What is an abdominal hernia?
An abdominal hernia occurs when an organ or other piece of tissue protrudes through a weakening in one of the muscle walls that enclose the abdominal cavity. The sac that bulges through the weak area may contain a piece of intestine or fatty lining of the colon (omentum) if the hernia occurs in the abdominal wall or groin. If the hernia occurs through the diaphragm, the muscle that separates the chest from the abdomen, part of the stomach may be involved.
The abdominal wall is made up of layers of different muscles and tissues. Weak spots may develop in these layers to allow contents the abdominal cavity to protrude or herniate. The most common abdominal hernias are in the groin (inguinal hernias), in the diaphragm (hiatal hernias), and the belly button (umbilicus). Hernias may be present at birth (congenital), or they may develop at any time thereafter (acquired).
What are the different types of abdominal hernias?
Hernias of the abdominal and pelvic floor
Inguinal hernias are the most common of the abdominal hernias. The inguinal canal is an opening that allows the spermatic cord and testicle to descend from the abdomen into the scrotum as the fetus develops and matures. After the testicle descends, the opening is supposed to close tightly, but sometimes the muscles that attach to the pelvis leave a weakened area. If later in life there is a stress placed on that area, the weakened tissues can allow a portion of small bowel or omentum to slide through that opening, causing pain and producing a bulge. Inguinal hernias are less likely to occur in women because there is no need for an opening in the inguinal canal to allow for the migration and descent of testicles.
A femoral hernia may occur through the opening in the floor of the abdomen where there is space for the femoral artery and vein to pass from the abdomen into the upper leg. Because of their wider bone structure, femoral hernias tend to occur more frequently in women.
Obturator hernias are the least common hernia of the pelvic floor. These are mostly found in women who have had multiple pregnancies or who have lost significant weight. The hernia occurs through the obturator canal, another connection of the abdominal cavity to the leg, and contains the obturator artery, vein, and nerve.
Hernias of the anterior abdominal wall
The abdominal wall is made up of two sets muscles on each side of the body, that mirror each other. They include the rectus abdominus muscles, the internal obliques, the external obliques, and the transversalis.
When epigastric hernias occur in infants, they occur because of a weakness in the midline of the abdominal wall where the two rectus muscles join together between the breastbone and belly button. Sometimes this weakness does not become evident until later in adult life as it becomes a bulge in the upper abdomen. Pieces of bowel, fat, or omentum can become trapped in this type of hernia.
The belly button, or umbilicus, is where the umbilical cord attached the fetus to mother allowing blood circulation to the fetus. Umbilical hernias cause abnormal bulging in the belly button and are very common in newborns and often do not need treatment unless complications occur. Some umbilical hernias enlarge and may require repair later in life.
Spigelian hernias occur on the outside edges of the rectus abdominus muscle and are rare.
Incisional hernias occur as a complication of abdominal surgery, where the abdominal muscles are cut to allow the surgeon to enter the abdominal cavity to operate. Although the muscle is usually repaired, it becomes a relative area of weakness, potentially allowing abdominal organs to herniate through the incision.
Diastasis recti is not a true hernia but rather a weakening of the membrane where the two rectus abdominus muscles from the right and left come together, causing a bulge in the midline. It is different than an epigastric hernia because, the diastasis does not trap bowel, fat, or other organs inside it.
Hernias of the diaphragm
Hiatal hernias occur when part of the stomach slides through the opening in the diaphragm where the esophagus passes from the chest into the abdomen. A sliding hiatal hernia is the most common type and occurs when the lower esophagus and portions of the stomach slide through the diaphragm into the chest. Paraesophageal hernias occur when only the stomach herniates into the chest alongside the esophagus. This can lead to serious complications of obstruction or the stomach twisting upon itself (volvulus).
Traumatic diaphragmatic hernias may occur due to major injury where blunt trauma weakens or tears the diaphragm muscle allowing immediate or delayed herniation of abdominal organs into the chest cavity. This may also occur after penetrating trauma from a stab or gunshot wound. Usually these hernias involve the left diaphragm because the liver, located under the right diaphragm, tends to protect it from herniation of bowel.
Congenital diaphragmatic hernias are rare and are caused by failure of the diaphragm to completely form and close during fetal development. This can lead to failure of the lungs to fully mature, and it leads to decreased lung function if abdominal organs migrate into the chest. The most common type is a Bochdalek hernia at the side edge of the diaphragm. Morgagni hernias are even rarer and are a failure of the front of the diaphragm.
Picture of different types of hernias.