Pleura & peritoneum

Pleura nonneoplastic conditions

Pleural effusion

Last author update: 1 December 2013
Last staff update: 2 September 2020

Copyright: 2003-2023,, Inc.

PubMed Search: Pleural effusion[TI] pathology free full text[sb]

Vaidehi Avadhani, M.D.
Page views in 2022: 5,983
Page views in 2023 to date: 3,418
Table of Contents
Definition / general
Cite this page: Avadhani V. Pleural effusion. website. Accessed June 7th, 2023.
Definition / general
  • 15 cc or more of fluid within pleural cavities
  • Most common causes are congestive heart failure and metastatic disease
  • Due to increased hydrostatic pressure (congestive heart failure), increased vascular permeability (pneumonia), decreased oncotic pressure (nephrotic syndrome), increased intrapleural negative pressure (atalectasis), decreased lymphatic drainage (carcinomatosis)
  • May or may not be inflammatory
  • Malignant effusions are usually greater than 500 ml; are often first evidence of malignancy
  • For lung, breast and ovarian metastases, 92% of pleural effusions are ipsilateral to primary lesion

Inflammatory pleural effusion:
  • Either serous, serofibrinous or fibrinous
  • Due to inflammation in lung (tuberculosis, pneumonia, infarct, abscess, bronchiectasis), collagen vascular disease (rheumatoid arthritis, systemic lupus erythematosis, uremia) or radiation therapy
  • Empyema: pus in pleural cavity; due to bacteria or fungal seeding of pleural space; often from lung infection; usually organizes into dense adhesions but does not disappear

Noninflammatory pleural effusion:
  • Hydrothorax: clear / straw colored fluid; usually due to congestive heart failure
  • Isolated right sided hydrothorax seen in Meigs syndrome (hydrothorax, ascites, ovarian fibroma)
  • Usually is NOT loculated, collects basally

  • Hemothorax: usually due to rupture of aneurysm or vascular trauma; associated with large clots
  • Chylothorax: accumulation of milky white fluid, usually lymph, contains fat (DD: turbid serous fluid); usually left sided, caused by thoracic duct trauma / obstruction due to malignancy
Back to top
Image 01 Image 02