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Objective:
Urinary tract fistulas constitute an abnormal connection between the urinary collecting system and other areas. Urinary fistulas may be formed as sequelae of malignancy, radiation, trauma, and other etiologies. Also, fistulas formed by the ureter may be complicated by infection due to the low pH of urine and presence of urokinase, which slows the healing process. Moreover, ureteral fistulas may be life-threatening due to abscess formation or urinoma leading to sepsis. One method to treat urinary tract fistulas, provide symptomatic relief, and reduce complications is ureteral embolization, a minimally invasive procedure performed under fluoroscopic guidance. A variety of agents have been used to embolize the ureter, which include platinum coils, gelfoam, AMPLATZ plugs, ethylene vinyl alcohol, balloons, and cyanoacrylate glue. This systematic review aims to summarize the most common methods to achieve ureteral embolization and analyze the available evidence for each embolic agent.

Materials and Methods:
A systematic literature search was performed of the PubMed, EMBASE, Web of Science, ClinicalTrials.gov, World Health Organization, and Cochrane databases. Retrospective cohort studies and case series of at least two patients were included. Screening was performed based on preestablished inclusion and exclusion criteria and was performed by two independent reviewers. Quality assessments were then performed for each study prior to data extraction. Data included number of patients and ureters treated, comorbidities, technical success, clinical success (long term cessation of leakage), repeat procedures, infection rate, and type of embolic used.

Results:
A total of 21 studies were included in the systematic review. Analyzed studies involved a range of 2 - 76 patients and 2 - 83 ureters embolized. Malignancy was the most common comorbidity. Technical success ranged from 80 - 100% (mean: 97%). Clinical success ranged from 55% - 100% (mean: 87%). Nylon plugs had the lowest technical success rate (80%), whereas coils alone or coils combined with glue or gelfoam had the highest (100%). The repeat procedure rate ranged from 0 - 100% (mean: 22.5%) in the subset of 14 studies that reported this outcome. Only one study noted an intraprocedural complication of getting the catheter tip stuck to the glue embolic. Rate of infection from the procedure ranged from 0% - 66% (mean: 8%). The most common embolic agent used was coils or coils combined with glue, which were used in 33% of all patients in these studies.

Conclusion:
These findings show that technical and clinical success rates are high overall and suggest that a variety of embolic agents can be used in this procedure. Low infection rates also suggest it is a safe procedure. The repeat procedure rate suggests that there is room for optimization and that cost effectiveness should be studied. Future research may include randomized trials to compare the efficacy of different embolic agents and the development of novel embolic agents specifically designed for use in ureters rather than vasculature.