Digestive 
Blood
Cardiovascular
Dermatology
Genitourinary,
Hormones
Infections
Oncology and
Musculo-skeletal
Mental health and
Parasites
Respiratory
Senses
Various
Blood clots in the deep veins of the body may be formed in the following circumstances:
- If there is damage to the lining of a vein. Injuries due to physical, chemical or biological factors can cause damage to the veins. These factors include surgery, serious injury, inflammation and immune responses.
- If the blood flow is slow. The lack of movement can make blood flow more slowly. This may occur after surgery, when a person is sick and in bed for a long time, or during an extended trip.
- If the blood tends to clot more than what is normal. Treatment with hormones or birth control pills can also increase this risk.
