Fistula Size Considerations

The size of an airway fistula is one of the most important determinants of bronchoscopic strategy, as defect diameter influences both visualization and likelihood of successful endoscopic closure. For bronchopleural fistulas (BPFs), a commonly used framework categorizes defects by diameter:

Small BPFs (<3 mm):

These fistulas may close spontaneously or with minimally invasive interventions. Conservative measures, including chest tube drainage and reduction of airway pressure, are often sufficient. However, their diminutive caliber can hinder bronchoscopic detection, as surrounding tissue collapse or mucosal edema may obscure the opening.

Medium BPFs (3–8 mm):

Management often involves endoscopic interventions such as stent placement, tissue sealants, or, in selected patients, surgical repair. Stents are frequently employed in this group to achieve reliable closure.

Large BPFs (> 8 mm):

These defects usually require more aggressive surgical or combined surgical–endoscopic strategies. While stents may serve as temporizing or adjunctive therapy, large BPFs often fail conservative or purely bronchoscopic approaches and ultimately necessitate operative repair (Fig. 1).

Fig. 1

Management algorithm for malignant fistulas. Algorithm outlining an anatomy driven approach to malignant and transplant associated airway wall defects adapted and modified from Kim HS, Khemasuwan D, Diaz-Mendoza J, et al. Management of tracheo-oesophageal fistula in adults. Eur Respir Rev. 2020;29(158):200094

In contrast to BPFs, tracheoesophageal fistulas (TEFs) and other airway–esophageal or airway–mediastinal defects lack a standardized size-based classification. Based on clinical experience and extrapolation from BPF data, small malignant or post–lung transplant fistulas (excluding vascular fistulas) may close with conservative measures or selective stenting, whereas larger defects generally require more structured interventions.

Size appears to influence outcomes: in a study by Wang et al., malignant TEFs that failed to close were significantly larger (2.40 ± 0.07 mm) than those that healed (1.98 ± 0.05 mm, p < 0.001) [3]. These findings underscore the need for standardized, size-informed management algorithms and highlight the importance of early identification before the defect enlarges, which limits the likelihood of successful endoscopic repair.

Thermal Therapy, Tissue Sealants, and Matrix GraftsThermal Ablation Techniques

Argon plasma coagulation (APC) is used to promote closure of small (< 3 mm) airway fistulas by inducing localized coagulation, fibrosis, and tissue contraction. It is a non-contact modality that delivers ionized argon gas to ablate tissue. APC is best suited for well-visualized, narrow defects but may worsen tissue injury if excessive energy is applied or if the fistula is large (Fig. 2). It is frequently used in combination with stenting or sealants to improve closure rates [23, 24].

Fig. 2

Tracheal–mediastinal fistula following lymphoma therapy treated with argon plasma coagulation. (a) Bronchoscopic image demonstrating a small posterior tracheal wall defect with active air leak communicating with the mediastinum (black arrow). (b) Post treatment appearance following argon plasma coagulation applied to the fistula margins with early granulation tissue formation and defect contraction (blue arrow)

Other thermal modalities including laser therapy and electrocautery have been successfully applied to small airway defects; however, similar to APC, their use is limited by the risk of enlarging the fistulous tract in fragile tissues [25, 26].

Tissue Sealants

Fibrin glue is a minimally invasive option for selected patients, especially those with small defects who are not ideal candidates for surgery. Fibrin sealants mimic the final common pathway of the coagulation cascade, forming a stable fibrin clot that creates mechanical closure while serving as a scaffold for tissue regeneration.

A case report described bronchoscopic closure of a 5-mm iatrogenic TEF in a mechanically ventilated patient using fibrin glue, with near-complete closure at 24 h and successful extubation 10 days later [27].

Matrix Grafts

Matrix grafts provide biologic scaffolding for tissue repair and neovascularization. In a cohort of 244 lung transplant recipients, 18 developed airway complications, including three with airway dehiscence managed using matrix grafts (abdominal aortic homograft, CoreMatrix, or latissimus dorsi muscle flap) [7, 28]. These techniques are generally reserved for larger (> 5 mm) or structurally unstable defects unsuitable for primary closure or endoscopic therapies. Grafts are often paired with airway stents to maintain lumen patency during healing [28].

