Overview
A fistula is a granulomatous duct that connects to the skin of the perineum, with the inner opening located near the dentate line and the outer opening located at the perineum and skin. The wall of the fistula consists of thickened fibrous tissue with a layer of granulation tissue that does not heal over time. The incidence is second only to that of hemorrhoids, and is most often seen in young male adults, probably related to the high secretion of sebaceous glands, one of the sex hormone target organs in men.
Diagnosis
At present, most anal fistulas are divided into 4 categories according to the relationship between the anal canal and the sphincter. 1. Inter-sphincter fistulas are mostly low anal fistulas, the most common, accounting for about 70%, as a consequence of perianal abscesses. The fistula only crosses the internal sphincter and often has only one external opening, about 3-5 cm from the anal verge. a few fistulas go upward, forming a blind end between the rectal cricothyroid and longitudinal muscles or penetrating into the rectum to form a high intersphincteric fistula.
2. Trans-sphincteric fistulas can be low or high anal fistulas, accounting for about 25% of cases, as a consequence of abscesses in the sciatic rectal fossa. The fistula passes between the internal sphincter, the superficial external sphincter and the deep part, and there are often several external openings with branches communicating with each other. The external opening is close to the anal verge, about 5 cm, and a few fistulas pass upward through the anal raphe to the pararectal connective tissue, forming a pelvic rectal fistula.
3, supra-sphincter anal fistula is a high anal fistula, rare, accounting for 5%. The fistula passes upward through the levator muscle and then downward to the colorectal fossa to penetrate the skin. Because the fistula often involves the anorectal ring, it is more difficult to treat and often requires staged surgery.
4. Extra-sphincter fistulas are the least common, accounting for 1% of cases, as a consequence of a pelvic rectal abscess combined with an abscess in the colorectal fossa. The fistula passes through the levator muscle and communicates directly with the rectum. This type of fistula is often due to clonorchiasis, intestinal cancer or trauma, and treatment should pay attention to its primary lesion. The above classification is more detailed in terms of high and low levels, which facilitates the choice of surgical approach.
If there is an external opening on both the left and right side of the anal canal, it should be considered a “hoof and iron” type of fistula. This is a special type of fistula that penetrates the sphincter and is also a high curved fistula that surrounds the anal canal and passes from one side of the sciatic rectal fossa to the opposite side, becoming a semicircular type, so named because it is hoof-shaped. There is an internal opening near the dentate line, while the external opening can be multiple, scattered on the left and right sides of the anus, with many branches that spread around. The hoof-shaped anal fistula is divided into two types: anterior hoof-shaped and posterior hoof-shaped. The latter is more common because the posterior part of the anal canal is looser in tissue than the anterior part and the infection spreads easily. If the fistula is located in front of the line, the fistula is usually in a straight line towards the anal canal, and the internal port is located in the corresponding position of the external port; if the external port is behind the line, the fistula is often curved, and the internal port is mostly in the middle of the posterior canal. Most anal fistulas conform to the above rule, but there are exceptions, such as anterior high hoof fistulas that may be curved and posterior low perianal abscesses that may be straight. It has been observed clinically that the straightness and curvature of fistulas are related to the anterior and posterior aspects of the anal canal, but also to the high and low position of the fistula and to the proximity of the external opening to the anal verge.Cirocco (1992) performed a retrospective analysis of a group of fistula cases to test the accuracy of Goodsall’s rule in predicting the course of fistulas and concluded that the rule was quite accurate in predicting the course of fistulas with posterior external openings. In particular, in female patients, 97% of the internal orifices were located in the posterior median anal fossa, but the prediction of anterior external fistulae was not accurate, and only 49% of the fistulas with radial fistulae fit the rule, because Goodsall did not recognize that 9% of the anterior fistulas also originated in the anterior median anal fossa.
Rectal palpation: mild tenderness at the internal orifice and, in a few cases, a hard nodule may be palpable. X-rays, with 30% to 40% iodine oil injected into the external orifice, are used to visualize the distribution of the fistula, mostly for high anal fistulas and hoof fistulas.
In the case of fistulas, the former is sometimes of diagnostic value for intersphincteric fistulas, but not for fistulas that cannot be detected by routine clinical examination. The latter is absolutely superior and accurate for complex high anal fistulas, hoof fistulas and difficult cases that are difficult to diagnose clinically.
