What is an abscess, and what are its CT and MRI features?
An abscess is a loculated collection of pus.
On CT and MRI, an abscess appears as a complex loculated fluid collection that may contain debris, complex fluid, or hemorrhage with increased attenuation and T1-weighted signal intensity, sometimes with internal septations or very low attenuation/signal intensity gas bubbles. An abscess often has a thick enhancing rim of fibrous tissue peripherally ( Figure 32-1 ). When an abscess arises within a parenchymal organ, multiple small adjacent abscesses (i.e., “satellite lesions”) are also commonly encountered.