One case report described repair of a 30 × 25 mm bronchial dehiscence using an aortic homograft reinforced with a bare-metal stent to prevent expiratory collapse, resulting in favorable recovery and improved lung function at 10-month follow-up [29]. Ongoing bronchoscopic surveillance is required to monitor graft integration and detect early complications.

Stenting Strategy

Stenting remains one of the cornerstone strategies for managing airway fistulas, particularly in malignant and transplant-associated cases where tissue fragility, ischemia, or necrosis limits the success of surgical repair.

General Principles

In malignant tracheoesophageal fistulas, management often begins with placement of a fully covered esophageal SEMS, especially when dysphagia predominates or the esophageal defect is more accessible.

When airway symptoms predominate or the airway wall is involved, a silicone or hybrid airway stent may be required.

Dual stenting is considered when single stenting fails due to persistent communication, stent migration, or compression of the adjacent lumen. It is worth noting that this is not without complications.

Dual Stenting Approach

If initial esophageal stenting does not adequately seal the fistula or if airway compromise persists, dual stenting may be necessary. Typically:

1.

The esophageal stent is placed first to minimize aspiration.

2.

Bronchoscopy is performed to assess airway patency and fistula status.

3.

A covered airway stent is then deployed if needed to reinforce fistula closure and restore airway structure.

Airway stents include:

Silicone stents, valued for removability and low tissue reactivity,

Covered SEMS, offering strong radial force and good conformability but with higher risk of migration and granulation formation.

Accurate stent sizing and positioning are critical to prevent pressure necrosis or incomplete sealing. Post-deployment bronchoscopy confirms placement and evaluates for migration, obstruction, or persistent leakage.

A notable example of multimodal therapy comes from Mattioli et al., who treated a large malignant in a 67-year-old man using double silicone stents with an autologous fascia lata graft between them, achieving successful fistula closure [30].

A representative case of esophageal stent associated airway fistula requiring airway stenting is shown in Fig. 3. A 58-year-old patient with esophageal carcinoma treated with chemoradiation developed fistula formation three months later and underwent esophageal stent placement at an outside institution. The migrated stent was subsequently removed via rigid bronchoscopy, and a Y-shaped silicone airway stent was deployed to restore airway–digestive tract separation, demonstrating airway rescue in a stent-related secondary fistula.

Fig. 3

Esophageal stent associated left mainstem bronchial fistula managed with airway rescue. (a) Bronchoscopic image showing proximal esophageal stent erosion into the posterior wall of the left mainstem bronchus. (b) Distal end of the esophageal stent visualized within the esophagus. (c) Distal left mainstem bronchial fistula identified on bronchoscopy (arrow). (d) Silicone Y stent deployed to cover the fistulous defect and restore airway digestive tract separation

Figure 4 illustrates the use of airway stenting for palliation in a necrotic malignant airway fistula. Due to tumor related necrosis, prior radiotherapy, and airway structural instability, palliation with a Y stent was performed.

Fig. 4

Necrotic malignant airway fistula involving the right mainstem bronchus in metastatic leiomyosarcoma. (a) Bronchoscopic image depicting right upper lobe involvement and a large airway wall defect consistent with fistula formation (arrows). (b) Post deployment appearance of a Y stent with extension into the right upper lobe and bronchus intermedius

An additional case showing the role of airway stenting in the setting of complex post-surgical anatomy is shown in Fig. 5. A large airway wall defect involving the distal right mainstem bronchus with extension into the bronchus intermedius was identified on bronchoscopy and computed tomography imaging in a 36-year-old patient with esophageal cancer treated with esophagectomy and multimodality radiotherapy. Given the extent of tissue injury, defect size, and airway structural instability, and the inability to place a gastrointestinal stent due to gastric conduit anatomy, bronchoscopic closure was not feasible and airway stenting was pursued to restore luminal integrity and palliate symptoms.

