Pneumonectomy in Dogs and Cats

Pneumonectomy in Dogs and Cats

Outcome after pneumonectomy in 17 dogs and 10 cats: A Veterinary Society of Surgical Oncology Retrospective Study

Wavreille V1, Boston SE1, Souza C1, Ham K2, Chanoit G3, Rossetti D4, Takacs J5, Milner R1

1Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL

2Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Ohio State University, Columbus, OH

3School of Veterinary Sciences & Bristol CardioVascular, University of Bristol, University of Bristol, Langford, UK

4Small Animal Surgery Department, Centre Hospitalier Vétérinaire Frégis, Arcueil, France

5Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA

ABSTRACT

Objective: (1) To report signalment and outcome data from dogs and cats undergoing pneumonectomy; and (2) to document presenting clinical signs, surgical complications, histologic diagnosis, and postoperative complications.

Study Design: Retrospective, multicenter study.

Sample Population: Seventeen dogs and ten cats.

Methods: Signalment, clinical signs, side affected, surgical data, pre-operative diagnostic tests (including complete blood count, serum biochemistry, cytological diagnosis, chest radiographs and computed tomography), histopathologic diagnosis, surgical complications, adjunctive therapy, and date and cause of death were collected from records of dogs and cats that underwent pneumonectomy. Survival estimates, and complication were assessed.

Results: Seventeen patients had a left-sided pneumonectomy performed (12 dogs and 5 cats) and ten patients had a right-sided pneumonectomy (5 dogs and 5 cats). Fourteen patients were diagnosed with neoplasia (52%). The overall incidences of complications were 76% and 80% for dogs and cats, respectively. The incidences of major complications were 41% and 50% for dogs and cats, respectively. Respiratory complications (persistent pleural effusion, oxygen dependence, persistent increased respiratory rate or coughing) were the most commonly reported complications. No patients died or were euthanized intraoperatively or within the first 24 hours post operatively. However, one dog (6%) and 2 cats (20%) died or were euthanized in the first 2 weeks post-operatively.

Conclusion: Based on this small cohort, right and left pneumonectomy can be performed with a relatively low perioperative mortality rate in dogs and cats, with some animals experiencing prolonged survival.

INTRODUCTION

Pneumonectomy, defined as surgical excision of the entire left or right lung, is an uncommonly performed procedure in veterinary surgery. A small number of reports have described outcome after pneumonectomy in companion animals1-4 and two of these reports were not directly focused on the clinical outcome: one study3 assessed the impact of the procedure on the right-side of the heart and the second report was focused on the anesthesia and perioperative management of a pneumonectomized dog.4 Factors associated with perioperative mortality, complications or successful outcome remain largely unknown in dogs and cats.

This procedure has also been reported in clinically normal research dogs. Because of the differential in lung volume between the right and left lung, it has been reported that removal of more than 60% of the lung volume can lead to potentially fatal pulmonary hypertension.5,6 A left-sided pneumonectomy is considered to be better tolerated as the left lung represent 42% of the lung volume.6 It has also been suggested that in some slow and progressive disease processes, a right pneumonectomy is a possible treatment option because of compensation of the remaining functional lung.2,6 Experimental studies performed in healthy dogs showed increased pulmonary vascular resistance and right ventricular hypertrophy after left pneumonectomy but pulmonary arterial pressure remained within the normal reference range.7,8 There is also evidence of compensation via more efficient oxygen transport across the alveoli after pneumonectomy exceeding 50% of the lung volume. This has been explained by three principal mechanisms: recruitment of physiologic reserves of diffusing capacity, remodeling of the existing alveolar-capillary network, and new or regenerative alveolar-capillary growth.8-12

In contrast to veterinary medicine, outcome following pneumonectomy in humans is reported in numerous studies.13-15 It is associated with a high morbidity and mortality rate in people13. Three recent studies reported a 30 day mortality rate of 5.1%13, 14 and 5.7%15 in pneumonectomy patients operated for cancer. Rivera et al reported a postoperative in-hospital mortality rate of 22.1% for pneumonectomy patients treated for benign disease.13 In a recent review,16 morbidity rates between 25 to 60% were reported. The primary indication for pneumonectomy in human medicine is the treatment of lung cancer.13 In the 14 cases in the veterinary literature, seven were treated for neoplasia.1-4

Because pneumonectomy is uncommonly performed in veterinary medicine, information about the procedure, success-rate and complications are lacking.

Our aims in this retrospective, multi-institutional Veterinary Society of Surgical Oncology (VSSO) study were: (1) to report signalment and outcome data from a relatively large number of dogs and cats undergoing pneumonectomy; and (2) to document presenting clinical signs, histologic diagnosis, potential prognostic factors, and complications. We hypothesized that right and left pneumonectomies are not associated with a poor outcome.

