Spigelian hernias occur through a defect in the linea semilunaris
, a fibrous union of the rectus sheath with the aponeuroses of the transverse abdominal and abdominal internal oblique muscles that extends from the level of the ninth rib cartilage to the pubic symphysis.
SH, also known as hernia of semilunar line, is the protrusion of preperitoneal fat, peritoneal sac or intraabdominal organs through a congenital or acquired defect in the Spigelian zone.This zone is formed by the fusion of transverse abdominis and internal oblique aponeurosis, and is bounded medially by the lateral margin of the rectus muscle and laterally by the linea semilunaris
. Although the Spigelian aponeurosis extends from the pubic tubercle to the costal cartilage of the eighth rib, most of SHs are located in a 6 cm wide region inferior to the umbilicus and superior to the interspinous line, which is called as the Spigelian hernia belt (Figure 1).