A hernia is the protrusion of an organ or tissue out of the body cavity in which it normally lies.

The most common hernias, by a generous margin, are inguinal hernias, both direct and indirect. Indirect inguinal hernias are more common in the young as it is due to a congenital defect in the processes vaginalis whilst direct inguinal hernias are more common in the elderly as they are cause by mechanical breakdown of the fascia over many years.

Terms used to describe a hernia:
reducible - the hernial contents can be returned to their normal site
irreducible - duh
incarcerated - a.k.a. irreducible; the contents are fixed within the hernial sac
strangulated - incarcerated hernia with ischaemia of contents; often associated with signs and symptoms of intestinal obstruction
complete - hernia sac and contents protrude all the way through the defect
incomplete - hernial contents do not protrude completely

Types of hernias
Common or important hernia types in bold.

• sliding hernia - the hernia sac is partially formed by the wall of a viscus
• Littre's hernia - hernia involving a Meckel's diverticulum
• Spigelian hernia - hernia through the linea semilunaris (spigelian fascia); a.k.a. spontaneous lateral ventral hernia
• internal hernia - hernia into or involving an intraabdominal structure
• obturator hernia - hernia through obturator canal
• lumbar hernia
  • Petit's hernia - hernia through Petit's triangle (inferior lumbar triangle)
  • Grynfeltt's hernia - hernia through Grynfeltt-Lesshaft triangle (superior lumbar triangle)
• pantaloon hernia
• incisional hernia - hernia through an incisional site, most often caused by a wound infection
• ventral hernia
• Richter's hernia - incarcerated or strangulated hernia involving only one sidewall of the bowel. can result in bowel perforation through ischaemia without causing bowel obstruction.
• epigastric hernia - hernia through the linea alba above the umbilicus
• umbilical hernia - hernia through the umbilical ring, associated with ascites, pregnancy and obesity
• intraparietal hernia
• femoral hernia - hernia through the femoral ring
• Hesselbach's hernia
• Bochdalek's hernia
• Morgagni's hernia
• propertitoneal hernia
• Cooper's hernia
• inguinal hernias
  • direct inguinal hernia
  • indirect inguinal hernia
• hiatal hernia (hiatus hernia) - hernia through the esophageal hiatus

Reference: Surgical recall, 2nd edition, by Lorne. H. Blackbourne, published by Lippincott Williams & Wilkins

Her"ni*a (?), n.; pl. E. Hernias (#), L. Herniae (#). [L.] Med.

A protrusion, consisting of an organ or part which has escaped from its natural cavity, and projects through some natural or accidental opening in the walls of the latter; as, hernia of the brain, of the lung, or of the bowels. Hernia of the abdominal viscera in most common. Called also rupture.

Strangulated hernia, a hernia so tightly compressed in some part of the channel through which it has been protruded as to arrest its circulation, and produce swelling of the protruded part. It may occur in recent or chronic hernia, but is more common in the latter.

© Webster 1913.