What is true of Spigelian hernia?

Spigelian hernia occurs at the semilunar line, which extends along the lateral border of each rectus abdominis muscle. The posterior rectus sheath is deficient at the level of the arcuate line (semicircular line) about one-third of the distance between the umbilicus and the pubic symphysis; this is the most common site for Spigelian hernia to occur through the linea semilunaris. It occurs in both sexes. The Bassini technique refers to inguinal hernias only. A hernia that involves part of the bowel wall is known as a Richter's hernia. The appendix may or may not form part of the contents of the sac.