Lung lobe torsion in seven juvenile dogs

Christian R. Latimer Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.

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Cassie N. Lux Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996.

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Jessie S. Sutton Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616.

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William T. N. Culp Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616.

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Abstract

CASE DESCRIPTION 7 juvenile (< 12 months old) dogs with lung lobe torsion were evaluated.

CLINICAL FINDINGS All patients were male; breeds included Pug (n = 5), Chinese Shar-Pei (1), and Bullmastiff (1). Dyspnea and lethargy were the most common initial complaints, with a duration of clinical signs ranging from 1 to 10 days. A CBC showed leukocytosis and neutrophilia in all dogs. Anemia was present in 6 dogs, 2 of which received packed RBC transfusions. The diagnosis was made on the basis of results of thoracic radiography, CT, ultrasonography, or a combination of modalities. The left cranial lung lobe was most commonly affected (n = 4), followed by the right middle lung lobe (2) and the right cranial lung lobe (1).

TREATMENT AND OUTCOME A lateral intercostal thoracotomy with lobectomy of the affected lobe was performed in all patients. All dogs survived to be discharged between 1 and 2 days postoperatively. Six of 7 owners contacted for follow-up information 7 to 170 months after discharge reported satisfaction with the treatment and no apparent signs of recurrence of disease.

CLINICAL RELEVANCE The juvenile patients of this report were successfully treated surgically with no apparent complications. Clinicians should be aware of the possibility of lung lobe torsion when evaluating young dogs with clinical signs related to the respiratory system, including those with vague signs, to avoid undue delays in treatment.

Abstract

CASE DESCRIPTION 7 juvenile (< 12 months old) dogs with lung lobe torsion were evaluated.

CLINICAL FINDINGS All patients were male; breeds included Pug (n = 5), Chinese Shar-Pei (1), and Bullmastiff (1). Dyspnea and lethargy were the most common initial complaints, with a duration of clinical signs ranging from 1 to 10 days. A CBC showed leukocytosis and neutrophilia in all dogs. Anemia was present in 6 dogs, 2 of which received packed RBC transfusions. The diagnosis was made on the basis of results of thoracic radiography, CT, ultrasonography, or a combination of modalities. The left cranial lung lobe was most commonly affected (n = 4), followed by the right middle lung lobe (2) and the right cranial lung lobe (1).

TREATMENT AND OUTCOME A lateral intercostal thoracotomy with lobectomy of the affected lobe was performed in all patients. All dogs survived to be discharged between 1 and 2 days postoperatively. Six of 7 owners contacted for follow-up information 7 to 170 months after discharge reported satisfaction with the treatment and no apparent signs of recurrence of disease.

CLINICAL RELEVANCE The juvenile patients of this report were successfully treated surgically with no apparent complications. Clinicians should be aware of the possibility of lung lobe torsion when evaluating young dogs with clinical signs related to the respiratory system, including those with vague signs, to avoid undue delays in treatment.

A 3-month-old sexually intact male Bullmastiff (dog 1) was examined for a 12-hour history of hemoptysis and hematemesis. The dog had undergone a ventral midline laparotomy and gastropexy for treatment of gastric dilation and volvulus 5 days prior to evaluation. On initial physical examination, the patient was mildly tachypneic (respiratory rate, 50 breaths/min; reference range, 18 to 34 breaths/min). A CBC revealed leukocytosis (40,890 cells/μL; reference range, 5,100 to 14,000 cells/μL) with mature neutrophilia (37,087 cells/μL; reference range, 2,650 to 9,800 cells/μL) and anemia (Hct, 34.4%; reference range, 41% to 60%; Table 1). Hypoalbuminemia (albumin, 2.3 g/dL; reference range, 3.2 to 4.1 g/dL) was evident on a serum biochemical analysis.

Table 1—

Results of preoperative clinical laboratory testing in 7 juvenile (< 12 months old) dogs with lung lobe torsion.

