title: Etiology and pleural fluid characteristics of large and massive effusions.
abstract: OBJECTIVE
  To report the etiology of large and massive pleural effusions, and to compare their biochemical fluid characteristics with those of smaller size, and between malignant and nonmalignant conditions.
  
  
  METHODS
  Retrospective chart review of all patients undergoing thoracentesis at an academic medical center in Lleida, Spain, during a 10-year period.
  
  
  METHODS
  Posteroanterior chest radiographs were available in 766 patients during the study period. Large pleural effusions (ie, two thirds or more of the hemithorax without its complete obliteration) were identified in 70 patients (9%), and massive pleural effusions (ie, hemithorax was completely opacified) were identified in 93 patients (12%).
  
  
  RESULTS
  A similar etiologic spectrum between large and massive pleural effusions was observed. The most frequent cause of these pleural effusions was malignancy (89 patients; 55%), followed by complicated parapneumonic or empyema (36 patients; 22%), and tuberculosis (19 patients; 12%). Compared with nonmalignant pleural effusions, patients with large or massive malignant pleural effusions were more likely to have pleural fluids with higher RBC counts (18.0 x 10(9) cells/L vs 2.7 x 10(9) cells/L, respectively; p < 0.001) and lower adenosine deaminase (ADA) activity (11.5 vs 31.5 U/L, respectively; p < 0.001), which were the two parameters that were selected by a stepwise logistic-regression model as independent predictors of malignancy. In addition, large/massive malignant pleural effusions showed higher median RBC counts (18.0 x 10(9) cells/L vs 4.3 x 10(9) cells/L, respectively; p < 0.001), higher lactate dehydrogenase levels (641 vs 409 U/L, respectively; p = 0.001), lower pH (7.39 vs 7.42, respectively; p = 0.006) content, but similar cytologic yield (63% vs 53%, respectively; p = 0.171) than smaller malignant pleural effusions.
  
  
  CONCLUSIONS
  The presence of a large or massive pleural effusion enables the clinician to narrow the differential diagnosis of pleurisy, since most effusions are secondary to malignancy or infections (either bacterial or mycobacterial). Bloody pleural fluid with low ADA content favors a malignant condition.
authors.affiliation: Department of Internal Medicine, University Hospital Arnau de Vilanova, Alcalde Rovira Roure 80, 25198 Lleida, Spain. jporcelp@medynet.com
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Porcel
authors.forename: Manuel
authors.initials: M
authors.lastname: Vives
mesh_terms: D000243:Adenosine Deaminase / Q000378:metabolism; D000368:Aged; D003937:Diagnosis, Differential; D004906:Erythrocyte Count; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010996:Pleural Effusion / Q000175:diagnosis / Q000201:enzymology / Q000209:etiology*; D016066:Pleural Effusion, Malignant / Q000175:diagnosis / Q000201:enzymology / Q000209:etiology*; D010998:Pleurisy / Q000175:diagnosis / Q000201:enzymology; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013907:Thoracostomy; D014396:Tuberculosis, Pleural / Q000175:diagnosis / Q000201:enzymology
chemical_list: D007770:L-Lactate Dehydrogenase; D000243:Adenosine Deaminase