A 25 year old man came with scrotal pain and swelling since three weeks. This was accompanied by low-grade fever and mild lower abdominal discomfort. There was no history of trauma or urinary complaints.
Ultrasonography of the scrotal region shows multiple dilated, anechoic spaces in the epididymis. Colour Doppler excludes vascularity in these spaces. In these channels there were highly mobile, echogenic, twisted tubular structures. These structures exhibited continuous, vigorous swirling or “dancing” movements, a phenomenon termed the “filarial dance sign”.