VariableNo. of dogs*MeanMedianRangeReference range
WBCs (cells/μL)724,724.2920,80015,800–40,8905,100–14,000
Hct (%)729.732719–4341–60
Total protein (g/dL)66.3765.4–7.75.4–6.9
Neutrophils (cells/μL)719,557.2916,64010,921–37,0872,650–9,800
Band neutrophils (cells/μL)7578.4300–2,7030–300
Platelets (platelets/μL)7355,600353,000273,000–448,000150,000–400,000
Albumin (g/dL)42.652.62.3–3.13.2–4.1
Globulins (g/dL)43.233.651.8–3.82.0–3.2
Alanine aminotransferase (U/L)4385.253027–1,45421–97
Alkaline phosphatase (U/L)4213.7519471–39615–164
Glucose (mg/dL)5117.610682–18386–118
BUN (mg/dL)410.75117–1411–33
Lactate (mmol/L)41.351.20.6–2.40–2
Prothrombin time (s)37.47.36.9–8.07–9.3
Partial thromboplastin time (s)313.431411.9–14.410.4–12.9

Results of some tests (CBC, serum biochemical analysis, and coagulation profile) were not available for some patients.

Results of platelet counts for 2 dogs were reported as “clumped but appear adequate.”

The patient underwent standard 3-view thoracic radiography, which revealed consolidation and severe emphysema of the right middle lung lobe and possible involvement of the right caudal lung lobe. Trans-abdominal ultrasonography was also performed, and findings included multiple intraabdominal cystic structures located dorsal and caudal to the pancreas.

In view of the clinical signs and results of diagnostic imaging, the primary differential diagnoses were lung lobe torsion or abscess formation of the right middle and possibly the right caudal lung lobes, although intrapulmonary hemorrhage and pulmonary neoplasia could not be completely ruled out. The decision was made to perform an immediate exploratory thoracotomy because of the suspicion of lung lobe torsion or abscess formation and the presence of hemoptysis and mild tachypnea. Therefore, an IV catheter was placed, and general anesthesia was induced with administration of fentanyl (5 μg/kg [2.3 μg/lb], IV), midazolam (0.4 mg/kg [0.2 mg/lb], IV), and propofol (2 to 6 mg/kg [0.9 to 2.7 mg/lb], IV) to effect. An endotracheal tube was placed, and anesthesia was maintained with delivery of isoflurane in oxygen, with a constant rate infusion of fentanyl (5 to 7 μg/kg/h [2.3 to 3.2 μg/lb/h], IV) for analgesia. Monitoring included heart rate (lead II ECG), indirect blood pressure, arterial oxygen saturation (measured by means of pulse oximetry), respiratory rate, and end-tidal carbon dioxide concentration (measured by means of capnography). After standard aseptic preparation for surgery, and with the patient positioned in left lateral recumbency, a right lateral intercostal approach was made to the thorax. On thoracic exploration, torsion of the right middle lung lobe was evident. A right middle lung lobectomy was performed by means of isolation of the lung vasculature and main bronchus, application of a vascular stapler,a and transection distal to the staple line. During initial thoracic cavity exploration, a bulla was also noted in the right caudal lung lobe; therefore, a partial lung lobectomya was performed to treat this lesion and avoid possible spontaneous pneumothorax. On completion of the surgery, the thoracotomy was closed via placement of large monofilament absorbable suture (size-1 polydioxanoneb) in a circumcostal, dorsal-to-ventral, simple interrupted pattern. The thoracic wall musculature was closed with absorbable monofilament suture (2-0 poliglecapronec) in simple interrupted and cruciate suture patterns, and the subcutaneous tissues were closed with absorbable monofilament suture (2-0 poliglecapronec) in a simple continuous pattern. The skin was apposed with skin staples. An indwelling 24F thoracostomy tubed was placed and secured by means of a purse-string and finger-trap suture pattern with nonabsorbable monofilament suture (size-0 nylone).

A dopamine constant rate infusion was required for 12 hours after surgery to maintain a mean arterial pressure of 65 to 70 mm Hg, after which time dopamine administration was no longer necessary. For postoperative analgesia, the patient was maintained on constant rate infusions of morphine (0.1 to 0.2 mg/kg/h [0.05 to 0.09 mg/lb/h]) and ketamine (0.1 to 0.2 mg/kg/h). Additionally, bupivacaine (0.5 mg/kg [0.23 mg/lb]) was administered per hospital protocol into the thoracostomy tube every 6 hours until tube removal. A fentanyl transdermal patch (100 μg/h) was placed at surgical recovery and removed 3 days postoperatively. Timentin (50 mg/kg [22.7 mg/lb], I V, q 8 h) and enrofloxacin (5 mg/kg, IV, q 24 h) were administered perioperatively and throughout hospitalization.

