Figure 10a. Flash artifact in a patient with polycystic kidney disease. (a) Longitudinal US image of the superior pole of the right kidney shows a large, complex renal cyst (C). (b) Color Doppler US image shows multiple areas of color in the cyst that represent flash artifact. Note also the normal vessels in the adjacent liver. (c) Doppler spectrum of the vessel-like color pattern in the cyst fails to demonstrate a true vascular flow pattern.