A 72-year-old woman with a history of congestive heart failure undergoes CT chest for evaluation of bilateral pleural effusions. All of the following CT findings are consistent with transudative pleural effusion EXCEPT:

Question

Accepted Answer

D. Enhancing pleural thickening and nodularity on contrast-enhanced CT. ## CT Imaging of Pleural Effusion: Transudative vs. Exudative

**Key Point:** CT attenuation values and morphological features help distinguish transudative from exudative effusions. Transudates are simple fluids; exudates show inflammatory changes.

### CT Characteristics of Transudative Pleural Effusion

| Feature | Transudative | Exudative |
|---------|--------------|----------|
| Attenuation (HU) | 0–20 HU (water-like) | 20–40 HU or higher |
| Pleural thickening | Absent or minimal | Present (>3 mm) |
| Pleural enhancement | None or minimal | Marked enhancement |
| Pleural nodularity | Absent | Present (suggests malignancy, TB, infection) |
| Loculation/septation | Absent | May be present |
| Distribution | Dependent, bilateral (symmetric) | Variable |
| Associated findings | Heart failure signs, elevated hemidiaphragm | Lung consolidation, lymphadenopathy |

**High-Yield:** **Pleural enhancement and nodularity are hallmarks of exudative effusion**, particularly in malignant, tuberculous, or complicated parapneumonic effusions. Their presence excludes simple transudative effusion.

**Clinical Pearl:** In CHF-related transudative effusions, you expect:
- Bilateral symmetric effusions (right > left due to right heart failure)
- Simple fluid attenuation (0–20 HU)
- **No pleural thickening, enhancement, or nodularity**
- Cardiomegaly and pulmonary edema on the same study

### Why Option 2 Is Incorrect

Option 2 describes "**enhancing pleural thickening and nodularity**" — these are **exudative features**, not transudative. Transudates are passive accumulations of ultrafiltrate and do NOT cause pleural inflammation, thickening, or enhancement. The presence of these findings indicates an exudative process (malignancy, infection, TB, autoimmune disease) and excludes simple transudation.

**Mnemonic: SIMPLE** — **S**ingle attenuation (0–20 HU), **I**nflammation absent, **M**inimal/no thickening, **P**assive fluid, **L**oculation absent, **E**xudative features absent.

[cite:Hansell et al. Imaging of Diseases of the Chest 5e Ch 14]

Answer

A. Absence of loculation or septation within the effusion

Answer

B. Fluid attenuation value between 0–20 HU (similar to simple fluid)

Answer

C. Bilateral symmetric effusions with dependent distribution

A 72-year-old woman with a history of congestive heart failure undergoes CT chest for evaluation of bilateral pleural effusions. All of the following CT findings are consistent with transudative pleural effusion EXCEPT:

Explanation

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