ingrown hair. Pilonidal cysts can grow in clusters and sometimes create a hole or cavity in the skin. Treatment includes draining the cyst or surgical removal.
• Sebaceous cyst – the skin is lubricated by sebaceous fluid. This fluid can build up inside a pore or hair follicle and form a hard lump filled with thick, greasy matter. When squeezed, a small dome-shaped projection will appear (the punctum), representing the opening of the cyst. This may allow material to be expressed (squeezed out). Treatment includes drugs, draining the cyst with a small needle, or removal by surgery. Sebaceous cysts are common on the face, back, scalp and scrotum.

All unusual lumps need to be investigated. Some cysts are cancerous and early treatment is vital. If left untreated, benign cysts can cause serious complications including:

• Infection – the cyst fills with bacteria and pus, and becomes an abscess. If the abscess bursts inside the body, there is a risk of blood poisoning (septicaemia).
• Peritonitis – if an internal cyst bursts, there is a risk of peritonitis, which is inflammation of the membrane lining the abdominal wall.

If a cyst is cancerous, treatment will depend on its size and location and on whether or not cancer cells have spread to other parts of the body. The cyst will be surgically removed along with surrounding tissue. Further treatment might include radiotherapy (using x-rays to kill cancer cells) or chemotherapy (drugs).

• Cysts are abnormal sacs of fluid that can form anywhere in the body.
• If left untreated, benign cysts can lead to a range of serious complications, including blood poisoning.
• Surgical removal is the most common treatment.

A hair-containing cyst or sinus, occurring chiefly in the coccygeal region.A hair-containing cyst or sinus, occurring chiefly in the coccygeal region.

Introduction

Pilonidal derives its name from Latin- pilus meaning “hair,” and nidus meaning “nest.” The name “pilonidal disease” has been attributed to R.M. Hodges in 1880. The disease was first described in 1833 by O.H. Mayo. Another early reference of the disease, with a description of management, followed shortly after by A.W. Anderson, in 1847. Many U.S. soldiers were diagnosed with pilonidal disease during the wars, and was referred to as “Jeep disease.”

Etiology

Early after its description, many clinicians considered the disease as congenital in origin, being derived from vestiges of the medullary tube, dermoid traction, inclusion dermoid, or preen glands. Currently, pilonidal disease is considered an acquired disease. Patey et al. proposed the hypothesis of pilonidal disease being an acquired disease., suggesting that pilonidal disease results from the suction of hair from surrounding soft tissue and skin, ultimately leading to a foreign body reaction and foreign body granuloma. This proposal of pilonidal disease being an acquired, infective, and foreign body reaction was corroborated by King around the same time.

Karydakis simplified the description of the etiologic process citing three main factors- the hair or foreign body, a force causing deposition of hair into the sinus, and skin vulnerability.

Epidemiology

The incidence of pilonidal disease is estimated to be 26 per 100,000 people and affects men 2.2 times more than women. It is estimated that pilonidal disease affects approximately 70,000 people in the United States annually.

Pathophysiology

The pathophysiology is mostly unknown; the etiology is thought to be related to trapped hair follicles (as noted above).

Histopathology

Microscopically it’s noted that hair within the pilonidal cysts originates from the overlying, surrounding skin; but, the follicles are never found within the wall of the cyst but rather free in granulation and scar tissue. The walls of pilonidal cysts are not lined with squamous epithelium but are composed of vascular pyogenic granulation tissue. In 1984, Stelzner used light microscopy to note hairs obtained from pilonidal pits had a hook architecture and suggested hair migration was unidirectional. Electron microscopy has also been used to evaluate hair involved in the pathogenesis of pilonidal disease; Dahl et al. confirmed the hook morphology and proposed sharp ends contribute to hair piercing the skin, with hooks preventing retraction. Gosselink et al. suggest the orientation of the hair scales likely encourages hair to be driven deeper into the tissue.

History and Physical

Pilonidal disease is a clinical diagnosis based on history, physical exam (including anorectal exam), and evaluation of symptoms and risk factors. Physical exam findings include midline pits in the superior gluteal cleft and may be associated with cephalad or lateral tracking sinuses. Risk factors include male sex, family history, being overweight or obese, trauma or irritation, sedentary occupation or lifestyle, hirsute habitus, and poor hygiene.

Evaluation

Diagnosing pilonidal disease is clinical, and no further labs, tests, or imaging is required. However, imaging may be helpful in cases where the diagnosis is less clear. Imaging modalities have been used to differentiate and/or rule out more significant disease processes and can aid in determining the extent of disease and required excision when combined with surgical treatment.

