PRELIMINARY REMARKS

 Surgical approach is obtained through a thoracotomy: special needs related to anesthesia and artificial ventilation

 Operating in the thorax cavity requires adequate size instruments. Placement of a thoracostomy tube may be indicated after surgery.

 Thoracic esophagus is not movable out of the thoracic cavity. Great care must be taken when opening the lumen to avoid peripheric contamination. Need of several laparotomy pads. Suction unit mandatory.

 Esophagus is a fragile structure which must be handled with great care, and atraumatic instruments

 Unlike the other parts of the digestive tract there is no serosa on the outer part of esophagus. No early fibrin apposition will help in «sealing»» the suture, which shall be carefully performed.

 Aspiration pneumonia, esophagitis, nutritional debilitation are often associated with esophageal problems. Should they happen, they require specific treatment before and after surgery

INDICATIONS

Main indications for intrathoracic esophagus surgery are:

 Intraluminal foreign bodies,

 Tumor or parasitic granuloma of the esophageal wall,

 Constriction of the esophagus by an abnormal vascular ring (persistent right aortic arch or ligamentum arteriosum) and consecutive cranial dilatation of the esophagus,

 Stricture, fistula of the esophagus

INTRALUMINAL THORACIC ESOPHAGEAL FOREIGN BODIES (FB)

FB are generally situated at the heart base or the esophageal hiatus. Most of them are bone fragments, sometimes very sharp and spiculated, that risk laceration if they stay a too long time trapped or on removal.

If possible, FB must be removed by a non-surgical management. Should this not be possible, the esophagus is approached via an intercostal thoracotomy . If the FB lies cranial to the heart, the thoracotomy is performed on the left side, and centered on the location of the FB, as seen on a lateral thoracic X-ray. If the FB is situated at the base of the heart, the thoracotomy is a right 4^th or 5^th intercostal one, if the FB is caudally situated in the thoracic esophagus, a left 8^th intercostal thoracotomy, or a trans-diaphragmatic approach is performed. The esophagus is identified in the mediastinum. If necessary, the lung lobes are packed out of the surgical field with moistened pads. The esophagus is carefully dissected from the mediastinal pleura, with great respect to the adjacent vessels and vagus nerve. Secretions are suctioned via an intraesophageal tube introduced «per os». Several laparotomy moistened pads are used to isolate the surgical esophageal area from the peripheric tissues. Two stay sutures are placed adjacent to the incision site. Esophageal wall is incised longitudinally, long enough to allow an easy extraction of the FB. The incision is performed caudal to the FB if the esophageal wall looked compromised, or over the FB if the wall looks normal. The FB is removed, and the inner layer of the esophagus is inspected. If large necrotic areas are present, consider surgical patching with adjacent muscle (such as sternothyroideus muscle) or resection- anastomosis (see surgical treatment of tumors and parasitic granuloma). We close routinely the esophageal wound with a two-layer suture (mucosa+sub-mucosa / muscularis+ serosa ) using a resorbable mono-filament suture (polydioxanone).

TUMOR OR PARASITIC GRANULOMA

Esophageal neoplasia is very rare in small animals. In our clinic, we see more often granuloma or pseudo-tumors of the esophageal wall due to Spirocerca lupi on dogs which stayed in Africa, or in the Réunion Island. The condition is associated with esophageal obstruction, pain and regurgitation. If the lesion is not two large (max 3-5cm, depending on the dog size) , limited local resection or partial esophagectomy and anastomosis is performed. It is necessary to limit longitudinal tension on the anastomosis suture otherwise there is a high risk of dehiscence. A circumferential incision of the outer muscularis (longitudinal muscle layer) may be performed 2 cm cranial and caudal to the suture line to remove tension. In most of the cases with extensive lesions, surgical treatment is impractical because efficient substitution techniques for intrathoracic esophagus have not been developed in clinical field, though some have been described in research literature but with minimal clinical experience.

CONSTRICTION BY AN ABNORMAL VASCULAR RING AND CRANIAL DILATATION

Different types of vascular ring anomaly have been described mainly in the dog but also in the cat and may lead to esophageal obstruction and fibrosis, with dilatation of the esophagus cranial to the constriction site. The most common anomaly is the persistence of a right aortic arch with left ligamentum arteriosus.

Most abnormal vascular ring can be corrected via a left 4^th or 5^th thoracotomy approach. To expose the mediastinal area dorsal to the heart, the cranial lug is packed caudally. Anatomic structures to identify are the aorta, the pulmonary artery, the vagus and phrenic nerves, the anomalous structure (ligamentum arteriosus, prominent hemiazygos vein, constricting sub-clavian artery...).

Surgical treatment is based on precise determination and dissection of the «entrapment» structure, then on its double ligation and transection. An inflated Foley catheter passed «per os» to the stenotic area may help to identify bands of fibrous tissue which are dissected with extreme care. Plication or resection of the redundant portion of the cranially dilated esophagus is unlikely to produce any clinical benefits to the patient, and increase the risk of complications.

Results are better if the surgery is performed very early after signs appear, but esophageal diameter and motility rarely become completely normal after surgery. Upright feeding with semi-liquid diets may be continued for several weeks and attempts at more solid food are then initiated. As the situation is generally considered as a genetic disorder, the affected animals must not be used for breeding.

STRICTURE, FISTULA

Stricture may be consecutive to ingestion of corrosive materials, thermal burns, reflux esophagitis, foreign bodies. Balloon catheter dilatation can be undertaken as a conservative treatment. Surgical options include transverse closure of a longitudinal esophageal incision, patch esophagoplasty, resection and anastomosis.

Acquired esophagobronchial fistula, secondary to a foreign body injury is the most common condition. Diagnosis may be difficult. Anesthesia is challenging if the defect is distal to the end of the endotracheal tube, and may require selective intubation. Surgical treatment usually requires extraction of the foreign body if still present, lung lobectomy if local pulmonary infection has developed, then suturing of the esophageal defect or more extensive esophageal resection and reconstruction techniques.