Pneumothorax

From Dog
Pneumotharax in the great Dane involved in a motor-vehicle accident[1]

Pneumothorax is a pathological condition in which air accumulates within the thoracic cavity[2].

This disease must be distinguished from the presence of fluid (i.e. hemothorax, chylothorax or pyothorax), some of which may occur contiguous with pneumothorax.

This condition may develop insidiously or as an acute emergency case, depending on the underlying etiology.

Most dogs with pneumothorax present with acute respiratory distress and other symptoms may be correlated with underlying pathologies unrelated to pneumothorax.

In dogs, there are many causes, including:

  • Chest Trauma - resulting in flail chest, or open abdominal wounds with diaphragmatic rupture
  • Post-anaesthesia[3]
  • Neoplasia - causing penetration of the trachea, bronchi or bronchioles due to growth of neoplastic tissue
  • Chronic respiratory disease - resulting in pulmonary bulla rupture
  • Idiopathic spontaneous pneumothorax
  • Pulmonary thromboembolism - usually secondary to metabolic disease, e.g. hyperadrenocorticism)[4]
  • Verminous pneumothorax due to parasites
- Dirofilaria immitis - spontaneous pneumothorax due to bulla formation and rupture
- Spirometra erinacei - plerocercoid penetration of bronchioles
- Echinococcus spp - cysticercoid penetration of bronchioles
- Aelurostrongylus spp and other lungworms such as Strongyloides spp, Paragonimus spp, Filaroides osleri, Angiostrongylus vasorum, Eucoleus aerophilus, Crenosoma vulpis, Paragonimus spp and Lagochilascaris spp
- Mycobacterium bovis[5]
  • Post-operative complications from thoracic surgery
  • Foreign body abscess - e.g. migrating grass awn[6]
  • Congenital lobar emphysema[7]

Although a full workup of each case is required, with minimum hematological assessment, critical cases require stabilization with emergency IV fluids and oxygen therapy.

Diagnosis of pneumothorax is readily ascertained with radiographic and ultrasonographic images which may provide supporting evidence of air surrounding the pulmonary parenchyma, being careful to distinguish between free pleural air and intrapulmonary air.

In cases of traumatic pneumothorax, closure of the primary wound is required with either surgical dressing or bandaging, or via suturing.

Indwelling thoracic drainage tube suction is required to maintain negative pulmonary pressure in the affected lung for normal lung inflammation. If pneumothorax fails to resolve after 5 days, an exploratory thoracotomy is indicated.

Isolated pulmonary lesions causing pneumothorax are an indication for partial lobectomy. treatment of underlying parasitism is essential in verminous pneumothorax.

In most cases, unilobar pneumothorax occurs, allowing normal respiratory function by the unaffected lung.

Oxygen therapy is essential to minimize the risk of hypercapnea.

References

  1. My San Antonio
  2. Pawloski DR & Broaddus KD (2010) Pneumothorax: a review. J Am Anim Hosp Assoc 46(6):385-397
  3. Harvey L et al (2010) Fatal post-anaesthetic pneumothorax in a dog. Vet Anaesth Analg 37(1):83-84
  4. Sobel KE & Williams JE (2009) Pneumothorax secondary to pulmonary thromboembolism in a dog. J Vet Emerg Crit Care (San Antonio) 19(1):120-126
  5. Gay G et al (2000) Pulmonary Mycobacterium bovis infection in a dog. N Z Vet J 48(3):78-81
  6. Hopper BJ et al (2004) Imaging diagnosis: pneumothorax and focal peritonitis in a dog due to migration of an inhaled grass awn. Vet Radiol Ultrasound 45(2):136-138
  7. Gopalakrishnan G & Stevenson GW (2007) Congenital lobar emphysema and tension pneumothorax in a dog. J Vet Diagn Invest 19(3):322-325