Methylene blue has been used to evaluate the extent of pilonidal sinuses and can be used in conjunction with surgery. One study found that the use of methylene blue may reduce the long term recurrence rate of pilonidal disease by showing the extent of necessary resection of soft tissue at the time of surgery. Doll et al. studied 247 patients with a mean follow up of about 15 years and found that intraoperative methylene blue had a decreased recurrence rate of 16% vs. 30%. Another study evaluated 33 patients in a prospective randomized trial where methylene blue was injected into each sinus, with subsequent resection of stained areas; microscopic parameters were assessed, but the authors warn that the use of methylene blue to direct surgical excision may cause inadequate excision. This differs from a more recent study assessing the volumes of specimens surgically removed with methylene blue. In a retrospective study looking at 135 specimens, Ardelt et al. found that samples excised using methylene blue had significantly higher volumes facilitating complete resection; interestingly, volumes were also larger in recurrent disease. Modifications to methylene blue have been used to make it more manageable by turning it into a gel with the addition of chloramphenicol ointment.

Ultrasound can be used to evaluate pilonidal disease. Mentes et al. evaluated 73 patients with preoperative ultrasound and found that determining pilonidal disease borders with ultrasonography was consistent with palpation 76.7% of the time, but in the remaining patients, ultrasound detected sinus tracts that exceeded the planned margins of excision with palpation alone. They concluded that ultrasound provides more information in regards to the borders of pilonidal disease when compared to palpation and methylene blue. Both external ultrasound and endoanal ultrasound were found to be useful in evaluating the extent of pilonidal disease and excluding perianal sepsis in a more recent study. This was corroborated with another study using transperineal ultrasound to evaluate for low perianal fistula. When comparing ultrasound findings of pilonidal disease with hidradenitis suppurativa, there were no statistically significant differences in morphological characteristics, but the density of hair tracts was higher in pilonidal disease.

MRI is more expensive and time-consuming than ultrasound but may aid in diagnosis when there is a concern for inflammatory bowel disease, fistula in ano, pelvic sepsis, or neoplastic processes. Recent studies have also suggested a role for a photodynamic eye with indocyanine green for the elucidation of disease extent to aid in resection.

Treatment / Management

Treatment can be divided into two broad categories - nonoperative vs. operative, and often there is a combination of the two. Pilonidal disease is largely considered a surgical disease, especially in acute instances with secondary infection and abscess. Infection or abscess requires incision and drainage. Definitive treatment is delayed the majority of the time if there is an acute infection or abscess until after the infection has been addressed. There are many options when it comes to surgical treatment of pilonidal cysts and pilonidal sinuses. The surgical treatment must be individualized to the patient. Lifestyle changes and modifiable risk factors should be addressed and be incorporated into the treatment algorithm.

Because of the role of hair in the pathogenesis of pilonidal disease, epilation and hair removal may be used as a primary or adjunct treatment, in the absence of abscess. Epilation may take the form of shaving, waxing, laser, or creams.

A study at an Army medical center found that conservative therapy in the form of weekly shaving a 5cm strip from the anus to the rectum, combined with hygiene education, resulted in decreased operations, and near-normal work status. In the treatment of chronic pilonidal disease, Solla et al. found good results when operative techniques were combined with shaving skin weekly or biweekly; patients were advised to keep the gluteal cleft free from hair for three to six months. Despite the rationale for hair removal, there is some evidence that hair removal may actually increase the rate of long-term pilonidal recurrence after surgery.

Laser epilation has been used in pilonidal disease with mixed results. Oram et al. evaluated 60 patients that were treated with laser therapy as an adjunct to surgery and found an overall recurrence rate of 13.3% and concluded laser hair removal after surgery decreases recurrence long-term with a mean follow up of 4.8 years. Conroy et al. evaluated 14 patients who underwent adjunct laser therapy and reported that of the 12 patients who completed the full course of therapy, and none developed recurrence. They recommend that laser depilation should be routinely offered to all patients suffering from pilonidal disease. Other studies have corroborated the effectiveness and safety of laser epilation, which requires multiple treatments. Pain was the most frequent side effect and can be seen in up to 40% of patients.A review study evaluating the effectiveness of laser hair removal included 35 studies and found that the recurrence rate after laser depilation ranged from 0-28%. However, among all five comparative studies, there was a decreased recurrence rate associated with laser hair removal. The authors of the study note the heterogeneity in studies and caution their generalizability. Laser hair removal often requires multiple treatments, can be limited by cost and may require local or topical anesthetic. Some hair removal products may be irritating to the anal mucosa or cause rashes.

