-Tuberculosis: History of exposure, can be sanguineous; > 1000 lymphocytes, positive for acid-fast bacilli, positive tuberculin skin test, positive pleural biopsy, glucose < 60 mg/dL
-Cancer: 67% bloody, cytology positive in 50%, glucose rarely < 60 mg/dL
-Congestive heart failure (CHF): Presence of CHF, serous, < 10,000 RBCs, right-sided in up to 70%, may be bilateral; interlobal fissure fluid collection called "pseudotumors"
-Pneumonia: Respiratory infection, serous, neutrophils predominate in fluid, culture and stain positive for organisms, infiltrate on chest film
-Rheumatoid arthritis: Joint involvement, turbid or yellow-green color, lymphocytes predominate, glucose < 20 mg/dL, rapid clotting time, eosinophils present
-Pulmonary embolism: Risk for embolism, often sanguineous
-Other causes: Nephrotic syndrome, rupture of hydronephrosis into pleural space (elevated creatinine in fluid), pancreatitis (left-sided, elevated amylase), cirrhosis (5% of patients with ascites)