Topical polyphenol treatment of sacrococcygeal pilonidal sinus disease: use of ultrasonography to evaluate response to treatment – clinical case series study - Aksoy, Hasan; Aksoy, Berna; Ozkur, Ezgi; Calikoglu, Emel (Advances in Dermatology and Allergology/Postępy Dermatologii i Alergologii, 2019)