Incidence and risk factors of pneumothorax following pre-procedural ultrasound-guided thoracentesis

Background: Data regarding the incidence and risk factors of pneumothorax following pre-procedural ultrasound (US)-guided thoracentesis is scarce. We aimed to evaluate the incidence and risk factors of pneumothorax following pre-procedural US-guided thoracentesis in a tertiary medical center. Methods: Retrospective analysis of patients who underwent pre-procedural US-guided thoracentesis in Sheba Medical Center between January 2016 and December 2018. Data collected included incidence of pneumothorax following thoracentesis, baseline clinical and demographic characteristics, and thoracentesis- associated factors. Outcomes evaluated included length of hospital stay, mortality, chest tube insertion and intensive care unit admission. Results: A total of 550 patients with pleural effusions underwent pre-procedural US-guided thoracentesis. Sixty-six (12%) of them developed pneumothorax. Compared to patients who did not develop pneumothorax, those who developed pneumothorax had a higher rate of congestive heart failure (32.2% vs . 47%, P=0.026), a smaller depth of pleural fluid marking (3.4 vs . 3.2 cm, P=0.024), a larger amount of pleural fluid drained (1,093 vs . 903.5 mL, P=0.01), and were more likely to undergo bilateral procedures (7.6% vs . 2.3%, P=0.044). In the multivariate regression analysis, volume of pleural fluid drained was significantly associated with the development of pneumothorax (OR, 1.001, 95% CI, 1–1.001; P=0.042). Conclusions: The incidence of pneumothorax following pre-procedural US-guided thoracentesis was relatively high in the present study. The amount of pleural fluid drained was the main factor associated with the risk of developing pneumothorax in these cases.