An anal fistula is an anorectal fistula. It is a sequel to the breakdown of a perianal abscess. In the acute inflammatory phase, there is a lot of pus and often a foul odor, and because the fistula is curved, branches and drains poorly, there is often pus accumulation. In the chronic inflammatory stage, the pus flow is less, sometimes intermittent, and the pus is thin or in the form of rice slop secretions. Itching of the anus is caused by the discharge from the external fistula opening that irritates the local skin of the anus. Pain is caused by poor drainage, blockage of the canal by secretions, or recurrent inflammation. The pain can be distension or burning pain in the anus, but if there is no pus accumulation and blockage, there is usually no pain. The inflammatory phase of anal fistula may also be accompanied by systemic symptoms, such as chills and fever, and increased peripheral blood count. If the fistula is complicated by prolonged suppuration, it may be accompanied by anemia, emaciation, and loss of appetite. The first stage is the inflammation of the anal saphenous fossa and flap. This is limited to local inflammation, which can spread around the anus if not treated in time. In the second stage, the inflammation starts in the localized anal fossa and flap and gradually spreads to form perianorectal inflammation. If the inflammation is not controlled, it may invade the tissue interstices with low resistance to disease. In the third stage, as the resistance of the perianorectal tissue gap decreases, it becomes a place for germs to invade, spread, accumulate and multiply, making the tissues here susceptible to infection and inflammation. If anorectal abscess can be handled properly in the early stage, it can often be dissipated and cured without leaving sequelae; if the early treatment time is delayed or improperly handled, the tissue necrosis and pus can spread along its local gap, which will aggravate and complicate the condition. The fourth stage is that the perianal abscess breaks down on its own or is treated by incision and drainage for a change of medication, but the pus cavity gradually shrinks, but the ulcerated sore does not close for a long time. Modern medical pathogenesis of anal fistula 1) The theory of infection of the anal saphenous glands The theory of infection of the anal saphenous glands suggests that the infection enters the anal glands from the anal ducts and spreads to the perirectal space through the tubular branches of the glands, or the joint longitudinal fibers up, down, and out, forming abscesses in various places. (2) Central space infection theory The central space infection theory believes that the inflammation starts with the formation of a central abscess in the central space, and then the pus spreads to the perianorectal space along the fibrous partition of the central tendon. (3) The theory of close relationship between perianal abscess and anal fistula There is no doubt that most perianal abscesses eventually form anal fistulas, and the literature reports that the rate of fistula formation in perianal abscesses is about 87-100%. Perianal abscesses and fistulas are actually different stages of one disease. Problems and perspectives Anal fistulae, especially for complex anal fistulae, are considered to be an urgent research problem in the current surgical field. Currently, complex anal fistulas are internationally recognized as one of the three most difficult anal diseases. Currently, the best means of treatment for anal fistula is through surgery, but there are many problems with the current traditional surgical methods, mainly the following: 1) long and painful recovery time after surgery, and the resulting scar tissue can often reduce the diastolic function of the anal sphincter. It is easy to produce anal canal defect and affect the function of the anus. (2) Premature tightening of the line, early detachment of the rubber cord, formation of local depression and defect, is one of the main causes of anal deformation, displacement, incontinence, subluxation of the intestinal mucosa, leakage of mucus and other sequelae. (3) Excision of the wall of the tube involves the removal of all the normal anal margin skin and sphincter muscle within the range of the tube to achieve drainage patency, which is bound to seriously damage the morphology of the anus and its sphincter function. At the same time, the large scar tissue produced after the incision also restricts the sphincter function of the anus, leading to sequelae. (4) The fistula is located above the rectal ring of the anal canal and crosses the deep part of the external sphincter, and in deep cases, it can cross the scirorectal space to reach the pelvic rectal space, which damages more tissues during the operation and easily causes sequelae such as subrectal mucosa, anal deformity and incontinence. The correct surgical approach is a prerequisite for the cure of anal fistula, and repeated and multiple inappropriate surgeries are also one of the causes of complex anal fistula. In recent years, scholars at home and abroad have proposed many new methods for treating complex anal fistula through continuous exploration and research, but all of them have limitations and shortcomings, so the search for an optimal procedure still needs further exploration and efforts. At present, Prof. He Yongheng, a doctoral supervisor of the Department of Anorectal Surgery of the Second Affiliated Hospital of Hunan University of Traditional Chinese Medicine, has pioneered the “minimally invasive treatment” of anal fistula, i.e. segmental opening and opening combined with incision and dilation/hanging tube drainage (this research is a key project of scientific research of Hunan Provincial Education Department). I followed my supervisor after graduation and came to work in the Department of Anorectal Surgery of Chenzhou First People’s Hospital under the supervision of Gu Chengyi, the department director, Tang Qingzhu and superior physicians such as Tang Shijia and Luo Jikong. Our team got the true essence of this minimally invasive treatment for anal fistula from Prof. He, and the staff of the department is skilled in operating with theory and practice and surgical modality, hoping that this surgical modality can bring good news to those patients with anal fistula, especially complicated anal fistula.