Maurice and Greenwood proposed phenol, a sclerosing agent, as a treatment for pilonidal disease in 1964. It has been used in liquid and crystallized forms. It has been employed as a primary nonoperative treatment, as well as an adjunct to surgical treatment. Dogru et al. found success using phenol as an outpatient treatment. They reported a success rate of 95.1%, and had decreased recurrence rates, and decreased lost work time; they propose phenol as a viable first-line treatment. The patients in the study were shaved throughout treatment, and the majority required multiple phenol applications. Kaymakcioglu et al. reported an 8.3% recurrence rate using 80% phenol on a study of 143 patients; the volume of the sinus tract and the number of sinus orifices were risk factors affecting recurrence. A randomized controlled study of 140 patients compared phenol injection with excision and open healing found no significant difference in the recurrence rate. They reported that phenol was associated with decreased time to complete wound healing, less operative procedure time, decreased time to resume daily activities; and, visual analog pain scores and analgesic use were both decreased with phenol, compared to excision and open healing. This was corroborated with another more recent, smaller randomized trial of 100 patients. Pronk et al. compared radical excision with phenol application and found shorter return to normal activities, less pain, and more frequent complete wound epithelialization associated with phenol; they also noted an increased risk of surgical site infection with radical excision. Dag et al. reported early return to work with phenol use, and low rates of recurrence and complications, noting an overall success rate of 67% with only one patient having a recurrence; mean time to complete healing was 16 days, and time off of work was 0 days. There was a higher risk of treatment failure with a history of abscess drainage and greater than three sinus openings. Overall, phenol administration is relatively cheap, can be performed as an outpatient, and has success either as primary nonoperative treatment or adjunct to surgical options. Patients may require multiple treatments with phenol.

Fibrin and thrombin products have also been used for the treatment of pilonidal disease, either as a primary treatment or as adjuncts to surgical techniques. Greenberg et al. proposed using fibrin glue in addition to surgical excision, using the fibrin glue to obliterate the dead space; 30 patients were treated in this fashion, and there were four patients with temporary purulent drainage with an average of 11 days to return to work/ normal activities. A similar method was employed by Seleem et al., which reported primary healing in 24/25 (96%) of patients within two weeks. Patti et al. reported mean healing of 25.8 days, with a mean return to work 5.3 days when using fibrin glue with minimal surgical excision. Randomized control studies have studied the use of fibrin glue. When comparing standard Limberg flap vs. Limberg flap with fibrin glue, it was found that the addition of fibrin glue was associated with decreased drainage volume, and decreased hospital length of stay. A review study determined that the effectiveness of fibrin glue, alone as monotherapy or as a surgical adjunct, was uncertain. The use of fibrin glue appears to have high patient satisfaction, and up to 82% would recommend fibrin glue for the treatment of pilonidal disease.

Another nonsurgical option that has been proposed is platelet-rich plasma (PRP). Platelet-rich plasma is derived from autologous blood that is centrifuged and contains a high concentration of platelets and growth factors; it has been used in many subspecialties for its proposed wound healing properties and regenerative factors. A study by Sevinc et al. evaluated the long term results of a minimally invasive approach to treating pilonidal disease with PRP; their study evaluated 138 patients with a median follow up of 60.2 months. They reported a success rate of 97.1% after the first month with a recurrence rate of 8.2% at 60.2 months; mean healing time was 13.3 days, with 82.6% complete healing after a single application. The methods employed by Sevinc et al. included preparing PRP from 40 cc of the patient’s blood, and once the gel form was obtained, the procedure was performed under local anesthesia in the outpatient setting. There were no complications related to the use of PRP during their study. There has been a meta-analysis evaluating PRP for the treatment of pilonidal disease which included four studies and a pooled 484 patients, which found that the healing time was 36% less than the healing time of the control group which was calculated as 27.1 days in the PRP group versus 43 days in the control arm. They also reported a decreased return to work of 24.99 days in the treatment group versus 34.82 days in the control group.

A prospective randomized clinical trial from Turkey evaluated the benefits of adjunct hyperbaric oxygen, specifically regarding pilonidal disease. They reported a significantly shorter complete epithelization time in surgically excised pilonidal disease, allowed to heal by secondary intention, 50 days versus 83 days.

