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© Borgis - New Medicine 4/2005, s. 54-56
Małgorzata Kołodziejczak1, Iwona Sudoł-Szopińska2
Causes of recurrences of anal fistulae
1Proctology, Subdepartment of Surgery, Śródmiejski Hospital, Warsaw, Poland
Head of Department: Małgorzata Kołodziejczak, MD, PhD
2Central Institute of Occupational Health – National Research Institute
Director: Professor Danuta Koradecka, MD, PhD
Department of Diagnostics Imaging, Second Faculty, Warsaw Medical Academy, Warsaw, Poland
Head of Department: Professor Wiesław Jakubowski, MD, PhD
The paper discusses the problem of anal fistula recurrence after surgery. The recurrence rate after surgical treatment of anal fistulae ranges from 0 to 26.5%, according to literature data. Most recurrences develop within a year following surgery. In most cases of recurrence, the fistulae are of type 3 and 4 according to Park´s classification (i.e. high suprasphincteric and extrasphincteric fistulae), fistulae in Crohn´s disease, and also fistulae in patients with decreased immunity and diabetes mellitus. The prophylaxis of fistula recurrence includes three stages: 1) preoperative diagnostics, 2) appropriately conducted surgery, and 3) correct postoperative management of the patient. In the preoperative diagnostics of fistula, transrectal ultrasonography, which is presently regarded as "gold standard”, should be used for assessment of both anatomical location of the fistula and sphincter muscles, and also, in individual cases, classic fistulography and the most recent imaging techniques, i.e. magnetic resonance imaging (MRI) and tri-dimentional (3D) endosonography, should be applied. The latter are used in the diagnosis of ramified fistulae of complex shape, e.g. in Crohn´s disease. Leaving of the main canal, failure to find the internal opening, which in most cases is the cause of fistula, or failure to excise all ramifications, are basic errors in surgical technique leading to disease recurrence. Other causes of fistula recurrence include too tight suturing of the surgical wound, insufficient drainage and consequent development of a new inflammatory canal as well as incorrect diagnosis of the cause of fistula, e.g. failure to remove a foreign body or to diagnose Crohn´s disease. Incorrect postoperative management, a factor that is frequently omitted in the literature, is also discussed in detail in the paper.
For many years anal fistula has been a surgical problem in view of the high number of postoperative complications such as incontinence of gases and faeces and recurrent course of the disease. The complications after anal fistula surgery can be divided into early – analogous to those after other proctologic operations, and late – characteristic only of fistula. Early complications that develop most frequently include postoperative bleeding, infectious complications and urine retention. Late complications after anal fistula surgery may include recurrence of fistula (in the form of anal abscess or anal fistula) and various degrees of symptoms and signs of anal sphincter insufficiency from slight gas incontinence to complete solid stool incontinence. The complication in the form of postoperative incontinence is a significant problem but it is not the subject of this paper. Late complication in the form of recurrence of fistula is frequent and is estimated by various authors as developing in 0 to 26.5% of cases (1, 2, 3, 4). In the Proctology Department, Srodmiejski Hospital, the percentage of fistula recurrences is about 10% and the risk factors of recurrence in our material include female sex and operations for recurrent fistulae (5). As is known, the key to anal fistula surgery is to find a golden middle between surgical procedure radicalism and preservation of anal sphincters. The authors who reported high numbers of complications in the form of faecal incontinence had a low recurrence rate and, conversely, surgeons preferring more cautious procedures had more recurrences.
It seems that such great differences result not only from application of different operation techniques. It happens, however, that different authors using the same operation technique obtain totally different results. The causes of that situation may include the fact that the clinical material is not uniform, e.g. the results of surgical treatment of low fistulae cannot be compared with those of high fistulae, and the results differ also in the case of fistulae in Crohn´s disease where recurrence rate is high, or in the case of high rectal fistulae, which usually cannot be cured without creating an artificial anus. Healing is impaired also in patients with diabetes and decreased immunity; such patients are also more prone to recurrences.
Most recurrences develop within a year following surgery (1). Taking into account the type of fistula determined according to Park´s classification of 1976 (6), most recurrences are seen in type 3 and 4 fistulae, i.e. high suprasphincteral and extrasphincteral fistulae (4). When analysing the causes of recurrences of fistulae most authors stress the errors in surgical technique (7). A high recurrence rate in the case of high fistulae can result from the surgeon´s fear of cutting the whole muscle mass and from selection of a more cautious operation method. This is a very important although not the only cause of fistula recurrence.
The prophylaxis of fistula recurrence comprises three stages:
1. Preoperative diagnostics of anatomical location of fistula.
2. Well performed operation.
3. Correct postoperative management.
Re 1. Preoperative diagnostics of anatomical shape of fistula includes in the first place physical examination and imaging examinations, particularly endosonography. The aim of proctologic examination is to assess passive and active tonus of anal sphincters, and to perform anoscopy and rectoscopy in order to localize the internal opening. During rectoscopy rectal mucosa is also examined to preclude non-specific colitis, which also can be a cause of fistula and, if untreated, can lead to disease recurrence.
Transrectal ultrasonography, regarded presently as the "gold standard”, is also used for preoperative assessment both of the anatomical course of fistula and of sphincter muscles (8, 9, 10, 11, 12, 13, 14). The accuracy of endosonography in the diagnosis of anal fistulae is, according to various authors, from 25% to 100% and, unfortunately, is lowest in the case of anal fistulae of recurrent character (14). In primary fistulae, endosonography allows the type of fistula and the site of its internal opening to be determined with high accuracy. The technique is of great value for preoperative assessment of anal sphincters. In the case of recurrent fistulae, the differential diagnosis between scar after fistula operation and active fistula, particularly its ramifications, causes some difficulties. The administration of contrast (hydrogen peroxide solution) through the external opening, and use of the most recent imaging techniques, such as MRI (15, 16) and 3D endosonography (17, 18, 19, 20), are helpful in such situations. These methods are used especially in the diagnosis of ramified (i.e. complex), high, recurrent fistulae, e.g. in Crohn´s disease. Traditional fistulography should also be kept in mind, especially in cases of iatrogenic fistulae or fistulae developing "around a foreign body”.
