Lecture 14: Diseases of the pleura

Question 1

what are the functions of mesothelial cells that line the pleural cavity

Answer 1

• 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

Question 2

what are the other defences of the pleural cavity?

Answer 2

lymphocytes and macrophages

Question 3

what does post mortem decomposition look like?

Answer 3

blood stained watery fluid that does not clot

Question 4

what are the consequences of fibrin exudation into the pleural cavity?

Answer 4

fibrinous attachments to the walls of the pleural cavity –> restricted lung disease

Question 5

what are the clinical signs associated with an animal in pleural disease?

Answer 5

• 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

Question 6

what is pneumothorax?

Answer 6

air in the pleural cavity

Question 7

what is tension pneumothorax?

Answer 7

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

Question 8

what domestic animals are most likely to have pneumothorax? what is the most common possible cause?

Answer 8

dogs and cats - car accident

can also be spontaneous, or a complication of carfdiact resuscitation, trans-thoracic lung biopsy or thorascopy

Question 9

what does pneumothorax lead to?

Answer 9

collapse of the lung due to the positive intra-pleural pressure –> dyspnoea and tachypnoea

Question 10

what is pneumomedisastinum?

Answer 10

air in the mediastinum

Question 11

from where can air enter the pneumomediastinum?

Answer 11

air can track down from tears in trachea, bronchi, alveoli or oesophagus

Question 12

what domestic animal is pneumomoediastinum common in and why?

Answer 12

common in cattle usually due to interstitial emphysema of lung, or domestic animals as a result from bite wounds to the neck

Question 13

what is pleural effusion?

Answer 13

accumulation of excess fluid within the pleural cavity

Question 14

what are common causes for pleural effusion?

Answer 14

haemorrhage, venous or lymphatic obstruction, decreased plasma oncotic pressure, increased plasma hydrostatic pressure, inflammation or intra-cavity neoplasia

Question 15

what are the consequences of pleural effusion?

Answer 15

excess fluid raises intrathoracic pressure and can cause lung collapse, especially ventrally due to gravitational pooling of fluid

Question 16

what is thoracocentesis - why is it important?

Answer 16

cytological evaluation of pleural effusions, essential in animals to allow accurate diagnosis and therapy

Question 17

how is aspirated fluid usually sampled? what tests are preformed?

Answer 17

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

Question 18

how are pleural cavity effusions categorised on laboratory analysis?

Answer 18

• 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

Question 19

what does a pink-red coloured fluid aspirated indicate?

Answer 19

presence of free Hb

Question 20

what is haemothorax?

Answer 20

blood in the pleural cavity

Question 21

what is the mot common cause of haemothorax within he chest cavity?

Answer 21

chest trauma

Question 22

why is hydrothorax?

Answer 22

a non-inflammatory transudate in the pleural cavity

Question 23

what does hydrothorax look like grossly?

Answer 23

typically clear, colourless, odourless, may be watery or faintly cloudy or blood stained
typically modified transudate

Question 24

what are some causes of pleural transudates

Answer 24

most commonly caused by severe hypoalbuminaema e.g. chronic starvation, protein losing nephrophathy, chronic hepatic insufficiency

Question 25

modified transudate class of effusion is the least aetiologically specific, what are some causes causes?

Answer 25

• right sided congestive heart failure
• left sided congestive heart failure
• lymphatic or venous obstruction
• extension of ascites
• FIP: feline infectious peritonitis

Question 26

what is chylothorax?

Answer 26

lymph in the pleural cavity

Question 27

how does chylothorax occur?

Answer 27

result from physical or functional obstruction of intra-thoracic lymph –> leakage of lymph into cavity

Question 28

in which species is chylothorax most commonly diagnosed?

Answer 28

it is an uncommon disease but most commonly diagnosed in dogs and cats

Question 29

what can cause chylothorax?

Answer 29

chest trauma, severe coughing or vomitting, thoracic neoplasia, heart worm infection
most are idiopathic

Question 30

what is pleuritic/ pleurisy

Answer 30

inflammation of the pleura with accumulation of exudate in the cavity

Question 31

what is pyothora/thoracic empyema

Answer 31

accumulation of pus in the pleural cavity

Question 32

what is the most common cause of pleuritis in the domestic animals?

Answer 32

increased vascular permeability and chemotaxis of leukocytes
septic pleuritis = most common cause
bacteria reach cavity via bloodstream or via direct extension from inflammatory foci in the lungs

Question 33

how does septic pleurits appear grossly?

Answer 33

suppurative, fibrinous, fibrinosuppurative, pyogranulomatous or hemorrhagic, typically malodorous

Question 34

what is the most dominant cell type in septic pleuritis

Answer 34

neutrophils

Question 35

what are some causes of non-septic pleurtitis in animas

Answer 35

FIP - feline infectious virus
lung lobe torsion
sterile foreign bodies
diaphragmatic hernia
intra-thoracic neoplasm
chronic hydrothorax
resolving sepsis

Question 36

what is the most dominant cell type in non-septic pleuritis

Answer 36

non-degenerate neutrophils