[Measuring pH in pleural fluid is valuable when identifying the cause of purulent pleural effusion].

A 79 year-old woman with disseminated ovarian cancer and recurring pleural effusions, had thoracocentesis performed with drainage of purulent pleural fluid (plf) after preceding symptoms of pneumonia. Pleural empyema was suspected. However, a plf-pH-measurement of 7.3 made this diagnose less likely. A subsequent analysis of plf revealed an elevated plf-triglyceride concentration, thus confirming chylothorax. In order to distinguish between pleural empyema and chylothorax plf-pH should be considered as a routine analysis in patients with underlying malignancy and drainage of purulent pleural fluid.