The main character is a pseudonym to protect the privacy of the patient, Xiao Zhao is a healthy and handsome guy, sturdy, hairy, very “androgynous charm”, usually some colleagues on the work of strength, Xiao Zhao are willing to help complete, “a handful” more let him Become female colleagues in the “standard version of the fierce man”. But recently Xiao Zhao began to worry up. One morning after drinking, Zhao woke up feeling uncomfortable after the hip and sacrum position, feeling with his hands “tailbone tip” there is a small bulge, pain and discomfort, at first he did not care, think this is “on fire”, did not care, the results 2 days later the pain The pain worsened 2 days later, and he simply took some antibiotics orally, thinking it was okay. The result was that after a few days, the lump became hard and broke down, and left a blood-red pus, which seemed to have a foul odor. The first thing you need to do is to get a good idea of what you are getting into. The first thing you need to do is to get a good idea of what you are getting into. This time Xiao Zhao was confused, he hurriedly googled, ask friends, find acquaintances, and finally came to colorectal surgery. After the outpatient doctor examined him carefully, he was diagnosed with “sacrococcygeal sinus infection” according to his clinical manifestations, and was issued an admission certificate. After the surgery and post-operative systematic treatment, Zhao finally recovered his health. When he was discharged from the hospital, Zhao expressed his gratitude to the doctors and nurses, but also asked his own questions: What is a hairy sinus? Why do I have a hairy sinus? Why did my first surgery fail? The next, we will take you to understand, this is not rare and easy to recur “sacro-caudal hair sinus”. 1.Hair hiding sinus: Hair hiding sinus (pilonidal sinus) and hair hiding cyst are collectively called hair hiding disease, which is a kind of chronic sinus or cyst formed in the soft tissue of sacrococcygeal intergluteal fissure, and hair hiding inside is its characteristic. The clinical manifestations are repeated abscess formation in the sacrococcygeal region, which breaks down and forms a chronic sinus tract that does not heal over time. This disease is rare, mostly seen in white, young male, obese, hairy, and deep intergluteal groove. 2, the prevalence of the Tibetan hair sinus population Tibetan hair disease is a rare disease, the pathogenesis of which still has different views. The congenital theory believes that the hidden hair sinus is caused by congenital epithelial residue or congenital skin depression, and the hair in the hidden hair sinus is due to the presence of hair follicles in the invaginated epithelium. The acquired theory suggests that the hidden hair sinus is caused by the twisting and friction of the buttocks during walking, especially in hairy males, which causes the hair between the mid buttock cleft to pierce the nearby skin and form a short duct, while the hair is still connected to its root, and the short duct is then dermatomized, and when the hair is shed from the follicle, it is sucked in by the gravitational force generated by the dermatomized duct. Thus, it is proposed that the first stage is the piercing sinus tract and the second stage is the aspiration sinus tract. The hair collects in the subcutaneous fat and becomes a foreign body, secondary to bacterial infection, i.e., a chronic infection or abscess is formed. At present, most scholars prefer the acquired theory, and the author believes that the development of the hairy sinus is related to genetic factors, anatomical characteristics of the gluteal cleft, endocrine, obesity, and environment, etc. The specific mechanism needs further study. Recently, it was found that the recurrence of the hairy sinus after surgery was related to family history, and the recurrence rate of patients with family history was 1.5-2 times higher than that of patients without family history 15-20 years after surgery, while weight was not significantly related to the recurrence of the hairy sinus. 3.Sacrococcygeal sinus is easily misdiagnosed. The hairy sinus is usually manifested as recurrent abscesses in the sacrococcygeal region, which mostly break down on their own to form sinus tracts. It needs to be differentiated from anal fistula and paranal abscess and tuberculosis granuloma. Three cases have been diagnosed as “anal fistula” and “perianal infection”, respectively. Clinically, the sinus orifices due to Tibetan hair disease are mostly at the gluteal groove, and the sinus tracts are mostly cranially oriented, rarely downward toward the anal canal. There is no internal orifice in the anal canal, and the typical strip-like mass of an anal fistula cannot be palpated. irregular small holes, about 1 mm to 2 cm in diameter, are visible in the skin at the midline of the sacrococcygeal region during the resting phase. the surrounding skin is red and swollen, often with scarring, and in some cases hair is visible. A probe can penetrate 3-4 cm, and when squeezed, it can discharge a thin, foul-smelling fluid, thus distinguishing it from anal fistulas and paranal abscesses. In contrast, tuberculous granuloma often involves bones, and bone destruction can be seen on X-ray, and other parts of the body may have tuberculous lesions. In our six cases, the sinus orifice was located in the sacrococcygeal region, and the sinus tracts traveled to the cranial side. A mass of about 3-4 cm in diameter was seen in the sacrococcygeal region, and no internal orifice was seen, and no mass was palpated with the anal canal. Therefore, those who have the above characteristics clinically should consider the possibility of hidden hair disease, and the presence or absence of hair should not be used as the only basis for diagnosing this disease. 4.How to treat the hair hiding sinus? The sacrococcygeal hidden hair sinus can only be cured by surgical excision. There are various surgical methods which have not been unified, such as incision and drainage of pus, anhydrous alcohol injection, cryosurgery, complete excision of open wound, excision and one-stage suture, zigzag excision and suture, excision wound filled with gentamicin collagen and suture, excision and post-excision flap graft, etc. The surgical approach can be decided according to the number and extent of cysts and sinus tracts and whether they are complicated by infection. (1) If the hidden hair sinus is complicated by infection, anti-infection should be performed first, and if it is accompanied by abscess, the cavity should be fully incised and drained, and the granulation tissue and hair follicles and hairs in the cavity should be removed as much as possible, and excision and suturing should be performed at a later stage after the inflammation is limited. If the abscess is small and the infected lesion is limited, the lesion can also be excised completely and the incision can be sutured in one stage. In this group, one case was admitted with complication of infection, and after anti-infection treatment to control infection, complete excision of the lesion was performed, and the wound was closed in one stage. (2) In patients without obvious infection, if only a cyst or a single sinus tract or a small lesion with low tension, a one-stage excisional suture is feasible [7]. Complete excision of the fibrous cyst wall and surrounding granuloma is required, and the incision is closed in layers with absorbable sutures, with intensive postoperative dressing changes and local physical therapy to promote healing. In this group, 7 cases were resected and sutured in one stage, and one case of postoperative fat liquefaction of the incision occurred, which healed in 6 weeks after the usual drainage, and the remaining 7 cases healed in one stage. (3) For patients with more sinus openings and sinus tracts and larger lesions, after complete excision of the lesion, the wound surface is larger, and the wound surface can be closed by partial excision suturing or flap grafting. Partial lesion excision suture closes the skin, subcutaneous fat and sacral fascia on both sides of the incision, so that the majority of the wound heals in one stage and the middle part of the wound is healed by granulation tissue. In the study of K Topgl*, the length of hospitalization, healing time, incision infection rate and recurrence rate were significantly better with Limberg flap graft. The 5-year recurrence rate was 2.5% and the 9-year recurrence rate was 2.9%, which were significantly better than those of conventional excisional sutures and other flap grafting methods. The reason for recurrence is related to the incomplete excision of sinus tissue; and for larger lesions, although the surgical removal of the lesion is complete, infection and delayed healing can occur secondary to the oversized wound, dead space left in the incision suture, excessive skin tension leading to local ischemia or incision splitting. Therefore, the thoroughness of lesion removal and the rationality of wound closure methods are the keys to prevent postoperative recurrence.