Physical trauma, inflammation, infections, and surgery can all cause significant damages to both the human skin and its underlying tissues or organs that result in abnormal defects called fistulas. These pathological abnormalities contribute significantly to the morbidity and mortality statistics associated with chronic wounds. It is therefore imperative for wound care professionals to know how to properly diagnose and treat these defects.

What Is a Fistula?

A fistula can be defined as any abnormal communication between two epithelial surfaces. Fistulas can occur between two body organs, or an organ and the skin in virtually any anatomical area of the body. These connections are particularly dangerous as they may introduce harmful fluid contained in one body space into another which lacks adequate protection against it. Consequently, unchecked fistulas have the propensity to cause extensive tissue damage.

Categorizing Fistulas

Fistulas can be grouped according to their degree of communication, or the anatomical location in which they occur. When considering fistula connections, three major types are recognized:

• Complete fistulas which have both an internal organ opening and external skin opening.
• Incomplete fistulas where there is a visible opening on the skin but the internal opening ends short of any internal organs.
• Blind or sinus tracts which possess a single opening.

The most commonly cited fistula types by anatomical location include:

• Anal fistulas (fistula-in-ano)
• Rectovaginal fistulas
• Enterocutaneous fistulas
• Arteriovenous fistulas

Etiology and Risk Factors

The causes and risk factors for fistulas can be grouped according to the type of fistula involved. Risk factors for anal fistulas include chronic diseases, such as tuberculosis, HIV, and diabetes mellitus. Trauma, radiation therapy, and inflammatory GI disease can also contribute to the development of anal fistulas. Factors that predispose patients to rectovaginal fistulas mostly occur around the time of childbirth. Prolonged or obstructed labor, inappropriate prenatal care, very young and elderly ages at pregnancy all increase risk of having traumatic childbirth leading to fistula formation. The major predisposing factor for enterocutaneous fistulas is iatrogenic with complicated abdominal surgery representing the most commonly cited etiology for the development of this particular type of fistula. Trauma, radiation therapy, bowel disease, and cancers account for the spontaneous cases of enterocutaneous fistulas.

Clinical Signs and Symptoms

Some clinical manifestations of fistulas are listed below.

• Discharge of blood, mucus, pus, or feces
• Abdominal pain or cramps
• Fever
• Diarrhea
• Bleeding from the anus
• Dehydration
• Rapid weight loss

Diagnosing Fistulas

Clinically, fistulas are diagnosed by combining patient history, physical and rectal examinations of affected areas, and useful laboratory or radiological investigations. The relevant investigations include blood tests, contrast tests, x-rays, CT or MRI scans, proctoscopy, anorectal/transvaginal ultrasonography, and barium or methylene enemas. 

Treatment Principles

Various techniques can be used to treat fistulas depending on their location, and severity. Management can either be conservative or surgical with rapid intervention the key to a more favorable prognosis. Fistula repair should be conducted by multidisciplinary teams of wound care professionals including gynecologists, and colorectal surgeons. To improve outcomes, experienced, high volume surgeons should undertake the surgical repair of fistula defects.

Conservative Approaches

Conservative approach to treating fistulas involve the non-invasive techniques and methods outlined below:

• Infection control with antibiotics
• Fibrin glue/collagen matrix plugs to seal off fistula channels
• Catheters to drain purulent or bloody fluid within fistula tracts

For a majority of patients, conservative therapies show limited success and are seldom effective in the management of larger, high-output fistulas.

Surgical Approaches

Surgical procedures are suitable for moderate to severe fistula defects. Trans-abdominal and laparoscopic surgeries can be performed to correct various types of fistulas. 

Anal Fistulas

Anal fistulas can be treated surgically by these methods:

• Fistulotomy where the fistula tract is surgically incised and allowed to heal by secondary intention
• Seton placement within a fistula tract to collapse and heal the defect
• Advanced flap placement with rectal tissue graft following excision of the fistula
• Ligation of the intersphincteric fistula tract (LIFT)
• Endoscopic ablation with electrodes guided by endoscopic cameras
• Laser surgery to seal the fistula tract

Rectovaginal Fistulas

Surgical techniques effective in treating rectovaginal fistulas include:

• Simple fistulotomy
• Transabdominal fistula repair
• Transanal advancement flap placement
• Bioprosthetic repair
• Transvaginal inversion repair

Enterocutaneous Fistulas

Surgical management for enterocutaneous fistulas includes tract excision, restoration of bowel continuity, and drainage of any associated abscesses. High output enterocutaneous fistulas can be treated with a mucocutaneous or fasciocutaneous flap derived from the back muscles (latissimus dorsi, serratus). Regardless of the surgical approach taken, the postoperative period is crucial to the successful fistula repair. Patients should be placed on high-nutrient diets while avoiding constipation or diarrhea. Further antibiotic cover and bowel resting for the first 24 hours after surgery will help boost clinical outcomes.

Fistula Prevention Strategies

General prevention steps for fistulas are listed below.

• Adequate rehydration with oral fluids
• Dietary modification to a high fiber diet
• Regular mild to moderate exercises
• Reduction in alcohol intake, smoking cessation
• Compliance with medication or treatment strategies for chronic illnesses
• Proper personal hygiene.