Resp path - pulmonary edema and thomboemboli

Question 1

What is excessive interstitial fluid in the alveoli?

Answer 1

Pulmonary oedema

Question 2

Which part or the lung does pulmonary oedema occur first?

Answer 2

Occurs first in the basal regions of the lower lobes of lung (dependent oedema)

Question 3

microscopically, what would you see in pulmonary oedema?

Answer 3

The alveoli(left panel)are filled with a smooth to slightly floccular pink material (♦) characteristic of pulmonary edema. Capillaries within alveolar walls are congested, filled with many red blood cells (RBCs).

Question 4

In which medical conditions is pulmonary oedema common?

Answer 4

Pulmonary congestion with oedema is common in patients with heart failure (with elevated B-type natriuretic peptide)+
in areas inflammation of the lung

Question 5

Consequences of pulmonary oedema

Answer 5

Pulmonary congestionwith dilated capillaries and leakage of blood into alveolar spaces.

Question 6

Histologically, what will you see in pulmonary congestion?

Answer 6

Engorged alveolar capillaries, intra-alveolar finely granular pink transudative material, haemosiderin-laden macrophages (‘heart failure cells’).
RBC breakdown results in brown cytoplasmic hemosiderin granules
If long-standing, fibrosis and thickening of the alveolar walls with numerous haemosiderin-laden macrophages result in a grossly firm brown-coloured lung (‘brown induration’)

Question 7

In long-standing pulmonary oedema, what will you see histologically and grossly?

Answer 7

If long-standing, fibrosis and thickening of the alveolar walls with numerous haemosiderin-laden macrophages result in a grossly firm brown-coloured lung (‘brown induration’)

Question 8

What are the causes of pulmonary oedema? (3)

Answer 8

Increased hydrostatic pressure: Increased pulmonary venous pressure from left-sided heart failure, volume overload or pulmonary vein obstruction
* Decreased oncotic pressure: Less common e.g. hypoalbuminemia, nephrotic syndrome, liver disease, protein-losing enteropathies
Oedema due to alveolar wall injury

Question 9

What are the types of alveolar wall injury?

Answer 9

• Direct injury: Damage from infections e.g. bacterial pneumonia, inhaled gases, liquid aspiration, radiation, lung trauma
• Indirect injury: Systemic inflammatory response syndrome, drugs/chemicals
  Major component of acute respiratory distress syndrome
  Damage to either alveolar microvasculature or epithelium results in an inflammatory exudate starting in the interstitium and in severe cases, extends into the alveoli.

Question 10

Describe gross appearance of a thromboembolus?

Answer 10

Irregular surface, pale tan areas admixed with dark red areas. Embolus has the outlines of the vein in which it originally formed as a thrombus.

Question 11

Where can a large emboli lodge?

Answer 11

Main bronchial artery, it’s branches/at the bifurcation (saddle emboli)

Question 12

Where can smaller emboli lodge?

Answer 12

travel more distally (usually lower lung lobes) and can cause a wedge- shaped area of haemorrhage or infarction

Question 13

In which cases does an infarct occur as a result of smaller pulmonary emboli?

Answer 13

Infarct more common if the patient’s cardiovascular function is already poor and the bronchial artery supply is insufficient to sustain the lung parenchyma

Question 14

Describe lung infarcts

Answer 14

Hemorrhagic, and the pleural cavity becomes covered by fibrinous exudate
Then within 48 hrs, the infarct becomes paler and red-brown as the red blood cells lyse and hemosiderin is produced.
Eventually, the infarct is replaced by fibrous tissue and forms a scar.

Question 15

Microscopic appearance of a pulmonary embolus

Answer 15

Lines of Zahn distinguish a pulmonary embolus from a postmortem blood clot.
Areas of infarct show ischaemic necrosis of alveolar walls, bronchioles and vessels