How is dx of renal abscess?

Utrasound is the quickest and least expensive method to demonstrate a renal abscess. An echo-free or low–echo-density space-occupying lesion with increased transmission is found on the sonogram. CT of a chronic abscess shows obliteration of adjacent tissue planes,thickening of Gerota's fascia, a round or oval parenchymal mass of low attenuation, and a surrounding inflammatory wall of slightly higher attenuation that forms a ring when the scan is enhanced with contrast material . The ring sign is caused by the increased vascularity of the abscess wall.