Treatment measures
Anal fistula cannot heal on its own and must be treated surgically. The principle of surgical treatment is to cut open the fistula and, if necessary, remove the scar tissue around the fistula at the same time, so that the wound gradually heals from the base upwards. Depending on the depth and curvature of the fistula, the fistula can be treated with a wire, an incision or excision. In a few cases, the fistula can be excised and then sutured or implanted. (a) Threaded treatment
This is a slow incision of the fistula. It is a method of slow incision of the fistula. It uses the mechanical action of rubber bands or threads (the threads still have the corrosive effect of drugs) to make the tissues at the ligature blood flow obstruction and gradually compress the blanks painstakingly; at the same time, the ligature threads can be used as fistula drains to drain the fistula tract and prevent acute infection from occurring. In the process of cutting the surface tissue, the basal wound begins to heal gradually at the same time. The greatest advantage of this method of gradual fistula cutting is that the anal sphincter is severed, but does not change position due to excessive sphincter contraction and generally does not cause anal incontinence.
This method is suitable for simple rectal fistulas with low or high internal or external openings within 3-5 cm of the anus, or as an adjunct to incision or excision of complex anal fistulas.
1.Method
(1) In the lateral position, first tie a rubber band to the end of the probe, then gently probe the tip of the probe from the outer mouth of the fistula inward to find the inner mouth near the dentate line of the anal canal; then stick your index finger into the anal canal, feel the tip of the probe, bend the tip of the probe and pull it out from the anal opening. Be careful not to use violence when inserting the probe in order to prevent false passage.
(2) Pull the probe tip completely out of the inner opening of the fistula so that the rubber band passes through the outer opening of the fistula into the fistula.
(3) Lift the rubber band, cut the skin layer between the inner and outer openings of the fistula, pull it tight like a skin band, and clamp it tightly against the subcutaneous tissue with a hemostat; tighten the rubber band with a thick silk thread under the hemostat and make a double ligature, then release the hemostat. The incision is dressed with petroleum jelly gauze, and the postoperative daily sitz bath with hot 1:5000 potassium permanganate solution, and change the dressing, generally in about 10 d after surgery, the anal fistula tissue is cut by the rubber band, and the wound can be healed after 2-3 weeks.
2. The advantages of this method are
(1) The operation is simple, fast and with little bleeding.
(2) When the rubber band does not fall off, the skin incision generally does not occur “bridging”.
(3) easy to change the medicine.
3.The key points to keep the successful hanging thread
(1) To accurately find the internal opening, generally when the probe penetrates the internal opening, if there is no bleeding, it proves that the position of the internal opening is more correct.
(2) The wound must start from the base, so that the wound in the anal canal heals first and prevent the surface skin from prematurely adhering to the seal. Generally the rubber band can fall off in 7-10 d. If it does not fall off after 10 d, it means that the wire of the rubber band is loose and needs to be tightened again.
(b) Anal fistula incision
The principle of surgery is to cut all the fistula and to remove the scar tissue on both sides of the incision, so that the drainage is unobstructed and the incision gradually heals. This method is only applicable to low-level straight or curved anal fistulas. The operation methods are as follows.
If the fistula is bent or branched, the probe cannot be inserted into the internal opening, then inject a small amount of 1% Mebrane solution into the external opening to determine the internal opening site, and then probe with a slotted probe from the external opening to gradually cut open the tube and probe until the internal opening is detected. If you can’t find the inner mouth even after careful probing, you can treat the suspected lesioned anal sinus as the inner mouth.
2, cut the fistula and fully excise the marginal tissues cut all the superficial tissues of the fistula, from the external to the internal orifice and the corresponding anal sphincter fibers. The fistula should be checked for branches after incision, and if found, they should also be incised. The entire fistula should be cut and scraped clean of decaying granulation tissue, but it is not usually necessary to remove the entire fistula to avoid excessive trauma. Finally, the wound edges should be trimmed so that the wound is in a “V” shape with a small bottom and a large mouth to facilitate deep wound healing first.
The anal sphincter cut should be carefully felt in the relationship between the location of the probe and the anal rectal ring, such as the probe in the anal rectal ring below the entry, although all cut fistula and most of the external sphincter and the corresponding internal sphincter, due to the preservation of the puborectal muscle, does not cause anal incontinence, such as the probe in the anal rectal ring above the rectum (such as the sphincter on the anal fistula, sphincter outside the anal fistula), it can not do fistulotomy, should do Hanging wire therapy or hanging wire staged surgery. In the first stage, the fistula below the ring is incised or excised, and the fistula above the ring is hung with a thick silk shallow and tied tightly. In the second stage, once most of the external wounds have healed and the anorectal ring has been fixed with adhesions, the anorectal ring is then incised along the hanging wire.
After the fistula is incised, its posterior wall granulation tissue can be scraped away with a spatula, but generally does not need to be removed to minimize bleeding and avoid damage to the posterior wall sphincter. The excised fistula tissue should be sent for pathological examination.
