Radiographically, an acute apical abscess:

Correct answer: B. May not be evident at all

• A. Size does not distinguish it. Chronic lesions — granulomas and cysts — have had time to resorb bone and are typically the LARGER lesions.
• B. CORRECT. An acute apical abscess develops rapidly, and the radiograph lags well behind the pathology. In a tooth that has just become necrotic there may be nothing more than a slightly widened PDL space, or a completely normal-looking film, while the patient has severe pain, swelling and tenderness. The clinical picture drives the diagnosis here, not the radiograph.
• C. A well-corticated round radiolucency suggests a slow-growing chronic lesion such as a cyst, not an acute abscess.
• D. Diffuse margins are a feature of lesions that are radiographically visible; the point about an acute abscess is that it may not be visible at all.

Note: Acute = symptoms without radiographic change. Chronic = radiographic change with few or no symptoms. The pairing is worth memorising.