Color Doppler ultrasonography in paramedian sagittal oblique view of the sacral and lumbar spine. The observed color spectrum suggests the flow of injectate reaching L4-5 level. The inset shows the position of the ultrasound transducer. L3L: L3 lamina; L4L: L4 lamina; L5L: L5 lamina; DS: dorsal surface of sacrum.