Background: Vascular access-related infection is more frequent in patients using the buttonhole method for cannulation of the arteriovenous access for hemodialysis. Deformity of buttonhole entry sites is frequently observed among patients on the buttonhole method for extended periods of time. With deformed buttonhole entry sites, moreover, scabs are often incompletely removed at the time of buttonhole cannulation. Method: In 166 patients using the buttonhole method at Hino Clinic in Osaka, Japan as of June 30, 2014, the shapes of buttonhole entry sites were categorized into the following 3 types: flat, depressive deformity, and bulging deformity. A multivariate logistic regression method was used to analyze associations between various data including shapes of buttonhole entry sites and occurrence of access-related infection. We also examined microscopic features of the buttonhole entry site tissue that was removed from a patient who died after 3 years of buttonhole cannulation. Results: For the flat buttonhole entry sites, frequency of access-related infection was 0.12 events/1,000 arteriovenous fistulas as compared to 0.47 events/1,000 arteriovenous fistulas for the entry sites with bulging deformity. Such infection did not occur for the entry sites with depressive deformity. The multivariate logistic regression analysis revealed a significant association between an entry site with bulging deformity and occurrence of access-related infection (odds ratio = 5.369, p = 0.0085). Furthermore, the microscopic section showed granulations beneath the skin at the buttonhole entry site and around the buttonhole tract. Conclusion: A significant association was shown between an entry site with bulging deformity and occurrence of access-related infection. The microscopic features of the buttonhole entry site of the patient on the buttonhole method for 3 years suggest that the entity of bulging deformity at the entry site is hypertrophic granulation.
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