Accessory lung lobe torsion and chylothorax in an Afghan hound

Anatomical considerations for the surgical approach to the canine accessory lung lobe

OBJECTIVE

To describe (1) the surgical anatomy of the accessory lung lobe (ALL) including vasculature and pulmonary ligamentous attachments and (2) lobectomy through a right thoracotomy and median sternotomy.

STUDY DESIGN

Cadaveric anatomical study.

ANIMALS

Nine adult canine cadavers, free of disease affecting the thoracic cavity and lung parenchyma.

METHODS

Median sternotomy and right and left lateral thoracotomies were performed to describe and image relevant variations in anatomy using accompanying photographs and thorough voice notes. Consideration for ALL removal via right thoracotomy at the fifth through seventh intercostal spaces and median sternotomy were documented and compared.

RESULTS

The median weight of the cadavers was 20.85 kg (6.9-45.5 kg). Variation in the configuration of venous drainage of the ALL was identified. The lateral vein varied in its location and was also observed to combine with the medial vein in one cadaver. The pulmonary ligament attached to the ALL in a caudally pointing apex on the dorsal process of the lobe. Medial and lateral extensions of the ALL parenchyma were found. The ALL was most easily accessed by a right lateral thoracotomy at the sixth intercostal space. Although not optimal, removal of this lung lobe via median sternotomy was feasible.

CONCLUSION

Significant variations were found in the blood supply to the ALL. A right lateral thoracotomy at the sixth intercostal space was preferred for a surgical approach to the ALL.

CLINICAL SIGNIFICANCE

Surgeons should be aware of several anatomical particularities including the venous drainage, ligamentous attachments, and parenchymal extensions of the ALL.

Lung lobe torsion in dogs: 52 cases (2005-2017)

OBJECTIVE

To report outcomes and risk factors for mortality in dogs that underwent surgical management of lung lobe torsion.

STUDY DESIGN

Retrospective case series from 5 veterinary teaching hospitals (2005-2017).

ANIMALS

Fifty dogs with 52 instances of lung lobe torsion.

METHODS

Data collected from medical records included signalment, clinical findings, results of clinicopathologic testing and diagnostic imaging, surgical treatment, lung lobe affected, intraoperative and postoperative complications, histopathologic and microbiologic findings, and outcome. Follow-up was obtained from medical records and telephone contact with primary care veterinarians.

RESULTS

Fifty-two instances of lung lobe torsion were identified in 50 dogs, with a median follow-up of 453 days (range, 0-3075). Forty-six (92%) dogs survived to discharge. Dogs with concurrent torsion of the right cranial and middle lung lobes were less likely to survive (2/4) than those with torsion of the left cranial lung lobe (22/22). No other risk factors for mortality prior to hospital discharge were identified. Overall median survival time after hospital discharge was 1369 days. Four dogs had >1 episode of lung lobe torsion.

CONCLUSION

The percentage of dogs surviving to discharge after surgical treatment of lung lobe torsion was higher than previously reported. The short- and long-term prognosis was excellent with surgical treatment of lung lobe torsion.

CLINICAL SIGNIFICANCE

Surgery should be recommended when lung lobe torsion is suspected because of the high survival to discharge rate and excellent long-term prognosis.

Spontaneous Resolution of Postoperative Chylothorax Following Surgery for Persistent Right Aortic Arch in Two Dogs

Two young dogs underwent surgical management of a persistent right aortic arch (PRAA) and developed chylothorax postoperatively. In both cases, the surgical procedure and anesthetic recovery were uncomplicated and routine. Following surgery, both patients appeared bright, alert, responsive, and previous signs of regurgitation had resolved. Dyspnea and tachypnea developed 1–2 days postoperatively in each patient, and chylous effusion was detected on thoracocentesis. For each case, a diagnosis of chylothorax was based on cytology and triglyceride concentrations of the aspirated pleural fluid. Similar protocols for monitoring were used in the treatment of each patient’s chylothorax. The duration and volume of chylous effusion production were closely monitored via routine thoracostomy tube aspiration. Both dogs rapidly progressed to recovery with no additional complications. With diligent monitoring, chylothorax secondary to surgical trauma can resolve in a rapid, uncomplicated manner.

