Spigelian hernia is seen in -

A spigelian hernia occurs through the spigelian fascia, which is composed of the aponeurotic layer between the rectus muscle medially and the semilunar line laterally. Nearly all spigelian hernia occur at or below the arcuate line (Arcuate line lies midway b/w the umbilicus and the pubic symphysis) Spigelian hernias are variety of intraparietal hernia with the hernial sac dissecting beneath the internal oblique muscles. More often, it advances through the muscle and spreads out like a mushroom between the internal and external oblique aponeurosis. It is seen in older age group (>50 yrs of age) Most spigelian hernias are small and present with localized pain in the area without a bulge because the hernia lies beneath the intact external oblique aponeurosis - Ref. Sabiston Spigelian hernias have a high incidence of strangulation (because of the narrow & rigid neck) and should be repaired.