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. However, the generally accepted incidence is derived from surgeries to correct these fistulas and approximates 1 percent or less of all genitourinary operations (Harris, 1995). This is most likely an underestimation because many are unreported or unrecognized. The most common type of genitourinary fistula is the vesicovaginal fistula and is discussed later (Goodwin, 1980).
Knowledge of the principles and phases of wound healing is important in understanding the pathogenesis of genitourinary fistula. After injury, tissue damage and necrosis stimulate inflammation, and the process of cell regeneration begins (Kumar, 2005). Initially, at the injury site, new blood vessels form in a process termed 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 a number of weeks. Subsequent maturation and organization of the scar, termed remodeling, augments wound strength. These phases are interdependent and are intrinsically involved in wound healing. Any disruption of this sequence eventually may result in fistula formation. Most fistulas tend to present 1 to 3 weeks after tissue injury, 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 eventual epithelialize, and a chronic fistulous tract is thus formed.
Although many classification systems exist for genitourinary fistula, there is no single, accepted standardized scheme. Fistulas can develop at any point between the genital and urinary systems. Thus, one method of classification is based on anatomic communication (Table 26-1).
Table 26-1. Classification of Genitourinary Fistula Based on Anatomic Communication |Favorite Table|Download (.pdf)
Table 26-1. Classification of Genitourinary Fistula Based on Anatomic Communication
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 vesicovaginal fistulas are often proximal, or “high” in the vagina, and located at the level of the vaginal cuff.
Alternatively, some have classified vesicovaginal fistula based on the complexity and extent of involvement (Table 26-2) (Elkins, 1999). In this scheme, complicated vesicovaginal fistulas are those that involve pelvic malignancy, prior radiation therapy, shortened vaginal length, or bladder trigone; those that are distant from the vaginal cuff; or those that ...