Simple posteroanterior and lateral chest radiographs mav detect effusions as small as 200 mL. In addition, viewing the chest with the patient in a lateral decubital position allows better localization of small to moderate fluid accumulation and may guide diagnostic sampling. When the fluid does not layer dependently with change in patient position, loculation should be suspected. Ultrasound or CT is then particularly useful in defining the anatomy, as well as the safest approach to diagnosis and therapy.
Thoracentesis is the diagnostic procedure of choice to evaluate a new pleural effusion. Cytologic examination of the cellular components of the fluid provides definitive evidence of malignancy. In a patient with a history of malignancy, this is usually not difficult. In the absence of a known cancer, a single tap can be expected to be diagnostic half the time. Repeated thoracentesis has been reported to improve the diagnostic sensitivity of cytologic yield from 50 to 65%. The addition of a closed pleural biopsy using an Abram’s or Cope’s needle may improve the cytologic yield to between 80% and 90%. cialis professional
Biochemical analyses of pleural fluid at best support the diagnosis of malignancy. Most MPEs are exudative by the criteria of Light et al, admittedly a nonspecific finding. The pleural fluid pH also does not indicate malignancy, as a low value is also seen with infection and hemothorax. Once malignancy has been established, a low pH may be prognostic, as lower values seem to portend shorter patient survival. Assays for pleural fluid carcinoembryonic antigen (CEA) are available, but are also nonspecific for malignancy. Benign processes, including empyema, tuberculosis, pancreatitis, and cirrhosis, yield levels of CEA >10 ng/mL without malignancy. There is no agreement as to the diagnostic threshold for malignancy of CEA and pleural fluid. Prostate-specific antigen may be a more sensitive probe of malignancy. Unfortunately, prostate cancer accounts for <3% of MPE cases, making this assay impractical for screening pleural fluid.