The thoracostomy tube was removed 1 day after surgery, and the dog was discharged from the hospital 2 days postoperatively. The patient was discharged with amoxicillin–clavulanic acid (14 mg/kg [6.4 mg/lb], PO, q 12 h) for 14 days. The patient was lost to further follow-up after the recheck examination, which was performed 10 days postoperatively at the same hospital where the surgery was performed. At that time, the dog was clinically normal and healing well.

Histologic examination of the right middle lung lobe revealed acute diffuse necrosis and hemorrhage, consistent with the intraoperative diagnosis of acute lung lobe torsion. Histologic examination of the resected portion of the right caudal lung lobe revealed severe bullous emphysema and moderate acute neutrophilic interstitial pneumonia. The results of aerobic, anaerobic, and mycoplasmal cultures of samples of lung parenchyma from all resected lung tissues were negative.

A 7-month-old neutered male Chinese Shar-Pei (dog 2) was referred for evaluation of pleural effusion. The patient had a 2-day history of lethargy, inappetance, and dyspnea. The referring veterinarian had removed 250 mL of pleural fluid by means of thoracocentesis. On initial examination, the dog was tachycardic (heart rate, 200 beats/min; reference range, 80 to 120 beats/min) and tachypneic (respiratory rate, 50 breaths/min). Abnormalities on a CBC included anemia (Hct, 16.5%), leukocytosis (15,800 cells/μL), mature neutrophilia (11,330 cells/μL), and thrombocytosis (703,000/μL; reference range, 175,000 to 500,000/μL). A urinalysis revealed hematuria and proteinuria (3+ occult blood and 1+ protein). Results of bacterial culture of a urine sample were negative.

Thoracic radiography was performed following therapeutic thoracocentesis (350 mL of fluid). Findings included an alveolar infiltrate with air bronchograms of the right middle lung lobe, atypical orientation of the right middle lung lobe causing dorsal displacement of the right caudal lung lobe, truncation of the right middle lobar bronchus at the hilus, and a small volume of pleural effusion bilaterally. Computed tomography was then performed with the patient under general anesthesia and revealed a large (4.3 × 6.7 × 7.1-cm), roundish right middle lung lobe that appeared to be filled with an emphysematous soft tissue opacity. The right middle lobar bronchus terminated abruptly at the hilus and could not be traced into the lung lobe. There was a moderate amount of pleural effusion bilaterally and a large sternal lymph node measuring 0.8 × 1.0 × 2.3 cm.

The dog was administered 117 mL of packed RBCs, IV, and immediately taken to surgery for an exploratory right lateral intercostal thoracotomy. The diagnosis of torsion of the right middle lung lobe was confirmed, a right middle lung lobectomy was performed, and a thoracostomy tube (12F) was placed as previously described. Pleural effusion was noted during thoracotomy; results of cytologic analysis of a fluid sample were interpreted as a neutrophilic exudate with evidence of prior hemorrhage, consistent with the intraoperative diagnosis of lung lobe torsion.

The dog was provided oxygen supplementation via an oxygen cage with an inspired oxygen fraction of 30% to 40% for 40 hours postoperatively and was discharged 2 days after surgery. Histologic examination of the resected lung tissue revealed severe subacute diffuse pulmonary hemorrhage, necrosis, and pleural fibrosis. On telephone follow-up 13 months after surgery, the owner reported satisfaction with the outcome and noted the dog had had no apparent respiratory difficulties since initial discharge.

A 3-month-old sexually intact male Pug (dog 3) was evaluated for a 1-day history of coughing and dyspnea. On physical examination, the dog was dyspneic and had muffled lung sounds on auscultation of the right side of the thorax. It was also noted to have stenotic nares. A CBC revealed leukocytosis (18,500 cells/μL) characterized by neutrophilia (13,320 cells/μL) with a left shift (930 band neutrophils/μL; reference range, 0 to 300 cells/μL) and anemia (Hct, 27%).

