Management of a tracheal intussusception in a dog

Abstract

A 5-year-old Belgian Malinois dog was presented for evaluation of dyspnea of 1-month duration. Tracheal intussusception was diagnosed by tracheoscopy. Treatment consisted of surgical resection of the invaginated tracheal ring and the immediate cranial and caudal tracheal rings. The dog recovered uneventfully; complications included temporary emphysema after surgery. Seven months after surgery, the dog was still clinically normal. To the authors’ knowledge, this is the first report of a tracheal intussusception treated surgically in a dog.

The causes of tracheal obstruction most commonly reported in veterinary medicine include collapse, tumors, and tracheal foreign bodies. External trauma, complications relating to tracheostomy tubes and tracheal intubation can cause intraluminal stricture due to excessive granulation tissue (1,2). Tracheal intussusception is a rare condition in dogs and cats and there is only 1 report describing conservative treatment in a dog (3). The present study reports the diagnosis and treatment of a tracheal intussusception in a dog.

Case description

A 5-year-old Belgian Malinois dog was presented for evaluation of chronic dyspnea. Clinical signs, which had been present for 1 mo prior to presentation, included decreased exercise tolerance with increased respiratory effort and episodes of cyanosis. At rest, the dog was asymptomatic. Before the onset of clinical signs the patient had been in an altercation with another dog. At the time of the altercation, the owners reported no external signs of trauma such as bleeding, hematoma, or wounds.

Upon presentation, physical examination revealed a severe inspiratory dyspnea. Respiratory distress including tachypnea and cyanosis seemed to have been exacerbated by handling during the clinical examination. Stridor was audible. A focal 3 cm × 1 cm area of alopecia, without any wound or scar, was noted on the ventral aspect of the neck. The clinical examination was highly suggestive of an extra-thoracic airway dysfunction. Initial differential diagnosis consisted of laryngeal disease including laryngeal paralysis; inflammatory disease or neoplastic disease; tracheitis; extraluminal mass compressing the pharynx, larynx or trachea; foreign body; nasopharyngeal polyp; abscess or hematoma of the pharynx, larynx or trachea.

A direct laryngeal examination was performed under a light plane of anesthesia to assess laryngeal function. The dog was induced with midazolam (Midazolam; Aguettant, Lyon, France), 0.2 mg/kg body weight (BW), IV and propofol (Propovet; Axience, Pantin, France) IV to effect. The examination of the larynx was unremarkable. Thoracic and neck radiographs were performed under anesthesia. Thoracic radiographs were unremarkable. Neck radiographs revealed a 4-mm soft tissue opacity in the lumen of the trachea at the level of the 6th cervical vertebra (Figure 1).

Figure 1.

Tracheal intussusception represented by tissue opacification on cervical radiographs.

Upper respiratory endoscopy with a 5-mm flexible endoscope was then performed to further explore the lesion in the trachea. Examination of the trachea revealed severe stenosis in its cervical portion, located 20 cm caudally to the laryngeal inlet (Figure 2). The tracheal lumen was restricted to a vertical slot of 3 mm diameter surrounded by 2 cartilaginous pillars. Approximately 75% of the normal diameter of the tracheal lumen was constricted. It was possible to pass a 5-mm endoscope beyond the lesion, demonstrating a normal tracheal diameter and appearance immediately caudal to the lesion. No other abnormalities were identified such as tracheal rupture, pseudotrachea, or pseudotracheal membrane. Based on these images, an intussusception of a tracheal ring was suspected, without excluding a stricture due to excessive granulation tissue or an annular mass compressing the trachea. In the event that there was an intussusception, the invaginated tracheal ring would likely have been damaged since tracheal rings are rigid and C-shaped cartilage and tracheoscopy do not show a fornix as expected.

Figure 2.

Tracheoscopic view of stenosis induced by tracheal intussusception.

Due to the severity of the clinical signs, the location and the extent of the lesion, surgical management was recommended. General anesthesia was maintained with isoflurane (Isoflo 100%; Axience) in oxygen. Tracheal resection of the lesion including 1 ring cranial and 1 ring caudal to the lesion was performed by an end-to-end method as previously described (4–7). Briefly, a ventral approach was taken (Figure 3). The lesion was located by a narrow space between 2 tracheal rings suggesting that the distal ring was invaginated into the proximal ring. Reduction of the intussusception was not attempted due to the deformation of the invaginated tracheal ring revealed by tracheoscopy. The trachea was incised caudal to the lesion in order to allow intubation in the caudal aspect of the trachea with a sterile endotracheal tube (Figure 4). The lesion was then excised. The sterile endotracheal tube was removed and tracheal anastomosis was performed with simple interrupted sutures (3-0 monofilament absorbable) encircling the cartilage rings in order to minimize risk of postoperative stenosis (4,8,9). Three vertical interrupted mattress sutures were added around adjacent tracheal rings to relieve tension (Figure 5) (10).

Figure 3.

External visualization of the tracheal intussusception after ventral surgical approach of the caudal trachea.

Figure 4.

Sterile tracheotomy caudal to the lesion.

Figure 5.

