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A genitourinary fistula is defined as an abnormal communication between the urinary (ureters, bladder, urethra) and the genital (uterus, cervix, vagina) systems. The true incidence of genitourinary fistula is unknown and varies according to whether the etiology is obstetric or gynecologic. In Asia and Africa, up to 100,000 new cases of obstetric genitourinary fistula are added each year to the estimated pool of 2 million women with unrepaired fistulas (World Health Organization, 2014). For industrialized countries, most fistulas occur iatrogenically from pelvic surgery, and the generally accepted incidence derives from data on surgeries to correct these fistulas. For example, numbers from the National Hospital Discharge Survey of inpatient women show that approximately 4.8 per 100,000 women underwent lower reproductive tract fistula repair (Brown, 2012). This likely is underestimated as many cases are unreported, unrecognized, or treated conservatively. Of genitourinary fistulas, the vesicovaginal fistula is most common and develops significantly more frequently than ureterovaginal fistulas (Goodwin, 1980; Shaw, 2014).
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The principles and phases of wound healing aid the understanding of genitourinary fistula pathogenesis. After injury, tissue damage and necrosis stimulate inflammation, and the process of cell regeneration begins (Kumar, 2015). Initially at the injury site, new blood vessels form, that is, angiogenesis. Three to 5 days after injury, fibroblasts proliferate and subsequently synthesize and deposit extracellular matrix, in particular collagen. This fibrosis phase determines the final strength of the healed wound. Collagen deposition peaks approximately 7 days after injury and continues for several weeks. Subsequent scar maturation and organization, termed remodeling, augments wound strength. These phases are interdependent and any disruption of this sequence eventually may create a fistula. Most defects tend to present 1 to 3 weeks after tissue injury. This is a time during which tissues are most vulnerable to alterations in the healing environment, such as hypoxia, ischemia, malnutrition, radiation, and chemotherapy. Edges of the wound eventually epithelialize, and a chronic fistulous tract is thus formed.
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Although many classification systems exist for genitourinary fistula, no single system is considered the accepted standard nor is any one scheme superior in predicting surgical success. Fistulas can develop at any point between the genital and urinary systems, and one classification method reflects the anatomic communication (Table 26-1).
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Vesicovaginal fistulas can also be characterized by their size and location in the vagina. They are termed high vaginal, when found proximally in the vagina; low vaginal, when noted distally; or midvaginal, when identified centrally. For instance, posthysterectomy ...