Rectovaginal fistulas (RVFs) and anovaginal fistulas (AVFs) frequently result from obstetric trauma. These fistulas are frequently found in undeveloped countries where prolonged obstructed labor leading to pressure necrosis is more common. They also occur following an unsuccessful primary repair of a third or fourth degree laceration, from unrecognized injury at the time of vaginal delivery, and from episiotomy infection with formation of a fistulous tract.
RVFs may also result from difficult hysterectomies, especially those performed for severe endometriosis with involvement or obliteration of the posterior cul-de-sac (pouch of Douglas), and from surgical procedures involving the posterior vaginal wall, perineum, anus, and rectum. Inflammatory bowel disease, such as Crohn's disease and ulcerative colitis, is another important cause of RVFs in women . In elderly women, RVFs can occur as the result of diverticulitis, colon cancer, or fecal impaction. Vaginal trauma, induced by a retained foreign body such as a Pessary can also result in RVFs . In addition, operative procedures that incorporate the use of transvaginal and perineal mesh placement to repair pelvic organ prolapse have resulted in rectovaginal fistula .
Fistula-in-ano describes a communication between the anal canal and the perianal skin or perineum. These fistulas are typically initiated by an infection such as an anal abscess, trauma, anal fissure, or Crohn's disease, or as a complication of episiotomy . Anatomically, the fistula may originate anywhere below the dentate line internally and exists externally along the perianal skin or perineum. Histologically, fistula-in-ano differs from AVFs in that the fistulous tract is typically lined with chronically inflamed granulation tissue, rather than the epithelialized tract typical of anovaginal and RVFs.
Women suffering from anovaginal (AVFs) or rectovaginal fistulas (RVFs) present with complaints of uncontrollable passage of gas or feces from the vagina. A malodorous vaginal discharge and fecal soiling of the undergarments are also common complaints. Symptoms may be more pronounced when bowel movements are loose. Occasionally, a small fistula may be asymptomatic. It is important to inquire about fecal urgency and fecal incontinence associated with urgency as this often suggests that the external anal sphincter is also disrupted. (See "Delayed surgical management of the disrupted anal sphincter".)
Clinically, fistula-in-ano differs from AVF and RVF in that rectal and/or vaginal pain is a prominent symptom with fistula-in-ano, and may reflect its chronic inflammatory etiology. It is characterized by chronic purulent drainage or cyclical pain. Palpation of the fistula tract is very uncomfortable for the patient with a fistula-in-ano, in contrast to the relatively painless tract of a rectovaginal or anovaginal fistula. The course of a fistula-in-ano can be complex and circuitous with one or more blind sinus tracts. Their location is usually lateral from the midline, whereas most AVFs and RVFs are located close to the midline (related to their obstetric origin).