Re 2. Appropriate surgical technique to a large extent allows fistula recurrence to be avoided and it includes:
1. determination of fistula type, that is location of the fistula in relation to anal sphincters, particularly the external sphincter and puborectal muscles, and choice of surgical procedure type suitable for a given type of fistula,
2. finding and excision of the internal opening, i.e. the possible cause of the fistula,
3. excision of the whole fistula together with its ramifications.
The main errors in surgical technique that are the cause of disease recurrence include leaving of the main canal, failure to find the internal opening, which is regarded in most cases as the cause of fistula, and failure to excise all ramifications. The above-mentioned elements are very important for the prophylaxis of fistula recurrence but they are not the only causes of recurrence.
Postoperative management of patients after anal fistula surgery deserves special attention.
Re 3. Most surgeons, discussing the prophylaxis of anal fistula recurrences, still focus on errors in surgical technique. Only a few papers were found in the available literature which describe the role of postoperative care in the prophylaxis of fistula recurrence (21, 22). Wounds after excision of fistulae, in the authors´ opinion, in most cases should be left open or partially open, for healing by second intention. Care should be taken that the wound heals from the floor and formation of a new canal of fistula should be prevented (this is one of the very few situations in surgery when the surgeon knowingly interferes with wound healing).
The following principles of management of patients after anal fistula surgery have been accepted in the Proctology Department (23):
Early postoperative period:
– the anal canal takes at least six weeks to heal and, for that reason, during the first six weeks medical monitoring is conducted at least once a week, or more frequently if needed,
– daily dressing change, wound irrigation, seton change to prevent too rapid wound healing,
– if the patient has a "cutting” thread applied onto the external sphincter muscle, the patient is instructed to pull on the thread from the 4th week after the operation on, and if the doctor himself "cuts” the sphincter muscle, he starts to do that after 4-5 weeks minimum (when the scar "fixing” the sphincter starts to appear),
– in the above-mentioned cases care is taken that for the whole time the thread encircles only the muscle, not allowing epidermization of the muscle fragment encircled by the thread (the thread must not be applied onto the skin),
– if a "loose” seton is applied, the rule is observed to avoid epidermization of the muscle with the seton, and the wound is frequently irrigated in order to make possible its healing "from the floor” and not "from the skin”,
– in the first weeks after the operation the patient may have transient gas and/or faecal incontinence. Full assessment of sphincter competence is conducted six weeks after the operation. Until that time the patient is instructed to perform sphincter "exercises” including a dozen or so voluntary contractions and relaxations of the sphincter muscles several times a day;
– about 4-6 weeks after the cure (complete wound healing) a full assessment of sphincter muscle continence is carried out (according to the continence assessment scale accepted in a given department, using methods such as manometry and endosonography) and the result is compared with that of the preoperative evaluation.
A too early follow-up transrectal ultrasonography examination can give false positive results due to erroneous interpretation of the scar as the recurrence of fistula. The diagnosis of fistula recurrence should not be based only on ultrasonography. Basic proctologic examination still remains the main diagnostic tool.
Late postoperative controls:
As already mentioned most recurrences after surgery for fistulae occur within a year following the surgery. Successive control examinations of patients operated on for anal fistula are conducted in order to detect fistula recurrence early. Proctologic examinations are carried out in the first four months after surgery, and after 3-4 months endosonography is additionally repeated. If a positive result is obtained, it is recommended to repeat the examination after six months. During that visit another assessment of sphincter continence is carried out. The principles described above do not apply to rectal fistulae including high, complicated fistulae, which require seton maintenance for several months (e.g. fistulae in Crohn´s disease). In such cases, the postoperative follow-up period of fistulae is adequately longer and control examinations are more frequent, while in the case of rectal fistulae due to non-specific inflammations, the course of the underlying disease should be monitored and appropriate drugs should be given.
Other causes of fistula recurrence include too tight suturing of the surgical wound, insufficient drainage and consequent creation of a new inflammatory canal. This happens in situations when the surgeon cares too much about good cosmetic effect, not taking into account the fact that wounds situated radially to the anal canal heal instantly. Even extensive wounds, if treated according to proctologic surgery principles ("pear” shape – base outside), give a good cosmetic effect after healing. Incorrect diagnosis of the cause of fistula, e.g. failure to remove a foreign body or to diagnose Crohn´s disease, is a less frequent cause of recurrence. It should not be forgotten, however, that anal sinusitis is the most frequent but not the only cause of fistula recurrence.
The review of literature on anal fistula surgery suggests the afterthought that the leading idea of the surgeon operating on anal fistula is to avoid postoperative complications and not to cure the patient. Applying the above principles of surgical management concerning the three stages of preoperative diagnostics, appropriately conducted operation and postoperative management, it is possible to significantly reduce the number of recurrences after surgery for anal fistulae. It should be kept in mind that even a perfect operation for fistula is not sufficient to prevent its recurrence. Only an appropriate operation connected with careful postoperative management can ensure full success. Frequent postoperative follow-up examinations are stressful for both the patient and the attending doctor but are indispensable to achieve therapeutic success.
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