Pathways of extrapelvic spread of disease: Anatomic-radiologic correlation.

Extrapelvic spread of disease, particularly from gastrointestinal tract perforations which may be clinically occult, may first present in the buttock, hip, thigh, and even lower leg, and the extraperitoneal space of the abdomen itself. Clinical manifestations at these remote sites may be very misleading. Anatomic and roentgenologic observations establish the preferential pathways of extrapelvic spread. These are related to the insertions and fascial investments of the iliopsoas, pyriformis, and obturator internus muscles and the ensheathed penetrations of the superior gluteal arteries. Superiorly, extension from the pelvic tissues seeks out the posterior pararenal compartment of the extraperitoneal region of the abdomen. Roentgenologic signs may first identify the presence, extent, and localization of the primary process.