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THE MILLENNIUM PERSPECTIVE OF FISTULA-IN-ANO
Additional Modalities of Treatment
H L Chulani
Consultant Colon and Rectal Surgeon, Lilavati Hospital, Bandra, Mumbai.
The unenviable reputation of recurrence following an operation of fistula-in-ano will not diminish when the millennium ends this year though a wide variety of diagnostic aids are now available to assist the surgeon to identify tracts and an equal number of surgical procedures designed to reduce risk factors, recurrence and impairment of continence continue to hold attention as major complicating factors in surgery of fistula-in-ano. Risk factors as a cause of recurrence include complex type of fistula, horse-shoe extension, lack of identification or lateral location of the internal fistulous opening, previous fistula surgery and the surgeon performing the procedure. Incontinence is associated with female sex, high anal fistula, type of surgery and previous fistula surgery. There is a linear relationship between incontinence and the amount of sphincter muscle divided; being the lowest with intersphincteric fistula and the highest with extrasphincteric fistula. The goal of surgical treatment is thus two fold- to eradicate the suppurative process permanently without compromising anal continence.[1]The usual accepted aetiology of fistulous disease of the ano-rectum is infection of the crypto-glandular apparatus, the ducts of which open in the mid-anal canal while the terminal portion of the gland ramify within the anatomical spaces variously described as inter-muscular, sub-mucous, peri-anal and ischio-rectal. Infection of these spaces give rise to fistulas described by Parks as inter-sphincteric, sub-mucous, trans-sphincteric (High, intermediate and low), extrasphincteric and ischio-rectal. Majority of anal fistula tracts tend to follow these anatomical lines. Tracts following anatomical lines are generally of non-specific origin. However, fistula disease due to specific aetiology i.e. due to specific primary disease viz. tuberculosis, Crohn's disease, malignancy and lymphogranuloma venereum tend to breach anatomical barriers and may present in a bizarre fashion. Majority of external opening/s of an anal fistula are located on the surface of the body close to the anal margin. However, sometimes these external openings present a various distance from the anal margin and then could present difficulties in diagnosis. Many anteriorly located fistula tracts are often mistaken for urethral fistula and mistakenly incised as a peri-urethral abscess when presenting in an acute form. Fistula openings in the buttock region, lateral aspect of the thigh and even lower into the thigh are not unknown and special attention should be directed to these uncommon presentations and appropriate diagnostic aids used to correctly diagnose them. Between 5-7 per cent of fistula-in-ano do not have any external opening, the whole pathologic process being within the ano-rectum. These are termed incorrectly as 'blind internal' fistula-though the term fistula cannot be applied to them at all. The internal opening of an anal fistula is located by means of palpation of the anal canal during clinical examination when it is felt as an area of induration or by inspection, palpation and probing of the track after anaesthesia for operation has been administered. Probing prior to operation is painful and unrewarding and can set up an acute inflammation. The author has treated a case of E. coli fasciitis which followed probing. In some cases the internal opening cannot be located. In such cases, introducing hydrogen peroxide diluted with methylene blueor milk through the external opening, the internal opening can be visualized when hydrogen peroxide bubbles through it. On occasions infolding of the mucous membrane or fibrosis may give a guide to its location. Risk of recurrence, when the internal opening cannot be located may be as high as 50 per cent and every effort must be made to find and eradicate it. Over 80 per cent of internal openings are located in the posterior or anterior midline.
The classical lay open technique is still the gold standard of treatment in over 90 per cent of anal fistula. The complete tract, from the external opening to the internal opening is laid open. Tissue around the external opening and the internal opening is excised along with a small margin of tissue lining the tract (fistulotomy) and the wound kept open for healing by secondary intention. Since the lay-open technique is the standard surgical operation performed it is described in some detail. The position used for surgery varies according to the preference of the surgeon. Many low anal fistula surgery can be performed under local anaesthesia and requires good exposure. The three common positions used for surgery are- lithotomy position, prone (jack-knife) position and left lateral position. Lithotomy position gives good anatomical orientation of the tract and is used by most general surgeons. The position is not conducive when performing surgery under local anaesthesia since the patient often complains of pain in the thigh and can become uncooperative. The prone position is often used when doing the operation under local anaesthesia. However patients who have emphysema, bronchospasm, obesity or those who have had coronary artery by-pass surgery through a median sternotomy do not tolerate the prone position well. The left lateral position is eminently suitable position for patients who cannot be put in the prone position. Retraction of the buttocks in any position by means of adhesive needs meticulous attention since strong traction tends to distort the tract and can mislead the surgeon. Post-operative care consists of twice daily dressing after warm hip bath. Strong antiseptic solutions to cleanse the wound is avoided since allergic reaction to antiseptic solutions is not uncommon. Hydrogen peroxide (20 volumes per cent) diluted with an equal quantity of normal saline (0.9 per cent) is eminently suitable for cleansing the wound following which a dressing of Eusol (sodium hypochlorite) is used. Total healing time depends upon the extent of the wound but is generally between 10-20 days. Time off work is between 4-5 days and normal activity is resumed within three weeks. Stay in hospital is between 1-3 days in most instances. In some cases fistulas can even be treated on a day care basis. Recurrence rate is low (2-5 per cent) and mainly due to premature union of the skin edges, failure to excise the internal opening, failure to locate an extra arm (tract), failure to detect a cavity leading upwards from the main tract, presence of foreign bodies and specific diseases viz. tuberculosis, Crohn's disease and carcinoma. The reported rate of disturbance in continence is between 18 and 52 per cent. Fistulotomy and marsupialization is reported to cause less incontinence though this is debatable since merely suturing the edges of the fistula tract to the skin is unlikely to improve muscle function though healing time may be somewhat reduced.
