Bleeding and Blood Loss (Hemorrhage)

Bleeding is the loss of blood from a vessel and the medical term is hemorrhage. Although bleeding is often only associated with an open wound on the skin, there can be blood loss internally without any obvious signs of bleeding. Blood may pass out into environment any of the extravascular spaces – these are any spaces in the body apart from the space in the blood vessels. Bleeding into the environment is known as external bleeding. On the other hand bleeding within the body’s tissue spaces and cavities is known as internal bleeding.

The blood vessels are structured in a manner that allows fluid (plasma/serum) to pass out of it through pores but the red blood cells and blood proteins remain inside the blood vessel. Fluid from the tissue spaces can enter the blood vessels but in a normal blood vessel, proteins and blood cells cannot enter it. Bleeding occurs when the blood vessel is ruptured either partially or completely allowing blood cells to escape from the blood vessels and pass out into any of the body spaces or cavities (internal) or into the environment (external). It may occur for other reasons including changes in pressure within the blood vessel (intravascular), changes in permeability of the blood vessel wall and with blood clotting disorders.

Although all of the blood components will be lost with bleeding, it is the red blood cells and proteins that are most critical. These components are usually the most abundant within the blood vessels and the body may not be able to replenish it fast enough if large amounts are lost. This has a number of different effects on the body but if the blood loss can be stemmed, the body will be able to recover and restore normal blood composition. The blood cells and fluid lost in the blood with massive bleeding contributes to a reduced blood volume which can then lead to shock – hypovolemic shock or more specifically hemorrhagic shock. Minute bleeding on the other hand may not cause a significant loss of fluid volume but instead the loss of red blood cells can lead to anemia.

Location of Blood Loss

Although bleeding can be internal or external, it is necessary to explore the subject of blood loss further.


Bleeding may occur into a cavity within the body – either an open or closed cavity. This includes bleeding within the :

  • Open
    • nose and paranasal sinuses
    • mouth or throat
    • lung or airways
    • gut (gastrointestinal tract)
    • urinary tract
    • uterus and vagina in women
  • Closed
    • pleural space (around the lung ~ hemothorax)
    • pericardial space (around the heart ~ hemopericardium)
    • abdominal and peritoneal cavity (hemoperitoneum)
    • joint spaces (hemoarthrosis)
    • cranium of the skull (intracranial)

If the bleeding occurs within closed cavities, there may be no obvious signs of blood loss initially but signs and symptoms indicative of bleeding and pressure on the corresponding structures need to be noted. If bleeding is within an open cavity, then it will be passed out with saliva (mouth), vomit (upper gastrointestinal), feces (lower gastrointestinal), mucus (nose), urine (bladder) or discharge (uterus/vagina). At other times it can be overt where there will be bleeding through the relevant orifice without the respective excretion, discharge or expectorant.

Tissue Spaces

Bleeding can also occur within the tissue spaces and often passes unnoticed until the relevant organ or structure becomes engorged thereby compromising its function. At other times the blood may eventually exit the organ and pass into one of the open cavities where it will be detected as described above. Bleeding within the tissue is known as a hematoma. This bleeding may cause visible signs if it occurs within the submucosa lining the orifices, genitalia, eyes or if it occurs within the subcutaneous tissue (skin).

External Bleeding

Blood loss into the environment may occur when there is a break in the skin due to an injury like an incision, laceration or puncture wound. The severity of the bleeding can vary depending on the nature of the injury as well as the site. This may be independent of the size of the cut. Sometimes a long shallow cut like a laceration without damaging an artery may be profuse but not life threatening. Conversely, a small puncture wound that severs a medium to large artery can cause massive bleeding which is rapid and this can be fatal.

Signs and Symptoms

Blood loss, depending on the severity, triggers various sympathetic reflexes as the body tries to maintain cardiac output to ensure that all the tissues are sufficiently oxygenated. Up to 10% of the blood volume can be lost without causing any physiological changes. Even a loss of up to 20% which is clinically significant will not be life threatening with intact sympathetic reflexes.

External bleeding is obvious as the blood loss from the site is visible and the injury is usually painful. Other signs and symptoms of bleeding includes :

  • Bruising (hematoma ~ ecchymoses). Petechiae (small hemorrhages) or purpura (slightly larger hemorrhages) may also be visible.
  • Paleness of the skin (pallor)
  • Low blood pressure (hypotension)
  • Rapid heart rate (tachycardia)
  • Shortness of breath (dyspnea)
  • Light-headedness
  • Fatigue
  • Weakness

The features above with clammy skin, dizziness and confusion may be signs of shock.

Internal bleeding may not be obvious, especially if it is minute bleeding. Apart from the signs and symptoms above, internal bleeding may also lead to :

  • Abdominal distension often with pain in intra-abdominal bleeding
  • Bleeding through an orifice :
    • Hematemesis – vomiting of blood often with upper gastrointestinal bleeding
    • Melena – black tarry stools due to the presence of degraded blood seen with upper gastrointestinal bleeding
    • Hematochezia – bright red blood in stool with lower gastrointestinal bleeding, particularly rectal bleeding
    • Hematuria – blood in the urine due to urinary tract bleeding
    • Vaginal bleeding – blood in the vaginal discharge or spontaneous due to bleeding in the fallopian tube, uterus or vagina.

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