Fistula in Ano

Information for patients: About Anal fistula , perianal abscess, ischiorectal abscess, MRI fistulography, medical treatment for anal fistula, fistulectomy, surgery for anal fistula, treatment of complex and recurrent fistula, seton insertion etc. 

• What is anal fistula: Anal fistula is one or multiple small external opening in the skin near the anus which discharges pus off and on. The external opening leads to a tubular tract which opens inside the anal canal through an internal opening. Anal fistula result due to infection in the anal glands which spread in the perianal region and burst open through the skin near the anus. It is a chronic suppurative disease which is well-known for chronic perianal pus discharge, frequent exacerbations, and recurrences after treatment. The most accepted factor for causation of Fistula-in-ano is infection beginning in the anal crypt glands. 

• Symptoms of anal fistula: Pain in or around anus, pus discharge through external opening in the skin around anus or anal canal, swelling around anus, bleeding & pus discharge from anus, itching around anus etc. A history of abdominal pain, loss of weight, altered bowel habits, tenesmus, bleeding per rectum, tuberculosis, HIV, Crohn’s disease, diverticulitis, pelvic radiation therapy may suggest complex fistula. 

• Clinical evaluation of fistula: The surgeon will examine the perianal region and abdomen for evaluating the fistula. The external openings, fistula tract with its relationship to anal sphincters and internal opening inside the anal canal are confirmed. The surgeon will do perrectal examination and proctoscopic examination of anal canal to confirm the findings. 

• Investigations: Before planning a surgical intervention the surgeon may require imaging studies like fistulography, MRI fistulography or perineal ultrasound to see the course of fistula tract, presence of abscesses ( Pus collections), relationship of fistula tract to anal sphincters &  finding  the internal opening in the anal canal. Surgery guided by MR imaging has shown to reduce recurrence and complications like incontinence due to inaccurate surgical assessment of fistula. Routine blood tests and viral markers like Hbsag, HCV and HIV tests are also done.

 Type of fistula: Park’s classification which is most widely used defines four groups of fistula-in-ano that result from crypto glandular infections according to the course of fistula tract  in relation to anal sphincters. 

• Intershincteric (70%) 

• Transsphincteric (25%)

• Suprashincteric (5%)

• Extrasphincteric. (1%)

Complex fistula is a term used for high transsphincteric, suprasphincteric, extrasphincteric, multiple tracts or abscess, recurrent, rectovaginal, rectourethral & pouch related fistula 

Treatment of anal fistula: Treatment of anal fistula remains challenging. No definitive medical therapy is available for this condition. Surgery remains the main treatment for perianal abscesses and anal fistula. Fistulotomy (Laying open of fistula tract) and fistulectomy ( Excision of the fistula tract) are the most commonly performed operations for fistula in ano. It is important for the surgeon to ascertain the course of fistula tract in relation to anal sphincters ( Muscles that control anal continence). The sphincters must be preserved or repaired when excising the fistula tract otherwise feacal incontinence will result. Because of complexity of the fistula tract surgeon’s faced the problems of potential adverse effects on continence arising from division of the involved anal sphincter and there were recurrences in many cases.  

Ligation of the intersphincteric fistula tract (LIFT) is an alternative minimally invasive surgical option for complex trans-sphincteric fistulas first described in 2007 by Arun Rojansakul. It is performed by entering the intersphincteric plane, identifying the fistula tract and hooking it out to ligate and divide the tract with the intention to securely close the internal opening and excise the infected cryptoglandular tissue.  LIFT is associated with less incontinence & recurrence rate (8-28%) in complex anal fistula.

Seton placement has been found useful in complex fistulas (i.e., high transsphincteric, suprasphincteric, extrasphincteric), multiple fistulas, recurrent fistulas, anterior fistulas in female patients and in patients with poor sphincter pressures. Setons are to use to drain pus, to bit by bit cut through the remaining sphincters over few weeks and simultaneously promote fibrosis, and healing of sphincters thereby curing the fistula without causing incontinence. Setons used commonly are no-1 proline or nylon suture or silastic vessel markers. The success rates for cutting setons varies from 82-100%. Recurrence rate after seton placement in various studies are up to 17% and incontinence rates can be more than 30%. 

Video assisted anal fistula treatment (VAAFT) described by Piercarlo Meinero is done by rigid fistuloscope. The fistula tract is first irrigated to observe the tract, branches and internal opening. Then the fistula tract and its branches are electro cauterized under direct vision and all necrotic material is removed by perfusion. Finally the internal opening is closed by suture, stapler or mucosal advancement flaps. The limitations are inadequate exploration and identification of curved tracts, side branches and internal opening. Collateral thermal damage to adjacent normal tissue can also occur. 

Treating complex fistula still remains a challenge for the surgeons. Endoanal advancement flaps and fecal diversion may be required in patients with perineal necrotizing fasciitis, severe anorectal Crohn disease, rectovaginal fistulas, and radiation induced fistulas.Keeping in view the high recurrence rates and problem of incontinence associated with complex fistula alternative treatments for fistula were investigated. Advances in biotechnology led to the development of tissue adhesives and biomaterials used as fistula plugs. These less invasive therapies have decreased postoperative morbidity and risk of incontinence, but long-term data about recurrence needs to be validated.  

Thus resorting to fundamental principles of careful clinical evaluation, control of sepsis, identification of fistula tracts, secondary extensions and adequate drainage of the wound can improve the healing rates with minimal morbidity and recurrence.