Postoperative pleural effusion following upper abdominal surgery.

Of 128 patients who underwent upper abdominal surgery, examined by standard preoperative and postoperative chest roentgenograms for the formation of postoperative pleural effusions, 89 had postoperative pleural effusions. Their presence was not related to the type of operation, infection, serum amylases, sex, smoking habits, or weight. There was no correlation between the localization of the pleural effusions and that of the abdominal incisions. There was a positive correlation between atelectasis and pleural effusion, but no evidence of a causal relationship. Pleural effusions might be related to postoperative sodium and water retention, and aggravated by an age-related relative cardiac decompensation. Early postoperative pleural effusions are common and do not require specific treatment.