Definition of Hernia - Bailey and Love's Short Practice of Surgery (28th Edition)

The Definition

"A hernia is an abnormal protrusion of an organ or tissue through an opening in the layer that normally confines it."

• Bailey and Love's Short Practice of Surgery, 28th Edition, Chapter 64: Abdominal Hernia, p. 1080

Key Points Elaborating the Definition

• There are many varieties of hernia arising through areas of weakness in the abdominal wall.
• Because the hernia "pushes" from the inside to the outside, an abdominal hernia takes with it all the coverings of the abdominal wall, although they may be thinned and attenuated.
• However, not all abdominal hernias have a peritoneal sac - for example, many epigastric hernias arise in the interstitial layers and only draw peritoneum into the protrusion as a secondary phenomenon when they become larger.

Essential Components of an Abdominal Wall Hernia

1. A defect in the wall - the weakness may be through fascia and muscle, or through fascia alone (e.g. epigastric hernia), or may even have a bony component (e.g. femoral hernia).
2. The content - tissue that has been forced outwards through the defect.

Anatomical Causes of Abdominal Wall Herniation

• Areas of natural weakness due to absence of muscle (e.g. lumbar triangles, posterior wall of the inguinal canal)
• Natural defects that allow structures to enter or leave the abdomen (e.g. inguinal canal, oesophageal hiatus, femoral canal)
• Developmental abnormalities
• Disruptions of the abdominal wall as a result of injury

Causes of Hernia (Summary Box 64.1)

Pathophysiology of Hernia Formation

• A normal abdominal wall has sufficient strength to resist high abdominal pressure. Many patients notice a hernia after excessive straining - but the strain merely brings the hernia to attention rather than being its actual cause.
• There is good evidence of an inherited imbalance in the types of collagen (supported by histological evidence and its association with diseases like aortic aneurysm).
• In extreme collagen disorders such as Ehlers-Danlos syndrome, long-term repair is very difficult.
• Smoking is linked to impaired collagen maturation and increases hernia risk.
• Hernias are more common in elderly patients owing to degenerative weakness of muscles and fibrous tissue.
• Incisional hernias are more common after wound complications and in patients with a high BMI.

Clinical Image from Bailey & Love