Pilonidal sinus and Pilonidal cyst, collectively known as Pilonidaldisese, is a chronic sinus tract or cyst in the soft tissue of the sacrococcygeal intergluteal fissure, characterized by hidden hair. It may also present as an acute abscess in the sacrococcygeal region, which punctures and forms a chronic sinus tract, or heals temporarily and eventually punctures again, and so on. The cyst is accompanied by granulation tissue, fibrous hyperplasia, and often contains a tuft of hair. Although the disease can be seen after birth, but more in the puberty after the age of 20 ~ 30 years old, because of the increased activity of hair sebaceous glands, before the appearance of symptoms. I. Etiology The true cause of the disease is unknown, and there are two theories. One congenital inclusions in the skin due to residual medullary canal or developmental malformation of the sacrococcygeal suture. However, with infants, the midline position of the shallow post-anal recess is rarely found in the precursor lesions of hidden hair disease, while in adults it is indeed common. II Acquired think of sinuses and cysts as granulomatous disorders due to injury, surgery, foreign body irritation and chronic infections. Recently it has been confirmed that hairs entering from the external times are the main etiologic factor. The intertrochanteric fissure has a negative attraction that allows the shedding of hairs to penetrate subcutaneously. Too much hair in the fissure is too long, the top of the hair has a filtering and soaking soft hair skin effect, the hair penetrates into the skin, forming a short tract, and later deepen into the sinus, the hair root shedding to the sinus can also make the hair stem penetration, in the process of the onset of visible movement changes, but only half of the cases can be found in the hair, this disease is seen in the polydactyly flat, sebaceous hyperactivity, intergluteal fissure is too deep and buttocks are often injured in the patient. The skin of the sacrococcygeal region of automobile drivers is often subjected to prolonged upheaval and injury, which can cause sebaceous glandular tissue and debris to deposit in the sac and cause inflammation. The disease occurs more frequently in the U.S. Army and is known as Jeep’s disease. Common pathogens are anaerobes, staphylococci, streptococci, and Escherichia coli.Rainsbury and Southan analyzed static hide-and-hair disease, and individual bacteria accounted for less than half of the cases, while anaerobes accounted for 58%. Curiously staphylococci were uncommon and most aerobic bacteria were gram-negative. Hidden hair cysts are often asymptomatic in the absence of secondary infection, except for a sacrococcygeal protuberance, and some feel pain and swelling in the sacrococcygeal area. Usually the main and first symptom is an acute abscess in the sacrococcygeal area, localized redness, swelling, heat, pain and other features of acute inflammation. Most automatic breakthrough outflow of pus or surgical drainage after the inflammation subsides, a few drainage port can be completely closed, but most of the manifestations of recurrent episodes or frequent flow of water and the formation of sinus tracts or fistulas. Hidden hair sinus static in the sacrococcygeal midline skin can be seen irregular small holes, diameter of about 1mm ~ 1cm. the surrounding skin is red and swollen and hard, often with scarring, some visible hair. The probe can be probed into 3~4mm, some can be probed into 10cm, and dilute light odor liquid can be discharged when squeezed. There are acute inflammation manifestations during acute attack, with tenderness and redness, discharging more purulent secretions, and sometimes abscesses and cellulitis occur. Surgical treatment of hidden hair sinus Surgery is the main treatment method, but it is contraindicated when there is inflammation, and should be performed once the inflammation subsides. Surgical methods include the following: 1. Excision with one-stage suture Surgical excision of all diseased tissues, free muscle and skin, and complete suture of the wound for one-stage healing. In order to eliminate the deep intergluteal fissure and its negative pressure, and to reduce wound dehiscence, hematoma and abscess, Z formation is feasible (Figure 1). It is suitable for cysts and small non-infected sinus tracts on the midline, with a recurrence rate of 0% to 37%. The advantages are short healing time, soft and movable scar formed within the gluteal intertrochanteric fissure, and soft tissues between the scar and the sacrum, which can tolerate injury. 2.Excision of part of the suture Remove the lesion tissue, the skin on both sides of the wound and the sacral fascia suture, so that the large part of the wound healed in one stage, the middle part of the wound healed by the granulation tissue. It is suitable for cases with many sinus openings and sinus tracts, and the effect is the same as that of excision one-phase suture, but the healing time is longer. 3, excision wound open second period suture for serious infection cases and a period of suture infection wound incision drainage cases. 