A catheter is a tube passed through the body for the evacuation of fluids such as urine or blood, or the injection of fluids such as intravenous medications, or blood for transfusions. Catheters are typically made out of plastic, or elastic, but may also be made out of metal or glass.
In the body modification community, urinary catheters are often used as sounds for urethral stimulation in both men and women.
In addition, IV (Intravenous) catheters are often used in blood play for extracting large amounts of blood from an artery. Catheter needles are also used for body piercing, more commonly in Europe.