Hypoalbuminemia as a cause of pleural effusions

Background: Alterations in Starling forces that favor pleural fluid formati on include an elevation in capillary hydrostatic pressure and a fall in pla sma oncotic pressure. Although venous hypertension is a well-recognized cau se of pleural effusion, the frequency with which hypoalbuminemia in the abs ence of: volume expansion leads to pleural effusion is unclear. Study Objective: We determined the frequency with which unexplained pleural effusions occur in patients with normal and low plasma oncotic pressures. Design: A 2-month prospective screen of all admission patients to the Unive rsity of Oklahoma Hospital and the Oklahoma City Veterans Administration (V A) Medical Center identified 152 patients who had chest radiographs and ser um protein determinations on admission, but did not have an admission diagn osis that was a recognized cause of pleural effusion. In order to include m ore patients in the study with extremely low serum albumin levels, 20 addit ional study patients with serum albumin levels of < 2.0 g/dL were identifie d by a retrospective review of patients admitted during the previous 12 mon ths. On the radiograph, pleural effusions were identified as a new blunting of the costophrenic angles. Study patients were divided into the following three groups: group 1 had serum albumin levels of > 3.5 g/dL; group 2 had serum albumin levels between 2.1 and 3.5 g/dL; and group 3 had serum albumi n levels of less than or equal to 2.0 g/dL. Finally, the frequencies with w hich pleural effusions occurred were compared among the three groups. Results: Seven of 104 patients in group 1, 2 of 45 patients in group 2, and 3 of 21 patients in group 3 had pleural effusions, Within each group, ther e were no significant differences in serum albumin concentration or plasma oncotic pressure between patients with and without pleural effusions. In al l but two study patients, a careful review of records and a prospective fol low-up of the patients' clinical course identified a potential cause for th e effusions other than hypoalbuminemia. None of the 68 study patients with serum albumin levels of less than or equal to 3.5 g/dL had an unexplained p leural effusion. Conclusion: We conclude that hypoalbuminemia, per se, is an uncommon cause of pleural effusion. The recognition of pleural effusions in patients with low serum albumin levels should prompt careful clinical evaluations to iden tify other potential causes for the effusions.