Fig. 5

Malignant airway fistula extending from the right mainstem bronchus into the bronchus intermedius in a patient with esophageal cancer treated with esophagectomy and multimodality radiotherapy. (a) Computed tomography of the chest revealing a large airway wall defect involving the distal right mainstem bronchus (arrow). (b) Bronchoscopic visualization of the fistula extending into the bronchus intermedius. (c) Silicone Y shaped airway stent covering the fistulous defect. (d) Proximal limb of the silicone Y stent following placement

3D-Printed Patient-Specific Stents (PSS)

When anatomical complexity or prior treatments limit the utility of conventional stents, 3D-printed, patient-specific stents offer a tailored alternative. These devices are custom designed from high-resolution CT imaging to match the patient’s airway precisely, improving fit, reducing migration, and providing longer functional lifespan.

A recent review reported that PSS demonstrate similar safety profiles to traditional stents but with lower migration rates and reduced need for repeated bronchoscopy, thereby improving patient quality of life [31].

Deployment can be performed using conventional bronchoscopic techniques, facilitating adoption in clinical practice.

Cryotherapy

Cryotherapy, including spray cryotherapy (SCT), plays an adjunctive role in the management of airway wall defects by addressing complications related to airway stenting rather than serving as a primary fistula closure technique. Granulation tissue formation is a common cause of stent dysfunction and airway obstruction following stent placement or fistula repair. Cryotherapy allows controlled, non-contact debulking of granulation tissue through rapid freeze-thaw cycles that induce cellular injury, microvascular disruption, and delayed tissue necrosis, while minimizing damage to surrounding airway mucosa [32, 33].

In patients with complicated airway stents, targeted use of SCT may improve airway patency and stent performance by reducing excessive granulation tissue and preserving luminal integrity. When applied in carefully selected patients, cryotherapy complements stenting strategies and supports ongoing bronchoscopic management of malignant fistulas and post-transplant airway complications [34].

Endobronchial Valves and Septal Occluder Devices

Septal occluder devices, most commonly Amplatzer™ occluders, have emerged as a valuable option for airway fistula closure, particularly when conventional bronchoscopic or stent-based strategies have failed. Originally engineered for cardiac septal defects, these self-expanding nitinol mesh discs can be deployed endoscopically to anchor across the fistulous tract, providing immediate mechanical occlusion while promoting secondary tissue integration.

Their use in airway pathology remains off label but increasingly reported in complex or refractory cases. In a lung transplant recipient described by Orozco-Hernández et al., persistent anastomotic dehiscence with a broncho-mediastinal fistula was successfully closed with an Amplatzer device after multiple unsuccessful prior interventions [35]. Devices of this type are generally best suited for fistulas between 5 and 15 mm, where both the defect geometry and surrounding tissue stability allow secure anchoring [36].

Endobronchial valves (EBVs), while more commonly used for persistent air leak and hyperinflation therapies, may also assist with fistula closure by reducing airflow across the defect and promoting granulation tissue formation. However, EBVs rarely achieve closure as monotherapy in structurally unstable or malignant fistulas and are more commonly used as an adjunct or temporizing measure.

Collectively, the management of airway wall defects requires an individualized, anatomy-driven approach that accounts for defect size, tissue integrity, underlying etiology, and patient goals of care. In malignant and transplant-associated fistulas, bronchoscopic intervention prioritizes restoration of airway–digestive tract separation, preservation of airway patency, and mitigation of aspiration and infectious complications. Covered airway and esophageal stents remain foundational therapies, while septal occluder devices, endobronchial valves, and selected ablative techniques serve complementary roles in carefully selected cases. Optimal outcomes are achieved through early recognition, meticulous procedural planning, and close multidisciplinary collaboration, with bronchoscopic strategies increasingly enabling durable palliation and functional stabilization in patients previously considered unsuitable for intervention. These principles are summarized in a pragmatic management algorithm (Fig. 1).