Hydrothorax

Hydrothorax in a dog(Courtesy of Susan Rhind)

• Accumulation of oedema fluid
• Same causes as oedema elsewhere
• Due to congestive heart failure, neoplasia in the cavity (especially thymus or regional lymph nodes), protein-losing disease
• Grossly:
  • Whitening of pleura in long standing disease due to mesothelial hyperplasia and fibrosis
• Present in some specific diseaes:
  • Mulbery heart disease of pigs
  • African horse sickness
  • Black disease in sheep