1, the law of transmission of perianal infection and the formation of anal fistula The perianal infection is divided into glandular source infection and non-glandular source infection. Non-glandular infection can be cured by adequate incision and drainage and reasonable treatment without forming anal fistula, i.e. non-fistula abscess. Glandular-derived infections are caused by repeated contamination and infection of the opening of the anal glands after infection, resulting in recurrent anal fistulas, i.e. fistula abscesses. The non-glandular origin of the infection is not treated correctly and the infection invades the anal gland, repeating the pathological process of the glandular origin of the infection, also to occur anal fistula, which we can consider, secondary fistula. In other words: perianal infections do not necessarily form anal fistulas, but all anal fistulas originate from perianal infections. Early onset of perianal infection is confined to one of the perianal gaps, and when the infection is not controlled or reoccurs, it first invades adjacent gaps or spreads to other gaps through the muscle gaps, complicating the infection or fistula. In conclusion, perianal infection always spreads along the lax interstitial space, and the resulting fistula always travels along the interstitial space, and its cavity is also formed within the interstitial space. Some American scholars refer to perianal abscesses as “fluid abscesses”, which is a more appropriate image. By familiarizing ourselves with the anatomy of the anal canal and rectum, we can know that there are left and right pelvic rectal gaps and posterior rectal gaps in the lateral rectal wall, above the anal raphe, and the gaps are relatively loosely separated from each other at this level, which are both independent of each other and in traffic with each other, so that a large circumferential gap is formed in the periphery of the rectum. Similarly, at the level below the anal raphe, there are left and right sciatic rectal interstices and deep posterior anal canal interstices, which also form a large circumferential interstice with mutual traffic in the rectal periphery. This is the anatomical and pathological basis for the formation of horseshoe-shaped anal fistulas at both the upper and lower levels of the anal raphe, which are separated by the anal raphe and have dense tissue, making it relatively difficult for infection to penetrate this layer. If the infection crosses the levator ani muscle, the two large circumferential spaces above and below the levator ani muscle, the fistula formed will also be a three-dimensional structure with two layers, which is more complicated. Some scholars have suggested that the “dumbbell” and “gourd” structures of high complexity fistulas are due to the fact that the fistulae encroach on the upper and lower gaps of the levator muscle. The main point of the surgery is to completely remove the cavity formed in the fistula and protect the sphincter. The repeated application of antibiotics to control perianal infections is the cause of the transformation of perianal infections into complex anal fistulas The repeated infection of the internal opening formed by the anal glands is an important cause of perianal infections forming anal fistulas and complicating them. Due to the continuous upgrading of antibiotics and their increasing potency, early perianal infections, after the application of a large number of antibiotics, are often confined and wrapped in a certain gap, and the source of infection is not eliminated. When the infection is re-infected, if it is not controlled in time or the patient is afraid of surgery and fails to drain it in time, the infection spreads rapidly to the adjacent interstitial space and is wrapped again after the application of more advanced and massive antibiotics. With more and more such repeated violations, the anal fistula is bound to become more and more complicated, increasing the difficulty of treatment. We believe that the repeated and massive application of antibiotics is one of the reasons for the complexity of anal fistula. Many clinicians are often confused about the location and extent of deep fistulas and cavities and are not sure about the prognosis of this surgery. The second is the fear of excessive surgical trauma, which causes anal incontinence. Thus, the purpose of the surgery is not clear and the surgery is not complete, and the anal fistula is repeatedly treated but not healed, destroying the normal anatomical structure. The design of the surgical incision for anal fistula is not reasonable, resulting in a poor drainage pathway, or the drainage pathway crosses the original uninfected perianal space, and the fistula not only does not heal this space but also forms a new branch, and the surgical incision becomes a new external port. Therefore, the American scholar John H. Pemberton pointed out that almost always a simple fistula becomes an extremely complicated fistula due to the doctor’s lack of understanding of the anatomy of the area or the wrong diagnosis of the type of perianal abscess and its fistula. Surgical drainage of fistulas should be done in such a way that the deepest part of the fistula and cavity is the shortest distance to the incision, the gaps traversed are arranged longitudinally and at a minimum, and the trauma is kept open from beginning to end throughout the healing process. We believe that the surgeon treating a patient with a fistula for the first time has the best chance of identifying the fistula, detecting the internal opening, and providing effective treatment. If the first treatment does not achieve its goal, further surgery may be more complicated and the patient will suffer from increased risk of complications. The surgical treatment of anal fistula belongs to the category of surgery, and it is also impossible to depart from the basic principles of surgery. The progression of anal fistula tracts is regular but variable, and the existing inspection methods are not yet able to identify all the main and branching tracts and cavities in a precise and accurate way. It is particularly important to explore and identify fistulae during surgery, as scraping the fistula wall with a spatula can reveal inexhaustible areas of decaying tissue, which are often openings for branches that communicate with another gap. The exploration of the fistula emphasizes direct visualization and aims to observe the entire fistula. The purpose of debridement is to allow for the unobstructed growth of fresh granulation tissue on the one hand, and to detect cavities that were not detected by exploration within the fistula on the other. The process of debridement should be carried out carefully along the fistula wall, as far as possible within the invaded interstitial space. Blind, crude blunt separation is bound to result in the destruction and infection of the original normal perianal space, further complicating the anal fistula. The perianal infection is increasingly complicated by the lack of timely drainage, and the surgical trauma should be noted for unobstructed drainage throughout the healing process. The drainage path is direct and unbending.