Pilonidal disease is largely considered a surgical disease, despite the many nonoperative approaches. The mainstay of acute pilonidal disease, or abscess, is similar to any abscess and requires incision and drainage (I&D). An early study looking at simple incision and drainage reported an immediate return to work, with 58% of patients healing within ten weeks; 21% of patients developed recurrence, but the overall cure rate was reported as 76% at 18 months. The incision and drainage procedure prior to definitive surgery has been associated with lower long term recurrence rates. In a study of 583 patients over 20 years, Doll et al. reported a 16% recurrence rate in the I&D group compared to a 34% recurrence in the primary open treatment group, and concluded that a preceding I&D has a better outcome than primary surgical treatment; optimal timing between I&D and surgery was not determined. Often, an incision and drainage procedure will employ the use of wound packing, but in a study of 100 pediatric patients undergoing I&D of subcutaneous abscesses, there was no difference in recurrence rates in those abscess with packing versus no packing, and the discomfort and nuisance of wound packing were avoided.

Surgical options for treating pilonidal disease are numerous and can include “pit picking,” curettage, aspiration, unroofing, or surgical excision. Defects can be closed primarily, with flaps or grafts, or allowed to heal by secondary intention. Another tool used for the healing of surgical treated pilonidal disease is negative pressure wound therapy. A randomized control study of 49 patients comparing negative pressure dressings vs. healing by secondary intention found little difference.

In the early 1980s, Bascom described a technique, cleft lift procedure, to remove the hair follicles parallel to, but to the side of, the natal cleft using local anesthesia. The initial 50 patients averaged a disability of one day, and healing time without disability averaged three weeks; there was a recurrence of four patients that healed in an average of two weeks.The follow-up study of 161 patients reported 94% of patients healed at 0-6 months, and 71% remained healed at 5-9 years. More recently, 31 patients with refractory pilonidal disease were evaluated, and it was reported that 28 patients healed after a single procedure, without recurrence. In a subsequent study, there was a 96% healing rate in 69 patients treated for refractory pilonidal disease.

Karydakis described a technique to excise an ovoid area of pathologic tissue off-midline and provide coverage lateral to the midline by mobilizing a fasciocutaneous flap and securing it to the sacrococcygeal fascia. In his series of >6500 cases, there was a 2% recurrence rate with an 8% complication rate. In a randomized controlled study of 321 patients evaluating the Karydakis flap versus excision and healing via secondary intention, it was found the meantime of wound healing, return to work, rate of wound complications and recurrence were all significantly lower in the group undergoing the Karydakis flap, but operative time was longer; pain was higher on the first operative day, but was significantly less after one week.

Another type of flap used for the treatment of pilonidal disease includes the Limberg or rhomboid flap. The Limberg flap excises the pilonidal disease in a rhomboid shape and rotates a fasciocutaneous flap for wound closure. Bozkurt et al. evaluated the Limberg flap in 24 patients under spinal anesthesia and reported mean hospital length of stay 4.1 days, with an average 17.5 days until return to work; 12.5% of patients had minor complications, and during the follow up (range 6-27 months, mean 18 months), there were no recurrences. A randomized control study comparing the Limberg flap, to primary closure and deep suturing reported improved wound healing, decreased hospital stay, earlier return to work, and decreased recurrence. Another more recent randomized control trial of 200 patients reported less postoperative pain, earlier mobilization, decreased hospital stay, with fewer complications employing the Limberg flap compared to primary closure. Numerous randomized control studies and meta-analyses have compared the Limberg and Karydakis flaps, which have shown to be comparable in outcomes with the exception that the Limberg flap has less risk of seroma formation.

Other flaps include VY advancement flaps and Z-plasty. Small case series have demonstrated the ease and efficacy of a tension-free repair using the VY fasciocutaneous advancement flap. A larger study employing VY advancement in recurrent pilonidal disease reported tension-free repairs with reliable coverage and flattening of the natal cleft; however, 90.7% of patients were dissatisfied with the cosmetic appearance of scars. Z-plasty to treat pilonidal disease was introduced as early as the 1960s. In a randomized control study comparing Z-plasty with I&D or marsupialization, Z-plasty was definitive treatment compared to 40% of the control group requiring further surgery. Fazeli et al. compared Z-plasty with healing by secondary intention and found that wounds healed faster with the Z-plasty, and there were no complications.

