Effectiveness and Safety of Real-Time Transthoracic Ultrasound-Guided Thoracentesis

Purpose: The purpose of the present study was to specifically evaluate the effectiveness and safety of real-time ultrasound-guided thoracentesis in a case series of pleural effusion. Patients and methods: An observational prospective study was conducted. From February 2018 to December 2019, a total of 361 consecutive real-time transthoracic ultrasound (TUS)-guided thoracentesis were performed in the Unit of Diagnostic and Interventional Ultrasound of the Research Hospital "Fondazione Casa Sollievo della Sofferenza" of San Giovanni Rotondo, Foggia, Italy. The primary indication for thoracentesis was therapeutic in all the cases (i.e., evacuation of persistent small/moderate pleural effusions to avoid super-infection; drainage of symptomatic moderate/massive effusions). For completeness, further diagnostic investigations (including chemical, microbiological, and cytological analysis) were conducted. All the procedures were performed by two internists with more than 30 years of experience in interventional ultrasound using a multifrequency convex probe (3-8 MHz). For pleural effusions with a depth of 2-3 cm measured at the level of the costo-phrenic sinus was employed a dedicated holed convex-array probe (5 MHz). Results: In all the cases, the attempts at thoracentesis were successful, allowing the achievement of the therapeutic purpose of the procedure (i.e., the complete drying of the pleural space or the withdrawal of fluid till a "safe" quantity [a mean of 1.5 L, max 2 L] producing relief from symptoms) regardless of the initial extent of the pleural effusion. There were only 3 cases of pneumothorax, for a prevalence rate of complications in this population of 0.83%. No statistical difference was recorded in the rate of pneumothorax according to the initial amount of pleural fluid in the effusion (p = 0.12). All the pleural effusions classified as transudates showed an anechoic TUS appearance. Only the exudative effusions showed a complex nonseptated or a hyperechoic TUS appearance. However, an anechoic TUS pattern was not unequivocally associated with transudates. Some chronic transudates have been classified as exudates by Light's criteria, showing also a complex nonseptated TUS appearance. The cytological examination of the drained fluid allowed the detection of neoplastic cells in 15.89% cases. On the other hand, the microbiological examination of effusions yielded negative results in all the cases. Conclusions: Real-time TUS-guided thoracentesis is a therapeutically effective and safe procedure, despite the diagnostic yield of the cytological or microbiological examinations on the collected liquid being very low. Future blinded randomized studies are required to definitely clarify the actual benefit of the real-time TUS-guided procedure over percussion-guided and other ultrasound-based procedures.