Can We See Microfilaria On Ultrasound?: A Real-Time Ultrasound And Wet Smear Demonstration Of Dancing Microfilaria
N Shyamkumar, S Mehrotra, R Athyal, A Taranath, S Nair, S Govil, N Chacko
filaria, microfilaria, ultrasound
N Shyamkumar, S Mehrotra, R Athyal, A Taranath, S Nair, S Govil, N Chacko. Can We See Microfilaria On Ultrasound?: A Real-Time Ultrasound And Wet Smear Demonstration Of Dancing Microfilaria. The Internet Journal of Urology. 2003 Volume 2 Number 1.
A case with the filaria dance sign (FDS) in the epididymal region is described. Aspiration of fluid from an epididymal cystic lesion demonstrated motile microfilaria. We explore the possibility that the "dancing particles" described by the FDS are microfilaria and not the adult worm as previously described.
Man is the definitive host of filaria. The adult filarial worm resides in scrotal lymphatics. The female adult worm can release upto 50,000 microfilaria, the larval form, in one day. Imaging techniques can detect the presence of the adult worm and different features have been described on plain radiography (1), CT, lymphangiography (2,3), ultrasound (4), lymphoscintigraphy and MRI (5). Amongst these imaging modalities, ultrasound has proved to be the most widely used method for demonstrating the adult filarial worm. The term
A 35-year-old man presented with right-sided scrotal pain. Clinically, the right epididymis was thickened. High resolution ultrasound (10MHz) examination showed four cystic spaces in the right epididymal region and one in the left epididymal region measuring 2 mm to 8 mm with multiple small (<1mm) objects exhibiting peculiar random movements as described by the
Video Clip 1 - Real time Ultrasound (10MHz) showing nest with
Ultrasound guided aspiration of one of the cystic lesions yielded turbid viscous fluid. There was significant reduction in the number of particles on ultrasound following aspiration. Immediate microscopic examination of the wet smear showed motile microfilaria. On May-Grunwald- Giemsa stain, these were confirmed to be microfilaria of Wuchereria bancrofti.
Video Clip - Video-microscopy of the aspirate showing
We feel that these small dancing particles are microfilaria and not the adult worms in view of their size (<1 mm) and their location within minute lymphatic spaces (2 mm). Adult male filarial worms measure 10 mm to 40 mm in length and adult female worms measure 40 mm to 100 mm. The length of the microfilaria is 250 microns (0.25mm). In addition, there was no structural continuity or coordinated movement between the particles.
To support this hypothesis, aspiration of one of the dilated lymphatics exhibiting the FDS yielded microfilaria. There was a remarkable similarity in the movements of the microfilaria on wet smear microscopy and US. Microfilaria of Wuchereria bancrofti are known to move in graceful sweeping curves (9).
Because of their small size, microfilaria are theoretically beyond the resolution of high frequency US transducers. In these cases, however, they were probably rendered visible by their rapid movements within an ideal acoustic medium. Furthermore, part of their reflectivity may be due to turbulence within the surrounding fluid created by their movements.
In conclusion, despite their small size, microfilaria are eminently demonstrable on ultrasound examination and when aleatory movements are seen in scrotal lymphatics, the term
Dr Faye C. Laing, MD Professor of Radiology BWH Radiology
Boston for the valuable suggestions.
Dr Shyamkumar NK Senior lecturer, Department of Radiodiagnosis, CMC Hospital, Vellore, India. 632 004. Ph: (91)-416-222102 Fax: (91)-416-232035 E-mail: firstname.lastname@example.org