Fistula In Ano

FISTULA IN-ANO Definition

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An anorectal fistula (Fistula-in-Ano) is an abnormal communication between the anus and the perianal skin. Fistula is an abnormal passage from one epithelial surface to another epithelial surface It occurs as hollow tract lined with granulation tissue connecting a primary opening inside the anal canal to a secondary opening in the perianal skin. Secondary tracts may be multiple and from the same primary opening.

Sex and Age The male-to-female ratio approx. 2:1 The mean age of patients is 38 years. Etiology: -Fistula-in-ano is nearly always caused by a previous anorectal abscess. -Anal canal glands situated at the dentate line afford a path for infecting organisms to reach the intramuscular spaces. Other predisposing factors(anal pathology +others) 1) Trauma 2) Crohn disease 3) Anal fissures 4) Anorectal Carcinoma 5) Radiation therapy 6) Infection -actinomycoses, tuberculosis, and chlamydial infections. 7) Prolapsed internal hemorrhoid 8) Acute appendicitis, salpingitis, diverticulitis 9) Immunosuppression Pathophysiology: The cryptoglandular hypothesis

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The infection begins in cryptoglandular situated at the dentate line in the anal canal and progresses into the muscular wall of the anal sphincters to cause an anorectal abscess. Following surgical or spontaneous drainage in the perianal skin, occasionally a granulation tissue–lined tract is left behind, forming the fistula in-ano which causes recurrent symptoms.

Clinical presentation History (in order of prevalence) 1) Perianal discharge-intermittent or constant

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Perianal pain-worse during defecation, may be constant Swelling /lump in the perianal area Bleeding in the perianal area Diarrhea Discoloration of skin surrounding the fistula External opening in the perianal discharging Fever

Past medical history Important points in the history that may suggest a complex fistula include the following: -Inflammatory bowel disease -Diverticulitis -History of trauma -Previous radiation therapy for prostate or rectal cancer -Tuberculosis -Immune suppression-Steroid therapy, HIV infection Review of symptoms -Abdominal pain -Weight loss -Change in bowel habits

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Physical examination Physical examination findings remain the mainstay of diagnosis.  The examiner should observe the entire perineum  external opening that appears as an open sinus or elevation of granulation tissue  Spontaneous discharge via the external opening may be apparent or expressible upon digital rectal examination. DRE  External Anal sphincter tone  Tenderness on examination  Fibrous tract or cord beneath the skin.  Bogginess-any abscess.  Lateral or posterior induration suggests deep postanal or ischiorectal extension. Differential diagnoses The following do not communicate with the anal canal:  Perianal abscess  Urethroperineal fistulas

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Abcesses-Ischiorectal abscess,Submucous or high muscular abscess, Pelvirectal abscess (rare) Crohn's disease Carcinoma Retrorectal tumors Hidradenitis suppurativa is chronic suppurative folliculitis of apocrine sweat-gland–bearing skin of the perianal, axillary, and genital areas or under the breasts, developing after puberty and producing abscesses or sinuses with scarring. Infected inclusion cysts Pilonidal disease- a fistula or pit in the sacral region, communicating with the exterior, containing hair which may act as a foreign body producing chronic inflammation. Bartholin gland abscess in females

The Goodsall Rule Help to anticipate the anatomy of fistula-in-ano. The rule states that fistulae with an external opening anterior to a plane passing transversely through the center of the anus will follow a straight radial course to the dentate line. Fistulae with their openings posterior to this line will follow a curved course to the posterior midline.  In children, track is usually straight Classification of fistula in-ano Parks classification system (all are in relation to the sphincters) The Parks classification system defines 4 types of fistula-in-ano that result from cryptoglandular infections. 1.Intersphincteric-commonest-70% Common course - Via internal sphincter to the intersphincteric space and then to the perineum. They result from perianal abscesses 2. Transsphincteric -25% Common course - Low via internal and external sphincters into the ischiorectal fossa and then to the perineum. Originate from ischiorectal abscesses 3.Suprasphincteric -5% Common course - Via intersphincteric space superiorly to above puborectalis muscle into ischiorectal fossa and then to perineum. Result from supralevator abscesses 4. Extrasphincteric-1% Bypass the anal canal and sphincter mechanism, passing through the ischiorectal fossa and levator ani muscle, and open high in the rectum

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A probe is passed into the tract through the external and internal openings.

