Hernia, also known as hernia, is a cystic tumor formed by organ rupture holes or abnormally enlarged natural pores originally located in abdominal cavity protruding into subcutaneous or other anatomical cavities. The common hernias are umbilical hernia, scrotal hernia and abdominal hernia. The first two are the most common in pigs. The reasons are congenital and acquired. Congenital hernia is more common in piglets, which is caused by congenital oversize of some anatomical holes (umbilical foramen, inguinal ring, etc.). ) and related to genetic factors (especially boars). Acquired hernia often occurs due to mechanical trauma, increased abdominal pressure and improper castration in sows. Hernia is generally composed of hernia hole, hernia sac and hernia contents. Hernia holes are muscle rupture holes or enlarged natural holes from which internal organs are exposed. The hernia sac consists of peritoneum, abdominal fascia and skin. Hernia contents are some movable internal organs that extend into the hernia sac through the hernia hole, mostly small intestinal loops and omentum. When the posture of pigs changes or people press the hernia sac by hand, the contents of the hernia can return to the abdominal cavity through the hernia hole, which is called reversible hernia. Irreducible hernia refers to a hernia in which the contents of the hernia sac cannot be restored by pressing or changing the position by hand. The reasons why the contents of hernia can't return to abdominal cavity are: the hernia hole is narrow or the hernia is long and narrow; The hernia contents are attached to the hernia sac; Intestinal adhesion; The intestine is filled with too much feces or gas. If the hernia contents are occluded in the hernia hole, the organs are compressed and the blood circulation is blocked, resulting in congestion, inflammation and even necrosis, which is collectively called occluded hernia.