Thoracic radiographs revealed a severe alveolar pattern affecting the right cranial and right middle lung lobes without loss of volume of these lobes. A presumptive diagnosis of aspiration pneumonia was made, and the dog was hospitalized. It was treated with ampicillin-sulbactam (30 mg/kg [13.6 mg/lb], IV) every 8 hours as well as oxygen supplementation (via an oxygen cage; inspired oxygen fraction, 40%). Thoracic radiography was repeated 2 days later. There was a persistent soft tissue opacity in the right cranial hemithorax, with minimal change from the prior images. However, at this time, the opacity contained several small gas bubbles in the region of the right cranial lung lobe. Additionally, there was an abruptly terminating lobar bronchus of the right cranial lung lobe. Thoracic CT was performed thereafter and revealed pleural effusion, stippled gas opacities within the right cranial lung lobe, and an apparently abruptly termination of the right cranial lobar bronchus.

A right lateral intercostal thoracotomy was performed immediately following CT. Pleural effusion was present, which confirmed a diagnosis of torsion of the right cranial lung lobe. A right cranial lung lobectomy was performed, and a thoracostomy tube was placed at the completion of surgery as previously described. The patient's thoracostomy tube was removed 1 day postoperatively, and the patient was discharged 2 days postoperatively. Aerobic and anaerobic cultures of tissue samples from the right cranial lung lobe did not yield any growth. The owner was contacted 12 months after discharge and reported satisfaction with the outcome, further stating that no signs of respiratory difficulty had occurred since surgery.

A 4-month-old sexually intact male Pug (dog 4) was examined for a 1-day history of dyspnea, lethargy, and inappetence. On physical examination, the dog was dyspneic, and harsh lung sounds were evident bilaterally during thoracic auscultation. A CBC indicated leukocytosis (30,030 cells/μL) characterized by neutrophilia (22,523 cells/μL) with a left shift (2,703 cells/μL) and anemia (Hct 21.4%). Thoracic radiography revealed consolidation of the left cranial lung lobe. The mainstem bronchus of this lobe was not visible on radiographic images, and a mild amount of pleural effusion was present.

An exploratory thoracotomy was performed via a left lateral intercostal approach, and a diagnosis of left cranial lung lobe torsion was confirmed as well as the presence of pleural effusion. Lobectomy of the affected lobe was performed, and a thoracostomy tube (10F) was placed at the completion of surgery as previously described. The patient was provided with supplemental oxygen (inspired oxygen fraction, 30% to 40%) for 12 hours postoperatively. The thoracostomy tube was removed the day following surgery, and the patient was discharged 2 days postoperatively.

Results of histologic examination of the left cranial lung lobe were consistent with the diagnosis of lung lobe torsion and included severe diffuse acute lobar necrosis, hemorrhage, edema, and neutrophilic and histiocytic alveolar infiltrates. The dog's owner was contacted 101 months after surgery. The owner reported satisfaction with the outcome and described seeing the dog exhibit occasional mildly labored breathing since the surgery, which had not required evaluation or treatment.

A 4-month-old neutered male Pug (dog 5) was examined for a 10-day history of lethargy and dyspnea. On evaluation, the dog was dyspneic and tachypneic (respiratory rate, 102 breaths/min), with muffled lung sounds during auscultation of the left side of the thorax. A CBC revealed leukocytosis (16,300 cells/μL) with mature neutrophilia (10,921 cells/μL). Thoracic radiography showed consolidation of the left cranial lung lobe. Transthoracic ultrasonography was also performed, with findings including consolidation of the left cranial lung lobe and lack of demonstrable blood flow in the hilar vessels during color-flow Doppler assessment.

An exploratory thoracotomy was performed via a left lateral intercostal approach, and a diagnosis of torsion of the left cranial lung lobe was confirmed. No pleural effusion was evident. A lobectomy of the affected lung lobe was performed, and a thoracostomy tube was placed as previously described. The thoracostomy tube was removed, and the patient was discharged the following day. Aerobic and anaerobic cultures of samples of the resected lung tissue did not yield any growth. Histologic examination of the resected lung tissue revealed severe diffuse subacute necrosis with marked pleural fibrovascular proliferation. The owner was contacted 124 months postoperatively and reported satisfaction with the outcome. The owner also stated that, 24 months previously, the dog had developed tracheal collapse, which was being medically managed.