Tracheal anastomosis after resection of the lesion.

The dog’s recovery from surgery was uneventful. Postoperative treatment included oxygen, 3 L/min, by nasal tube. Weaning was possible within a few hours. Postoperative analgesia included morphine (Morphine; Lavoisier, Paris, France), 0.2 mg/kg BW, SC, q4h and carprofen (Carprieve; Bayer, Lyon, France), 4 mg/kg BW, IV, q24h. Amoxicillin (Clamoxyl; Pfizer, Paris, France), 20 mg/kg BW, IV, q8h was administered for 48 h after surgery. Upon discharge, medical treatment included carprofen (Carprieve; Bayer), 4 mg/kg BW, PO, q24h for 10 d and cefalexine (Rilexine; Virbac, Carros, France), 15 mg/kg BW, PO q12h for 7 d.

Twenty-four hours after surgery, a mild emphysema in the ventral cervical region was palpable, without any associated clinical signs. Five days after surgery, emphysema was completely resolved. Seven months after surgery, the owners reported that the dog had regained a normal life and they did not agree to an endoscopic examination.

Discussion

External tracheal injuries are most often secondary to bite injury or road traffic accidents (2,11). The altercation with another dog shortly before the onset of symptoms strongly suggests a traumatic cause, although it could not be proven. One case of trauma-induced tracheal stenosis was recently described in a horse (1). The stenosis was associated with extensive scar tissue and deformation of 1 tracheal ring, without intussusception. Other causes were sought to explain tracheal intussusception as a congenital abnormality. Mawby et al (12) described a case of local tracheal narrowing due to segmental tracheal dysplasia in a mixed breed dog. The diameter of the intrathoracic aspect of the trachea was reduced to half the size of the cervical part. The tracheal narrowing was due to marked abnormal overlapping of the tracheal cartilage at the level of the trachealis muscle, causing a winding of the tracheal ring to itself (12). In our case, the resected tracheal rings were sent for histology to assess the possibility of congenital structural or cellular abnormality or signs of trauma. A “modified target sign” was present on histology images including 2 layers of cartilage corresponding to the invaginated portion surrounded by a C-shaped external tracheal ring (Figure 6). Histology confirmed the intussusception. There was no abnormality to explain this intussusception. Histological findings revealed non-specific signs of tracheitis with submucosal neutrophilic, lymphocytic and histiocytic infiltrates, and multifocal areas of fibrous tissue as can be found in other inflammatory processes like tracheal collapse (13,14).

Figure 6.

Histology of the tracheal intussusception.

It is difficult to understand the physiopathology of tracheal intussusception, which is a rare condition. To the authors’ knowledge, only 1 case describing a similar lesion has been published (3). That case involved an 18-year-old male miniature poodle. The cause of the intussusception was unknown and no history of trauma was suspected. The patient had a cough during the latter years of its life and diagnosis was made by tracheoscopy and computed tomography (CT). A 3-D reconstruction CT showed that a segment of trachea at the level of the 6th cervical vertebra was displaced cranially and had invaginated. Computed tomography would have helped to determine if tracheal intussusception was present. However, CT was not performed due to organizational constraints and the patient going into respiratory distress after recovery from anesthesia following tracheoscopy. So, immediate surgical management was recommended. Tracheoscopy showed that the miniature poodle appeared to have had much less significant reduction in the airway diameter than the case presented here. Surgical resection and anastomosis of the abnormal tracheal segment was considered but was not performed due to the age of the dog and because the intussusception was well-tolerated. The dog was managed medically with amoxicillin and clavulanate potassium, prednisolone, and theophylline for 4 wk, and recovered partially with an intermittent dry cough (3). It is interesting that the intussusception affected tracheal rings at the level of the 6th cervical vertebra in those 2 cases; an area where the trachea is less accessible to external trauma as muscles, sternum and ribs protect the trachea (15). The cartilage of the tracheal rings is thinner at the thoracic inlet, which may create a mechanical weakness zone (15). Also, the direction of the intussusception is the same in both cases: the distal ring was invaginated into the proximal ring. As the diameter of tracheal rings decreases progressively from cranial to caudal at the level of the thoracic inlet, the direction of the intussusception seems logical (15).

Tracheal intussusception has not been described in the medical literature for humans. Prolapse of the epiglottis into the trachea is reported in children who have a concomitant swallowing dysfunction and gastroesophageal reflux disease (16,17). Nasopharyngo-laryngoscopy is used to diagnose the prolapse. As the direction of the intussusception is different from tracheal intussusception described herein, the tracheoscopic images are completely different. A grading system is used depending on the degree of epiglottic and base-of-tongue prolapse. The severity can range from normal to complete obstruction of the pharynx by the base of tongue with no epiglottis visible (16,17).

In conclusion, this report describes an unusual case of inspiratory dyspnea in a dog, due to tracheal intussusception with a suspected traumatic cause. This case was managed surgically due to the severity of the clinical symptoms but medical management for a less severe case has also been described. The dog had a good clinical outcome and surgical resection of the affected trachea should be considered if clinical signs are severe enough to warrant this. CVJ