*Anna Wiączek1, Małgorzata Kołodziejczak1, Iwona Sudoł-Szopińska1, 2, 3
Diagnosis and surgical treatment of complex anorectal fistulas
1Warsaw Proctology Centre, Saint Elizabeth’s Hospital, Mokotów Medical Centre, Warsaw
Head of Department: Małgorzata Kołodziejczak, PhD, Associate Professor
2Department of Radiology, Eleonora Reicher National Institute of Geriatrics, Rheumatology and Rehabilitation, Warsaw
Head of Department: prof. Iwona Sudoł-Szopińska, MD, PhD
3Department of Diagnostic Imaging, Second Faculty of Medicine, Medical University of Warsaw
Head of Department: prof. Wiesław Jakubowski, MD, PhD
Branching fistulas belong to the category of so-called complex fistulas since they contain secondary tracts with varying number and location. The most common causes of branching fistulas include: abscesses that have been incised too late or insufficiently drained, inflammatory bowel diseases and conditions with immunodeficiency. In rare cases, secondary tracts can develop in the course of tuberculosis, actinomycosis or as a complication after radiotherapy or anal wall erosion due to cancer or anorectal trauma. Surgery for this type of fistulas is difficult, frequently involving several stages and carrying a high risk of recurrence. In order to minimise the risk of complications, complex fistulas should be treated by surgeons specialising in proctology with adequate knowledge regarding contemporary surgical techniques. A significant factor that decides about treatment success is preoperative determination of the anatomical course of fistulas and their secondary tracts. This is possible with imaging: endosonography and magnetic resonance imaging. It is also necessary to conduct functional tests and colonoscopy in order to assess the bowel in terms of inflammatory diseases and other pathologies. Moreover, a bacteriological examination should be conducted in patients carrying a high risk of complications.
These patients include individuals with Crohn’s disease, diabetes, immune deficiency, cancer or considerable inflammation of anal soft tissues. The article presents surgical techniques for branching fistulas, such as two-stage seton fistulotomy (modified Hippocrates’ technique) and different one-stage sphincter-sparing procedures.
Anal fistula is a chronic infection of the anal canal and the perianal tissue in the form of a canal lined with inflammatory granulation tissue connecting the internal opening located in the anus with the external opening situated on the skin or anoderm. Fistula is caused by anal crypt inflammation in most cases, and is often preceded by an anal abscess. About 5% and, according to some reports, up to 30% of fistulas are branched (1). In this case, one or more tracts ending in the skin or ending blindly in the perianal tissues can branch off from the main canal at different levels. Depending on the location of these additional canals, three types of fistula tracts have been distinguished: intersphincteric, transsphincteric and suprasphincteric. Most of the tracts extend in the intersphincteric space, in the ischioanal fossa, above the pubic-rectal muscle loop, and even higher, above the level of the levator muscles, in the supralevator space and in the pelvis. A horseshoe-shaped fistula, which branches in the shape of a horseshoe and opens into the anal canal or rectum, is a special type of branching fistula. Most of horseshoe fistulas are located posteriorly and their internal opening is usually located in the posterior midline. These posterior tracts can extend in the superficial retroanal space, anteriorly to the anococcygeal ligament or deeper, in the deep retroanal space, posteriorly to this ligament. It is a recognized location of rear horseshoe fistulas which run in deep anal space and superficial anal space. Anterior horseshoe fistulas are much less common and represent a major therapeutic problem due to a significant risk of postoperative incontinence resulting from the lack of protection of the pubic-rectal muscle of the anterior circumference of the anal canal. The tracts of the anterior branching fistulas can run towards the perineal skin, approach or communicate with the vaginal lumen, or reach the scrotal skin in men. Even more extensive tracts can penetrate into the soft tissue of the buttock or groin. In very rare cases, they can even pierce the fascia, e.g. in the posterior femoral surface, and run between muscle bellies.
The presence of additional canals, particularly those occurring in high fistulas, represents a major dilemma for the operating surgeon, who decides on procedure radicality and, at the same time, aims to maintain the largest possible portion of the sphincter due to the postoperative risk of faecal and gas incontinence. High suprasphincteric fistula tracts, which, in most cases, are difficult to excise are most problematic. Due to the risk of postoperative incontinence, these tracts are frequently only opened and curetted, which increases the risk of recurrence.
Etiopathogenesis of complex fistulas
The most common causes of branching fistulas include abscesses that have been incised too late or insufficiently drained, inflammatory bowel diseases (usually Crohn’s disease and ulcerative colitis) and conditions with immunodeficiency (HIV infection, chemotherapy). Other causes of branching fistulas, such as tuberculosis, actinomycosis, anal wall erosion due to anorectal cancer or as a complication after radiotherapy as well as anorectal trauma, are casuistic.
Iatrogenic fistulas resulting from proctological, gynaecological or urological surgeries are another group of fistulas (2-4). Fistula tracts can also result from sphincter-sparing surgeries for anal fistula followed by abscess formation, which, in turn, underlies the development of new tracts (5, 6). Similarly, quick abscess diagnosis and incision is important for the prevention of branching fistulas. Otherwise, the purulent secretion penetrates the anatomical spaces adjacent to the abscess, resulting in the formation of additional tracts.
Classification of anal fistulas
Complex fistulas are generally subject to the same divisions as simple fistulas. Parks’ classification, which is based on the relationship between the fistula tract and the external anal sphincter, is the most commonly used classification (7).
Another quite common classification of fistulas, which was proposed by Goodsall and Miles, is based on the presence of the internal fistula opening (8) and divides fistulas into complete and blind, i.e.:
– complete fistula – having two openings, one external through the skin and one internal into the anal or rectal lumen,
– external blind fistula – without an external opening,
– internal blind fistula – without (a visible) internal opening.
MRI-based classification of fistulas (9) distinguishes the types described by Perks, but also points to the coexistence of abscess and fistulous tracts:
– simple intersphincteric fistula,
– intersphincteric fistula with an intersphincteric abscess or secondary fistulous tract,
– transsphincteric fistula,
– transsphincteric fistula with an abscess or secondary fistulous tract to the ischioanal fossa,
– supra- or translevator fistula.
Fistulas passing directly through the levator muscles are rarely encountered in surgical practice. Typically, fistulous canal located in this area passes above or below the levator muscle. It seems from the above classification that group V refers to suprasphincteric and extrasphincteric fistulas.
Only type 1 fistula is associated with a good prognosis. The treatment efficacy in other types of fistula is lower and depends on both, the height of fistula and the number of secondary tracts or the location of a coexistent abscess.
Similarly to simple fistulas, the diagnosis of complex fistulas is based on medical history (per rectum) physical examination as well as imaging and functional evaluation.
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