Diseases of the pleural space Flashcards
How common is pleural disease a cause of dyspnoea (SA and horses?
SA - relatively common
Horses - rare
What causes pleural disease?
wide variety of disease, generally result in the development of either fluid or air in the pleural space.
CS - pleural disease -7
- most consistent finding is dyspnoea
- Pyreixa with septic effusion
- hypoproteinaemia signs - chronic diarrhoea
- trauma - pneumothorax, haemothorax, diaphragmatic hernia
- bleeding - coagulopathy
- other signs - neoplasia
PE findings -pleural disease
- increased RR and RE, shallow
- orthopnoea
- dullness on percussion of ventral thorax (fluid)
- resonance on percussion of dorsal thorax (pneumothorax)
- displacement of apex beat of heart (mass)
- evidence of concurrent abdominal abnormalities
- other evidence of RCHF
What should you hear if you percuss a normal lung field?
Resonance (dullness indicates a problem such as fluid)
What does an ‘empty’ cranial abdomen with dyspnoea suggest?
diaphragmatic hernia
What does concurrent ascites with dyspnoea suggest
bi-cavity effusions imply a more generalised disease
How can the presence of a pleural effusion be confirmed?
- imaging (radiography or ultrasound - less manipulation so may be better for severe dyspnoea cases). THEN once confirmed, perform thoracocentesis
Indications - thoracocentesis - 3
- moderate volume pleural effusion
- diagnostic
- therapeutic
3 important technical aspects of thoracocentesis
- maintain a closed system
- maintain sterility
- cranial OR caudal to the heart.
How can you maintain a closed system with thoracocentesis?
Butterfly needle attached to an extension set with either a syringe or a 3-way tap attached to this.
How to you perform thoracocentesis in horses?
reliance on valves and gravity
How do you analyse pleural fluid?
EDTA tubes - cytology
Plain tube - culture and biochemical analysis
What do you analyse in pleural fluid? 6
- cytology, TCC and differential count
- TPC
- bacterial culture and sensitivity
- gram stain
- Tg and cholesterol levels (suspect chyle)
- NT-proBNP (cats to distinguish cardiogenic or non-cardiogenic effusions)
How are effusions classified? 2
Based on TNCC and TP
What is transudate in the pleural space called?
Hydrothorax
What is exudate in the pleural space called?
Pyothorax
What are transudates typically caused by?
hypoproteinaemia
How can exudates be classified?
Always inflammatory, determine whether septic or non-septic
List 5 causes of modified transudates?
- venous obstruction
- RCHF
- neoplasia
- lung lobe torsion
- diaphragmatic hernia
Why does chylothorax arise?
as a consequence of damage to the thoracic duct –> intestinal lymph drains into the thoracic cavity
Outline chylothorax sample
- grossly milky appearance
- high in Tg (fluid Tg > plasma Tg)
- TNCC and S.G. similar to modified transudate but cells are predominantly lymphocytes.
What does haemothorax usually indicate? 2
coagulopathy, trauma or neoplasia
Does a haemothorax sample usually clot?
NO because it is usually defibrinated since it has been in the cavity for some time. This does not usually indicate a coagulopathy.
Outline protein and cell content of a haemothorax sample.
usually similar to normal blood
Causes - pneumothorax
usually spontaneous or secondary to trauma
Where can air leak from to cause a pneumothorax?
lung, mediastinum or through the thoracic wall.
T/f: small to moderate volume pneumothorax is common after RTA
True
What further diagnostic tests might you want to do once you have determined there is a pleural effusion?
- BLOOD TESTS - hypoproteinaemia (renal, hepatic, GIT), hyperglobulinaemia (FIP in cats), neutrophilia (inflammation), cytopaenias (BM disease)
- SEROLOGY - FELV, FIV (association with mediastinal lymphoma), FIP, coronavirus (poor diagnostic value), clotting time (APTT and OSPT).
Why should you perform radiography after as well as before thoracocentesis?
may reveal changes obscured by fluid (e.g. soft tissue effusion of the lung parenchyma).
What may ultrasound allow you to identify when there is fluid in the thorax?
- mediastinal massess
- pulmonary masses, abscesses etc
What further sophisticated diagnostic measures can be employed? 3
- EXPLORATORY THORACOTOMY –> pleural biopsy and detection of abnormalities not detectable by any other means
- THORACOSCOPY- minimally invasive surgical technique available in some centres
- CT SCAN
How is pleural disease best treated?
Most effective method of management is to manage the underlying disease. Sometimes pleural disease needs to be managed as though it were the primary disease (pleuropnuemonia in horses, pyothorax in small animals, chylothorax in small animals and pneumothorax in small animals)
How is lube lobe torsion managed generally?
surgically
Pathogenesis - equine pleuropneumopnia
Mixed bacterial infection of organisms that are often the normal flora of the pharynx:
- beta-haemolytic streptococci
- E.coli
- Klebsiella spp.
- Pasteurella spp.
- Bordatella spp.
- Bacteroides spp (anaerobic)
What are the 2 main processes that lead to equine pleuropneumonia?
- suppression of pulmonary defence mechanisms (i.e MCE and macrophages)
- inhalation of bacteria with subsequent extension into the pleural space (–> cranioventral distribution)
What may suppress pulmonary defence mechanisms?
- transport over long distances in planes as horses heads are tied up (abnormal for them)
- strenuous exercise
- sx and anaesthesia
- recent respiratory viral infection
- recent stressful event
What do equine pleuropneumonia signs depend on?