MATERIAL AND METHODS

This study was approved by the Veterinary Society of Surgical Oncology (VSSO) research committee and was initiated by requesting case submissions from VSSO members through the VSSO list-serve. Medical records from contributing institutions were searched to identify dogs and cats that had had pneumonectomy. Inclusion criteria for this study were dogs and cats underwent pneumonectomy between 2004 and 2014 for neoplastic and non-neoplastic causes. Cases were excluded if there was not a histopathological diagnosis of the underlying disease and if a subtotal pneumonectomy was performed, defined as preservation of one or more lung lobes on the affected side. Data retrieved included: sex, breed, age, weight, clinical signs, side affected, surgical data (including surgical approach, method for lobectomy, and whether or not tracheobronchial lymph nodes were removed), preoperative diagnostic tests (including complete blood count, serum biochemistry, cytologic diagnosis, thoracic radiographs and computed tomography (CT), histopathologic diagnosis, perioperative and postoperative surgical complications, reason for performing a pneumonectomy if not planned prior to surgery, adjunctive therapy if any, and date and cause of death. Animals were classified by the underlying disease as having neoplastic or non-neoplastic disease as the reason for pneumonectomy. Complications were classified in 2 groups: major and minor complications. They were also evaluated as intraoperative and post-operative complications. Major intraoperative complications were defined as complications necessitating direct surgical management or cardiopulmonary resuscitation. Major complications were defined as any complication that was life threatening (serious complications that could cause death without urgent support), resulted in a second surgical procedure, death or euthanasia. Minor complications were defined as self-limiting or medically managed complications. Complications were also defined by the time-frame in which they occurred, including intra-operative complications, and (within 14 days) and late (greater than 14 days) post-operative complications. The overall incidence, severity and time frame of complications was reported.

Statistical analysis

Statistical software (GraphPad Prism version 5.00 for Mac OS X, GraphPad Software, San Diego California USA, www.graphpad.com) was used to generate descriptive statistics and median survival time (MST). Survival time was defined as the time between pneumonectomy and death. The cause of death was classified as either disease‐related or non-disease related. Patients with an unknown cause of death were presumed to have died from disease‐related causes. Patients that died because of non‐disease related causes or were lost to follow up were censored for the survival analysis. Kaplan–Meier survival plots as well as mean survival times and MSTs were calculated.

RESULTS

Signalment

Seventeen dogs and ten cats met the inclusion criteria for this study (9 institutions participated to this study). The median age of the dogs was 86 months (range, 3-164 months). There were seven male and ten female dogs. The median body weight of the dogs was 22.6 kg [range, 0.8–52.4 kg] of various breeds (Table 1).

Of the ten cats, the median age was 84 months [range, 6–181 months]. There were 7 male and 3 female cats. Domestic short hair cats were the most common breed represented (n=7). The median weight was 4.5 kg [range, 2.2–6.5 kg] (Table 2).

Presenting complaint

Most of the patients (21/27, 78%) presented with respiratory signs such as difficulty breathing and/or coughing. All of the cats and 11 dogs presented for respiratory signs. Five dogs (19%) were referred for non-specific clinical signs such as lethargy, inappetence and exercise intolerance. For one dog, the lung mass was an incidental finding, diagnosed on thoracic radiographs during staging for a cutaneous melanoma.

Pre-operative diagnostic tests

All patients had full serum biochemistry and complete blood count performed prior to surgery. In one case, the results were not available for review. Leukocytosis was reported in nine cases, with five of these cases (5/13, 38%) ultimately diagnosed with non-neoplastic disease and four of these cases (4/14, 29%) diagnosed with neoplasia. Albumin was decreased in seven cases (7/27, 26%), four of these cases were diagnosed with non-neoplastic disease (4/13, 31%).

Thoracic radiographs were performed in 25 (93%) cases. Computed tomography (CT) was performed for 15 cases (56%). Among these 15 cases, lesions involving the entire right or left lung lobe were described for 7 cases (47%). For the remaining 8 cases, extension of the lesion was limited to a part of the lung (left cranial lung lobe, left caudal lung lobe or right cranial and middle lung lobes) but for 3 cases (cases 6, 17 Table 1 and case 1, Table 2), the mass was described in close association with the hilus. For one case, a foreign body was identified (case 16, Table 1). Compression of the right lung by a thoracic wall mass causing increased density of the right lung lobes was described for one case (case 14, Table 1) on CT. Between 2004 and 2009, a third of the patients (3/9) had a CT prior surgery, whereas 2/3 of patients (12/18) had a preoperative CT between 2009 and 2014.