A 10-month-old neutered male Pug (dog 6) was evaluated for a 6-day history of lethargy and inappetance and a 2-day history of dyspnea. On physical examination, the dog was febrile (39.8°C [103.7°F]; reference range, 37.5° to 39.2°C [99.5° to 102.5°F]) and dyspneic, with muffled lung sounds evident over the left hemithorax during auscultation. A CBC revealed leukocytosis (20,800 cells/μL) characterized by neutrophilia (16,640 cells/μL) with a left shift (416 cells/μL) as well as anemia (Hct, 25.3%). Serum biochemical analysis revealed hypoalbuminemia (2.5 g/dL) and high alkaline phosphatase activity (396 U/L; reference range, 13 to 240 U/L). Thoracic radiography showed a soft tissue mass effect in the left hemithorax and pleural effusion. Results of transthoracic ultrasonography included pleural effusion, hepatized cranial and caudal segments of the left cranial lung lobe, and an abrupt termination of the lobar bronchus of the left cranial lung lobe.

The patient received a perioperative packed RBC transfusion, IV, and underwent an exploratory thoracotomy via a left lateral intercostal approach. A diagnosis of torsion of the entire left cranial lung lobe, with pleural effusion, was confirmed. Lobectomy of the cranial and caudal subsegments of the left cranial lung lobe was performed, and a thoracostomy tube (12F) was placed as previously described. The patient received supplemental oxygen (inspired oxygen fraction, 30% to 40%) for 12 hours postoperatively. The thoracostomy tube was removed 1 day after surgery, and the dog was discharged that same day.

Aerobic and anaerobic cultures of samples of the pleural effusion were performed, and the results were negative. Cytologic analysis of the pleural effusion revealed it to be hemorrhagic. The owner was contacted 170 months postoperatively and reported satisfaction with the treatment and outcome; the owner further stated that the dog had died of causes unrelated to the surgery 2 years prior to the follow-up interview at the age of 12 years.

A 10-month-old sexually intact male Pug (dog 7) was evaluated for a 1-day history of dyspnea and lethargy. Seven months prior to this evaluation, aspiration pneumonia had been diagnosed, which resolved in 1 month after initiation of treatment. Harsh lung sounds were auscultated in all lung fields on physical examination. A CBC revealed leukocytosis (30,700 cells/μL) with mature neutrophilia (25,080 cells/μL) and anemia (Hct, 38.0%). Serum biochemical analysis revealed hypoalbuminemia (2.7 g/dL) and high alanine aminotransferase activity (1,454 U/L; reference range, 21 to 97 U/L).

Thoracic radiography showed an alveolar pattern in the cranial segment of the left cranial lung lobe, an abruptly terminating lobar bronchus of this lobe, and pleural effusion. Computed tomography revealed a vesicular gas pattern within the cranial segment of the left cranial lung lobe, a narrowed lobar bronchus of this lobe, and pleural effusion. A left lateral intercostal thoracotomy was performed. A diagnosis of torsion of the left cranial lung lobe was confirmed, as well as pleural effusion. Lobectomy of the affected lung lobe was performed, and a thoracostomy tube (8F) was placed as previously described. The patient underwent staphylectomy for treatment of elongated soft palate, bilateral vertical wedge resections for treatment of stenotic nares, and castration during the same anesthetic episode.

The patient recovered with supplemental oxygen (inspired oxygen fraction, 30% to 40%) provided for 36 hours postoperatively. The thoracostomy tube was removed 1.5 days postoperatively, and the patient was discharged 2 days after surgery. The owner was contacted 7 months after surgery and reported satisfaction with the outcome, further stating that the dog was doing well, with no apparent respiratory clinical signs since surgery.

Discussion

Lung lobe torsion is an uncommon disorder that can occur spontaneously or secondary to a predisposing condition such as chylothorax or chronic respiratory disease.1–5 The pathophysiologic mechanisms of lung lobe torsion are incompletely understood, but may involve alterations in spatial relationships in the thorax and increased lung lobe mobility, with the affected lung lobes rotating about the hilus on the long axis, causing constriction of the involved bronchus and vessels.1,2,6–8 The resultant abnormalities typically include congestion and consolidation of the affected lobar tissue; concurrent pleural effusion is common.1,2 Potential underlying causes include pneumothorax, pleural effusion secondary to another disease process, prior thoracic surgery, trauma, or parenchymal lung disease (ie, pneumonia and pulmonary edema).9 Other implicated factors include the inherent shape and mobility of the affected lung lobe as well as bronchial cartilage dysplasia in brachycephalic dogs.2,5–7,10,11

