Safety Profile Study of Ultrasound-guided Transparietal Lung Biopsy in Patients With Diffuse Interstitial Lung Disease

The TOUCANS study is a prospective, interventional, single-center protocol designed to evaluate the feasibility and safety of transthoracic ultrasound-guided lung biopsy (BPTE) for the histopathological assessment of patients with interstitial lung disease (ILD). Surgical lung biopsy (SLB) remains the reference diagnostic standard when high-resolution CT and multidisciplinary evaluation are inconclusive; however, SLB requires general anesthesia and thoracoscopy and is associated with non-negligible morbidity. Cryobiopsy offers a less invasive option but still relies on general anesthesia and does not provide real-time guidance during tissue acquisition. BPTE, routinely used in oncology, may provide a safer and more accessible alternative by combining real-time thoracic ultrasound guidance with local anesthesia and outpatient feasibility. Its use in ILD has been limited due to a lack of prospective safety and diagnostic performance data.

Scientific Background ILDs often involve peripheral and subpleural abnormalities that can be visualized using thoracic ultrasound. Real-time ultrasound allows operators to identify pleural irregularities, increased B-lines, or localized reductions in aeration that may correspond to accessible sampling sites. These features form the basis for selecting BPTE target zones. BPTE has shown low complication rates in other clinical contexts, including pneumothorax and hemorrhage, but its applicability to ILD requires systematic evaluation given the underlying fragility of this patient population.

Study Rationale By performing both BPTE and SLB in each participant, the study aims to document the safety profile of BPTE relative to the current gold standard and compare tissue quality. This within-subject design allows direct assessment of histological adequacy and potential concordance between techniques, while limiting inter-individual variability. The protocol also aims to document patient-reported outcomes such as pain and dyspnea and to characterize local tissue effects at the BPTE site during subsequent thoracoscopy.

Study Procedures After standard diagnostic workup and confirmation of biopsy indication by multidisciplinary discussion, participants undergo baseline clinical assessment and high-resolution CT imaging. BPTE is performed 2-4 weeks before SLB to ensure procedural independence and adequate healing time. Under local anesthesia and spontaneous ventilation, the operator identifies an appropriate intercostal window using thoracic ultrasound. A target region is selected based on pleural surface abnormalities or an increased number of B-lines. One or two core biopsies measuring at least 1 cm are obtained using a dedicated cutting needle during a brief apnea. Post-procedure monitoring includes lung ultrasound and chest radiography to detect pneumothorax. Patients are discharged after a four-hour observation period unless complications occur.

SLB is performed under general anesthesia via video-assisted thoracoscopy. The thoracic surgeon documents the BPTE site, enabling evaluation of hematoma or other local effects. Standard postoperative care includes pleural drainage and scheduled follow-up visits. Histological samples obtained through BPTE are stored and analyzed at the end of the follow-up period to ensure blinded comparison with surgical specimens.