A hernia in the groin area, more properly termed an inguinal hernia, occurs when a a section of the peritoneum, or covering of the intestines, bulges out through an opening or a tear in the fascia tissue of the external oblique aponeurosis. A direct hernia may involve retroperitoneal fat being pushed through the opening in the peritoneal sac, while in an indirect hernia a section of the intestine is included in the sac. Indirect hernias can become trapped or strangulated, a complication in which the fascia opening, also known as a fascia ring, pinches the herniated material and cuts off the blood supply. A patient with a strangulated hernia is at risk of gangrene.
A number of different hernia classifications have been developed to describe the various locations and types of hernias. The Nyhus classification is used commonly in the United States, and is summarized on Medscape (see link) as follows:
Type 1 is an indirect hernia with a normal internal ring of fascia
Type 2 is an indirect hernia with an enlarged internal ring of fascia
Type 3a is a direct inguinal hernia
Type 3b is an indirect hernia causing posterior wall weakness
Type 3c is a femoral hernia
Type 4 represents all recurrent hernias