4, excision wound open For cases where the wound is too large to be sutured and surgical recurrence. The surgery is simple, but the healing period is long, the scar is extensive, only a thin layer of epithelium, sticking to the sacrum, if there is any injury, the scar is easy to rupture. 5.Pocket suture Remove the surface part of the sinus wall and the upper cover of the skin, with intestinal thread or absorbable artificial suture wound to promote healing. Careful postoperative care can often lead to satisfactory results. It is mostly used in unresectable cases or recurrent hair hiding sinuses. Non-surgical treatments for Hidden Hair Sinus The sacrococcygeal fossa does not require treatment as it is only an indentation in the sacrococcygeal joint, the lower part of the sacrum and the tip of the coccyx, is asymptomatic and of no clinical importance. Sacrococcygeal hidden hair sinus and sacrococcygeal swellings should be treated with antitreatment if infection occurs, local cleanliness should be maintained, and if abscesses are reproduced, they should be incised and drained. However, the sacrococcygeal skin and subcutaneous tissue is thicker and harder, there is no obvious performance in the early stage, and the inflammation often spreads to the surrounding tissues causing cellulitis. Deep tissue necrosis should be incised and drained early. Sclerotherapy is to inject corrosive drugs into the sinus tract, destroying the sinus and intracystic epithelium, so that the cystic cavity and sinus tract are closed. Since 1960, some people apply phenol solution injection therapy, but not many applicators, because the application of pure phenol solution, the pain is severe, and then changed to 80% concentration, and under general anesthesia; the sinus is injected into the colloid to protect the surrounding skin.Hegge (1987) used 80% phenol solution 1~5 ml injected slowly into the sinus, it takes about 15 min, the slow injection can prevent complications, such as skin burns, fat necrosis or severe pain. This method can be repeated every 4-6 weeks, about half of the patients can be cured after only 1 injection, 12% need to be injected 5 times or more. 43 cases were followed up for more than a year, and only 3 cases (6%) recurred. stansby (1989) injected 80% phenol solution into the sinus under general anesthesia, retained it for 1 min, scraped the sinus tract, and repeated the procedure 3 times, and aseptic abscesses occurred in 4 out of 104 cases, and a case of bees’ disease fossa was found. histitis, and no other complications. Compared with 65 cases of surgical excision, the treatment rate; excision is 86%, phenol injection is 75%; follow-up average 8 months (3 months ~ 4 years), 10 cases of recurrence of excision of injection of 12 cases of recurrence. Second, clinical manifestations Tibetan hair cysts such as no secondary infection often asymptomatic, just the sacrococcygeal protrusion, some feel sacrococcygeal pain and swelling. Usually the main and first symptom is acute abscess in the sacrococcygeal area, localized redness, swelling, heat, pain and other acute inflammatory features. Most automatic breakthrough outflow of pus or surgical drainage after the inflammation subsides, a few drainage ports can be completely closed, but most of the manifestations of recurrent episodes or frequent flow of water and the formation of sinus tracts or fistulas. Hidden hair sinus static in the sacrococcygeal midline skin can be seen irregular small holes, diameter of about 1mm ~ 1cm. the surrounding skin is red and swollen and hard, often with scarring, some visible hair. The probe can be probed into 3~4mm, some can be probed into 10cm, and dilute light odor liquid can be discharged when squeezed. Acute inflammatory manifestations of acute episodes, tenderness and redness, discharge of more purulent secretions, sometimes abscesses and cellulitis. Differential diagnosis should be differentiated from boils, anal fistula and granuloma. Boils grow on the skin, protrude from the skin, and are yellow at the top. Carbuncles have multiple external orifices lined with necrotic tissue. An anal fistula has an external opening close to the ****, a fistula traveling toward the ****, a cord on palpation, an internal opening in the anal canal, and a history of **** rectal abscess. The direction of travel of the hidden hair sinus, on the other hand, is mostly cranial and rarely downward. Tuberculous granuloma is attached to the bone, and X-rays show destruction of the bone and tuberculous lesions in other parts of the body. Syphilitic granuloma has a history of syphilis and positive syphilis seropositivity. Prognosis Carcinoma occurring in the hidden hair sinus is rare, and the lesions are mostly well-differentiated squamous cell carcinoma. Wound changes should raise the suspicion of carcinoma, such as ulcers that are easy to break, grow quickly, out of the sedan chair and mold-like edges. Wide excision should be preferred. As wounds are widely treated with implants or flaps. Enlarged abdominal and femoral lymph nodes should be biopsied to exclude whether there is metastasis; if there is metastasis, the prognosis is poor, and the literature reports a 5-year survival rate of 51%. The 5-year survival rate is 51% and the recurrence rate is 50%. Metastasis of the abdominal and femoral lymph nodes is found in 14% of cases at the time of initial diagnosis.