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The overlying skin, subcutaneous tissue, and internal sphincter muscle are divided with a knife or electrocautery, thereby opening the entire fibrous tract. If the fistula tract courses higher into the sphincter mechanism, seton placement should be performed.

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Fistulectomy-Excision of a fistula

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As above with Curettage performed to remove all granulation tissue in the tract base. Complete fistulectomy creates larger wounds that take longer to heal and offers no recurrence advantage over fistulotomy. Perform a biopsy on any firm, suggestive tissue

Seton placement

Current procedural terminology codes classification 1.Subcutaneous 2.Submuscular (intersphincteric, low transsphincteric) 3.Complex, recurrent (high transsphincteric, suprasphincteric and extrasphincteric, multiple tracts, recurrent) 3.Second stage Investigations Lab Studies: No specific laboratory studies are required; the normal preoperative studies are performed based on age and comorbidities. Imaging Studies: These are not performed for routine fistula evaluation. They can be helpful when the primary opening is difficult to identify or in the case of recurrent or multiple fistulae to identify secondary tracts or missed primary openings. 1. Fistulography This involves injection of contrast via the internal opening, which is followed by anteroposterior, lateral, and oblique x-ray images to outline the course of the fistula tract. 2.Endoanal/endorectal ultrasound To help define muscular anatomy differentiating intersphincteric from transsphincteric lesions. 3. MRI MRI is becoming the study of choice when evaluating complex fistulae 4.CT scan A CT scan is more helpful in the setting of perirectal inflammatory disease than in the setting of small fistulae because it is better for delineating fluid pockets that require drainage than for small fistulae Procedures Proctosigmoidoscopy/colonoscopy Rigid sigmoidoscopy can be performed at the initial evaluation to help rule out any associated disease process in the rectum. MANAGEMENT Medical Broad spectrum antibiotics Surgery Fistulotomy - Incision or surgical enlargement of a fistula  The laying-open technique (fistulotomy) is useful for 85-95% of primary fistulae (ie, submucosal, intersphincteric, low transsphincteric).

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A Seton can be placed alone, combined with fistulotomy, or in a staged fashion. This technique indicated in: 1.Complex fistulae -high transsphincteric, suprasphincteric ,extrasphincteric, multiple fistulae 2.Recurrent fistulae after previous fistulotomy 3.Anterior fistulae in female patients 4.Poor preoperative sphincter pressures 5.Patients with Crohn disease or patients who are immunosuppressed Setons have 2 purposes beyond giving a visual identification of the amount of sphincter muscle involved. (1) drain and promote fibrosis (2) Cut through the fistula. Setons can be made from large silk suture, silastic vessel markers, or rubber bands that are threaded through the fistula tract. Procedure -Pass the seton through the fistula tract around the deep external sphincter after opening the skin, subcutaneous tissue, internal sphincter muscle, and subcutaneous external sphincter muscle. -The seton is tightened down and secured with a separate silk tie. -With time, fibrosis occurs above the seton as it gradually cuts through the sphincter muscles and essentially exteriorizes the tract. -The seton is tightened on subsequent office visits until it is pulled through over 6-8 weeks. In complex multiple fistula -Colostomy may be fashioned -Posterior Sagittal anorectoplasty done for multiple fistulectomies Preoperative details: -Rectal irrigation with enemas should be performed on the morning of the operation. -Administer preoperative antibiotics. -Prone jackknife position with buttocks apart is the most advantageous position Post-operative management 1. Sitz baths, analgesics, and stool bulking agents (eg, bran, psyllium products). 2. Internal wound should not close prematurely, causing a

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recurrent fistula. Digital examination findings can help distinguish early fibrosis. 3.Wound healing usually occurs within 6 weeks COMPLICATIONS Early postoperative  Urinary retention  Bleeding  Fecal impaction  Thrombosed hemorrhoids Delayed postoperative  Recurrence  Incontinence (stool)  Anal stenosis: The healing process causes fibrosis of the anal canal. Bulking agents for stool help prevent narrowing.  Delayed wound healing: Complete healing occurs by 12 weeks unless an underlying disease process is present (ie, recurrence, Crohn disease)

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