Lung lobe torsion in association with a chronic diaphragmatic hernia and haemorrhagic pleural effusion in a cat

Clinical summary This report describes torsion of the right cranial lung lobe in a cat with haemorrhagic pleural effusion and a chronic diaphragmatic hernia. Surgical treatment comprising lung lobectomy without de-rotation, and repair of the diaphragmatic defect, led to an uneventful recovery.

Practical relevance Lung lobe torsion is a rare condition in cats. While spontaneous lung lobe torsions may occur, a frequent association with underlying thoracic disease has been recognised in cats. However, neither haemorrhagic pleural effusion nor diaphragmatic hernia have been previously described in cats with lung lobe torsions, although they have been documented in dogs and humans. In a cat with suspected lung lobe torsion, a thorough search for an underlying disease should be undertaken.

Chylothorax associated with tricuspid dysplasia and atrial septal defect in a bullmastiff

Transudate pleural effusion associated with tricuspid dysplasia and ostium secundum-type atrial septal defect was diagnosed in a 14-month-old bullmastiff. Following administration of furosemide and an angiotensin-converting enzyme (ACE) inhibitor, the dog remained free of pleural effusion for 10 months, until he showed severe dyspnea due to chylothorax. Medical therapy was unsuccessful to avoid recurrence of life-threatening pleural chylous effusion. Ligation of the thoracic duct and apposition of an omental pedicle flap were effective in the resolution of pleural chylous leakage.

Evaluation of lung lobe torsion in Pugs: 7 cases (1991–2004)

OBJECTIVE

To determine whether there is a predis-position for lung lobe torsion (LLT) in Pugs and describe clinical findings associated with LLT in that breed, compared with findings in other breeds.

DESIGN

Retrospective case series.

ANIMALS

7 Pugs and 16 dogs of other breeds.

PROCEDURE

Information collected from records included signalment, history, lung lobe affected, results of clinicopathologic testing, histologic findings, diagnostic imaging results, surgical treatment, and outcome.

RESULTS

23 dogs were diagnosed with LLT, 10 of which were large-breed dogs and 13 of which were small-breed dogs. Seven of the small-breed dogs were Pugs. Pugs with LLT were significantly overrepresented, compared with the general hospital population. Affected Pugs ranged in age from 4.5 months to 4 years (median, 1.5 years). Six of the 7 Pugs had no predisposing conditions, and 6 were male. Six Pugs survived to discharge. Of the other small- and large-breed dogs, 3 of 6 and 5 of 10 survived to discharge, respectively. None of the Pugs were readmitted for complications or recurrence.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that young male Pugs may be predisposed to developing spontaneous LLT. The prognosis for survival and resolution of clinical signs in Pugs with LLT appeared to be excellent. Factors contributing to the development of LLT in Pugs are not known.

RADIOGRAPHIC DIAGNOSIS OF LUNG LOBE TORSION

Clinical data, thoracic radiographs, ultrasonographic exams, and histopathologic reports in 13 dogs and two cats with confirmed lung lobe torsion were reviewed. Age of dogs ranged from 4 months to 11.5 years, (mean of 6.4 years) and several breeds of large and small dogs were represented. Right middle lobe torsion was predominant in large dogs (five of eight large breed dogs) and left cranial lobe torsion was more commonly seen in small dogs (three of five small-breed dogs). Two domestic short-hair cats, 10 and 14 years of age, had right cranial and right middle lobe torsion, respectively. Underlying thoracic disease was found in only five of 15 patients. On thoracic radiographs, increased lobar opacity and pleural effusion were found in all patients (100%). Small dispersed air bubbles were found within the affected lobe of 13 patients (87%). This pattern, which was the result of vesicular emphysema, was variably extensive, and became more evident on follow-up radiographs in five of six dogs. The lobar bronchi could be seen in only eight of 15 patients (54%), and appeared irregular, focally narrowed or blunted in six of the eight patients, and displaced in five of the eight. Other common radiographic findings included mediastinal shift (nine), curved and dorsally displaced trachea (seven), and axial rotation of the carina (seven). Ultrasonography was used in seven patients and considered generally useful, although variable signs were observed.

