Fourth lumbar artery continuation of the common iliac artery with a retro-psoas course demonstrated by CT

Purpose To describe a case of an anomalous common iliac artery (CIA) arising from the aorta as the fourth lumbar artery (4th LA) and following a retro-psoas course as the continuation of the 4th LA. Methods Contrast-enhanced abdominopelvic computed tomography (CT) findings of an incidentally detected anomalous CIA are described in an 8-year-old girl. Case report CT showed that the right CIA originated from the distal aorta at the L3–L4 level with an acute angle and continued posteriorly in the course of the 4th LA. The right CIA descended into the iliac fossa as a single artery, lying posterior to the psoas muscle. It gave off the internal iliac artery (IIA) low in the iliac fossa and continued as the external iliac artery (EIA). The median sacral artery (MSA) originated from the left proximal CIA and joined the posterior division of the right IIA. Discussion Fourth LA continuation of the CIA is a rare vascular anomaly with a few published reports to date. The anomaly occurs far more on the right side than the left and is mostly asymptomatic. An abnormal connection between the umbilical artery and the distal aorta probably results in this anomaly, as well as in another group of CIA anomalies that are characterized by the absence of one or two CIAs with trifurcation or quadrifurcation of the distal aorta. Conclusion Although the vascular anomaly is mostly asymptomatic, knowledge of it is important in the interventions of the area to prevent complications.