4, wound treatment postoperative wound treatment is often related to the success or failure of surgery, the key is to keep the wound from the base gradually to the surface healing. Change the dressing once a day, preferably after defecation, and gradually reduce the filling dressing in the wound until the wound in the anal canal heals. Rectal examination every few days can dilate the anal canal, moreover, it can prevent bridge-shaped adhesions and avoid pseudo-healing.
(iii) Anal fistula excision
The difference with incision is that the fistula is completely excised down to healthy tissue. This method is also suitable for low-level anal fistulas with more fibrotic canals.
Method: The fistula is first injected with 1% melphalan through the external opening, followed by gentle insertion of a probe through the external opening and exit through the internal opening. The skin of the external opening is clamped with tissue forceps, the skin and subcutaneous tissue around the external opening of the fistula is incised, and then all scar tissue around the skin, subcutaneous tissue, the blue-stained canal wall, the internal opening, and the fistula is cut away with an electric knife or scissors in the direction of the probe, leaving the wound completely open. After careful hemostasis, the wound is filled with iodoform gauze or petroleum jelly gauze.
(iv) One-stage suture for anal fistula excision
This method began with Tuttle (1903) but failed to spread, probably because it was not very adequate in theory; the surgical results were unsatisfactory; and many anorectal surgeons opposed it. In 1949, Starr proposed this method again, and proposed some effective measures with more satisfactory results, and only then was it promoted. This method is only applicable to simple or complex low rectal fistulas, and is more effective if the fistula is sclerotomized when palpated. Key points of surgery: ① the bowel should be prepared before surgery, antibiotics should be applied before and after surgery, and the stool should be controlled for 5-6 d after surgery. ② the fistula should be completely excised, leaving a fresh wound to ensure that no granulation tissue or scar tissue remains. ③The skin and subcutaneous fat should not be excised too much to facilitate wound closure. Therefore, high curved fistulas should not be sutured because they are more branched and often require too much tissue to be removed in order to cut the branches. ④ All layers of the wound should be completely sutured and aligned, leaving no dead space. ⑤ Strictly aseptic operation should be performed to prevent contamination, such as cutting through the fistula. In 1064 cases of anal fistula excision and suturing reported in the comprehensive domestic literature, the one-stage healing rate was 73.4%～97.6%, and the wound healing time was 20-22 d. Most of the cases with lower one-stage healing were complicated high anal fistulas.
(E) Post-anal fistula excision skin graft
If the wound is too large and superficial without special complications, free skin grafting can be considered after fistula excision. The requirements before and after surgery are the same as those for the first-stage suture of fistula excision. Key points of surgery: ① The trauma surface should be flat and hemostasis should be complete. ②The skin suture of the free skin graft area should be completely closed and fixed with pressure to prevent gas or blood under the wound surface, which is one of the important measures for successful surgery. If the wound surface is bleeding more, the implantation should be delayed, i.e., Vaseline gauze should be applied to the wound surface first, and then free implantation should be done after 2-3 d. Hughes (1953) reported 40 cases, 30 cases of implantation were completely successful, and the rest were mostly viable. Goligher (1975) reported 22 cases, all of which were low anal fistulas, and the results were poor, only 13 cases were completely viable.
(F) Treatment of hoof fistula
Fistulotomy with wire therapy should be used. In the case of posterior hoof fistula, a slotted probe is inserted from both sides of the external opening and the fistula is gradually cut until the two sides of the canal meet near the posterior midline, then the internal opening is carefully probed with a slotted probe. If the fistula passes below the rectal ring, the fistula and the lower and superficial part of the external sphincter skin can be incised all at once. If the internal opening is too high and the fistula passes above the anorectal ring, wire therapy must be used. This means that the fistula is incised in the lower part of the external sphincter, the superficial part and the lower part of the fistula, and then a rubber band is inserted through the remaining orifice and led out through the internal orifice and tied to the anorectal ring, which prevents anal incontinence caused by cutting the anorectal ring at once. The skin and subcutaneous tissue at the edges of the incision are then cut away, leaving the wound open and the granulation tissue of the fistula wall is scraped away. The trauma is filled with iodoform or petroleum jelly gauze.
(vii) Sliding mucosal flap anterior closure of the endograft
After complete excision of the fistula and the endograft, the defect at the rectum is repaired by transposition of the mucosal flap, which actually includes part of the thickness of the rectal wall to increase its strength.
Advantages of this method.
① preservation of most of the sphincter muscle, which is suitable for rectovaginal fistulas and high trans-sphincteric anal fistulas.
(ii) Less scar formation.
③Avoidance of anatomic deformities.
Aquilar et al. (1985) treated 189 cases of high trans-sphincteric fistulas with good results, with a recurrence rate of only 2%, but 8% for contaminated underwear and strictures, 7% for mild gas incontinence, and 6% for fluid incontinence. The success rate of this method in treating anal fistulas due to clonorchiasis was only 57%, while the success rate was higher in those without clonorchiasis. However, some authors have used direct suturing of the internal opening.
