Exudative pleural effusions secondary to gastrointestinal diseases.

Several different diseases of the gastrointestinal tract may have an associated exudative pleural effusion. In the acutely ill patient with a pleural effusion, the possibility of esophageal perforation should always be considered. It is important to establish this diagnosis as soon as possible since the mortality rate increases markedly if drainage of the mediastinum is delayed for even 12 or 24 hours. The best screening test for esophageal rupture is the level of amylase in the pleural fluid. All patients with undiagnosed exudative pleural effusions should have the amylase level in their pleural fluid measured to rule out a pancreatic etiology for their pleural effusion. In patients with acute pancreatitis, the clinical presentation may be dominated by chest symptoms. Such patients have small to moderately sized pleural effusions that resolve rapidly once appropriate therapy is instituted. If symptoms persist, the possibility of a pancreatic abscess or a pancreatic pseudocyst should be considered. Patients with pancreatic pseudocysts may develop a sinus tract between the pseudocyst and the pleural space. In this situation a large pleural effusion develops. Frequently there are no abdominal symptoms and the diagnosis will not be made unless a pleural fluid amylase is obtained. Patients with exudative pleural effusions that contain predominantly polymorphonuclear leukocytes should be suspected of having an intra-abdominal abscess, particularly when there is no associated parenchymal infiltrate. Subphrenic, intrahepatic, and splenic abscesses all have a high incidence of accompanying pleural effusion. Abdominal CT scanning is the method of choice to establish each of these diagnoses.