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Lungs Circulatory - Pathology (view source)
Revision as of 21:20, 6 August 2008
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==Hyperaemia==
*Localised of diffuse as part of acute inflammation
==Congestion==
*Decreased outflow of venous blood
*Most commonly caused by left-sided or bilateral cardiac failure
**Stagnant blood in pulmonary vessels -> red blood cells move into alveoli and are phagocytosed -> [[General Pathology - Pigmentation and Calcification#Haemosiderin|haemosiderin in macrophages]] (heart failure cells)
*One-sided in post-mortem hypostatic congestion
*Acute pulmonary congestion is seen after barbiturate euthanasia
*Leads to pulmonary oedema (below)
==Pulmonary oedema==
*Excessive fluid in the lung
*Normally, mechanisms are in place to protect the lung from the entry of circulatory fluid into alveolar spaces (See [[Respiratory System General Introduction - Pathology#Lungs|functional anatomy]])
*Occurs when exudation of fluid from vessels into interstitium or alveoli exceeds the rate of alveolar or lymph removal
*Generally a sequel to or part of congestion or inflammatory process
*Generally begins as '''interstitial oedema''' characterised by expansion of perivascular and peribronchial and peribronchiolar fascia and distension of interstitial lymphatics
*Only when this interstitial compartment is overwhelmed does fluid flood the airspaces causing '''alveolar oedema'''
*Gross pathology:
**Heavy wet lungs which do not properly collapse
**Subpleural and interstitial tissue distended with fluid
**Foamy fluid oozing from the cut surface and airways
*Micro pathology:
**Pinkish fluid in alveoli and airways in association with air bubbles, and also in dilated lymphatics of the interstitium
**Colour of the fluid enhanced in cases where the endothelium is damaged - more protein present
**In slowly developing cases, macrophages contain haemosiderin
*The major causes of pulmonary oedema are:
**Increased capillary or type I epithelial permeability caused by
***Systemic toxins
***Shock
***Inhaled caustic gases
**Increased capillary hydrostatic pressure ('''cardiogenic oedema''' - left-sided or biventricular heart failure, sympathetic stimulation in acute brain damage)
**Decreased plasma oncotic pressure (hypoalbuminaemia)
**Overloading in excessive fluid therapy
**As part of inflammatory process
==Pulmonary haemorrhage==
[[Image:Pulmonary haemorrhage.jpg|right|thumb|100px|<small><center>Pulmonary haemorrhage (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
*Potential sequel of septicaemias, bleeding disorders, disseminated intravascular coagulation, and severe congestion, severe acute inflammation, "back splashing" at slaughter (aspiration of blood)
*[[Exercise induced pulmonary haemorrhage|'''Exercise-induced pulmonary hemorrhage''' (EIPH)]] occurs commonly in horses during racing or training
**Shows as [[Respiratory System Clinical Signs - Pathology#Epistaxis|epistaxis]]
**Undetected in many horses
**Haemorrhage is dorsocaudal, large brown areas
**Micro - alveolar haemorrhage, macrophages containing [[General Pathology - Pigmentation and Calcification#Haemosiderin|haemosiderin]], mild interstitial fibrosis
==Embolism, thrombosis and infarction==
[[Image:Pulmonary infarction.jpg|right|thumb|100px|<small><center>Pulmonary infarction (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
[[Image:Segmental pulmonary infarction.jpg|right|thumb|100px|<small><center>Segmental pulmonary infarction (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
*Lungs are strategically situated to catch emboli carried in venous blood
*Because the lung is supplied by both pulmonary and bronchial arteries and has extensive collateral channels, infarction usually does not follow embolism or thrombosis unless pulmonary circulation is already compromised
*In animals, greatest risk comes from:
**'''Tumor emboli'''
***From e.g.: osteosarcoma and haemangiosarcoma in dogs, uterine carcinoma in cattle
**'''Septic emboli'''
***From bacterial [[Endocardial - Pathology#Inflammatory-Endocarditis|endocarditis]], jugular thrombophlebitis, [[Liver - inflammatory#Hepatic abscessation|hepatic abscesses]] etc.
***May cause unexpected death if in large numbers
***May develop [[Lungs - inflammatory|suppurative pneumonia]] -> [[Lungs - inflammatory#Pulmonary abscesses|pulmonary abscesses]], [[Arterial Disease - Pathology#Inflammatory-Arteritis|arteritis]], [[General Pathology - Thrombosis|thrombosis]]
*Pulmonary infarcts usually occur when there is embolisation or thrombosis during general circulatory collapse or passive congestion of heart failure
*Pulmonary thromboembolism is a sequel to in cattle to large emboli from liver abscesses close to the vena cava
**Death may ocur due to massive haemorrhaging into lung tissue
*Parasites (e.g. [[Respiratory Parasitic Infections - Pathology#Dirofilaria immitis|''Dirofilaria immitis'']], [[Respiratory Parasitic Infections - Pathology#Angiostrongylus vasorum|''Angiostrongylus vasorum'']]) may be responsible
*Long-term intravenous catheterisation may cuse thrombi pieces breaking off and lodging in pulmonary vessels
==Pulmonary hypertension==
*Caused by '''left-to-right vascular shunts''' or increased resistance of the pulmonary vascular system
*In animals, it is most commonly a sequel of '''widespread fibrosis in the lung''' or [[Bronchi and Bronchioles Inflammatory - Pathology#Chronic bronchitis|chronic bronchitis or bronchiolitis]] which stimulates hypertrophy in the walls of small arteries
*Severe prolonged pulmonary hypertension leads to [[Secondary Cardiac - Pathology|'''cor pulmonale''']], right-sided heart failure secondary to primary lung disease