Expansion
Through the linea semilunaris, usually just below the arcuate line
Expansion
- Occurs at the linea semilunaris, the curved lateral border of the rectus sheath
- Almost always in the Spigelian belt, a narrow zone just below the arcuate line
- The defect is in the Spigelian aponeurosis, between transversus abdominis and internal oblique
The site is a weak point for two reasons: the posterior rectus sheath is deficient below the arcuate line, and the aponeurotic fibres change direction here.
Because the sac passes through the deeper layers but is contained by the intact external oblique aponeurosis, it spreads between the muscle layers instead of forming an obvious lump. Patients present with localised pain and no visible swelling, so diagnosis often requires ultrasound or computed tomography. The narrow neck gives a high risk of strangulation, so repair is advised.