Dogs with lung lobe torsion may show signs of acute or chronic disease. Durations of clinical signs—including tachypnea, dyspnea, anorexia, vomiting, coughing (with or without hemoptysis), and weight loss (chronic disease)—ranging from 24 hours to 120 days have been reported.2,6 Thoracic radiography is generally the first diagnostic test performed, with advanced diagnostic imaging such as CT performed in many cases to confirm the diagnosis of lung lobe torsion or to rule out other disease processes. Once the patient's condition is stable, definitive treatment of lung lobe torsion includes thoracotomy and lobectomy of the affected lung lobes, whenever possible.2,6,12 The right middle and left cranial lung lobes are reported to be the most commonly affected lobes.2,6

Deep-chested large-breed dogs have been reported to have a higher incidence of lung lobe torsion, and Afghan Hounds, in particular, are overrepresented in the literature.2,5,10,13–22 Nonetheless, a wide variety of other large- and small-breed dogs have been reported with lung lobe torsion, and Pugs have been previously reported as being predisposed to spontaneous development of lung lobe torsion.1,2,5,6 The median reported ages for dogs with lung lobe torsion range from 1.5 to 7 years, depending on the breed type.2,6,11 Pugs have previously been reported to develop lung lobe torsion at a younger age, compared with age at the time of diagnosis in other breeds.2,6,11 Few prior reports6,11 have described lung lobe torsion in dogs that are < 12 months old.

In the present report, we described the treatment and outcome for a series of 7 juvenile dogs with lung lobe torsion. For this report, juvenile was defined as < 12 months old. All patients described in the present report were males, with 5 of 7 being Pugs and the remaining 2 representing breeds (Chinese Shar-Pei and Bullmastiff) not previously reported as having lung lobe torsion. The outcome was excellent; all 7 dogs survived to discharge, and 6 of 7 owners available for follow-up 7 to 170 months after discharge reported satisfaction with the treatment and no recurrence of lung lobe torsion.

The overrepresentation of males in the present report was consistent with results of previous studies.2,6 The reason for the predominance of males and the Pug breed is unclear and warrants further investigation. The most common clinical signs in the patients of this report, including dyspnea and vague signs such as inappetance and lethargy, were also similar to those of prior studies.2,6 In the present case series, all 7 dogs had leukocytosis with neutrophilia, a more frequent finding than in previous reports. A prior study2 of 22 dogs with lung lobe torsion reported that 13 patients had neutrophilia, with a regenerative left shift in 5 patients. Three patients (dogs 3, 4, and 6) described in the present report, all Pugs, had a regenerative left shift. These CBC results suggested that an inflammatory response occurs as a result of lung injury in dogs with lung lobe torsion, and we speculate that this may be more severe in juvenile patients.

Lung lobe torsion often occurs spontaneously, but in juvenile dogs, including brachycephalic dogs, bronchial cartilage dysplasia has been implicated as an etiologic factor.2,5,11 In the present report, dogs 1 and 7 had potentially predisposing conditions, with dog 1 having bullous emphysema and dog 2 having a prior history of pneumonia; however, none of the 7 patients had histologic evidence of bronchial cartilage dysplasia. Previous reports6,23 also note a lack of cartilaginous abnormalities on histologic examination of resected lung tissue, suggesting this may not be a common contributor to lung lobe torsion in juvenile dogs. Interestingly, dog 5 of the present report later developed tracheal collapse, as reported by the owner at the time of follow-up. The lack of cartilage abnormalities detected during histologic examination of surgical specimens of lung tissues in this dog may have been the result of examination of unaffected portions of the respiratory tract, owner misinterpretation of the new diagnosis, or true misdiagnosis of the reported tracheal collapse.

