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Small Animal Final Year > Pleural Disease > Flashcards

Pleural Disease Flashcards

1
Q

What is the serosa?

A

Serous membrane

  • The surface of the inner wall of the body cavities is lined by a serous membrane
  • single layered flat mesothelial cell layer with thin underlying propria (connective tissue)
  • the membrane is named pleura in the thoracic cavity and peritoneum in the abdominal and pelvic cavities
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2
Q

What is the serosal membrane called in the thoracic cavity?

A

Pleura

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3
Q

What is the serosal membrane called in the abdominal and pelvic cavities?

A

Peritoneum

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4
Q

What is the pleura?

What are the different types?

A
  • Pleura covering the surface of the lung is the visceral (pulmonary) pleura
  • It is reflected around the root of the lung and becomes continuous with the mediastinal pleura
  • This in turn is continuous with the diaphragmatic and costal pleura
  • Mediastinal, diaphragmatic and costal pleura are the parietal pleura
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5
Q

What is the function of the pleura?

A

Filled with a small amount of fluid produced by lymphatic system, so lungs help in apposition to the body wall. Fluid enables lungs to move smoothly, its under negative pressure – means they expand as we inhale

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6
Q

What is the pleural cavity?

A
  • The narrow ²space² between the parietal and viscera pleura is the pleural cavity
  • It contains a small amount of serous fluid spread over the surface of the pleura ~ 0.1ml/kg
  • Establishes adhesion
  • Smooth movement
  • Lung follows movements of diaphragm and thoracic wall
  • Sub-atmospheric pressure
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7
Q

What are the pleural sacs and mediastinum?

How does the mediastinum differ in horses compared to dogs/cats?

A
  • Left and right pleural sac around the lungs
  • Mediastinum is the space between them
  • More or less in the midline of the thorax
  • Mediastinum is continuous in most species
  • More delicate and discontinuous (?) in horses - both side usually get diseased at the same time
  • Thin in dogs/cats
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8
Q

What is pleural space disease?

A

•Accumulation of any of the following:

–Fluid – pleural effusion

–Air – pneumothorax

–Soft tissue mass e.g. abdominal organs

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9
Q

What does fluid/air etc in the pleural space lead to?

A
  • As fluid / air etc accumulate in the pleural space the resultant loss of negative pressure causes the lungs to collapse due to the loss of elastic recoil. Cannot expand the lungs which is one of the main problems.
  • Fluid etc restricts the ability of the lungs to inflate – can be called restrictive lung disease – restricting ability of lungs to inflate
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10
Q

What are some clinical signs of pleural space disease?

A
  • “Restrictive” breathing pattern
  • Short, shallow breaths
  • Tachypnoea
  • Open mouth breathing – mainly SA
  • Dyspnoea, Respiratory distress
  • Orthopnoea – when animal tends to sit in certain posture to aid with its breathing, often sternum, reluctant to lie on their side.

–elbow abduction (apart as helps them use muscles underneath the arm to expand the chest), sternal recumbency

•Cyanosis

–Depends on degree of compromise of gas exchange

•May be acute or chronic

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11
Q

What is the physiology of pleural fluid turnover (how is it produced?)

A
  • Fluid produced mainly from parietal pleural vessels by capillary filtration
  • Fluid reabsorbed primarily via parietal lymphatic vessels
  • BP forcing fluid out which then gets absorbed mostly through parietal pleura and lymphatic vessels, some ability of lymphatic can do some absorption as well but mainly parietal pleura that does it
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12
Q

What is pleural effusion controlled by?

A

•Pleural effusion is controlled by Starlings’ forces.

–Effusion occurs when pleural fluid dynamics favours decreased pleural fluid absorption or increased fluid formation.

–Pleural fluid can be unilateral but is usually bilateral

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13
Q

What are some things that can cause an INCREASE of fluid formation at the pleural space?

A
  • “leaky” capillaries (e.g. pleural inflammation)
  • Increase in intravascular pressure (e.g. CHF)
  • Increase in lung interstitial fluid (e.g. CHF)
  • Decrease in pleural pressure
  • Increase in pleural fluid protein – so increased oncotic pressure
  • Disruption of thoracic duct or blood vessels – leakage of fluid into the space
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14
Q

What are some things that can cause an DECREASE of fluid formation at the pleural space?

A
  • Obstruction of draining lymphatics (e.g. neoplasia, inflammation)
  • Increased systemic vascular pressures (right heart failure)
  • Reduced vascular oncotic pressure (hypoalbuminaemia)
  • Mesothelioma can cause an increase or decrease
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15
Q

What types of fluid types can be present with pleural space disease?

