Exploring the diagnostic value of multilayer spiral computed tomography (MSCT) in thoracogastric airway fistula

Background Thoracostomach-airway fistula is a rare complication of esophageal-cancer resection. We intended to explore the diagnostic value of multilayer spiral computed tomography (MSCT) in thoracostomach-airway fistula, to enhance its clinical understanding; evaluate an effective, convenient, and non-invasive diagnostic method; and provide the fundamentals for subsequent treatment. Methods The MSCT images and complete clinical data of 216 consecutive patients diagnosed with thoracogastric airway fistula were retrospectively analyzed. Results MSCT was able to determine the exact location, size of the fistula, and the adjacent bronchus between the fistula and bronchus in 192 out of 216 patients with thoracogastric airway fistula. All patients had pulmonary lesions including emphysema (n=68), ground glass density (n=25), bronchial wall thickening (n=28), patchy high densities along the lung texture (n=207), pulmonary consolidation (n=104), atelectasis (n=11), pulmonary nodules (n=53), bronchiectasis (n=19), lobular septal thickening (n=5), cavity (n=14), and pulmonary interstitial fibrosis (n=6). Further, 95 cases showed pleural effusion, 184 showed pleural thickening, 4 had pneumothorax, and 2 had subcutaneous pneumothorax. 12 patients with thoracogastric airway fistula had anastomotic wall thickening (mean: 20.63±9.57, range: 9.19–43.37 mm), while 13 patients showed thoracic gastric wall thickening (mean: 22.83(±)5.58 mm, range: 12.32–31.24 mm) on. 23 patients showed distant metastasis on MSCT. MSCT can accurately location and size of thoracogastric airway fistula, well lung lesions, tumor recurrence, and distant metastasis, provide the basis for the next thoracogastric Thoracogastric carina carina upper


Introduction
Thoracogastric airway fistula (TGAF) is a rare complication of esophageal cancer resection with an incidence ranging between 0.3% and 1.9% [1,2]. The literature on TGAF is rare, and most doctors lack a sufficient understanding of TGAF. TGAF has a very high mortality rate because it is often misdiagnosed as conditions including abnormal deglutition, esophageal tracheal fistula, and radiation pneumonitis, thereby preventing effective treatment [3,4]. The internal diameter of the airway is relatively constant, and stent placement can effectively seal the fistula. As the location and diameter of the fistula vary, stents should be customized to achieve functional sealing of the fistula [5]. Hence, it is essential to determine the specific location of the air-filled track and measure the airway-related meridians to ensure appropriate stents selection.
As a non-invasive examination method, multilayer spiral computed tomography (MSCT) can not only directly display the fistula and classify TGAF through plain scan and 3D reconstruction but also measure the length of the trachea, bronchus, internal meridian, and fistula size. At the same time, MSCT can also provide more comprehensive information about lesions, such as the presence of pulmonary infection, atelectasis, tumor recurrence, and distant metastasis. It provides more reliable imaging data for clinical diagnosis and treatment [6]. Therefore, to explore the imaging characteristics and diagnostic value of MSCT in thoracic gastric airway fistula, we summarized the MSCT findings of TGAF.

Materials And Methods Patients
The clinical data and MSCT imaging of 216 patients with TGAF who underwent chest computed topography (CT) in our hospital from January 2011 to April 2019 were retrospectively analyzed. The inclusion criteria were as follows: 1) All patients underwent anastomosis of esophagus, gastric arch, or neck after esophageal cancer resection. 2) The thoracic stomach was located in the original esophageal bed of the posterior mediastinum. 3) All patients had a confirmed diagnosis based on digestive tract radiography, bronchoscopy, or gastroscopy. 4) All patients underwent MSCT examination. This study had been carried out in accordance with the Code of Ethics of the World Medical Association and was approved by the First Affiliated Hospital of Zhengzhou University committee on human investigation. All methods were performed in accordance with the relevant guidelines and regulations. All patients provided signed informed consent.
CT Scanning Methods GE Light speed 64-slice spiral CT scanner was used to perform the plain and enhanced scans (delay time: 30 s and 75 s, respectively). The patient was placed in the supine position and scanned from the level of the hyoid bone to the lower edge of the liver. After deep inspiration, breath-hold scanning was performed. The CT scanning parameters were as follows: tube voltage, 120 kVp; tube current, 100 mAs; layer thickness, 5.0 mm; layer spacing, 5.0 mm; reconstruction layer thickness, 0.625 mm; pitch, 1. A high-pressure syringe was used to inject iohexol (350 mg I/mL), a non-ionic contrast agent, through the anterior elbow vein, at a dose of 1.5 mL/kg and a rate of 2.

MSCT Presentations Fistula
Briefly, MSCT could directly visualize the exact location, size, and the relationship between the fistula and bronchus in 192 patients with TGAF (Table 1, Fig. 1). On axial view, 192 cases of fistula could be clearly displayed on the mediastinal window (mean: 8.20 ± 5.03 mm and range: 1.43-25.92 mm) and 185 cases could be clearly displayed on the pulmonary window (mean: 7.23 ± 5.65 mm and range: 0.64-43.9 mm On sagittal view, 185 cases of fistula were clearly displayed on the mediastinal window and 177 cases were clearly displayed on the pulmonary window. The mean fistula size on lung window was 8.14 ± 6.29 mm (range: 0.64-43.49 mm) and on mediastinal window was 9.82 ± 6.64 (range: 1.14-46.54 mm). MSCT showed no fistula in 24 patients with TGAF. Table 1 Characteristic of fistula in patients with thoracogastric airway fistula

Discussion
Esophageal cancer is a common malignant tumor of the digestive tract. Surveys show that the annual global incidence of esophageal cancer is 455,800, while the annual death toll is 400,200 [7,8].
Esophageal resection remains the preferred treatment for resectable esophageal cancer [9].
Typically In this study, MSCT could clearly display the fistula in 192 patients with TGAF and had a positive detection rate of 88.9%. The negative results seen in 24 patients may likely be attributed to the small size of the fistula, circuitous course, or inflammation and edema at the fistula, but gastrointestinal radiography, bronchoscopy or gastroscopy verified the existence of the fistula. MSCT can display the location of the fistula and measure its size on multiple levels. It can also measure the length and diameter of the trachea and bronchus to provide effective reference data for the next treatment of airway-stent placement [12,13]. Based on the location of the thoracogastric fistula and its as chronic bronchitis, emphysema, pulmonary interstitial fibrosis, and bronchiectasis [14].
MSCT can detect tumor recurrence and distant metastasis in patients with esophageal cancer after operation. In this study, 25 patients showed complications of anastomotic wall and chest gastric wall thickening, and contrast-enhanced scan of the same could be seen in varying degrees of enhancement. At such times, clinicians should suspect tumor recurrence. Twenty-three patients had distant metastasis. Therefore, MSCT can comprehensively elucidate the clinical changes in patients and provide more comprehensive information for optimum treatment.
In conclusion, if irritating cough occurs after esophagectomy with esophagogastric arch or cervical anastomosis, TGAF should be suspected and interpreted to improve the prognosis [15]. MSCT can provide direct visual confirmation of the fistula, and it can also find other lesion features providing reliable imaging data for clinical diagnosis and treatment.

Declarations
Ethics approval and consent to participate