A fistula is an abnormal connection between 2 epithelial surfaces. This is a general definition that applies to most of the known fistula but not all of them. The general description differentiates fistulae from sinuses, abscesses, and other forms of luminal tracts or extra-luminal collections.
Fistula connects 2 surfaces or lumens. It begins on the offending side and makes its way to an adjacent lumen or surface. It follows the easiest and shortest path to the adjacent organ. Recto-vaginal fistula starts from the rectum and extends to the vagina. It is not a healthy situation or physiological status. There is usually an underlying pathology, injury, or surgical event.
Characteristics of rectovaginal fistula (RVF), for example, site, size, length, activity, and symptoms, vary depending on the cause of the fistula, patient factors, and the treatment received. It is a potentially challenging surgical condition for both the patient and health care team. The underlying etiology determines the method of assessment, management, and prognosis. This article reviews rectovaginal fistula under the general category of fistulae.
RVF formation results as a complication of an underlying disease, injury or surgical event. Diseases of the vagina or the pelvic organs can be complicated with a persistent connection between the rectum and vagina. The common causes of rectovaginal fistula are:
Obstetric-related injury: This is the most common etiology of traumatic RVF, and probably for all RVFs. This includes third- and fourth-degree lacerations during vaginal delivery.
Surgical procedure: Surgical interventions that cause unrecognized vaginal or rectal injury, insufficient tissue thickness between the two organs, or ischemia of the tissue may result in perforation and fistula formation through the damaged tissue.
Diverticular disease: Complex diverticular disease is a common cause of fistula connecting to an intra-abdominal organ like the bladder and vagina. Erosion of the diverticular wall with inflammation and abscess can extend, involve, and erode the adjacent organ walls resulting in a fistulous connection. An occasional increase in the luminal pressure on either side of the fistula and the continued inflammatory process will maintain the fistula patent.
Crohn's disease: Chronic inflammatory bowel diseases, especially Crohn's disease, is a well-known cause of intestinal fistulization. Crohn’s is a transmural disease that involves the entire thickness of the bowl making an extension to and involvement of adjacent tissues and organs very common.
Malignancy: Cancer of intestine or adjacent organs is a known cause of bowel perforation and fistulization. RVF can result from vaginal, cervical or more commonly rectal cancer that involves the entire wall thickness and extends to the adjacent vagina. These fistulae are also called malignant fistulae.
Radiation: Radiation causes long-term chronic tissue inflammation with poor healing and repair processes. Therefore, fistulae caused by radiation manifest after a lag period from the radiation exposure.
Non-surgical injuries and foreign bodies: Injuries in trauma or by a foreign body can result in a non-healing abnormal connection with the vagina.
There are a number of causes that are abbreviated in the mnemonic "FRIEND" (Foreign body, Radiation, Inflammation, Epithelization, Neoplasm, Distal obstruction). These are known causes of non-healing in fistulous diseases. They should not be mixed with the primary or underlying causes of fistula formation.
The frequency of rectovaginal fistula varies according to the cause. They are typically classified by etiology, location, and size which affects the treatment and prognosis.
Rectovaginal fistulas are divided into 2 groups by location:
RVF, like other fistulae, is a result of a complication of an underlying disease, surgical procedure or injury. A good understanding of the pathophysiological process helps to assess better, manage, and prevent fistulae. Loss of wall integrity with ongoing inflammatory, infectious, or neoplastic process at the rectal or vaginal wall can lead to erosion to the adjacent tissue or organ and establishing the abnormal fistulous connection. When the initial process is reversible or curable, like in diverticulitis, fistulae have a better chance to resolve.
Histopathologic examination of the tissue involved in the fistula reflects an acute inflammatory reaction besides the original pathology of the causative disease. Acute inflammation is caused by a combination of more than one factor like the primary pathology causing the fistula (diverticular disease, malignancy, Crohn's, among others), tissue irritation by the flow of intestinal content, and the resulting infection. Other histopathological findings like chronic inflammation from radiation, Crohn's disease, malignancy, and or injury related necrotic process can be identified depending on the cause of the fistula.
The clinical presentation of RVF is a result of a combination of the passage of rectal content to the vagina, and the underlying disease or injury. A detailed history of the underlying disease should be explored. Clinically, the escape of stool or gas from the rectum to the vagina through the fistula gives the abnormal signs and symptoms of foul-smell vaginal discharge, dyspareunia, passing air, bleeding, and passage of frank stool especially when the patient has diarrhea. Further symptoms of complications like symptoms of cystitis or vaginitis are occasionally encountered. Symptoms of an underlying disease like rectal obstructing cancer or diverticulosis may be present.