Postoperative care
The success of postoperative wound dressing changes is a key issue in the success of surgery. Even if the surgery is successful, if the wound dressing change is neglected, the surgery is often prone to failure. Therefore, the treating surgeon must change the dressing himself or at least check the wound regularly. Dressing change precautions.
① Sitz bath and flushing: Sitz bath should be performed every day after surgery, especially after stool, which should not be neglected. To ensure wound cleanliness and accelerate healing. Wound irrigation should be performed for large wounds, first with hydrogen peroxide solution and then with warm saline or antibiotic solution. A certain pressure should be maintained when flushing in order to make the cleaning solution reach every corner of the wound.
② Dressing: dressing inside the wound can prevent adhesions on the wound surface (skin bridging), so the wound should be small at the bottom and be able to heal from the bottom up. If pus is found in the wound when the dressing is removed, suggesting a residual pus cavity, the drainage should be expanded immediately, otherwise the wound will not heal.
③ Rectal palpation: It can find out whether there is dead cavity and pus in the wound, in addition, it can also find out whether there is a tendency of anal stenosis, if there is, it should be treated by regular anal dilation. Therefore, rectal examination should be performed regularly.
Etiology
There are two major types of perirectal abscesses: one is related to anal gland and fistula, called “primary acute intermuscular fistula abscess”, which is more common; the other is not related to anal gland and fistula, called “acute non-anal gland non-fistula abscess”. Acute non-anal glandular non-fistula abscesses”, referred to as “non-fistula abscesses” are less common. Most fistulas are due to general purulent infections, a few are specific infections such as tuberculosis, clonorchiasis, and more rarely ulcerative colitis. Infections secondary to rectal trauma can also form fistulas, and malignant tumors of the rectal canal can also ulcerate into fistulas, but they are rare and distinctly different from general purulent fistulas.
It has been hypothesized that the influence of sex hormones is the main cause of anal fistula. In the adolescence, the body’s own sex hormones become active, and then part of the sebaceous glands, especially the anal glands, begin to develop and proliferate, and young men are more proliferating than women. The fact that the anal glands are very active, if combined with poor drainage of the anal glands or blockage of the anal ducts, it is easy to get infected and cause anal adenitis, which explains the higher incidence of anal fistula in young adults in men. The female anal canal is straighter and less curved than the male, so secretions are less likely to accumulate, so the incidence of anal fistula is lower in women. In old age, the anal glands shrink along with the other sebaceous glands, so anal fistulas are rare in the elderly.
Pathological changes
Anal fistulas have primary internal ports, fistulas, branches and secondary external ports. The internal orifice, which is the entrance to the source of infection, is mostly in and around the anal sinus, mostly on either side of the posterior midline, but can also be in the lower rectum or any part of the anal canal. The fistulae are straight or curved, and a few have branches. The external opening, where the abscess breaks down or is incised and drained, is mostly located outside the skin around the anal canal. Because the primary lesion constantly enters the canal through the internal opening, and because the canal is tortuous and travels near the internal and external sphincters, the wall of the canal is composed of fibrous tissue and there is granulation tissue inside the canal, it does not heal over time. Generally, simple anal fistulas have only one internal and one external port, and these are the most common. If the external port is temporarily closed and the local drainage is poor, redness and swelling will gradually occur and then an abscess will form, and the closed external port can be re-perforated or another external port can be formed elsewhere. This repeatedly expands the lesion or sometimes causes several external openings that are connected to the internal opening. However, it has been suggested that complex fistulas should not be classified by the number of external openings, but rather by the involvement of the main canal in the rectal ring or above. Although this type of fistula has only one external and one internal port, it is more complicated to treat and is therefore called a complex fistula. On the contrary, sometimes there are multiple external openings, but the treatment is not complicated.
Clinical manifestations
Anal fistulas often have a history of perianal abscesses that have self-ruptured or cut open to drain pus, after which the wound does not heal and becomes an external fistula. The main symptom is that a small amount of pus repeatedly flows out from the external opening and pollutes the underwear; sometimes the pus irritates the perianal skin and causes itching. If the external opening is temporarily closed, the pus accumulates, the local area is red and swollen, there is swelling and pain, and the closed opening can be punctured again, or another new opening can be formed in the vicinity, and so on repeatedly, multiple openings can be formed and communicate with each other. If the fistula drains freely, there is no local pain and only slight swelling and discomfort, which the patient often does not mind. If the fistula is shallow, a stiff cord can be felt under the skin, leading from the external opening to the anal canal. High anal fistulae are often deeper and it is not easy to feel the fistula, but there are often multiple external openings. The perianal skin is often thickened and reddened due to irritation by secretions.