View source for 24. Classification of hemorrhages based on pathomechanism

== Haemorrhage ==
Extravasation of blood from vessels is the definition of haemorrhage, and it occurs in our everyday life but usually has little impact on our blood volume, like a small paper cut or regular menstruation. However, some may be life threatening and may lead to hypovolemic shock (discussed in topic 26).

Let’s look at some risks for haemorrhage other than paper cuts and menstruation:

* Trauma
* Atherosclerosis
* Inflammations
* Neoplastic erosion of vessel wall (cancerous growth)
* Haemorrhagic diathesis, a group of diseases.

=== Nomenclature and classification of haemorrhage ===
Also, the nomenclature is important here. Large bleedings inside body cavities is given names according to their location:

* Suffusion – Superficial bleeding in skin, that results in a bruise.
* Haematoma – Mass-like defined haemorrhage, can appear in skin, bones, joints and in organs.
* Apoplexy – Destructive bleeding inside an organ that, e.g. stroke
* Haemopericardium – blood in pericardium
* Haemothorax – blood in pleural cavity
* Haemascos/haemoperitoneum – blood in abdominal cavity
* Haemarthros – blood in joints
* Haematympanon – blood in middle ear
* Haemoptysis – blood in sputum (coming from the airways)
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* Haematochezia – fresh blood in feces
* Melena – dark blood in feces
* Haematuria – blood in urine
* Epistaxis nosebleed
* Metrorrhagia – blood from uterus, must not be mixed up with menstruation as this is more an abnormal bleeding.

The size also matters, and we have nomenclature for that also.

* Petechia – 1-3 mm haemorrhages into skin and mucosa.
* Purpura – 3-10 mm haemorrhages
* Ecchymosis – larger than 10 mm, becomes often a bruise.

We also classify by cause:

* Per rhexim – Due to blood vessels that break like in trauma
* Per arrosienem – blood vessel wall damage due to erosion by e.g. peptic ulcers, tuberculosis and tumours.
* Per diapedesim – Due to changes in permeability or thrombocyte function

=== Haemorrhage per diapedesim ===
We will take a closer look at this cause, as it is considered a “Step-over” bleeding, caused by many things. It can be divided into:

# Fragility of blood vessels
#* Scurvy
#* Vasculitis
#* Ehlers-Danlos syndrome
# Thrombocytopenia
#* Reduced production of platelets
#** Bone marrow infiltration by metastasis
#** Bone marrow fibrosis
#** Aplastic anaemia
#* Reduced platelet lifespan
#** Immune thrombocytopenia
#** Systemic lupus erythematosus
#** Mononucleosis
#** Disseminated intravascular coagulation
#** Thrombotic thrombocytopenic purpura
#** Haemolytic uraemic syndrome
#* Sequestration of platelets
#** Overactive spleen
# Platelet disfunction
#* Bernard-Soulier syndrome
#* Von Willebrand disease
#* Glanzmann thrombasthenia
#* Long-term aspirin use
# Coagulopathy
#* Haemophilia A and B

1. Fragility of blood vessels

Hypoxic damage to endothelium and collagen defects as in scurvy and Ehlers-Danlos syndrome can lead to fragile vessels. Recall that scurvy is due to vitamin C deficiency. Vasculitis is an inflammation that destroys both arteries and veins.

2a. Reduced production of platelets

Caused by bone marrow insufficiency like bone marrow infiltration that happens in metastasis of various cancers and leukaemia. Bone marrow fibrosis and aplastic anaemia (haematopoietic stem cells are damaged) can also be some of the causes.

2b. Reduced platelet lifespan

This can happen by immune-mediated destruction or increased destruction.

Immune-mediated destruction can be autoimmune diseases such as Immune Thrombocytopenia (ITP) or Systemic Lupus erythematosus (<abbr>SLE</abbr>), but also drug associated like with heparin or due to infection such as Mononucleosis.

Increased destruction can be Disseminated Intravascular coagulation (DIC), Thrombotic thrombocytopenic purpura (<abbr>TTP</abbr>) and Haemolytic uremic syndrome (<abbr>HUS</abbr>).

2c. Sequestration

This happens if the spleen is overactive (hypersplenism), leading to over filtration of platelets and thrombocytopenia.

3. Platelet disfunction

We have various hereditary defects that affects the platelets in different ways:

* Adhesion defects
** Bernard-Soulier syndrome
** Von Willebrand disease (vWF defect)
* Aggregation defects
** Glanzmann thombasthenia (glycoprotein IIB/IIIa defect, in other words, a defected receptor for fibrinogen)
* Secretion defect
** Storage pool deficiency, the granules inside platelets are impaired.

Acquired disfunctions are also possible. ''Long term Aspirin'' use blocks formation of Thromboxane A2 in platelets. ''Uraemia'' can inhibit platelet function.

4. Coagulopathies

Both hereditary and acquired diseases cause pathology in the coagulation process.

Hereditary diseases:

* Haemophilia A – where clotting factor VIII is missing.
* Haemophilia B – also known as Christmas disease where factor IX is missing.
* Von Willebrand’s disease – deficiency of von Willebrand factor and is the most common hereditary coagulopathy.

Acquired diseases:

* Vitamin K deficiency, affecting factor II, VII, IX and X
* Liver diseases, as the liver metabolizes Vitamin K.
* Disseminated Intravascular coagulation (DIC). More about this in topic 25.

== Hyperhaemia and congestion ==
Hyperaemia means increased blood''. Active hyperaemia'' is the increased arterial flow, while ''congestion'' (passive hyperaemia) means decreased venous drainage. It’s often visible as redness and marked vessels on the surface.

Active hyperaemia appears often with inflammation where vasodilating mediators are present and increase the permeability of the capillaries. This can happen in e.g. acute conjunctivitis, acute gastritis, acute bronchitis and erythaema (redness of skin).

Some examples of congestion are:

* Pulmonary congestion due to left ventricular failure.
** Pulmonary oedema is a severe acute lung congestion
** Brown induration of the lung is a severe chronic lung congestion
* Hepatic congestion where the venous drainage in the liver is impaired due to right ventricular failure.
** Leads to nutmeg liver (hepar moschatum)
* Portal congestion will lead to portal hypertension as the blood accumulates. This can lead to ascites, splenomegaly and porto-systemic shunts like caput medusae (recall from anatomy 2).
* Deep vein thrombosis
* Congestive gastropathy/colopathy

[[Category:Pathology 1 - Theoretical exam topics]]