Spigelian hernia

Overview
A Spigelian hernia (or lateral ventral hernia) is a hernia through the spigelian fascia, which is the aponeurotic layer between the rectus abdominis muscle medially, and the semilunar line laterally. These hernias almost always develop at or below the linea arcuata, probably because of the lack of posterior rectus sheath. These are generally interparietal hernias, meaning that they do not lie below the subcutaneous fat but penetrate between the muscles of the abdominal wall; therefore, there is often no notable swelling.

Most of these hernias are small, and, as such, there is a high risk of strangulation. Most of them develop around age 50 (4th-7th decade of life). As an entity, they are rare, when compared other types of hernias.

Symptoms and diagnosis
Patients typically present with either an intermittent mass, localized pain, or signs of bowel obstruction. Ultrasonography or a CT scan can establish the diagnosis.

Treatment
These hernias should be repaired because of the high risk of strangulation; fortunately, surgery is straight-forward, with only larger defects requiring a mesh prosthesis.

Eponym
Adriaan van den Spiegel, a surgeon-anatomist born in Brussels, described this hernia in 1645.