A. Incidence and etiology
- Incisional hernias
- Umbilical hernias
are congenital defects. They are more frequent in African Americans than in whites. Most newborn umbilical hernias close spontaneously by the second year of life. However, umbilical hernias are also common in adults. Patients with ascites have a high incidence of umbilical hernias. When large, the hernias may cause gastrointestinal tract symptoms. When small, they rarely cause symptoms and may go unnoticed. Umbilical hernias have a fairly high rate of incarceration, usually with preperitoneal fat or omentum.
- Epigastric hernias
are hernias of the linea alba above the umbilicus. They occur more frequently in athletically active young men. When small or in obese individuals, epigastric hernias may be hard to palpate, making the diagnosis difficult as well. Usually, they produce epigastric pain that may be falsely attributed to other abdominal diagnoses. The diagnosis is made by palpation of a subcutaneous epigastric mass; most such hernias occur within a few centimeters of the umbilicus and are associated with a small (1 to 2 cm) fascial defect.
- Spigelian hernias
protrude through the spigelian fascia, near the termination of the transversus abdominis muscle along the lateral edge of the rectus abdominis near the junction of the linea semilunaris and linea semicircularis. Because the herniated visceral contents are intraparietal (between the abdominal wall muscles), these hernias can be difficult to diagnose and therefore are included in the differential diagnosis of obscure abdominal pain. Ultrasonography, CT scan, or laparoscopy can be useful confirmatory tools in patients with focal symptoms in the appropriate region.
- lumbar hernia
The most common type of lumbar hernia is an incisional hernia from a previous retroperitoneal or flank incision. Lumbar hernias may also occur in two different triangles: the Petit triangle and the Grynfeltt triangle. Lower lumbar hernias of the Petit triangle are located in a weak area limited posteriorly by the latissimus dorsi, anteriorly by the external oblique muscle, and inferiorly by the iliac crest. Grynfeltt hernias are upper lumbar in location, below the lowest rib.