Spigelian hernias are spontaneous, lateral, ventral hernias protruding through the Spigelian fascia, ie, the area between the musculofascial junction of the transverse abdominal muscle laterally and the outer edge of the rectus muscle medially. The diagnosis is often overlooked because of the frequent lack of definitive physical findings, but must be considered in any case of lower, lateral, abdominal pain or tumor mass.
Singer JA, Mansberger AR. Spigelian Hernia. Arch Surg. 1973;107(4):515-517. doi:10.1001/archsurg.1973.01350220005003