One dog of the present report (dog 7) had been successfully treated for pneumonia of the left and right cranial lung lobes 7 months prior to examination. Because no pulmonary disease was evident on repeated thoracic radiography, we concluded that the pneumonia had resolved after 1 month of treatment. Although a prior history of pulmonary disease may be a predisposing factor for lung lobe torsion, the microbial cultures of surgical samples of resected lung tissues did not yield any growth, again suggesting that there was no active bacterial pneumonia at the time of lung lobe torsion. Another dog (dog 1) had a bulla in the right caudal lung lobe; however, there was no evidence of pneumothorax as a predisposing cause for lung lobe torsion in this patient. It is possible that dog 1 may have initially developed pneumothorax that resolved prior to diagnostic evaluation. Nonetheless, because of the acute onset of clinical signs, we suggest that this was less likely. In view of the bulla noted at surgery, this patient may have had some type of preexisting pulmonary parenchymal disease that predisposed to torsion,1–5,9 but this was not confirmed during histologic examination. This patient (dog 1) had also undergone gastropexy as part of treatment for gastric dilation and volvulus 5 days prior to evaluation and treatment for lung lobe torsion, with no apparent complications. Any relationship between gastric dilation and volvulus and lung lobe torsion is unclear in this instance. Gastric dilation and volvulus has been associated with torsion of other organs in dogs, including the spleen and liver, although this appears to be related to laxity of ligamentous attachments within the abdomen.24,25

A diagnosis of lung lobe torsion was suspected on the basis of results of thoracic radiography in 5 dogs of the present report (dogs 2, 3, 5, 6, and 7) and was confirmed with thoracic ultrasonography and CT in these patients. In dogs 1 and 4, results of thoracic radiography were highly suggestive of a diagnosis of lung lobe torsion; therefore, exploratory thoracotomy was performed without further evaluation. The most consistent diagnostic imaging findings were consolidation of the affected lung lobe and pleural effusion, although abnormal bronchial positioning and vesicular emphysema were also noted. Previously reported4,11,16 radiographic features of lung lobe torsion include pleural effusion, lung lobe consolidation, a vesicular lung pattern, axial rotation of the carina, and a displaced trachea, all of which are consistent with the findings for our patients. It is interesting to note that in 1 patient of this series (dog 3), initial thoracic radiographs were suggestive of aspiration pneumonia, and medical management was attempted because of this and the patient's age. However, on repeated thoracic radiography 2 days later, the findings were consistent with right cranial lung lobe torsion (ie, vesicular emphysema of the affected lobe, pleural effusion, and an abrupt termination of the lobar bronchus of the affected lobe). The delay in the appearance of definitive radiographic signs, such as pleural effusion, may have been because the patient was first examined relatively early in the course of disease (ie, < 24 hours after clinical signs were initially noted). Prior reports have noted a median duration of clinical signs prior to examination of 5 days2 and 3 days.6 Diagnostic imaging studies should be repeated when results are not definitive and lung lobe torsion is suspected. Transthoracic ultrasonography, including color-flow Doppler evaluation, may be useful.19,21 Computed tomography is the modality of choice for evaluation of the thorax in human patients and is becoming increasingly common for assessment of the lungs in small animal patients.17,21 In the present case series, CT was reliable for ruling out other lung lesions prior to surgery, and either CT or ultrasonography correctly identified torsion of the involved lung lobe in each case.

Pleural effusion, which may not be detectable on diagnostic imaging in patients with acute lung lobe torsion,16 occurred in 5 (dogs 2, 3, 4, 6, and 7) of 7 dogs in this study. It is a common clinical finding in dogs with lung lobe torsion and may be a predisposing factor.14 Conversely, it has also been theorized that lung lobe torsion causes pleural effusion because of venous congestion and inflammation associated with torsion of the affected lobes.6 Pleural effusion resolved after excision of the affected lobe in the 5 dogs with pleural effusion in this study, suggesting that lung lobe torsion was the cause of the effusion in those patients.

The Bullmastiff (dog 1) and the Chinese Shar-Pei (dog 2) in the present study each had torsion of the right middle lung lobe, an apparent predilection previously reported in non-Pug dogs.1,2,14 The long, narrow shape of this lobe and its relative mobility may predispose to torsion.2,5,7,23 Four (dogs 4, 5, 6, 7) of the 5 Pugs in this study had torsion of the left cranial lung lobe, previously documented as the most commonly affected lung lobe in Pugs.5,6,16,17,23,26 The remaining Pug (dog 3) had torsion in the right cranial lung lobe, which has also been reported to be affected, although much less frequently.6,17 The reason for an apparent predilection for left cranial lung lobe torsion in Pugs is unknown. Previous authors5,14 have hypothesized that both portions of the left cranial lung lobe are affected in combination because they share a common hilus. It has also been postulated that because the left cranial lung lobe has a more pointed shape, as for the right middle lung lobe in large, deep-chested dogs, it may be more likely to rotate around the hilus.23

