【Introduction】
For deep lung nodules with a diameter less than 1 centimeter, thoracoscopic-assisted surgery (VATS) resection is extremely challenging. Although various methods have been proposed to overcome this limitation, complications still cannot be ignored. Intraoperative lung ultrasound (ILU) is the latest minimally invasive technique currently proposed. This study aims to analyze the accuracy and effectiveness of ILU combined with VATS surgery in visualizing solitary deep lung nodules with a diameter less than 1 centimeter.

sorce:Gambardella C, et al. Intraoperative lung ultrasound improves subcentimetric pulmonary nodule localization during VATS: Results of a retrospective analysis. Thorac Cancer. 2023;14(25):2558-2566. PMID: 37470298; PMCID: PMC10481138.


【Methods】
Research Background and Study Population
The research center, in collaboration with the Department of Thoracic Surgery at the University of Napoli Fanvitelli, treated patients with solitary deep lung nodules (diameter less than 1 cm). The inclusion criteria were: a single undetermined deep lung lesion (diameter < 1 cm), suitable for thoracoscopic-assisted surgery (VATS); age > 18 years; no previous history of thoracic malignancy; no preoperative lung biopsy history; no surgical contraindications. The exclusion criteria were: recent myocardial infarction or unstable angina pectoris; severe neurological diseases; prothrombin time (PT-INR) > 1.5 or platelet count < 30,000; inability to tolerate single-lung ventilation; pregnancy; emphysema; and patients with nodules near the pulmonary hilum. All subjects underwent a specialized thoracic surgery assessment before the operation.

A total of 83 patients with isolated deep pulmonary nodules (diameter less than 1 cm) were referred for treatment. Among them, 74 patients met the inclusion criteria and underwent pulmonary wedge resection. 43 patients received transbronchial lung resection (Group A), and 31 patients received conventional transbronchial lung resection (Group B).

Traditional Thoracoscopic Surgery
The patient was placed in a lateral position, under general anesthesia, and a double-lumen endotracheal tube was inserted for bilateral lung ventilation. To alleviate postoperative pain, the patient underwent plane block of the chest wall fascia under ultrasound guidance, using a long-acting local anesthetic. The lung specimens were not ventilated but were subjected to semi-inflation and full inflation.

This study adopted a front approach with three incisions, including two 1-1.5 centimeter lower incisions, located at the seventh or eighth intercostal spaces on the posterior axillary line and the anterior axillary line respectively, for the placement of two thoracoscopic ports; and a 4-5 centimeter incision, located at the fourth intercostal space on the anterior axillary line, for the placement of auxiliary instruments.

VATS related to ILU
The small pulmonary nodules are located using an ultrasonic processor. A sterile endoscopic laparoscopic probe, 38 centimeters long, 10 millimeters in diameter, with a flexible tip, equipped with a convex array transducer with a frequency range of 4 to 12 MHz, is inserted through one of the thoracoscopic surgery (VATS) ports. The probe is inserted through the surgical hole into the chest cavity to examine the mediastinum, pleural surface and diaphragmatic surface of the lung, searching for sub-centimeter-sized nodules. These nodules can only be observed when the lung is completely collapsed. The operator applies gentle pressure to the lung surface with the ultrasonic probe to reduce residual gas and locate deeper nodules as much as possible. During the examination, the probe is perpendicular to the lung surface and uses warm sterile normal saline to improve surface contact.

VATS is used to determine the size and location of the lesion. If a pulmonary nodule is detected, its ultrasonic characteristics are recorded. Subsequently, a burning rod is used to burn the surface of the nodule, followed by a 2 cm wedge-shaped resection of the specimen, and the specimen is sent to the pathology department to confirm the accuracy of the resection.


【Results】
All nodules in Group A were correctly identified (43/43, 100%), while in Group B, there was 1 case (30/31, 96.7%) of positioning failure, requiring the incision to be expanded to approximately 2 centimeters to facilitate the insertion of the hand and the use of finger touch for locating the nodules. This situation increased the surgical difficulty. The identification time of the lesions in Group A was shorter (7.1 ± 2.2 minutes vs. 13.8 ± 4.6 minutes; p < 0.05). Additionally, due to the difficulty in sampling the nodules in 3 cases of Group B, further resection and intraoperative histological examination were performed. The median depth of the lesions from the lung surface in Group A and Group B was 3.9 ± 2.2 and 4.2 ± 1.5 (p = 0.679), respectively. After pathological reaction, patients with squamous cell carcinoma (27 cases in Group A and 19 cases in Group B) or adenocarcinoma (9 cases in Group A and 6 cases in Group B) underwent lobectomy. In contrast, for cases of metastasis of breast cancer (3 cases in Group A and 3 cases in Group B) or colon cancer (4 cases in Group A and 3 cases in Group B), wedge resection was sufficient.


【Discussion】

The introduction of minimally invasive thoracic surgery and the ability to locate sub-centimeter-sized lung nodules during the operation are of vital importance for the diagnosis and treatment of early-stage lung cancer. Video-assisted thoracoscopic surgery (VATS) has become an important minimally invasive approach for treating this fatal disease. VATS is particularly suitable for patients who are physically weak or have insufficient lung function reserve. In fact, compared with open chest surgery, VATS results in less postoperative pain and complications and a faster recovery. 

In this series of studies, intraoperative ultrasound during thoracoscopic surgery demonstrated that it is a safe and reliable real-time identification method for lung nodules that cannot be detected through digital palpation.