Wikipedia says this about internal bleeding.
Internal bleeding is bleeding occurring inside the body. It can be a serious medical emergency depending on where it occurs (e.g. brain, stomach, lungs), and can potentially cause death and cardiac arrest if proper medical treatment is not received quickly.Scientists and engineers are developing new techniques for the identifying and treatment of internal bleeding. Here are links to some of their research.
Internal bleeding can occur by traumatic injury such as high speed deceleration in an automobile accident, or by blood vessel rupture from high blood pressure. Also, internal bleeding can be caused by hitting or running against a sharp object in that area. Some diseases may also cause internal bleeding, such as the Filovirus Ebola. This infection, together with similar infections such as the Marburg virus, is rare. The most common cause of internal bleeding is carcinoma (cancer), either of the gastro-intestinal tract or of the lung, or more rarely of other organs such as the prostate, pancreas or kidney. Other diseases linked to internal bleeding include scurvy, hepatoma, liver cancer, Autoimmune Thrombocytopenia, ectopic pregnancy, malignant hypothermia, ovarian cysts, Vitamin K Deficiency, and hemophilia. Some medication interactions may also cause internal bleeding.
Progress toward a new emergency treatment for internal bleeding ― counterpart to the tourniquets, pressure bandages and Quick Clot products that keep people from bleeding to death from external wounds ― was reported in Philadelphia on August 20 at the 244th National Meeting & Exposition of the American Chemical Society.