The definition of hemorrhage is the presence of blood, specifically red blood cells, outside of the blood vessel.

The etymology is from the Greek "haima" meaning blood and "rhegnymi" meaning to burst forth.

The two ends of the spectrum with respect to volume of hemorrhage are

  • hemorrhage per diapedesis
  • hemorrhage per rhexis
Basically, it's a little hole - big hole thing.
In hemorrhage per diapedesis, blood can squeeze out of the blood vessel very slowly by squeezing through functionally damaged vessel walls.
Causes of hemorrhage per diapedesis include:
  • hypoxia or anoxia
  • abnormal coagulation of blood
  • toxic injury
  • inflammation of vessel wall
  • nutritional deficiency
Hemorrhage per diapedesis is often classified according to the size of the hemorrhagic spot:

We're looking into a cow's mouth here. The cow is infected with bovine viral diarrhea virus.

There are multiple pinpoint spots of hemorrhage on the gingiva. What will you call these?

Here is a spleen from a dog that had a systemic infection with Gram negative bacteria. The bacterial toxins were damaging to the endothelium throughout the body.

In this picture, hemorrhages are somewhat bigger than petechiae.

When hemorrhages are 2 to 20 mm in diameter, it infers a more serious insult than when just petechiae are present. These hemorrhages are referred to as "ecchymoses."

When the hemorrhage forms streaks, and it looks as if the surface has been painted with a red paint brush, the hemorrhage is called "paint brush."
Here is paint brush hemorrhage on the serosal surface of the bladder. This goat had cystoliths (stones in the urinary bladder).

One other term that needs to be defined is purpura.

Purpura refers to fusing of ecchymotic and petechial hemorrhages so that there are numerous red areas.

dog HBC cerebellar hemorrhage.jpg

This kitten was circling and acting bizarre, then dropped over dead. Owner said that his little nephews had been over recently and had carried the cat everywhere; he was worried about rabies. How to describe this change? How about "submassive cerebellar hemorrhage"?

And here's the good news – this is hemorrhage per rhexis, probably due to trauma, and so is NOT rabies.

The bad news – the nephews probably dropped the cat.
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