Trocar [https://eleps.ru/katalog/po-vidam-produktsii-instrumenty-laparo-torakoskopiya-instrumenty-dostupa-troakary-kanyuli-torakoporty-igly-/] is an instrument used by surgeons to penetrate the body cavity through the integument (while maintaining the geometry of the integument). The trocar provides access to the surgical field and creates an operative space through which various surgical instruments are introduced. In appearance, a trocar is a hollow tube into which a sharp stylet with a handle is inserted. But the structure of a surgical trocar is more complex than it seems at first glance. The composition of a classic trocar: - a stylet, designed to pierce the abdominal wall; - a tube (sleeve) - a hollow tube that is used to insert instruments into the abdominal cavity; - valve mechanism - which prevents gas leakage when replacing and removing instruments from the sheath; - gas supply tap - used to pump air in/out, as well as to maintain pneumoperitoneum during surgery. Trocars are divided into several groups: 1) by diameter - a trocar with a diameter of 2-3 mm is used to insert miniature instruments (minilaparoscopic surgery); - a trocar with a diameter of 5 mm is used for pediatric surgery and for inserting additional instruments; - a trocar with a diameter of 10-12 mm is a classic option, used to insert endoscopes, exposure instruments, a clipper, as well as for removing remote organs; - trocars with a diameter of 15, 18, 20 mm are used to insert tissue suturing agents and other equipment used in endoscopic surgery. 2) by valve type Trocars are classified by the valve design. The following types are distinguished: - plunger with a manual valve (the lumen is closed by a spring-loaded rod or plunger). When the slot coincides with the lumen, trocar patency is restored; after the instrument is removed, the spring returns the rod and the lumen is closed. Disadvantages include the risk of damage, difficulty in manipulation, short lifespan, and possible damage to the threads passed through the trocar lumen. - automatic ball valves. The ball, under pressure caused by gas, rests against the opening and closes the lumen. When the instrument is inserted, it automatically moves it to the side. A disadvantage of this type is the lack of manual control of the valve position. - universal petal valves. A spring-loaded petal flap closes the lumen. When the instrument is inserted, the valve opens mechanically. If necessary, it can be opened with a control lever. - rubber flap or diaphragm valves. Valve sealing is achieved through the elasticity of the material. The main disadvantage is their short lifespan. - Modular trocars with a universal valve allow the instrument diameter to be changed from 5 to 11 mm as needed. The size is changed by screwing a replaceable tube of varying diameters onto the universal valve. - A valveless trocar cannot ensure a tight seal in the cavity when the instrument is withdrawn. Therefore, the opening is closed with a finger when the instrument is withdrawn. Advantages include relative ease of manufacture and cost-effectiveness. 3) By purpose: Disposable trocars are used for laparoscopy (available in various diameters). They are sterile and intended exclusively for initial use. There is also a cystic trocar used for endoscopy or for removing fluid from the body. A separate category includes a catheter trocar for fluid administration and an intercostal trocar, as well as highly specialized trocars for dynamic laparoscopy or interoperative cholangiography. Trocar stylets also vary depending on the tip sharpening shape, divided into: - conical (less tissue trauma, more effort is required for insertion, better retention in tissue, since the tissue tightly fits the instrument), - eccentric cone-shaped (due to the tip shifting from the center during rotational insertion of the instrument, tissue penetration is improved), - pyramidal (more tissue trauma, less effort is required for insertion, tissue is cut during insertion, which improves insertion, but the hermetic seal is compromised), - complex sharpening shapes and blunt (for insertion of blunt-ended stylets, the tissue is pre-cut). Trocar stylets can be either unprotected or protected from tissue damage (atraumatic trocars [https://eleps.ru/katalog/po-vidam-produktsii-instrumenty-laparo-torakoskopiya-instrumenty-dostupa-troakary-kanyuli-torakoporty-igly-/]). This protection typically comes in the form of caps and sheaths of various shapes that extend forward and close after the tip has entered the cavity. It can also be a mechanism that retracts the tip into the sheath. The trocar sheath may have an external screw thread for screwing and fixation into the abdominal wall (screw-type trocar [https://eleps.ru/katalog/po-vidam-produktsii-instrumenty-laparo-torakoskopiya-instrumenty-dostupa-troakary-kanyuli-torakoporty-igly-/]). A screw fixation may also be supplied separately. The sheath end may have a cross-section or a beveled cross-section; the latter is believed to facilitate trocar passage through tissue.