The use of fistulectomy as an alternative to simple fistulotomy is debatable. The rate of recurrence is similar in the two procedures. The wound requires longer to heal. Fistulectomy is also associated with a higher rate of incontinence since muscle separation necessarily occurs after excision of the complete tract. In addition, there is more bleeding during the surgical procedure. Primary closure of the wound can sometimes be done when the wound left after fistulectomy is linear (lateral fistulas) but a high percentage of these wound break down to heal by secondary intention. Skin grafts applied to the raw areas has been attempted but most grafts do not take since they get lifted due to passage of stools and infection. Coring out of the fistula tract between the external and internal opening leaving the tissue in between intact can only be used for straight tracts (lateral tracts). Rate of recurrence is not diminished using the coring technique. A modified open coring-out technique has been described by Yoshiyuki Hongo et al[2] though only low fistulas have been treated by this method.
Use of a cutting seton is used on the rationale of eliciting an inflammatory reaction and fibrosis that is induced in the tissue surrounding the fistulous tract. This fibrosis is intended to fix the sphincter and prevent its retraction. A staged fistulotomy has been proposed as a means of preserving continence in transsphincteric fistula but data to support efficacy of these modifications in treatment are lacking though a seton is often used in high and complex fistulas. Use of advancement flaps consisting of mucosa and internal sphincter muscle to cover the internal opening after excising it is often difficult and the recurrence rate varies from 5 to 15 per cent.
The use of medicated seton (Ksharsutra) as an alternative to surgical operation has many claimants to its success. Disadvantages include-introduction of the medicated seton requires general anaesthesia, correct identification of the internal opening, multi-stage replacement of the medicated seton (the seton is required to be changed weekly-a painful experience), prolonged healing time, antibiotic treatment during total healing process and discharge from the wound till complete healing occurs. A medicated seton may have limited use-when the surgeon is in doubt about the extent of division of the external sphincter during surgery.
Alberto del Pino et al[3] have described an island flap anoplasty for treatment of transsphincteric fistula - in - ano which seeks to eliminate incontinence and mucosal ectropion. They report on the results of 11 patients, three of whom had Crohn's disease. Follow-up of ten months showed recurrence in thee patients. A 10 month follow-up is too short to assess long term results by this technique though the technique of anoplasty is similar to that used to treat anal stricture and ectropion. Early experience was used to treat only lateral fistulas but was later extended to include mid-line disease as well.
Cintron et al[4] have described results of a pilot study using autologous fibrin tissue adhesive derived from the precipitation of fibrinogen obtained from the patient by drawing out 100 ml of blood about 90 minutes before surgery and preparing fibrin tissue. After identifying the external and internal openings the fistulous tract was curetted and the autologous fibrin tissue adhesive was injected into the external fistula tract opening until the glue was seen to emerge from the internal opening. An overall success rate of 85 per cent has been reported. The mean follow-up period is only 3.5 months. It is too early to comment upon the feasibility of the method.
REFERENCES
1.Garcia-Aguilar J, Belmonte C, Wong WD, Goldberg SM, Madoff RD. Anal fistula surgery : factors associated with recurrence and incontinence. Dis Colon Rectum 1996; 39 : 723-9.
2.Hongo Y, Kurokawa A, Nishi Y. Open coring-out (function-preserving) technique for low fistulas. Dis Colon Rectum 1997; 40 (Suppl) : S104-6.
3.Del Pino A, Nelson RL, Pearl RK, Abcarian H. Island flap anoplasty for treatment of transsphincteric fistula-in-ano. Dis Colon Rectum 1996; 39 : 224-6.
4.Cintron JR, Park JJ, Orsay CP, Pearl RK, Nelson RL, Abcarian H. Repair of fistula-in-ano using autologous fibrin tissue adhesive. Dis Colon Rectum 1999; 42 : 607-13.
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