Physical exam of the vagina, the source of the symptoms, will likely reveal irritation, erythema, swelling, discharge, stool and possible fistula opening in speculum exam. Office colposcopic exam may reveal more details of the vaginal epithelium and the fistula site as an indurated indentation. A rectovaginal examination may reveal signs of the underlying disease like an obstructing low rectal tumor or phlegmon, Crohn's disease, or tissue atrophy from radiation.
When RVF is suspected, a workup should be started to confirm the diagnosis, assess the extent of the fistula, and identify the underlying diagnosis. Work up, in addition to history and physical examination, should be complemented by the imaging and endoscopy if needed.
Laboratory tests to assess the baseline hematocrit, biochemical and infectious parameters are usually obtained. Signs of the overall disease impact, complications, and the severity can be estimated from these tests. Further tests may be needed according to the initial assessment.
Endoscopy like colposcopy and/or proctosigmoidoscopy (rigid or preferably flexible) may reveal the site of the fistula with the underlying disease. Signs of the underlying diseases like Crohn’s, diverticular disease, or rectal cancer are likely to be identified with endoscopy. Colposcopy can help detect cervical or vaginal cancers.
Imaging is commonly used and useful to confirm the diagnosis and identify the underlying disease. CT scan provides accurate, objective and detailed information of the fistula, the underlying disease, and the related nearby area. Rectal and intravenous contrast will outline the fistulous tract and the related structures. Presence of rectal contrast in the vagina is a confirmation of the diagnosis even if the fistulous tract itself cannot be visualized.
Further assessment includes laboratory workup to evaluate the general patient condition, underlying disease or complications of the fistula like infection or electrolytes imbalance. Tissue biopsy from suspected masses will help to confirm malignancy and its origin.
Treating RVF involves treating the underlying disease, the fistula itself and any related complications. Therefore, confirming the fistula etiology should be done before planning treatment. Treatment approach depends on many factors like condition severity, acuity, presenting symptoms, patient's general condition, underlying etiology, and complications resulting from the fistula.
Treatment of Crohn's disease, diverticular disease or colorectal or gynecologic cancers should follow the principles of treating these diseases primarily. Treating RVF depends to a great extent on treating the underlying primary disease. There is more than one approach to the treatment of fistula with curative intent. In 2016, the American Society of Colon and Rectal Surgeons reviewed the approaches and developed guidelines to manage RVF.
Conservative or non-surgical treatment approach of the symptoms and possible complications like UTI, local irritation, and site infection can be used in selected patients. This approach can be considered in high-risk patients and severe underlying disease. Medical treatment includes treating the infection and the associated symptoms, maximizing medical treatment of the underlying disease like in Crohn's or diverticulitis, and support of the general patient's condition. Other conservative treatment includes non-operative measures to close the fistula like fibrin glue or other occlusive measures. The success rate of these measures is not high. They are still an option to consider in high-risk patients who are not fit for surgery or for those who failed a prior surgical approach.
Multiple operative approaches are used to treat RVF depending on complexity, recurrence, and the underlying disease. Simple measures like draining seton in recurrent or acute infection may be used to optimize local tissue integrity and treat the infection.
The proximity of rectal wall to vaginal wall with minimal tissue in between makes repairs connecting fistula challenging. The principles of successful repair are to remove the unhealthy fistula tissue, replace with healthy tissue that has a good blood supply to enhance healing, and maintain thick interposing tissue between the rectal and vaginal walls. Following these principles (although not always possible) increase the chance of successful fistula treatment.
Fistula debridement and flaps are common surgical approaches. Advancement local endo-rectal flaps in simple RVF or gracilis regional myocutaneous flap in more complicated RVF are of the common flaps.
In proximal or high RVF, surgical excision of the rectal wall in regimental resection is the other surgical radical approach.
Management of RVF is a complex and potentially tremendously challenging due to multiple factors. It requires interprofessional efforts, collaboration, assessment, and planning. Prevention or early detection and treatment may save the unnecessary suffering of patients. Suspected fistula patients should be evaluated and appropriately referred to specialists. All pertinent information including previous surgical information details should be obtained. Proper planning and involvement of the required services are essential for successful treatment. Finally, an RVF has enormous adverse mental morbidity. Thus, these patients should be referred to a mental health counselor.