Validity of ultrasound in dignosis of scrotal filariasis in a filarial endemic area in Uganda

Abstract

ABSTRACT Scrotal filariasis is a devastating and disfiguring disease that is a major public health problem with socioeconomic impacts. It is a disease condition resulting from infestation with the mosquito borne parasitic nematode, Wuchereria bancrofti. The disease is widely distributed in tropical and sub tropical areas of the world, where it results in considerable suffering and debilitation.. The clinical manifestations of the disease are due to obstruction of the lymphatic vessels draining the body parts that are affected. Several studies have shown that adult Wuchereria bancrofti can be detected in the scrotal area of the infected by ultrasound. These adult worms are found mostly in dilated intrascrotal lymphatic vessels, and the locations of the worm nests are stable over time. The typical movement of these filariae, called the filarial dance sign (FDS), provides an opportunity to observe the adult worms in vivo. At the same time, ultrasound examination offers a method to detect pathological changes, such as the degree of dilatation in the lymphatic vessels, early and advanced stages of hydrocele, and the number of worm nests over time. Objective This study was aimed at determining the validity of ultrasound in diagnosis of scrotal filariasis in males 14years and above infected with scrotal filariasis in a filarial endemic area in Uganda. Methodology A Descriptive Cross Sectional study was used; patients 14 years and above presenting with scrotal complaints were taken in for scrotal ultrasound using a high frequency linear probe. These patients also had a sample of blood taken off and the blood was dropped onto a BinaxNOW (gold standard) Filariasis antigen sensitive rapid test card, to test for filarial antigens. Data was collected using a coded questionnaire, entered into a computer using Epi data version 3.1 and analyzed using Stata version 11 with the help of a biostastician. The variables that were considered in this study included, scrotal hydrocele, scrotal skin thickness, lymphatic vessel dilatation, worm nests, presence of filarial dance sign and the antibody test results.

Results A total of two hundred twenty seven patients were enrolled, 21 of whom were below the age of 18 years while 206 were adults. The majority of clients were peasants (132), with primary level of education (135). A large proportion of these clients were married (145) and the main scrotal complaint was swelling (128) followed with itching (47), and pain (43), 9 clients had itching or burning sensation. One hundred seventy (170) clients tested negative for filarial antigens while 46 tested positive, and 11client blood samples were non reactive. Conclusion From this study ultrasound has a specificity of 100% if the filarial dance is observed and a sensitivity of 93% if scrotal hydrocele is observed. Thus ultrasound can be used in screening of those affected in the endemic areas. There is a close correlation between lymphatic vessel dilatation, abnormal scrotal skin thickness, presence of worm nests and infestation with scrotal filariasis. Though scrotal hydrocele was demonstrated in majority of clients, it only had a significant sensitivity but a small specificity.