Incidence and significance of pleural effusion after abdominal surgery

Two hundred patients who had undergone abdominal surgery received bilateral decubitus chest roentgenograms between 48 and 72 hours after surgery to evaluate the incidence of pleural effusion after abdominal surgery. Ninety-seven (49 percent) had some pleural fluid visible on the x-ray films. In 50 patients the thickness of the fluid was less than 4 mm on the decubitus film; in 26, it was between 4 mm and 10 mm; and in 21, it was greater than 10 mm. The incidence of pleural effusions was higher after upper-abdominal surgery, in patients with postoperative atelectasis, on the side on which the surgery was performed, and in patients with free abdominal fluid. Thoracocentesis was performed on 20 patients, and in 16 patients the effusions were exudates. All of the effusions resolved without specific therapy except one. The pleural fluid in this patient was characterized by a low pH (6.93) and positive culture for Staphylococcus aureus. Small pleural effusions are common after abdominal surgery, and most resolve spontaneously within a few days.