When an organ within the abdomen pushes out an opening or weak area in the abdomen wall it is called an external hernia. External hernias create a bulge under the skin that can be seen and felt; whereas, internal hernias do not. Examples of external hernias include umbilical (naval) hernias, femoral hernias, and inguinal (groin) hernias.
Internal hernias involve part of an organ within the abdomen pushing through an opening in the wall of another organ in the abdomen. Many internal hernias are often not detected until they become painful, incarcerated, or strangled of its blood supply.