A trocar is a surgical instrument consisting of a sharply pointed stylet enclosed within a hollow cannula. When the trocar is thrust through the body wall into a fluid- or gas-filled cavity, the stylet is withdrawn, leaving the cannula in place as a port through which the contents can drain or through which instruments can be introduced. In equine medicine, trocars are most commonly employed in emergencies involving cecal or large-colon gas accumulation during gas-distension colic.
Cecal trocarization is a field procedure performed when a horse has massive cecal tympany (gas distension) that has not responded to initial medical management and when transport to referral surgery is not immediately available. Under sedation and after surgical preparation of the right flank, a large-bore trocar is inserted through the body wall into the cecum to release the accumulated gas and reduce intraluminal pressure. The procedure carries risks of peritoneal contamination and local infection, but in extreme circumstances it may be the measure that keeps the horse alive until surgery is possible.
Trocars are also used in thoracocentesis (draining pleural effusions from the chest cavity), abdominocentesis (collecting peritoneal fluid for diagnostic analysis), and in laparoscopic procedures as ports for instrument access. The term derives from French “trois-quarts” (three-quarters), historically referring to the triangular cross-section of the cutting tip.
Proper trocar technique requires accurate anatomical knowledge of insertion sites and strict aseptic preparation to avoid introducing peritoneal contamination risk-producing contamination into sterile body cavities.