A

•A number of different fluid types can be present:

–Transudate (with hypoalbuminaemia)

–Modified transudate

–Exudate

  • Non-septic
  • Septic – often pyrexia also
  • Blood – collapsed and weak usually also
  • Chyle
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16
Q

With pleural space disease and pleural effusion, what do you hear on ascultation and percussion?

A
  • Auscultation: muffling of lung and heart sounds especially ventrally (when standing),
  • Percussion: increased dullness (fluid “line”)
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17
Q

With pleural effusions, what are some of the causes of transudate formation?

A

–Most common cause of pure transudate:

–decreased oncotic pressure – hypoalbuminaemia

»Causes of hypoalbuminaemia?

»protein losing enteropathies

»Nephropathies

»Liver disease

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18
Q

With pleural effusions, what are some of the causes of modified transudate formation?

A
  • The most common cause is:
  • Due to increased hydrostatic pressure – right sided heart failure:

–pericardial disease, pulmonic stenosis, tricuspid dysplasia, cardiomyopathy, pulmonary hypertension,

  • Diaphragmatic hernia
  • Lung lobe torsion

–Pretty uncommon, can happen with trauma – lung lobe twists around on itself and changes the circulation to the rest of the lung and stops fluid getting backwards and forwards

•Neoplasia

–Cellular kind of transudate

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19
Q

With pleural effusions, what are some of the causes of non-septic effusion formation?

A

–FIP, neoplasia, chronic chylothorax, chronic lung lobe torsion, fungal infection

•If chyle hangs around in the chest for some time it can get very annoying and inflamed

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20
Q

With pleural effusions, what are some of the causes of septic effusion formation?

A

Penetrating chest wound, foreign body inhalation (grass seed), ruptured oesophagus, ruptured pulmonary abscess / tumour, haematogenous bacterial spread

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21
Q

With pleural effusions, what are some of the causes of chyle (chylothorax) formation?

A

–Disruption of the thoracic duct most commonly, associated with lots of different disease essentially, sometimes idiopathic

•Lymphangiectasia, cranial vena cava obstruction, neoplasia, heart disease, fungal infection, lung lobe torsion, diaphragmatic hernia, trauma of the thoracic duct

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22
Q

With pleural effusions, what are some of the causes of blood (haemothroax) formation?

A

Trauma, coagulopathy, neoplasia, lung lobe torsion

23
Q

What diagnostic imaging are you best to use for diagnsosi of pleural disease?

A

Easiest to see fluid with US probe and less stressful to do US rather than radiography

Lung lobes at the back – lighter than we expect and can see obvious border of the lungs, slightly rounded lung margins

Sometimes called scalloping as margins between lungs are very clear

24
Q

What is the initial management for the treatment of pleural disease?

A
  • Oxygen supplementation
  • Emergency thoracic ultrasound to make the diagnosis
  • In severely dyspnoeic patients DO NOT RADIOGRAPH - these patients are very unstable and will die if they are stressed!
  • Immediate thoracocentesis

–Immediate relief from clinical signs

–Diagnostic

•Cytology, cell counts, protein content, bacterial culture

–Stabilise the patient prior to further investigations

25
Q

How do you perform a thoracocentesis briefly?

A
  • Local anaesthetic rarely needed unless large bore catheter
  • Clip area – if possible use quiet clippers (minimal stress esp. cats)
  • Quickly surgically prepare skin
  • Butterfly needle / catheter at ICS 6-8
  • Ideally localise large pocket of fluid with u/s first
  • Use 20ml syringe, 3 way tap and extension set
  • Aseptic technique
26
Q

What is a thoracostomy?

A

A thoracostomy is a small incision of the chest wall, with maintenance of the opening for drainage

27
Q

What are some indications for a thoracostomy?

A

–Animals that will require multiple thoracocentesis over a short period of time

–If large volumes of effusion

–Pneumothorax

–Chest wall injuries

•Flail chest / Flail segment

–Bite wounds

–Most pyothorax cases

28
Q

With pleural effusions, there is a cause for it, name some things that can go on to cause pleural effusion (4 things) and what you should do to treat the underlying cause

A

•Heart failure

–Treatment of HF

•Pericardial effusion

–Treat effusion - drainage etc..

•Pyothorax

–Antibiotics, systemic & local (broad spectrum and treat anaerobes)

–Be aware - often cultures will come back as negative!

