Imaging of hidradenitis suppurativa allows the study of both the lesion morphology and evolution. Hidradenitis lesions of different stages were studied using 3D ultrasound in a cross sectional pilot study. A total of 25 HS patients (18 female/ 7 male, aged 18-46 year-old) and 10 healthy controls (5 female/5 male, aged 21-49 year-old) were studied. All patients were referred by dermatologists. All examinations were performed on the right axilla and compared with both controls and the skin outside the lesional areas. 3D ultrasound images demonstrated enlargement of the deepest portion of the hair follicles in early stages. In more advanced stages dermal and subcutaneous sinus tracts were identified that were commonly connected to the base of the regional hair follicles. At the end stage of the disease, these sinus tracts were further dilated and multiple. Ultrasound allows early detection and characterization of the morphological changes in hidradenitis, which include the variable degrees of involvement of the hair follicles and the appearance of fluid collections and sinus tracts. Knowledge of this anatomical information may allow the identification of lesions that can benefit from medical or surgical management.