Rigid mini-thoracoscopy versus semirigid pleuroscopy for undiagnosed exudative pleural effusion: a randomized controlled trial

Background: Medical thoracoscopy is the diagnostic procedure of choice for undiagnosed exudative pleural effusion. Evidence comparing the smaller-caliber rigid mini-thoracoscope with the contemporary semirigid pleuroscope remains limited and conflicting. We compared procedure duration and biopsy specimen size between the two platforms in routine clinical practice.

Methods: We conducted a single-center, parallel-group, open-label randomized controlled trial. Adults with an undiagnosed exudative or suspected malignant pleural effusion were randomly assigned 1:1 to medical thoracoscopy with a 5.5-mm rigid mini-thoracoscope or a 7-mm semirigid pleuroscope. Pulmonology fellows performed all procedures under supervision using a standardized single-port technique with conscious sedation. The primary outcome was total procedure duration (skin incision to chest-tube fixation). Secondary outcomes included biopsy specimen size, diagnostic yield, pleurodesis success at 6 weeks, intra-procedural pain [visual analog scale (VAS)], and complications.

Results: Forty-four patients were randomized (22 per arm). Baseline characteristics were balanced between groups. The primary outcome favored rigid mini-thoracoscopy: median total procedure duration was 27.5 [interquartile range (IQR), 24.0–30.0] vs. 38.0 (IQR, 30.3–41.8) minutes (P=0.001). Pleural specimens obtained with the rigid mini-thoracoscope were larger in maximum dimension (median 6.0 vs. 4.0 mm; P=0.005), with a calculated surface area nearly twice that of the semirigid pleuroscope (50.5 vs. 27.3 mm²; P=0.001). Diagnostic yield (81.0% vs. 87.0%; P=0.69), pleurodesis success at 6 weeks (82.4% vs. 73.7%; P=0.70), pain VAS, and sedative-analgesic doses did not differ significantly. Operator satisfaction was higher with the rigid mini-thoracoscope (median 8 vs. 7; P=0.02). Chest-tube duration was modestly longer with rigid mini-thoracoscopy (median 4 vs. 3 days; P=0.04), without a significant difference in length of stay (median 6 vs. 4 days; P=0.17). Procedure-related complications occurred in 5 of 22 patients in each arm, with no procedure-related deaths.

Conclusions: The 5.5-mm rigid mini-thoracoscope yielded substantially larger pleural specimens than the 7-mm semirigid pleuroscope and shortened total procedure time, with no statistically significant difference in diagnostic yield, pleurodesis success, sedation requirements, or safety, even when procedures were performed by trainee operators. The larger specimens may be advantageous when ample tissue is required for the molecular and genetic characterization increasingly central to the management of thoracic malignancy.

Trial Registration: Thai Clinical Trials Registry TCTR20260508007 (retrospectively registered).