–Lavage? Put some fluid in, mix it around and suck it back out again

–Long course of treatment, guarded prognosis

•Chylothorax

–2 ways of managing it: Diet (low fat, less of a reason for chyle to be produced), surgery (go into the chest and ligate any leaking vessels)

29
Q

What is a pneunothorax?

What can cause it?

A
  • Accumulation of Air: Pneumothorax
  • Rupture of major airways / lung parenchyma
  • Thoracic trauma
  • Penetrating wounds
  • Perforation of the oesophagus – stick injuries common cause, also chicken bones etc.
  • Bullous, necrotising or neoplastic lung disease
  • Iatrogenic
30
Q

What do you hear/feel with auscultation and percussion with a pneumothorax?

A

–Auscultation reveals dull lung sounds dorsally, increased sounds ventrally (bronchovesicular)

–Percussion – increased resonance, sounds like a drum

31
Q

Give some examples under the following headings of how things can cause a pneumothorax

  • Traumatic
  • Iatrogenic
  • Spontaneous
  • Infectious
A

–Traumatic

  • Rib fractures causing laceration of the pleura
  • Open wounds through the chest wall
  • Compression of thorax with a closed glottis leading to trauma to the conducting airways / alveoli resulting in rupture

–Iatrogenic

•Bronchoscopy, thoracocentesis, FNAB of lungs, prolonged periods of ventilation

–Spontaneous

•Leakage from pulmonary abscesses, neoplasia, foreign body migration, ruptured intrapulmonary bullae, ruptured subpleural blebs, pneumonia, feline asthma

–Infectious

•Gas forming bacteria in the pleural space

32
Q

What is a tension pneumothorax?

A

Leads to severe lung compression and a severe and profound hypoxaemia develops. Equilibration of pleural pressure and CVP develops leading to reduced venous return leading to reduced CO. Hypoxaemia, hypercapnia and systemic hypotension develop and are rapidly life threatening

33
Q

What is the pathophysiology of a pneumothorax?

A

–Loss of coupling efficiency between the elastic rib cage and elastic lungs

–Leading to partial lung collapse, decreased tidal volume and increase in overall lung volume due to expansion of the rib cage

–Severity of clinical signs depend on the degree of pneumothorax and the extent and presence of other pathology.

34
Q

What are some ways that you can diagnose a pneumothorax?

A
  • Physical examination
  • Assessment of respiratory status
  • Thoracic radiographs – if stable enough
  • [Routine haematology / biochemistry]
  • Blood gases
  • Pulse oximetry
35
Q

How can you go on to treat a traumatic pneumothroax?

A
  • Oxygen
  • Assess patient, dull lung sounds caudodorsally, hyper resonance on percussion
  • Drain pneumothorax as necessary, avoid over drainage
  • Many with strict cage rest will recover, strict cage rest for 2 weeks after
  • Some will require chest drains and Heimlich valve – platic tube with join on ends, air can only go one way so if you attach right way, air can come out of the chest and can drain it, but air cannot go back in again – stops build up of pressure within the chest
  • If no improvement then surgical exploration and correction will be required.
  • If open wounds then sterile dressings and surgery as soon as patient is stable
36
Q

What can cause a spontaneous pneumothorax and what is the history usually?

Diagnosis?

A

•History – usually unusual history and being a bit off colour

–Dyspnoea

–Anorexia

–Vomiting

–Most present with rapid progression of respiratory distress

  • Most common cause is ruptured pulmonary bulla or sub pleural bleb
  • Diagnosis as for traumatic pneumothorax
37
Q

What is the treatment and prognosis for a spontaneous pneumothorax?

A
  • Medical management to stabilise until diagnostic tests decide whether surgical intervention is required
  • Lobectomy as necessary
  • Prognosis is dependent on the underlying cause
38
Q

What are some differentials for pleural effusion in the horse?

What is by far the most common?

A

•_Pleuropneumonia ***_

Majority of horses with PE have pleuropneumonia

The rest of the following can happen, but pleuropneumonia is the most common and most important

•Neoplasia

–cranial mediastinal lymphosarcoma

–malignant melanoma

–mesothelioma

–others

  • Right-sided heart failure
  • Pericarditis
39
Q

What is the definition of pleuropneumonia?

A
  • inflammation of the mesothelial lining of pleural cavity with associated lung parenchymal disease
  • due to bacterial infection
  • exudation

–serum, fibrin

–WBC and protein

40
Q

What is the pathogenesis of pleuropneumonia in horses?

A
  • Mixed bacterial infection
  • Organisms are often that are normal flora of the pharynx – they often come down from pharynx and go into pleura

–Beta-haemolytic Streptococcus

–E coli

–Klebsiella spp.

