ABSTRACT
A hernia is the protrusion of a viscus (organ) through its normal coverings to an ectopic site. The most common hernias (or herniae) are abdominal hernias. Abdominal contents protrude through their peritoneal coverings, due to weaknesses in the abdominal wall. This may be congenital (e.g. a congenital inguinal hernia due to a persistent processus vaginalis), or acquired due to straining combined with weak muscles (e.g. direct inguinal hernia) or at sites of penetration of normal structures through the abdominal wall (e.g. femoral hernias protruding through the femoral canal) or after an operation (incisional hernias). Even coning, in which the medulla oblongata of the brain protrudes through the foramen magnum, is a type of herniation.
