Background: Alterations in Starling forces that favor
pleural fluid formation include an elevation in capillary hydrostatic
pressure and a fall in plasma oncotic pressure. Although venous
hypertension is a well-recognized cause of pleural effusion, the
frequency with which hypoalbuminemia in the absence of volume expansion
leads to pleural effusion is unclear.
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 University of Oklahoma Hospital and the Oklahoma
City Veterans Administration (VA) Medical Center identified 152
patients who had chest radiographs and serum protein determinations on
admission, but did not have an admission diagnosis that was a
recognized cause of pleural effusion. In order to include more
patients in the study with extremely low serum albumin levels, 20
additional study patients with serum albumin levels of < 2.0 g/dL
were identified by a retrospective review of patients admitted during
the previous 12 months. 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 albumin levels of≤
2.0 g/dL. Finally, the frequencies with which 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, there were no significant differences in serum
albumin concentration or plasma oncotic pressure between patients with
and without pleural effusions. In all but two study patients, a careful
review of records and a prospective follow-up of the patients’
clinical course identified a potential cause for the effusions other
than hypoalbuminemia. None of the 68 study patients with serum albumin
levels of ≤ 3.5 g/dL had an unexplained pleural 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 identify other potential
causes for the effusions.
Abbreviations: CHF = congestive heart failure;
CI = confidence interval; VA = Veterans Administration