–Pasteurella spp.

–Bordetella spp.

–Bacteroides spp. - NB anaerobes

41
Q

This is a horses lung, what is your diagnosis?

A

PLEUROPNEUMONIA

(most common cause of pleural disease in horses)

Lots of orange fibrinous stuff

42
Q

What can pleuropneumonia often follow?

A

•Often follows recent stressful event

–transport over long distances

–pulmonary haemorrhage

–trauma

–strenuous exercise

–surgery and anaesthesia

–mixing with other horses

–foaling

•Thought that it can cause suppression of pulmonary defence mechanisms

43
Q

What are some clinical signs of pleuropneumonia in horses?

A

•pleurodynia = pleural pain

–inflamed pleura

–reduction of pain with chronicity

  • formation of firm fibrous adhesions – reduces the pain slightly
  • cushion created by fluid
  • reluctance to move, pointing forelimb to try and ease pressure on pleura, just want to stand there,
44
Q

When/How can you identify pleural effusion in a horse - e.g. when does it become apparent?

A

–small amount of fluid

•respiratory signs may be absent

–several litres of fluid

•may be dyspneic at rest,
or following slight exertion

  • > 10 L of fluid often results in dyspnea
  • If just a couple of litres, they maybe just need a bit more rest after exertion
45
Q

What are some clinical signs of pleural effusion in the horse?

A

•auscultation - not consistent, often not useful – not very helpful!

–absent airway sounds ventrally

–dorsal sounds may be normal or abnormal

–fluid in the trachea

–pleural friction rubs?

•cardiac sounds radiate over a wide region – these things can be quite subtle

–NB may also have pericarditis

•Percussion – if there is a lot of fluid there its more useful

–ventral dullness

46
Q

How can you diagnose pleuropneumonia in horses?

A
  • Ultrasonography
  • Radiography
  • Transtracheal aspirate
  • Examination of pleural fluid
47
Q

What is the identification of pleural effusion in horses?

A

Ultrasound

Radiography

48
Q

WIth pleural effusion in horses, on ultrasound what do you look for/see with the pleural fluid and lungs?

A

Pleural fluid

–volume

–location

–character (echogenicity increases with cell count, gas bubbles suggest anaerobes)

–Borders of lungs are ragid

Lungs

–consolidation

–Abscessation

–Looks like contained pocket of puss on this photo

49
Q

On thoracic radiography in the horse, what do you see in the acute and chronic stages of pleural effusion?

A

ACUTE STAGE

  • pleural effusion obscures lung pathology
  • May see fluid line, but might see perfusion obscuring the lungs

CHRONIC STAGE

•identification of consolidation, abscesses and pneumothorax

50
Q

Other than ultrasound and radiography, what else can you do to diagnose pleuropneumonia in the horses?

A

•Transtracheal aspirate

–important to obtain sample that is not contaminated by upper airway

–Want diagnostic sample – need to make sure take precautions such as being aspetic and not getting contamination of the sample taker as you put it down etc.

•Examination of pleural fluid

–physical

–cytology

–bacteriology (culture, antibiotic sensitivity and gram stain)

–chemistry (low glucose concentration suggests presence of bacteria)

–pleural drainage has therapeutic benefit in
most cases

51
Q

What is the treatment for the acute stages of pleuropneumonia in horses?

A
  • Drain effusion vigorously, keep it as clear as you can
  • Broad-spectrum antibiotics including anaerobic cover for long enough
  • Supportive treatment as possible
52
Q

Why is drainage of the pleural effusion in horses with pleuropneumonia important?

A

•Drainage - an important therapy

–removal of the restrictive forces

–re-expansion of the pulmonary tissue

–improves pulmonary clearance

–removes debris, organisms,
inflammatory mediators, toxins

53
Q

What is the treatment for the chronic stages of pleuropneumonia in horses?

A
  • pleural and pulmonary abscesses may be amenable to drainage, via resection of intercostal muscle and/or rib
  • providing they are walled off from the rest of the pleural cavity
  • Get a lot of inflammation and walling off and fibrin formation with chronic stages – may need to get to surgery! If walled off from rest of the chest, may stand a better chance
54
Q

What is the prognosis of pleuropneumonia in horses?

A

•Milder cases, diagnosed early

–may return to previous career with early and aggressive therapy

•Severe cases

–can be salvaged for breeding

–may require months of antibiotic treatment and multiple surgeries

Small Animal Final Year (317 decks)

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