- amount of fluid, pathogen and extent of parenchymal disease
- chronicity
Acute CS - equine pleuropneumonia
- pyrexia
- lethargy
- slight nasal discharge
- shallow breathing
- guarded cough
- painful stilted gait
- pleurodynia (pleuritic pain in the chest)
Late acute CS - equine pleuropneumonia
- nostril flare
- tachycardia
- increased jugular pulse height (to 1/3 up the neck)
- toxic MM
- guarded, soft, moist cough
- foetid nasal discharge
Chronic CS - equine pleuropneumonia
- intermittent fever
- weight loss
- ventral limb oedema
Dx - equine pleuropneumonia - 8
- hx
- CS
- PE
- Haematology
- ultrasonography
- thoracocentesis
- (radiography)
- transtracheal aspirate
Auscultation findings - equine pleuropneumonia - 6
- not consistent, often not useful
- absent airway sounds ventrally
- dorsal sounds normal or abnormal
- fluid in the trachea
- pleural friction rubs?
- cardiac sounds radiate?
Percussion findings - equine pleuropneumonia
ventral dullness
What signs would be present on thoracic ultrasound in equine pleuropneumonia?
- PLEURAL FLUID - volume, location, character (echogenicity increases with cell count whilst gas bubbles suggest anaerobes)
- LUNGS - consolidation and abscessation
What signs would be present on thoracic radiography in equine pleuropneumonia?
- ACUTE STAGE - pleural effusion obscures lung pathology
- CHRONIC STAGE - identification of consolidation, abscesses and pneumothorax.
What are the 2 most important diagnostic methods for equine pleuropneumonia?
- TRANSTRAHCEAL ASPIRATE: important to obtain a sample that is not contaminated by the URT
- THORACOCENTESIS - physical characteristics, cytology and bacteriology
Aims - equine pleuropneumonia treatment 4
- remove excess pleural fluid
- AB therapy
- anti-inflammatory and analgesic therapy
- supportive care
What does drainage of the thoracic cavity allow? 4
- removal of restrictive forces
- re-expansion of the pulmonary tissue
- improves pulmonary clearance
- removes debris, organisms, inflammatory mediators and toxins
How can the thoracic cavity be drained?
indwelling cannula or via repeated intermittent drainage
What is pleuroscopy?
a camera is inserted in between the 2 pleural layers. allows visualisation, and excellent drainage along with break down of adhesions.
Treatment - equine pleuropneumonia - 3
- ANTI-INFLAMMATORY AND ANALGESIC THERAPY - opiates and NSAIDs
- ABs - broad spectrum initially, then based on culture and sensitivity, needs to cover aerobes and anaerobes
- SUPPORTIVE CARE - oxygen, bronchodilators, fluids, nutrition
Treatment - chronic stages of equine pleuropneumonia
pleural and pulmonary abscesses may be amenable to drainage, via resection of intercostal mm and/or rib. Providing they are walled off from the rest of the pleural cavity.
Prognosis - equine pleuropneumonia
- MILD, DIAGNOSED EARLY - may return to previous career with early and aggressive therapy, survival of 50-100%
- SEVERE - can be salvaged for breeding with months of AB treatment and surgery.
Complications - equine pleuropneumonia -7
- thrombophlebitis
- laminitis
- diarrhoea
- pulmonary abscess
- pleural adhesions
- bronchopleural fistula
- constrictive pericarditis
What is the principle of pyothorax therapy in small animals?
= removal of infective material, isolation and removal of cause and resolution of infection. Various ways to achieve this. A less aggressive therapy risks there being a nidus of infection remaining and the problem recurring/.
Outline 3 methods of treating pyothorax in small animals
- thoracocentesis followed by systemic ABs
- implantation of indwelling drains to facilitate pleural lavage, leave in situ for 5-7 days, systemic AB therapy
- exploratory thoracotomy, debridement and lavage of thoracic cavity and placement of indwelling drains
What are the problems of treating a pyothorax with thoracocentesis followed by systemic ABs
- single thoracocentesis unlikely to remove sufficient infective material
- systemic ABs unlikely to penetrate inspissated purulent material in the pleural space
- high likelihood of recrudescence
Outline pros/cons of treating a pyothorax with implantation of indwelling drains to facilitate pleural lavage, leave in situ for 5-7 days, systemic AB therapy
PROS - more likely to remove all infective material, lavage should facilitate AB penetrations
CONS - still risk of recurrence if FB present to act as a nidus.
Pros/cons of treating a pyothorax with exploratory thoracotomy, debridement and lavage of thoracic cavity and placement of indwelling drains
PROS - greatest likelihood of success at resolving pyothorax
CONS - perioperative morbidity and mortality
Prognosis - chylothorax
low likelihood of success with surgical or medical management of chronic chylothorax
Medical management - chylothorax - 3
- detect underlying cause although usually idiopathic
- reduce formation of intestinal lymph (low fat diet?, medium chain Tg oil, diuresis)
- enhance resorption of fluid from the pleura (Rutin = benzopyrone)
Surgical management -chylothorax
- attempts to ID and ligate the thoracic duct in an attempt to redistribute the pleural fluid.
- attempts to enhance absorption of pleural fluid
What is a salvage surgical technique for chylothorax?
Pleurodesis = artificial obliteration of the pleural space by adhesion of the 2 pleurae.
Actions - small volume pneumothorax (traumatic or spontaneous origin)
rest patient and see if it resolves
Actions - moderate volume pneumothorax (traumatic or spontaneous origin)
drain air, rest patient and manage conservatively
Actions - large volume of recurrent air (pneumothorax) (traumatic or spontaneous origin)
place an indwelling drain and drain repeatedly but likely that exploratory laparotomy will be required to identify and correct the underlying cause.
What is the best treatment for a pneumothorax?
ID the underlying cause and treat this (e.g. ruptured bulla)
