Ultrasounic Elastography-guided Pleural Biopsy Followed by As-needed Medical Thoracoscopic Pleural Biopsy Versus Immediate Medical Thoracoscopic Pleural Biopsy for the Diagnosis of Pleural Effusion

Brief Summary The goal of this clinical trial is to determine whether an initial diagnostic approach using ultrasound elastography-guided pleural biopsy (UEPB) is non-inferior to immediate medical thoracoscopic pleural biopsy in terms of diagnostic yield for obtaining a definitive histopathological diagnosis in patients with exudative pleural effusion of unclear etiology. The main questions it aims to answer are: Is the step-up strategy (UEPB first, reserving thoracoscopy for non-diagnostic cases) non-inferior to immediate medical thoracoscopy in diagnostic yield? Does the step-up strategy provide advantages in safety, patient tolerance, hospital stay, and cost-effectiveness compared to immediate thoracoscopy? Researchers will compare a step-up strategy (initial UEPB, followed by medical thoracoscopy if UEPB is non-diagnostic) versus immediate medical thoracoscopic pleural biopsy to see if the step-up approach achieves comparable diagnostic accuracy while potentially reducing procedure-related burden and healthcare resource use. Participants will: Be randomly assigned in a 1:1 ratio to either the step-up strategy arm or the immediate medical thoracoscopy arm. If assigned to the step-up arm: undergo UEPB under local anesthesia; if the biopsy is non-diagnostic, proceed to semi-rigid medical thoracoscopy. If assigned to the immediate thoracoscopy arm: undergo semi-rigid medical thoracoscopic pleural biopsy as the initial and sole diagnostic procedure. Provide tissue samples for histopathological, immunohistochemical, and molecular analyses as clinically indicated. Complete short-term follow-up at 7 days post-procedure (by telephone or clinic visit) to monitor adverse events and symptom recovery. If initially diagnosed with non-specific benign disease or remain undiagnosed, complete a long-term follow-up at 12 months to establish a final diagnosis.