Cellular Swelling

• Cellular swelling is
  • The earliest detectable degenerative change.
  • The mildest form of cellular degeneration.
  • The first stage in injury to a cell.
  • Caused by a variety of insults, e.g.
    • Lack of oxygen (anoxia) to a tissue.
    • Toxic influences.
• Is due to the impairment of the integrity of the cell membrane.
• Cellular swelling is characterised by a moderate swelling of the individual cells.
  • Due to an influx of water into the cell.

Gross Appearance

• Organs diffusely affected with cloudy swelling grossly appear pale.
  • This may be partly due to the swollen cells impeding the tissue's blood supply.
• Without cutting into an organ, it may be difficult to appreciate a gross enlargement of it. Looking for rounded edges to some organs can help.
  • Each individual cell is increased in size, meaning the entire volume of the organ is also increased.
  • E.g. on cutting the liver or kidney capsule, the underlying swollen parenchyma bulges outwards, making the cut ends of the capsule retract.
• The degree of gross swelling is not great.
  • Could be easily confused with early post-mortem changes in the organ.

Histological Appearance

• Individual cells appear somewhat swollen.
• The cytoplasm appears more red in colour in hematoxylin and eosin (H&E) stained sections.
• The nucleus of the cell remains normal.
• Cellular swelling is best histologically appreciated in the liver and kidney in damage caused by circulating toxins that are not powerful enough to actually kill the cells.

Significance of Cellular Swelling

• Cellular swelling is an important stage in degeneration.
  • Not commonly observed on its own without more serious changes
    • Not easy to identify at post-mortem unless the examination is performed very soon after the animal's death.
      • Early post-mortem (autolytic) change in dead tissue looks rather similar.
    • Cellular swelling is also reversible.
      • When the toxin is no longer exerting its effect, the tissue returns to normal.
    • Cellular swelling may be a transient stage in the more serious forms of degenerations which follow.