Management of pyothorax

Feline pyothorax - new insights into an old problem: part 2. Treatment recommendations and prophylaxis

Until recently, pyothorax in the cat has been generally considered to have a poor prognosis. However, it has become clear that most cats that survive the first 48 h following presentation can be successfully treated with aggressive medical management. In this second part of a two-part review, logical guidelines for the management of the disease are discussed, with particular emphasis on antimicrobial selection. Patient stabilisation and supportive care, techniques for pleural space drainage and lavage and indications for surgery are reviewed.

Successful medical treatment of 15 dogs with pyothorax

OBJECTIVES

To review the success of non-surgical management, which included antibiotics and a single thoracocentesis, in 15 dogs presenting with pyothorax.

METHODS

Sixteen dogs were selected retrospectively from case files at the Veterinary Cardiorespiratory Centre.

RESULTS

One dog was diagnosed with a mass suspected to be a pulmonary abscess on ultrasound examination and was referred for surgery. Fifteen dogs were treated medically. Springer spaniels were the most commonly presented breed (six cases) followed by Labrador retrievers (three cases). Under sedation or general anaesthesia, thoracocentesis was performed unilaterally and as much purulent effusion as possible was removed. Lavage of the thorax was not undertaken. In most dogs, antibiotic treatment was ampicillin at a mean dose of 33 mg/kg administered three times daily and 25 mg/kg metronidazole administered twice daily. Antibiotics were provided for a minimum of six weeks. All dogs recovered completely and did not show relapse on prolonged follow-up. This included one dog, which had very widespread pleural adhesions and minimal effusion.

CLINICAL SIGNIFICANCE

In dogs that do not have evidence of pulmonary masses or consolidations and no evidence of granular pleural effusion, medical therapy may be curative even in chronic cases of pyothorax with pleural adhesions.

Pyothorax in a cat managed by intrathoracic debridement and postoperative ventilatory support

: A domestic-longhair cat presented due to lethargy, dyspnoea and hypersalivation. Radiographic examination revealed a bilateral pleural effusion, which was diagnosed as pyothorax based on cytological examination. Ultrasonographic examination revealed extensive loculations within the thoracic cavity. Exploratory sternotomy, under general anaesthesia, allowed the removal of approximately 100 ml of purulent fluid and debridement of a partially walled-off abscess and necrotic material from the pleural cavity. Postoperative positive-pressure ventilation was required due to severe respiratory depression. Intensive postoperative care, including intensive continuous monitoring, thoracostomy tube drainage and lavage of the pleural cavity and oesophagostomy tube feeding, was performed. Complete resolution of clinical signs had occurred by 15 days postoperatively. Clinical or radiographic abnormalities were not detected at a follow-up examination one year after surgery.

Risk factors, prognostic indicators, and outcome of pyothorax in cats: 80 cases (1986-1999)

OBJECTIVE

To identify risk factors associated with development of pyothorax in cats, assess survival rates for cats that are treated, determine prognostic indicators, and determine recurrence rates.

DESIGN

Retrospective study.

ANIMALS

80 cats with pyothorax and 212 control cats.

PROCEDURE

History; month of evaluation; physical examination findings; results of hematologic, serum biochemical, and retrovirus testing; radiographic findings; outcome; recurrence rate; and necropsy findings were recorded. For control cats, age, sex, breed, indoor versus outdoor status, vaccination history, and single- versus multi-cat household status were recorded.

RESULTS

Cats from multi-cat households were 3.8 times as likely (95% confidence interval, 1.9 to 8.2) to develop pyothorax, compared with cats from single-cat households. Indoor or outdoor status was not a risk factor. Cats with pyothorax were significantly younger (mean, 3.83 +/- 3.43 years) than controls (mean, 5.62 +/- 5.27 years). Nonsurvivors had significantly lower heart rates than survivors. Hypersalivation was significantly more common in nonsurvivors (11/39; 26.8%) than survivors (1/39; 3%). Overall, 48.8% (39/80) of cats survived. When cats that were euthanatized without treatment were excluded from analyses, the survival rate was 66.1% (39/59). Pyothorax recurred in 1 of 17 cats for which follow-up information was obtained.

CONCLUSIONS AND CLINICAL RELEVANCE

Cats with pyothorax that received treatment had a fair to good prognosis, with low recurrence rates in survivors. Hypersalivation and low heart rate were associated with worse clinical outcome. Cats with pyothorax were likely to come from multi-cat households.

Medical and surgical treatment of pyothorax in dogs: 26 cases (1991-2001)

OBJECTIVE

To compare outcomes of dogs with pyothorax treated medically versus surgically and to identify prognostic indicators for dogs with pyothorax.

DESIGN

Retrospective study.

ANIMALS

26 dogs.

PROCEDURE

Medical records were reviewed to obtain information regarding signalment, results of physical and laboratory evaluations at the time of initial examination, results of bacterial culture of pleural fluid, radiographic abnormalities, treatment (surgical vs medical), complications, whether the disease recurred, disease-free interval, survival time, and cause of death.

RESULTS

Calculated proportions of dogs free from disease 1 year after treatment were 25 and 78%, respectively, for dogs treated medically and surgically. Treatment was 5.4 times as likely to fail in dogs treated medically as in dogs treated surgically. Two regression models relating treatment group (medical vs surgical) to disease-free interval were found to be significant. The first contained terms for medical treatment and isolation of Actinomyces spp from pleural fluid; the second contained terms for medical treatment and radiographic detection of mediastinal or pulmonary lesions at the time of initial examination.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that surgical treatment is associated with a better outcome than medical treatment in dogs with pyothorax. In addition, surgery should be considered if radiographic evidence of mediastinal or pulmonary lesions is detected or if Actinomyces spp is isolated from the pleural fluid.

Catheter drainage of pleural fluid collections and pneumothorax

A technique for virtually atraumatic placement of small size chest catheters for suction drainage of pleural effusions and pneumothorax in the dog and cat is described. Thirty-nine dogs and two cats were treated for pyothorax (10 cases), hydrothorax (eight), chylothorax (three), haemothorax (three), haemothorax/ pneumothorax (three) and pneumothorax (14). In all 41 cases, thin or viscous fluid and/or air were efficiently drained. The mean period of drainage was four days (range, 0.5 to 18 days). The average amount of fluid removed from each patient in 24 hours was 530 ml in pyothorax cases (range, 140 to 1100 ml) and 1300 ml in the other cases (range, 20 to 5000 ml). In 40 cases there were no complications related to the procedure. One dog with severe pleural adhesions was euthanased because of lung perforation and pneumothorax secondary to misplacement of the catheter.