Utility of the sliding lung sign for the prediction of preoperative intrathoracic adhesions

Background: To assess the potential of the ultrasonographic sliding lung sign to detect severe intrathoracic adhesions before surgery. Methods: This was a prospective, single-center, observational study including all patients aged 20-89 years undergoing elective thoracic surgery. Patients with pneumothorax, pyothorax, hemothorax, chylothorax, and hydrothorax were excluded. We recorded the ultrasound sliding lung sign, surgical characteristics, and follow-up parameters: past medical history, respiratory function, chest X-ray findings, and computed tomography (CT) findings. Severe intrathoracic adhesion was defined as the need for adhesiolysis requiring more than 30 minutes. Results: A total of 168 patients consented to participate. All 15 patients without the sliding lung sign had hard severe adhesions [specificity 100%, sensitivity 88.2%, positive predictive value (PPV) 100%, negative predictive value (NPV) 98.7%, and area under curve (AUC) 0.94]. There were two false-negative results, both of which were soft adhesions. Although blunting of the costophrenic (CP) angle, CT findings, past medical history, and restrictive lung disease were identified as significant risk factors of severe intrathoracic adhesion, all areas under the curve were low (0.71, 0.71, 0.69, 0.61, respectively). Thoracotomy frequency, intraoperative bleeding, operative time, and postoperative hospitalization were significantly greater in these patients than in those with non-severe adhesions. Conclusions: The ultrasound sliding lung sign could be used to predict severe intrathoracic adhesions before surgery. Preoperative confirmation of the ultrasound sliding lung sign is important for planning surgical approaches and implementing appropriate safety management.