Hernias usually develop in the abdomen but they may affect other parts of the body. Hernias can be classified in several ways, according to their location, severity or origin, for example.

Classification according to anatomical location

Most hernias occur in the abdomen when a weakness in the abdominal wall leads to a hole forming. Some examples of the most common hernias to occur in the abdomen are given below.

Inguinal hernias

Inguinal hernias occur when bowel tissue or fatty tissue protrudes into the groin area at the top of the thigh. These hernias make up 75% of all abdominal hernias and mainly affect men.

Femoral hernia

These also occur when abdominal contents protrude through to the groin area. However, these hernias tend to be more rounded than inguinal hernia and mainly occur in women rather than men.

Umbilical hernia

Here, intra-abdominal tissue pokes through the abdomen, near the naval area. These hernias are more common among pregnant women and obese people.

Hiatus hernia

A hiatus hernia occurs when part of the stomach or intestine protrudes into the chest area through a hole in the diaphragm.

Less common hernias

Less common hernias that are also classified according to their location in the body include:

• Epigastric hernia: Fatty tissue protrudes through the abdomen in the area between the belly button and the breast bone.
• Spigelian hernia: A bowel part protrudes through the abdomen, below the belly button and at the side of the abdominal muscle.
• Muscle hernia: A piece of muscle pokes through the abdomen.
• Incisional hernia: These occur when a piece of tissue protrudes through a surgical wound that has not healed properly.

Classification according to cause and severity

Hernias can also be classified according to their origin or cause. For example, congenital hernias occur as birth defects that have affected the abdominal wall of the newborn. Acquired hernias on the other hand, develop later in life for a variety of different reasons.

Hernias may also be categorized according to their severity and may be described as either complete or incomplete, for example. Complete hernia refers to when the entire organ protrudes through a weakened area of tissue, while incomplete hernia refers to when only part of the organ protrudes through.

Other classifications

Some other ways of categorizing hernia are described below.

• Intraparietal hernias are hernias that do not reach the subcutis and only protrude as far as the musculoaponeurotic layer. These hernias may cause less bulging and can therefore be more difficult to detect.
• Internal hernias protrude within the body, while external hernias protrude through to the outside of the body.
• Reducible hernia refers to when the protruding tissue can be moved back to its original site using simple manipulation, while an irreducible hernia cannot be moved back.
• Irreducible hernia can lead to the following complications:
  • Strangulation: The contents of the hernia become pressured and blood supply is compromised leading to cell death and gangrene.
  • Obstruction: Bowel contents may no longer be able to pass through an area of herniated bowel, leading to cramps and vomiting.