A Case of Esophago-Respiratory Fistula due to Inhalation Smoke Injury Diagnosed by Upper Endoscopy

Esophago-respiratory fistula (ERF) refers to the formation of a pathological connection between the esophagus and respiratory tract. Acquired ERF is a rare but life-threatening diagnosis in adults. We describe a 79-year-old male who was admitted with an inhalation smoke injury. He was diagnosed with ERF by endoscopic visualization and sampling of the hyaline cartilage within the wall of the esophagus. Percutaneous endoscopic gastrostomy placement and conservative measures were effective in the management of ERF.


Introduction
Esophago-respiratory fstula (ERF) refers to the formation of a pathological connection between the esophagus and respiratory tract. Although rare in adults, it can cause signifcant morbidity and mortality in patients [1,2]. Malignancy, trauma, and infections are the most common causes of the formation of these fstulas [1][2][3][4][5]. Tissue damage from intubation and endoscopic interventions, foreign body ingestions such as taco shells, and blunt chest injuries have been reported in the literature as traumatic events that cause ERF [4,6,7]. However, inhalation injury in burn patients is rarely reported as the underlying cause of ERF [8,9]. Here, we are describing a patient who was admitted with an inhalation smoke injury and was found to have an ERF.

Case Report
A 79-year-old male was initially admitted for cardiac arrest after being rescued from a house fre. Te hospital course was notable for intubation for smoke inhalation injury, confrmed by bronchoscopic fndings of infammation including moderate erythema, carbonaceous deposits, and bronchorrhea [10]. On the 30 th day of admission, the patient developed acute melena and anemia while on a heparin drip for atrial fbrillation. Vitals were remarkable for hypotension and tachycardia, and his hemoglobin level was 6.5 g/dL. Esophagogastroduodenoscopy (EGD) was remarkable for a midesophageal ulcer and associated mucosal tear surrounded by granulation tissue. On the anterior wall of the esophagus, there was a yellow-tan foreign body that appeared to be embedded onto the esophageal wall ( Figure 1). Te initial impression of the foreign body was a hard food material such as a taco shell that had been ingested before the house fre and had become frmly embedded within the esophageal wall. Te midesophageal ulcer and associated mucosal tear due to the embedded foreign body were likely the sources of the patient's anemia and melena. Two small biopsy samples of the foreign body were sent for pathological analysis.
Given the midesophageal ulcer and projected need for prolonged nasogastric tube feeding due to dysphagia, a percutaneous endoscopic gastrostomy (PEG) tube was placed the following day. Eventually, the pathology of the foreign body samples revealed fragments of hyaline cartilage, similar to that found in the tracheobronchial tree, which was concerning for ERF. Chest CT scan without contrast showed a narrowed left mainstem bronchus abutting the esophagus with foci of suspected extraluminal air along the left lateral margin of the esophagus (Figure 2). Tis was concerning for an esophageal injury or tear with localized perforation and possible bronchial injury. Terefore, the suspicion was high that the patient had an ERF, likely from the initial inhalation smoke injury. A confrmatory esophagogram was not performed due to the patient's dysphagia and given the high likelihood of an ERF with the EGD and imaging fndings. Bronchoscopy was performed 2 weeks after the initial EGD to assess for a true fstulous connection between the left bronchus and esophagus. Bronchoscopy revealed extrinsic compression of the left mainstem bronchus without mucosal defects or obvious fstulous connection to the esophagus. However, there was difusely infamed left-sided mucosa and extensive purulent distal mucous plugging, suggestive of prior fstulous connection. Tis was followed by the placement of a stent in the left mainstem bronchus.
Te fstula had either resolved by the time of bronchoscopy or was too small to be visible during the procedure. Te follow-up chest CTscan 11 days after stent placement no longer visualized the previously seen foci of air between the esophagus and left mainstem bronchi.

Discussion
Acquired ERF is a rare but life-threatening diagnosis in adults [4]. A study of patients with ERF who were diagnosed between 2001 and 2011 showed those with benign ERF had a median survival of 74 months [11]. ERF can present as a late complication of thermal inhalation injury. Te incidence of inhalational injury in burn patients who required hospitalization ranged from 20% to 30%, and the risk of mortality was increased by 24 times in this population [12,13]. Mucosal edema along with hypotension and shock in burn patients may compromise the perfusion of the upper airway mucosa, leading to ERF formation. Prolonged intubation and tracheostomy can also be contributing factors for the development of ERF in patients with inhalation injury, especially in those with high cuf pressure, infection, hypotension, steroid use, diabetes, and the use of a nasogastric tube [14].
Although the initial symptoms of ERF can be insignifcant, a delayed diagnosis can lead to severe complications such as pneumonia, life-threatening hemoptysis, and respiratory failure [4,6,15]. In intubated patients, increased secretions, pneumonia, and evidence of aspiration of gastric contents are concerning for ERF formation [15]. Bronchoscopy and esophageal endoscopy are frst-line diagnostic and therapeutic modalities [16]. Although EGD or bronchoscopy may not identify the fstula orifce, like in our case, they may reveal infammatory changes in the luminal mucosa suggestive of a prior or current fstula [17]. Plain radiography and CT scan of the chest can be helpful with diagnosis if there is evidence of pneumomediastinum or an   Case Reports in Gastrointestinal Medicine obvious mucosal tear [17]. An esophagogram with ingestion of barium contrast can be used to confrm the diagnosis [4,6,16,17]. Gastrografn is not recommended due to the risk of acute pulmonary edema and respiratory failure associated with aspiration of it. Te goal of treatment of ERF is to prevent severe complications and optimize nutritional status [16]. Surgical interventions for the closure of fstulas have been recommended for certain cases, especially in large and traumatic ERF [14,16]. Tere was no signifcant diference in survival between surgical and nonsurgical treatment of ERF such as airway or esophageal stent placement in those with nonmalignant ERF [11]. Conservative treatment options such as removing nasogastric tubes and placing gastrostomy or jejunostomy feeding tubes have also been shown to aid the healing of ERF [14].
In summary, we present a case of ERF due to inhalation burn injury, which was diagnosed by endoscopic visualization and sampling of hyaline cartilage within the wall of the esophagus. Te most likely cause of ERF was infammation and irritation of the bronchial mucosa secondary to smoke inhalation. PEG placement and conservative measures were efective in the management and healing of ERF. As in our case, the collaboration between pulmonology and gastroenterology services is essential for the diagnosis and management of this condition.

Data Availability
Te data used to support the fndings of this study are available from the corresponding author upon reasonable request, for protecting the patient's identity.

Conflicts of Interest
Te authors declare that there are no conficts of interest.