Pulmonary Congenital Atelectasis

• Incomplete expansion of the lung at birth (congenital) or collapse of previously air-filled lung (acquired)
• Failure of lung tissue to expand at birth
• Ranges from total in stillborn animals to patchy areas in the case of weak neonates, showing more in the dependant lobes in recumbency
• The neonatal respiratory syndrome
  • Best documented in foals but reported in other species
  • Also features extensive atelectasis
  • These animals are called 'barkers' due to the noise made during forced expiration
• Gross pathology:
  • Red fleshy appearance to the affected part, depressed below the surface if there are adjacent normal aerated areas
  • Cut surface oozes blood, perhaps some froth in 'barkers'
  • Affected areas sink or are submerged in fixative
• Micro pathology:
  • Close approximation of capillary walls
  • Little normal alveolar pattern
  • 'Barkers' may have a proteinaceous fluid in alveoli with hyaline membranes in lower airways
• Cause:
  • In weak neonates -inadequate respiratory effort or damage to the respiratory centres in the brain, aspiration of amniotic fluid or meconium
  • In 'barkers'- defective production of surfactant by the Type 2 alveolar epithelium
• Foals that survive may have hypoxic damage to their brain, walk aimlessly and lack normal sense of fear - "wanderers"