Differential Diagnosis for a Large Effusion

• Single most likely diagnosis
  • Malignancy (e.g., metastatic cancer): This is often considered the most likely diagnosis due to the high prevalence of cancer and its potential to cause large effusions through various mechanisms, including direct tumor involvement, lymphatic obstruction, or secondary infections.
• Other Likely diagnoses
  • Heart failure: A common condition that can lead to fluid accumulation in body cavities, including large effusions, due to the heart's inability to pump blood efficiently.
  • Pneumonia or other infections: Severe infections, especially those affecting the lungs, can cause significant inflammation and fluid buildup, resulting in large effusions.
  • Trauma: Physical injury can lead to bleeding or fluid leakage into body cavities, causing effusions.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Tuberculosis (TB): Although less common in some regions, TB can cause large effusions and has a high mortality rate if not treated promptly.
  • Pulmonary embolism: A life-threatening condition that can cause sudden onset of symptoms, including large effusions, and requires immediate medical attention.
  • Esophageal rupture: A rare but potentially fatal condition that can lead to large effusions, particularly if not recognized and treated promptly.
• Rare diagnoses
  • Chylothorax: A condition characterized by the accumulation of lymphatic fluid (chyle) in the thoracic cavity, often due to trauma or malignancy.
  • Amyloidosis: A group of diseases caused by abnormal protein deposits, which can lead to fluid accumulation and large effusions in various body cavities.
  • Lymphangioleiomyomatosis (LAM): A rare lung disease that can cause large effusions, primarily affecting women of childbearing age.