Inflamed testis. Three-dimensional power Doppler ultrasound scan of blood vessels (orange) in the inflamed testis of a 32-year-old man suffering from orchitis. This bacterial infection of the testes (the male sex organs) and the scrotum, can be sexually transmitted. Some of the bacteria that cause orchitis include those that cause gonorrhoea and syphilis. Treatment with antibiotic drugs can prevent infertility and, in severe cases, death. Doppler ultrasound scanning detects moving fluids, like blood, by the frequency change they cause when reflecting high-frequency sound waves. Power doppler scans use colour to show the moving fluid, but do not show the direction of the flow.