Spigelian Hernia

Semilunar line is the slight groove in the external abdominal wall parallel to the lateral edge of the rectus sheath. It is also called Spigelian fascia and first described by Adrian van der Spieghel, in 1578 [1]. Spigelian hernia is a hernia through the spigelian fascia, which is the aponeurotic layer between the rectus abdominis muscle medially, and the semilunar line laterally. The first report of a spigelian hernia was in 1764 by Klinkosch [2]. He called it as Spiegel’s linear hernia. Probably because of the lack of posterior rectus sheath, these hernias almost always develop at or below the linea arcuata,. These are generally interparietal hernias, that means they do not lie below the subcutaneous fat but go between the muscles of the abdominal wall; so, there is often no manifest swelling. Patients typically present with either an intermittent mass, localized pain, or signs of bowel obstruction [3]. Spigelian hernias have high risk of strangulation. They most occur on the right side. Most of them present around age 50 (4th-7th decade of life). Compared to other types of hernias they are rare[1]. Abdominal ultrasound may show the focal defect of the echogenic aponeurosis line of the anterior abdominal wall and the content of hernia. Mesentery and omentum shows high echogenicity and air filled bowel shows acoustic shadowing on ultrasound images. But CT scan provides the greatest sensitivity and specificity to show Spigelian hernia and its content [4]. These hernias should be repaired because of the high risk of strangulation [5].