Imaging in infectious diseases

At a glance

• Imaging answers three questions in infection: where is the source, is there a collection that needs draining, and what is the complication (abscess, empyema, epidural spread, valve destruction).
• Pick the test by the question, not by habit. Plain films are cheap but lag; CT is fast and finds collections; MRI is best for the spine, bone and brain; FDG-PET/CT helps with prosthetic material and fever with no source.
• Imaging never replaces cultures. A scan that finds a collection is the cue for aspiration or biopsy before antibiotics where it is safe.