May 2010|Vol 7|Issue 5

May 2010 | Volume 7 | Issue 5

 

Article
 
Fistula in Ano
 



 


Dr. S.R.Ameerkhan Babu, BHMS., MD(Hom)
Lecturer, VMHMC&H, Salem.
Sharme Homoeo Clinic
109, Dr.Babu House, Nalli Thottam,
Vettukattuvalasu (Bus stop), Erode – 638011.
Mobile : (0) 9443273335, 9976874435.

    Introduction
       An anal fistula, or fistula-in-ano, is an abnormal connection between the epithelialised surface of the anal canal and (usually) the perianal skin.Anal fistulae originate from the anal glands, which are located between the two layers of the anal sphincters and which drain into the anal canal. If the outlet of these glands becomes blocked, an abscess can form which can eventually point to the skin surface. The tract formed by this process is the fistula.

       Abscesses can recur if the fistula seals over, allowing the accumulation of pus. It then points to the surface again, and the process repeats.Anal fistulas per se do not generally harm and they often do not hurt, but they can be irritating because of the pus-drain (and, it is not unknown for formed stools to be passed through the fistula); additionally, recurrent abscesses may lead to significant short term morbidity from pain, and create a nidus for systemic spread of infection.

    Causes of fistula in ano:
    Anorectal abscess especially perianal abscess is the most common cause.

    Fistula in ano develope secondary to:

    Piles or hemorrhoids.

    Trauma, especially obstetric, after traumatic delivery.

    Ulcerative colitis.

    Crohn’s disease.

    Anal fissures.

    Colloid Carcinoma of the rectum.

    Previous Radiation therapy for prostate or rectal cancer.

    Constipation.

    Diverticulitis.

    Steroid therapy.

    Actinomycoses.

    Tuberculosis.

    Chlamydial infections &

    Surgery for fissures or piles usually gives rise to fistula in future.

    And patients who are immunocompromised for any reason.

    Frequency of fistula in ano:
    The prevalence rate is 8.6 cases per 100,000 populations.
    The prevalence in men is 12.3 cases per 100,000 populations.
    In women, it is 5.6 cases per 100,000 populations.

    Patho physiology of fistula in ano:
    Anal fistulae originate from the anal glands, which are located between the two layers of the anal sphincters and which drain into the anal canal. If the outlet of these glands becomes blocked, an abscess can form which can eventually point to the skin surface. The tract formed by this process is the fistula.

    Abscesses can recur if the fistula seals over, allowing the accumulation of pus. It then points to the surface again, and the process repeats.

    Anal fistulas per se do not generally harm and they often do not hurt, but they can be irritating because of the pus-drain (and, it is not unknown for formed stools to be passed through the fistula); additionally, recurrent abscesses may lead to significant short term morbidity from pain, and create a nidus for systemic spread of infection.

    The cryptoglandular hypothesis states that an infection begins in the anal gland 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, causing recurrent symptoms. Multiple series have shown that the formation of a fistula tract following anorectal abscess occurs in 7-40% of cases.

    Classification:
    The Parks classification system defines 4 types of anal fistula:-

    1) Inter-sphincteric

    2) Trans-sphincteric

    3) Supra-sphincteric

    4) Extra-sphincteric

    The majority of extra and intersphincteric fistulae (85%) are straight forward to deal with. The remainder (trans-sphincteric and supra-sphincteric) are much more difficult to treat and demand specialist care.

    Clinical History:
    Patients often provide a reliable history of

    Previous pain,

    Swelling,

    Spontaneous or planned surgical drainage of an anorectal abscess.

    Signs and Symptoms:

    Pain

    Pruritis ani

    Perianal discharge- either bloody or purulent.

    Swelling.

    Bleeding.

    Diarrhea.

    Skin excoriation.

    External opening

    Systemic symptoms if abscess becomes infected

    On Examination:
    Digital rectal examination may reveal a fibrous tract or cord beneath the skin. It also helps delineate any further acute inflammation that is not yet drained.
    Lateral or posterior indurations suggests deep post anal or ischio-rectal extension.
    Anoscopy is usually required to identify the internal opening.

    Clinical Diagnosis:
    Diagnosis is by examination, either in an outpatient setting or under anesthesia (referred to as EUA - Examination Under Anesthesia). The examination can be an anoscopy. The possible findings are:
    The opening of the fistula onto the skin may be seen

    The area may be painful on examination

    There may be redness

    An area of induration may be felt- thickening due to chronic infection

    A discharge may be seen

    It may be possible to explore the fistula using a fistula probe (a narrow instrument) and in this way it may be possible to find both openings of the fistula.

    Laboratory Diagnosis:

    Fistulography.

    Endoanal & endo rectal ultrasound, (sometimes with hydrogen peroxide injected into the track) identifies the course of the track.

    MRI scanning is probably the most sensitive method of determining the course of the track and identifying any occult perianal or pelvic sepsis.

    CT scan.

    A barium enema or small bowel series.

    Flexible sigmoidoscopy & colonoscopy, if associated colorectal disease, e.g. Crohn’s disease, is suspected.

    Anal manometry.

    Differential Diagnosis:

    Hidradenitis suppurativa

    Infected inclusion cysts

    Pilonidal disease

    Bartholin gland abscess in females