Lecture 14: Diseases of the pleura Flashcards
what are the functions of mesothelial cells that line the pleural cavity
- following mild irritation mesothelial cells may undergo hypertrophy, hyperplasia or metaplasia to a cuboidal or columnar cell
- activated cells capable of phagocytosis
- activated cell can produce plasminogen activator –> fibrinolysis
- can produce procoagulents
what are the other defences of the pleural cavity?
lymphocytes and macrophages
what does post mortem decomposition look like?
blood stained watery fluid that does not clot
what are the consequences of fibrin exudation into the pleural cavity?
fibrinous attachments to the walls of the pleural cavity –> restricted lung disease
what are the clinical signs associated with an animal in pleural disease?
- interference with normal expansion of the lung = dyspnoea with laboured inspiration and a short effortless expiratory phase
- lung sounds may be reduced on auscultation and there may be dullness on percussion, especially in VENTRAL aspect
- intercostal spaces may budge
- severe effusion may cause compression of the cardiac atria –> impaired venous return to the heart and obvious jugular pulse
- pleurites (fever, anorexia, depression, tachycardia, coughing, flaring of nose)
- ventral subcut oedema
what is pneumothorax?
air in the pleural cavity
what is tension pneumothorax?
flap of pulmonary tissue or penetrating injury to cheat wall acting as a one way valve, allowing air to enter cavity in inspiration but trapping it there during expiration
what domestic animals are most likely to have pneumothorax? what is the most common possible cause?
dogs and cats - car accident
can also be spontaneous, or a complication of carfdiact resuscitation, trans-thoracic lung biopsy or thorascopy
what does pneumothorax lead to?
collapse of the lung due to the positive intra-pleural pressure –> dyspnoea and tachypnoea
what is pneumomedisastinum?
air in the mediastinum
from where can air enter the pneumomediastinum?
air can track down from tears in trachea, bronchi, alveoli or oesophagus
what domestic animal is pneumomoediastinum common in and why?
common in cattle usually due to interstitial emphysema of lung, or domestic animals as a result from bite wounds to the neck
what is pleural effusion?
accumulation of excess fluid within the pleural cavity
what are common causes for pleural effusion?
haemorrhage, venous or lymphatic obstruction, decreased plasma oncotic pressure, increased plasma hydrostatic pressure, inflammation or intra-cavity neoplasia
what are the consequences of pleural effusion?
excess fluid raises intrathoracic pressure and can cause lung collapse, especially ventrally due to gravitational pooling of fluid
what is thoracocentesis - why is it important?
cytological evaluation of pleural effusions, essential in animals to allow accurate diagnosis and therapy
how is aspirated fluid usually sampled? what tests are preformed?
sampled using an
- EDTA tube for nucleated cell count, packed cell volume, total proteins concentration and cytological examination
- sterile plain tube for aerobic and anaerobic culture
- air dried smears to prevent in vitro auto lysis of cells ad identify infectious agents
how are pleural cavity effusions categorised on laboratory analysis?
- transudate <25 g/L protein, <1.5 total nucleated cell count
- modified transudate <25-75 g/L protein, 1.0-7.0 TNC
- exudate >30 g/L protein, >7.0 TNC
what does a pink-red coloured fluid aspirated indicate?
presence of free Hb
what is haemothorax?
blood in the pleural cavity
what is the mot common cause of haemothorax within he chest cavity?
chest trauma
why is hydrothorax?
a non-inflammatory transudate in the pleural cavity
what does hydrothorax look like grossly?
typically clear, colourless, odourless, may be watery or faintly cloudy or blood stained
typically modified transudate
what are some causes of pleural transudates
most commonly caused by severe hypoalbuminaema e.g. chronic starvation, protein losing nephrophathy, chronic hepatic insufficiency
