Figure 1.

Transverse scan of a patient's left testis. Upper left: In para-testicular position an enlarged lymphatic vessel with one or more adult worms can be seen (arrow). The blue line depicts the cursor position of the following m-mode, upper right. The corresponding video image can be seen as Additional File 1: Movie1A.mpg. Middle left: The same worm nest as seen above. Middle right: The use of the Colour Power Doppler shows that this worms nests contains much free lymphatic fluid which induces a red signal due to the worm movements in different parts of the worm nest. Different to vessels, the signal is non-rhythmic and non-pulsating. The corresponding video image can be seen as Additional File 2: Movie1B.mpg. Lower left: The same worm nests as seen above. The caliper marks the position at which the Pulse Wave Doppler (PWD) is performed. Lower right: After switch to the PWD mode the filaria dance sign (FDS) is seen as an undulating band as a function of time, with sharp, irregular peaks (turquoise arrowhead). The corresponding video image can be seen as Additional File 3: Movie1C.mpg.