A hernia occurs when a tissue or organ pushes through a weakened spot in the muscle or connective tissue wall that normally contains it. Ventral hernias are a common type of hernia, with “ventral” referring to the front of the body or the abdomen. This means a ventral hernia specifically involves a protrusion through a defect in the anterior abdominal wall, the front muscular and fascial layer. The hernia sac, which contains internal tissues like intestines or fat, creates a visible or palpable bulge on the surface of the abdomen.
Anatomical Location of a Ventral Hernia
A ventral hernia can occur anywhere along the anterior abdominal wall, extending from the lower rib cage down to the pelvis. The protrusion happens when abdominal contents push through a tear in the fascia, a strong layer of connective tissue that reinforces the abdominal muscles. This defect allows the internal tissue to bulge outward beneath the skin.
The most frequent site is along the midline of the abdomen, a fibrous structure called the linea alba. This structure is formed where the layers of fascia from the side abdominal muscles meet in the center. The linea alba represents a natural area of weakness, making it susceptible to intra-abdominal pressure. The location of the hernia is defined by the site of the fascial defect, not the resulting external bulge.
Classifications Based on Location
Ventral hernias are classified into specific types based on their precise anatomical site, indicating the exact point of structural failure in the abdominal wall.
Umbilical and Epigastric Hernias
One of the most common subtypes is the umbilical hernia, which occurs at or immediately around the navel. The umbilicus is a remnant of fetal circulation and represents a naturally weak point in the midline fascia. The epigastric hernia forms in the upper central part of the abdomen, specifically between the navel and the breastbone (xiphoid process). This type is also located along the linea alba, but higher up than an umbilical hernia. Often, epigastric hernias are small and contain only fatty tissue.
Incisional Hernias
The incisional hernia develops at the site of a previous surgical incision on the abdomen. Since cutting and healing tissue reduces the tensile strength of the abdominal wall, this type of hernia can appear anywhere a surgeon has previously operated. Incisional hernias are a frequent complication of abdominal surgery, occurring in up to 10% of patients who have undergone a procedure.
Spigelian Hernias
A less common type, the Spigelian hernia, occurs on the side of the abdomen, usually below the navel. It pushes through a natural weakness in the abdominal muscle layers.
Factors That Cause Abdominal Wall Weakness
Ventral hernias form when increased pressure inside the abdominal cavity pushes against a weakened or defective area of the wall. The strength of the abdominal wall can be compromised by various factors, including previous abdominal surgery, as the resulting scar tissue is less strong than the original muscle and fascia.
Conditions that chronically increase intra-abdominal pressure place a strain on the fascial layers. These include obesity, pregnancy due to physical distention, and activities involving repetitive straining, such as heavy lifting. Chronic medical issues like persistent coughing or constipation can also contribute to hernia formation. Even congenital factors, where an individual is born with a structurally weaker abdominal wall, can predispose a person to developing a ventral hernia.