The Effect of Cisterna Chyli Ablation Combined with Thoracic Duct Ligation on Abdominal Lymphatic Drainage

OBJECTIVE

To evaluate the effect of cisterna chyli ablation (CCA) and thoracic duct ligation (TDL) on abdominal lymphatic drainage in normal dogs.

STUDY DESIGN

Experimental study.

ANIMALS

Nine female beagle dogs.

METHODS

TDL was performed in 3 dogs and was combined with CCA (CCA-TDL) and local omentalization in 6 dogs. Contrast lymphangiography was attempted in all dogs immediately before and after TDL. Dogs were reanesthetized at 31-37 days for lymphatic studies by new methylene blue (NMB) injection into a mesenteric lymph node and by contrast lymphangiography.

RESULTS

In 6 CCA-TDL dogs, 2 had direct shunting of contrast from the lymphatic system into major abdominal veins, 3 had contrast material that dissipated into abdominal vessels within the mesenteric root, and 1 had shunting into the azygous vein. NMB was not observed within the omental pedicle after CCA-TDL. Chylous drainage was by the azygous vein in all 3 TDL dogs.

CONCLUSIONS

CCA-TDL disrupted chylous drainage to the thoracic duct and resulted in direct intraabdominal lymphaticovenous anastomoses identified by shunting of lymphatic flow directly into the abdominal vasculature in 5 of 6 CCA-TDL dogs. Omentalization of the cisternal ablation site was not beneficial in augmenting extrathoracic lymphatic drainage and is not recommended with CCA-TDL.

CLINICAL RELEVANCE

CCA-TDL represents a novel approach to surgical redirection of chylous drainage to the venous circulation outside of the thorax and may be useful in the treatment of spontaneous chylothorax in the dog.

Spontaneous Midlobar Lung Lobe Torsion in a 2-Year-Old Newfoundland

A 2-year-old, intact male Newfoundland was presented for evaluation of a 1- to 2-day history of coughing, retching, and progressive lethargy. Thoracic radiographs demonstrated right-sided pleural effusion and lobar vesicular emphysema. An exploratory thoracotomy revealed midlobar torsion of the right caudal lung lobe. A partial lung lobectomy was performed, and following surgery, the dog recovered without complications. Lung lobe torsions in dogs typically occur at the hilus of the affected lung lobe. This report documents that midlobar lung lobe torsions occur in dogs and should be considered as a differential diagnosis in cases of lobar vesicular emphysema and pleural effusion.

Resolution of chylothorax after resection of rib chondroma in a dog

A six-year-old, male dobermann was presented with a history of dyspnoea and bouts of coughing. Radiography and computed tomography of the thorax showed pleural effusion and a well-circumscribed, calcified mass of 10 cm in diameter, appearing to originate from the left first rib. Thoracocentesis revealed that the pleural fluid was chylous in nature. An incisional biopsy was performed, which gave a histological diagnosis of chondroma. Resolution of the chylothorax after en-bloc surgical removal of the tumour suggested that the rib tumour was the initiating cause of the chylothorax. Seventeen months later, rib neoplasia recurred without pleural effusion, and was removed successfully. To the authors' knowledge, rib chondroma, which is an unusual tumour in dogs, has not been previously documented as a cause of chylothorax.

The accessory lung lobe in thoracic disease: a case series and anatomical review

Diseases of the accessory lung lobe (AccLL) are often overlooked in dogs and cats, perhaps because of its recessed location. Diseases of this lobe also can mimic diseases of the diaphragm or structures comprising the caudal mediastinum. Normal anatomy of the AccLL and the diagnostic tools used today will be reviewed to help differentiate disease of adjacent organs. Four cases will also be described to illustrate disease presentation and radiographic findings affecting this lobe.

Recurrence of Spontaneous Lung Lobe Torsion in a Pug

Lung lobe torsion (LLT) results from a displacement and twisting of a lung lobe around its bronchovascular pedicle. This relatively rare disorder affects dogs, cats, and humans. Etiologies include primary (i.e., spontaneous) and secondary torsion due to thoracic trauma, pleural space disease, thoracic surgery, pulmonary parenchyma disease, and diaphragmatic hernia repair. Although both spontaneous and secondary torsion have been described in small-breed dogs, a spontaneous LLT followed by recurrence of a spontaneous LLT >2 years later has not been documented. This article describes the presentation, diagnosis, management, and outcome of a pug with recurrent spontaneous LLT.

