Pathology of Pulmonary Vascular Disease and Pleural Disease Flashcards
Describe the pulmonary circulation
LOW PRESSURE system with a DUAL BLOOD SUPPLY:
Pulmonary arteries (deoxygenated blood) - receive entire cardiac output
Bronchial arteries
Vessels of the pulmonary circulation
Thin-walled vessels with a low incidence of atherosclerosis (at normal pressures)
What is pulmonary oedema?
Abnormal accumulation of fluid IN THE LUNG:
In the interstitium, firstly
Then in the alveolar spaces
Causes a RESTRICTIVE PATTERN of disease with PFTs
Causes of pulmonary oedema?
- Haemodynamic (hydrostatic pressure increase - less water out of vessels/plasma osmotic pressure decrease - less water back into vessels)
- Due to cellular injury to:
Alveolar lining cells
Alveolar endothelium
Causes of increased hydrostatic pressure and decreased plasma osmotic pressure?
Increased hydrostatic pressure:
Left ventricular failure (causes backwards pressure increase and fluid leaks out, into interstitium and then into alveolar spaces)
Decreased plasma pressure:
Low albumin levels
Effects of pulmonary oedema?
Localised - pneumonia
Generalised - Adult Respiratory Distress Syndrome (ARDS)
What is ARDS?
AKA Diffuse Alveolar Damage Syndrome (DADS) and shock lung
Causes:
Sepsis
Diffuse infection (viruses, mycoplasma, etc)
Severe trauma
Oxygen - O2 therapy can be dangerous due to oxygen free radicals being produced by leukocytes
Pathogenesis of ARDS?
Characteristic hyaline membranes (fibrinous exudate lining alveolar walls)
Cellular regeneration
Inflammation
Injury, e.g: with a bacterial endotoxin, leads to:
Infiltration of inflammatory cells
Cytokines
Oxygen free radicals production by leukocytes
Injury to cell membranes
Outcomes of ARDS?
Tissue death
Resolution (potential with ventilation, vascular support in ICU, etc)
Fibrosis (chronic restrictive lung disease)
What is neonatal RDS?
Occurs in PREMATURE infants, who are deficient in SURFACTANT (secreted by type 2 alveolar lining cells) - increased surface tension leads to stiff lungs
So, increased effort in expanding lungs leads to physical cell damage
What is an embolus?
Detached intravascular mass carried by blood to a site in the body distant from its point of origin
Most are thrombi; others are gas (bone through skin - exposure to air), fat, foreign bodies, tumour clumps
What is a pulmonary embolus?
Cause of sudden death and pulmonary hypertension
Common and often sub-clinical
95% ARE THROMBOEMBOLI
Source of most pulmonary emboli is a DEEP VENOUS THROMBOSIS (DVT) of lower limbs
Risk factors for PE?
Same as for DVT; VIRCHOW’S TRIAD:
- Factors in vessel wall, e.g: endothelial hypoxia
- Abnormal blood flow, e.g: venous stasis
- Hypercoagulable blood, e.g: in cancer patients, post-MI, etc)
Effects of PE?
Sudden death Severe chest pain/dyspnoea Haemoptysis Pulmonary infarction Pulmonary hypertension
What do the effects of a PE depend upon and give examples?
Size of embolus
Cardiac function
Respiratory function
Large emboli:
Death
Infarction
Severe symptoms
Small emboli - tend to be clinically silent but, if recurrent, can lead to pulmonary hypertension
What is a pulmonary infarct?
Ischaemic necrosis
Embolus is necessary for this but not everybody with an embolus infarcts
BRONCHIAL ARTERY supply COMPROMISED, e.g: in cardiac failure
Types of pulmonary hypertension?
Primary (rare but tends to be in young women)
Secondary
Mechanisms of pulmonary hypertension development?
HYPOXIA - vascular constriction
Increased flow through pulmonary circulation - congenital heart disease (shunting of blood from left to right)
Blockage (PE) or loss (emphysema) of pulmonary vascular bed
Back pressure from left-sided heart failure
Morphology of pulmonary hypertension?
Medial hypertrophy of arteries Intimal thickening (fibrosis) Atheroma Right ventricular hypertrophy Extreme cases, e.g: congenital heart disease, primary pulmonary hypertenson) - plexogenic change (plexiform lesions - complex vascular formations originating from remodeled pulmonary arteries) /necrosis
What is Cor Pulmonale?
Pulmonary hypertension complicating lung disease:
Right ventricular hypertrophy
Right ventricular dilatation - can cause cardiomegaly
Right-sided heart failure (causing swollen legs, congested liver, etc)
What are the pleura?
Mesothelial surface lining lungs and mediastinum; have mesothelial cells designed for fluid absorption
What are pleural effusions?
HALLMARKS OF DISEASE
Accumulation of fluid in pleural space
Types of pleural effusion?
Transudate (low protein/low albumin levels) - caused by cardiac failure and in hypoproteinaemia
Exudate (high protein) - caused by either an inflammatory process in pleura, e.g: pneumonia, TB, connective tissue disease, or malignancy (primary/metastatic)
What is a purulent effusion?
Full of acute inflammatory cells and contain pus, e.g: in an:
Empyema (can be a pneumonia complication and can become walled off, leading to an abscess)
Can become chronic
What is a pneumothorax?
Air in pleural space due to:
Trauma, e.g: fractured rib punctures pleura)
Spontaneous (rupture of bulla)
Types of pleural neoplasia?
Primary:
Benign pleural neoplasias are rare
Malignant mesothelioma
Secondary - spread from elsewhere and are common, e.g: from adenocarcinomas in lung, GIT, ovary, etc)
What is mesothelioma?
Primary malignant tumour of pleura that is ASBESTOS-RELATED - bad prognosis
Mixed epithelial/mesenchymal differentiation (looks between a carcinoma and sarcoma in appearance, i.e: are BIPHASIC TUMOURS)
METASTASES IN PLEURA CAN MIMIC A MESOTHELIOMA
Determining differential diagnosis of malignant effusions?
Difficult to differentiate between primary and secondary tumours but can use:
Cytology, biopsy
Immunohistochemistry for lineage specific antigens may help
Medicolegal importance