Pneumonectomy

Seventeen patients had a left-sided pneumonectomy performed and ten patients had a right-sided pneumonectomy. A lateral thoracotomy was employed in 22 patients at the 4th to 6th intercostal space. The intercostal space was not recorded in one patient that had a lateral thoracotomy. A median sternotomy was performed in five patients, for left (n=4) or right (n=1) pneumonectomy. A thoracic wall resection (6th and 7th ribs) combined with a right-sided pneumonectomy was performed in one case (case 14, Table 1). One case was a completion pneumonectomy for a pulmonary abscess as the right cranial lung lobe had been partially removed for treatment of a spontaneous pneumothorax 2 months previously (case 17, Table 1). Hemostasis and pneumostasis were achieved with a surgical stapler alone in 16 cases (56%) (thoraco-abdominal stapling device n=15, gastrointestinal anastomosis device n=1). A hand suture ligation technique was used in four cases. A combination of surgical stapler and hand suture ligation was used in three cases and a combination of a surgical stapler and hemoclips was used in one case. Hemoclips alone were used for one case (case 3, Table 2). For 2 cases, the surgical technique was not recorded.

For eight cases, the pneumonectomy was unplanned. The reported reason for performing an unplanned pneumonectomy was unexpected consolidation of the other lung lobes (case 13 and 9, Table 1), unexpected diffuse disease (expanding to the entire right or left lung) (case 2 Table 1 and case 1, Table 2), presence of adhesions between the mass/affected lung lobes and the other lung lobes (case 6, 16 and 17, Table 1), or pulmonary involvement of a chest wall mass (case 14, Table 1).

Tracheobronchial lymph nodes were removed and submitted for histopathology in six cases (22%, 4 dogs and 2 cats) and sampled via intraoperative fine needle aspiration for cytology in one case (4%, one cat). This cytology was consistent with reactive lymphoid hyperplasia. Histopathology reports were available for 2 dogs and revealed sinus histiocytosis with multifocal pyogranulomatous inflammation for one dog diagnosed with a chronic hemorragic pleuritis (case 16, Table 1) and metastasis of pulmonary carcinoma for the other dog (case 15, Table 1).

Surgical complications and outcome

Dogs – Intraoperative complications

Intraoperative complications were recorded in 5 cases (29%). Two cases had major complications (12%) and included hemorrhage (n=1) and cardiac arrest (n=1). Minor complications occurred in 3 dogs (18%) and included: hypotension (n=2) and hypothermia (n=2). One case developed both hypothermia and hypotension. The case that developed hemorrhage received a blood transfusion during the procedure. The patient that developed cardiac arrest was resuscitated successfully. Intra-operative death was not reported.

Dogs – Early Postoperative Complications (0-14 days)

Early postoperative complications were recorded in 12 cases (71%). Four cases had major complications (24%) and included persistent pleural effusion (n=2), oxygen dependence (n=2) and cardiac arrest (n=1). Minor complications occurred in 12 cases (71%) and included: anemia (n=3), anorexia (n=2), regurgitation/vomiting (n=2), coughing (n=2), hypertension (n=1), hypotension (n=1), hypothermia (n=1), tachycardia (n=1), second degree atrioventricular block (n=1), phlebitis (n=1), nausea (n=1), hypoglycemia (n=1), incisional infection (n=1), persistent increased respiratory rate (n=1), infection pressure sores right front leg (n=1), and suspected immune mediated vasculitis (n=1). The dog that developed cardiac arrest at day 10 post operatively died (case c1, Table 1) in the hospital. This young dog (3 months old) was diagnosed with a marked, severe, bronchopneumonia with pulmonary necrosis and abscess formation. The bacterial culture revealed Bortella bronchiseptica.

Dogs – Late Postoperative Complications (>14 days)

Late postoperative complications were recorded in 6 cases (38%). Three cases had major complications (19%) and included persistent pleural effusion (n=1), degradation of the clinical status leading to euthanasia due to persistent pleural effusion and suspected carcinomatosis (n=1), and draining tract on the cranial aspect of the sternum (n=1) that led to surgical removal of a sternal sequestrum. Minor complications occurred in 3 cases (19%) and included: coughing (n=2), vomiting (n=1) and exercise intolerance (n=1). One case developed vomiting and coughing.

Overall, complications were recorded in 13 dogs (76%). Seven cases had major complications (41%) and 12 cases had minor complications (71%). Three dogs with a right pneumonectomy (60%) and 4 dogs with a left pneumonectomy (33%) had major complications.