Popliteal and mesenteric lymph node injection with methylene blue for coloration of the thoracic duct in dogs

OBJECTIVE

To describe and compare the time of onset and intensity of thoracic duct coloration after injection of methylene blue into a mesenteric or popliteal lymph node.

STUDY DESIGN

Experimental study.

ANIMALS

Twenty adult dogs.

METHODS

A right tenth intercostal thoracotomy, a right paracostal laparotomy, and an approach to the right popliteal lymph node were performed on each dog. Methylene blue (0.5 mg/kg of a 1% solution, maximum 10 mg) was injected into either a mesenteric (group M, 10 dogs) or popliteal (group P, 10 dogs) lymph node. Thoracic duct color was graded (0 to 3) every 5 minutes for 60 minutes. Statistical analysis was performed on mean thoracic duct color grade data, on number of successful outcomes between groups M and P, and between weight groups.

RESULTS

Coloration of the thoracic duct occurred in all group M dogs and 6 group P dogs. Coloration was first recorded 0 to 10 minutes after injection in all dogs and persisted for 60 minutes in 15 dogs. Mean thoracic duct color grade was significantly increased postinjection compared with preinjection at all times in group M. More successful outcomes occurred in group M (P =.03).

CONCLUSIONS

Methylene blue injected into mesenteric or popliteal lymph nodes was successful in coloring the thoracic duct, but both mean grade and number of successful outcomes were significantly higher after mesenteric injection.

CLINICAL RELEVANCE

Thoracic duct coloration after lymph node injection occurred within 10 minutes and persisted for 60 minutes. This information is useful in planning thoracic duct ligation in cases of chylothorax when observation of the duct is desired. Injection of both lymph node sites was successful, but mesenteric node injection was a more reliable technique.

Concurrent torsion of the right cranial and right middle lung lobes in a whippet

A four-year-old, entire male whippet was presented with a three-day history of lethargy, inappetence, occasional retching, a soft cough and intermittent episodes of haemoptysis. Clinical and laboratory findings, and thoracic radiographic and ultrasonographic studies suggested a diagnosis of lung lobe torsion. A concurrent lung lobe torsion of the right cranial and right middle lung lobes was confirmed at exploratory thoracotomy. Management included resection of both the affected lung lobes. No obvious underlying aetiology for the condition was apparent. The dog made a full recovery from the procedure and at the time of writing (11 months postoperatively) was reported to be well, exercising normally and showing no breathing abnormalities.

Lung lobe torsion in dogs: 22 cases (1981-1999)

OBJECTIVE

To identify breed disposition, postoperative complications, and outcome in dogs with lung lobe torsion.

DESIGN

Retrospective study.

ANIMALS

22 client-owned dogs.

PROCEDURE

Information on signalment; history; clinical findings; results of clinicopathologic testing, diagnostic imaging, and pleural fluid analysis; surgical treatment; intra- and postoperative complications; histologic findings; and outcome were obtained from medical records.

RESULTS

All 22 dogs had pleural effusion; dyspnea was the most common reason for examination. Fifteen dogs were large deep-chested breeds; 5 were toy breeds. Afghan Hounds were overrepresented, compared with the hospital population. One dog was euthanatized without treatment; the remaining dogs underwent exploratory thoracotomy and lung lobectomy. Eleven dogs recovered from surgery without complications, but 3 of these later died of thoracic disease. Four dogs survived to discharge but had clinically important complications within 2 months, including chylothorax, mediastinal mesothelioma, gastric dilatation, and a second lung lobe torsion. Six dogs died or were euthanatized within 2 weeks after surgery because of acute respiratory distress syndrome, pneumonia, septic shock, pneumothorax, or chylothorax. Chylothorax was diagnosed in 8 of the 22 dogs, including 4 Afghan Hounds.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that lung lobe torsion is rare in dogs and develops most frequently in large deep-chested dogs, particularly Afghan Hounds. Other predisposing causes were not identified, but an association with chylothorax was evident, especially in Afghan Hounds. Prognosis for dogs with lung lobe torsion was fair to guarded.