Trocars and Cannulas

In its simplest configuration, a trocar is a pen-shaped instrument with a sharp triangular point at one end, typically used inside a hollow cylinder, known as a cannula or sleeve, which provides an access port into a cavity during surgery. A cannula is a tube-shaped metal or plastic shaft placed in the patient to allow access into the abdominal cavity during a laparoscopic procedure. A seal is located at the top of the cannula, which allows instruments to pass through the cannula while preventing carbon dioxide from escaping from the abdominal cavity. An obturator is the tool that allows the cannula to penetrate the abdomen for initial placement. The Veress needle technique is the oldest and the most traditional technique. In the direct insertion technique, the primary cannula–trocar assembly is placed without preinsufflation. Disposable cannulas are very common in human medicine, but their cost limits their use in veterinary medicine.