instruction: calculate the number of patients with endoscopic insertion of stent (tube) into bile duct who had a pleural fluid test.
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN procedures ON demographic.hadm_id = procedures.hadm_id INNER JOIN lab ON demographic.hadm_id = lab.hadm_id WHERE procedures.long_title = "Endoscopic insertion of stent (tube) into bile duct" AND lab.fluid = "Pleural"