All dogs of the present case series were successfully managed with surgical intervention by means of a lateral intercostal thoracotomy and lung lobectomy. In all cases, surgery was performed, as previously recommended, once the patient's condition was deemed stable and a diagnosis of lung lobe torsion was suspected.6,22 All dogs survived surgery, with no apparent intraoperative complications. With no definitive predisposing cause for the lung lobe torsion in the dogs in this study, recurrence of lung lobe torsion in a different lung lobe was considered a possibility, especially considering the young age of the dogs. Recurrence of lung lobe torsion in different lung lobes has been reported in a Doberman Pinscher, 3 Afghan Hounds, and a Pug.7,14,26 However, long-term outcome information (7 to 170 months) did not reveal any apparent recurrence of lung lobe torsion or related complications, such as pleural effusion, in our patients.

Pugs, especially young adult males, have been reported5,6 to be predisposed to spontaneous lung lobe torsion, although the etiology is unknown. In a case series,6 6 of 7 pugs had no history of predisposing conditions; those results are similar to those of the present report, in which 4 of 5 Pugs had no known predisposing factors. Additionally, a regenerative left shift on a CBC has been more consistently reported for Pugs versus other breeds.5,6,23,26 In this report, Pugs were the only 3 dogs to have a regenerative left shift observed on CBC. Anemia was also present in 6 of 7 dogs of the present report, 2 of which received packed RBC transfusions perioperatively. Anemia has also been reported6,26 previously in several dogs with lung lobe torsion. The cause of anemia in these patients is unknown, but may be the result of congestion and alveolar hemorrhage in the affected lung lobe as well as hemorrhage during pleural effusion.

The prognosis after lung lobectomy for dogs with lung lobe torsion is affected by the presence of concurrent conditions such as neoplasia or infection and complications of surgery or anesthesia.2,6 Prognosis is fair to guarded for patients with spontaneous lung lobe torsion or with lung lobe torsion secondary to thoracic trauma, but can be poor for those that have lung lobe torsion associated with chylothorax.2 Breed has been reported to be a predictor of a negative outcome in Afghan Hounds and Borzois, whereas the Pug breed has been associated with a better prognosis for survival.2,6 Of the previously reported cases of lung lobe torsion in Pugs in which outcome was reported, most had a favorable outcome.2,5,6,11,23,26 The short-term survival rate (ie, to hospital discharge) in the present series of 7 juvenile dogs was 100%. Six of 7 owners available for long-term follow-up reported that they were satisfied with the surgical outcome in the present series. One Pug was described as having a mild amount of increased respiratory difficulty; however, it is unclear whether this was related to surgery or to another cause, such as brachycephalic airway syndrome. Survival rates for dogs with lung lobe torsion have previously been reported to be 48% to 61%.2,6 However, results of the present report suggested that juvenile dogs evaluated for this disorder may have better outcomes.

Although we are not aware of prior reports of lung lobe torsion in juvenile dogs, only 7 dogs were included in the present series, and 5 of 7 patients were Pugs. As such, further investigation of lung lobe torsion in juvenile dogs to fully evaluate the incidence, outcome, and prognosis in dogs with this disease is warranted. Young male Pugs may be predisposed to the development of lung lobe torsion; however, lung lobe torsion can occur in juvenile dogs of other breeds. Clinicians should be aware of the possibility of a diagnosis of lung lobe torsion when evaluating immature male dogs with clinical signs related to the respiratory system, including those with vague signs, to avoid undue delays in treatment.

Footnotes

a.

TA30 V3 TA Auto Suture Vascular Stapler with DST Series Technology, Covidien, Mansfield, Mass.

b.

PDS II, Johnson & Johnson, Ethicon, Somerville, NJ.

c.

Monocryl, Johnson & Johnson, Ethicon, Somerville, NJ.

d.

Argyle trocar thoracic catheter, Kendall, Tyco Healthcare, Mansfield, Mass.

e.

Ethilon, Johnson & Johnson, Ethicon, Somerville, NJ.

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