1.3.1 Structure
Derived from the Greek word “hernos” (bud, sprout, protrusion), the term hernia means an opening, for example in the abdominal wall, through which the peritoneum, possibly together with parts of the intestines, can protrude. This opening can be of congenital or acquired origin. The medical designation for this opening is hiatal orifice and the protruding peritoneum is called the hiatal sac, and any organ structure contained therein is called the hernia contents. The hernial openings can be situated in the abdominal wall, in the vicinity of surgical scars, in the diaphragm, inguinal region, floor of the pelvis, abdominal cavity and even in the muscles of the back.
As such, a hernia is made essentially of the following three parts [Fig. 4]:
- Hernial orifice: Disease-induced gap, for example in the abdominal wall. Depending on its location, it runs through different tissue layers (muscles, tendons, scar tissue, etc.). The location of the hernial opening determines how the hernia will be designated, for example, one uses the term inguinal hernia, umbilical hernia (close to the navel), incisional hernia (in the region of a surgical scar), diaphragmatic hernia, etc.
- Hernial sac: Projection of the peritoneum protruding through the hernial opening. On the outside the hernial sac is covered by subcutaneous adipose tissue and skin. These layers are called the hernia covering.
- Hernia contents: The hernial sac is either empty or – as in the majority of cases – filled with the hernia contents. The hernia contents can be made of different components, for example of intestinal loops and/or parts of the greater omentum (this is an apron-like peritoneal structure made of fat and connective tissue which is normally spread across the intestinal loops). The hernia sac generally contains a fluid called hernia water, promoting sliding of the hernia contents.
Fig. 4: Structure of a hernia