A challenging case: Lethargy and inappetence in a Pekingese - Veterinary Medicine
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A challenging case: Lethargy and inappetence in a Pekingese
If it were not for the suspicious thoracic radiography results, this dog would likely have been discharged before its primary problem was discovered.


VETERINARY MEDICINE


SURGERY

A left seventh intercostal thoracotomy was performed, which is standard procedure at the VMC. There were adhesions from the lung to the mediastinum and pericardium, which were broken down by using a LigaSure Atlas 20-cm Hand Switching Sealer/Divider Instrument (Covidien). The main bronchus and vessels supplying the left cranial lung lobe were ligated by using a TA 35 stapler (Tyco Healthcare). The lung lobe was then excised.

The pleural cavity was filled with warm sterile saline solution and observed for leaks before being lavaged several times. A chest tube was placed and directed into the cranioventral pleural space. The thoracotomy was closed in routine fashion. The chest tube was then suctioned until negative pressure was achieved.

POSTOPERATIVE CARE AND HISTOPATHOLOGY RESULTS

The patient recovered from anesthesia uneventfully. Hydromorphone (0.05 mg/kg intramuscularly every four hours) and bupivacaine 0.5% (2 ml through the chest tube q.i.d.) were administered for analgesia. Negative pressure was confirmed before instilling the bupivacaine. The chest tube was drained every six hours and removed after 24 hours.

The patient continued to do well and went home two days after surgery. No episodes of cough or respiratory distress were noted after surgery.

Numerous sections of the resected lobe were examined. Histopathologic results were consistent with lung lobe torsion, with abundant atelectasis, necrosis, hemorrhage, and thrombosis. No abnormalities in bronchial cartilage were evident.

FOLLOW-UP

The patient continued to do well four weeks after surgery, with no episodes of cough or respiratory distress.

DISCUSSION

Lung lobe torsion is a rare condition in small-animal practice. Torsion occurs when the lung rotates along the long axis, twisting the bronchovesicular pedicle at the hilus. This twist collapses the thin-walled pulmonary vein before collapsing the more muscular artery, causing pulmonary vascular congestion and consolidation of the parenchyma of the twisted lung lobe and pleural effusion.1,2

Clinical signs

Clinical signs associated with lung lobe torsion typically include dyspnea, cyanosis, coughing, weakness, lethargy, and anorexia. Less common historical findings include vomiting, diarrhea, weakness, and collapse. Signs of dyspnea related to a rapid accumulation of pleural fluid are often rapidly progressive, resulting in life-threatening respiratory distress and requiring emergency intervention.

Less commonly, dogs present for evaluation of mild or vague signs, as in this case report. This dog's cough was relatively mild, and the major reasons for its presentation for veterinary evaluation were anorexia and lethargy, which resolved with symptomatic fluid therapy. Clinical examination was largely unremarkable, and if radiography had not been performed, this dog might have been discharged from the hospital without the primary problem having been treated.

Predisposing conditions and breed predisposition

Lung lobe torsion in dogs is most often associated with predisposing conditions such as trauma, previous thoracic or abdominal surgery, diaphragmatic hernia, parenchymal disease, or pleural effusion.3 Partial collapse of a lung lobe within a pleural effusion—due to any underlying cause—may increase lung lobe mobility and lead to torsion.

Spontaneous lung lobe torsion has also been reported in dogs with no previous history of thoracic disease or trauma. Spontaneous lung lobe torsion has been reported most often in large-breed, deep-chested dogs. In this population, lung lobe torsion is most likely to affect the right middle lung lobe, presumably because of the narrow shape of that lobe and lack of attachment to surrounding tissues.2-6

Lung lobe torsion has also been reported in small-breed dogs with an apparent predisposition in young male pugs.2-10 Spontaneous lung lobe torsion has been reported in pugs 4 months to 4 years old (median age = 1.5 years).2-10 Torsion of the left cranial lung lobe is most common in small-breed dogs, including pugs.1,2,4-7,9,11 Factors contributing to spontaneous lung lobe torsion in pugs have not been determined, though bronchial cartilage dysplasia in brachycephalic breeds has been speculated to be a factor.1,4,7

Lung lobe torsion has not been commonly reported in brachycephalic breeds other than pugs, though there are two previous reports in Pekingese2,9 and English bulldogs.8,10 When evaluated, bronchial cartilage has been reported to be histologically normal in affected pugs, as it was in this Pekingese.1,4

Radiography

Thoracic radiographs of dogs with lung lobe torsion typically reveal consolidation of the affected lung lobe and pleural effusion. Pleural effusion is present in nearly all reported cases of dogs with lung lobe torsion, but as in this case, it may be absent in the early stages of this condition or in mildly affected dogs.1,2,4,7,9 Small dispersed air bubbles are commonly seen within the parenchyma of an affected lung lobe. Lobar bronchi can be visualized in about half of all cases, but recognition of the displacement of the bronchus is variable. Enlargement of the affected lobe resulting in a mediastinal shift with or without dorsal displacement of the trachea occurs in 50% of cases.1,7,9,11

Tracheal wash cytology

Tracheal wash cytology has not been previously reported in cases of dogs with lung lobe torsion. Lung consolidation in conjunction with respiratory signs, systemic signs, and sometimes fever may prompt evaluation for possible pneumonia in dogs with lung lobe torsion.

In this case, the tracheal wash cytologic examination revealed minimal inflation with ongoing hemorrhage into the lung parenchyma, presumably because of congestion. Hemoptysis and hematemesis have been reported in dogs with lung lobe torsion.9,12,13

Ultrasonography

An ultrasonographic examination of the thorax of dogs with lung lobe torsion usually reveals a pleural effusion, a densely consolidated lung lobe, and scattered reverberating foci (artifact resulting from the production of spurious echoes that are caused by reflections at the skin-transducer interface or by bone or gas) consistent with gas located centrally within the lobe.

As experienced in this case, it can be difficult to interpret Doppler detection of blood flow. The cranial mediastinum should always be evaluated for a mass, which could serve as an underlying cause for pleural effusion leading to secondary lung lobe torsion.


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Source: VETERINARY MEDICINE,
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