Other, less widely used methods of treating pilonidal disease include endoscopic treatment and video-assisted ablation. Endoscopic pilonidal sinus treatment (EPSiT) was introduced as a minimally invasive video-assisted technique, performed under spinal anesthesia or local anesthesia, that uses a fistuloscope to remove hair and debris while performing ablation under direct visualization. In multinational prospective studies, Meinero all reported healing rates of 95%, with the incomplete healing rate being related to the number of external pits; it was deemed to be safe, effective in primary pilonidal disease and recurrent disease, and had good patient satisfaction.

The use of antibiotics for the treatment is controversial. It has been evaluated in regards to perioperative prophylaxis, postoperative treatment, and topical use; the American Society of Colon and Rectal Surgeons provide a “weak recommendation based on moderate-quality evidence, 2B.”

Differential Diagnosis

Pilonidal disease is diagnosed clinically, through history and physical, and the treatment is surgical. If there is concern for other differential diagnoses, imaging modalities can be used. Other conditions on the differential diagnosis include abscess, hidradenitis suppurativa, inflammatory bowel disease (Crohn, ulcerative colitis), anal fistula, or epidural abscess. It can also represent other soft tissue infections like folliculitis, furuncles, or carbuncles. Various types of cancer have been diagnosed as or in conjunction with pilonidal disease.

Pilonidal disease is typically found in the sacrococcygeal region but has been reported in other parts of the body. Benharroch et al. performed a retrospective review of unexpected pilonidal sinus locations and reported pilonidal disease on the penis, scalp, abdomen, neck, groin, and axilla. There have been case reports of pilonidal sinus located on the nasal dorsum, and nose. Pilonidal disease has been found on the vulva and clitoris. Additionally, pilonidal disease has been found on the hand, interdigital, and periungual; often, these patients have a history of occupational exposure as barbers, hairdressers, or animal groomers. Pilonidal disease of the hand has also been reported associated with Dupuytren contracture. Pilonidal disease has been reported in the anal canal, and there may be a higher prevalence of sacrococcygeal pilonidal disease in those patients with ankylosing spondylitis. Epidural abscesses and osteomyelitis may be associated with pilonidal disease and should be included in the differential diagnosis, in rare instances. Tuberculosis has also been reported in association with pilonidal disease. Other infectious processes, such as syphilis and actinomycosis, have been reported as resembling pilonidal disease.

Most surgeons elect to send pilonidal specimens for pathological evaluation. Some authors have questioned the need to perform histologic evaluation, but Tamer et al. reviewed articles spanning 2000 to 2018 and found twenty-two articles reporting 83 patients with malignancy including squamous cell carcinoma, epidermoid carcinoma, basal cell carcinoma, and malignant degeneration; they advise all specimens should be sent for histopathologic evaluation.

Prognosis

The prognosis associated with pilonidal disease is very good as it is a benign disease, despite some reports of malignant degeneration, or skin cancer. Pilonidal disease, however, has a relatively high recurrence rate and may require multiple procedures. The overall prognosis with pilonidal disease is very good with lifestyle modifications and accurate diagnosis.

Complications

Complications associated with pilonidal disease largely include recurrence and wound healing issues such as wound breakdown or surgical site infection. They may initially present as an abscess or can become secondarily infected. In rare cases, pilonidal disease has been associated with osteomyelitis or malignant transformation.

Deterrence and Patient Education

Patients should be educated about risk factors, which include male sex, family history, being overweight/obesity, trauma or irritation, sedentary occupation or lifestyle, hirsute habitus, and poor hygiene. Modifiable risk factors should be directed towards weight loss, lifestyle modification, good hygiene, and hair removal.

Enhancing Healthcare Team Outcomes

Pilonidal disease is a relatively common and benign disease process where surgery is usually the definitive treatment. Certainly, these patients should be evaluated by a surgeon, but they are usually not the first clinician to which a patient presents. Interprofessional communication is necessary as these patients can present to any clinician, primary care provider, or general practitioner. The diagnosis is clinical, so prompt recognition and diagnosis can lead to faster treatment and resolution. Pilonidal disease is a relatively common disease, and there is an extensive amount of published material. This includes various types of studies, including randomized control studies, cohort and case-control studies, case series, and expert opinions. Pilonidal disease is a broad topic, so narrowing the specific question can provide specific publications and research studies. There are numerous treatment modalities and treatment combinations. There is no single best treatment modality, and treatment must be individually tailored to the patient.