Clinical History
The patient had a recent ultrasonographic diagnosis of an aneurysm of the right common iliac artery. He had not symptoms of arterial insufficiency of lower limbs. History revealed a right nephrectomy because of a renal cell carcinoma; previous radiological reports were not available at the time of the MRA.
Imaging Findings
MRA showed a high bifurcation of the abdominal aorta and a fusiform aneurysm of the right common iliac artery. The left iliac artery was rightward angulated below its origin and just distally rectilinear in course and homogenously dilated; a further angulation was evident just proximally to the left common femoral artery. The left internal iliac artery was not visible (Fig. 1). On axial contrast-enhanced T1-weighted MRI the left iliac artery proximally run backward between the lumbar spine and the ipsilateral psoas muscle (Fig. 2a) and then posteriorly to the psoas muscle (Fig. 2b). Distally the left iliac arterial axis lay medially to the psoas muscle (Fig. 2c). The right fifth lumbar artery and the arteria sacralis originated from the proximal segment of the left iliac artery; the left fifth lumbar artery was not visible (Fig. 3). Multiple bone metastases were also evident (Fig. 2c).
Discussion
The common iliac and external iliac arteries derive from the umbilical artery at the end of the fourth gestational week. The external iliac artery origins as a ventral branch of the umbilical artery just proximally to the sciatic artery; the segment of the umbilical artery proximal to the external iliac artery connects with the fifth lumbar intersegmental branch of the aorta and becomes the common iliac artery [2]. Congenital anomalies of iliac artery are very rare and can be distinguished in anomalies of origin and course, and hypoplasia or atresia compensated or not compensated by a persistent sciatic artery [1]. Tamisier et al. distinguish four type of anomalies in origin or course of the iliac artery [1]: (a) a retro-psoas course, (b) a unilateral or (c) bilateral absence of the common iliac artery with direct origin from the aorta of the external and internal iliac arteries, (d) a pelvic course; in the last type the internal iliac artery is not opacified at arteriography [1, 2]. In cases of a retro-psoas course of the iliac artery the internal iliac artery can be or cannot be present, as in our patient [1-3]. It is hypothesised that a retro-psoas iliac artery with a high bifurcation of the abdominal aorta could be related to agenesis of the common and external iliac arteries and an abnormal connection of the umbilical artery to the fourth lumbar intersegmental artery [3, 4]. In our patient the abnormal origin of the right fifth lumbar artery and the arteria sacralis from the left iliac artery as well as the absence of the left fifth lumbar artery patient could support this hypothesis. A retro-psoas iliac artery can be asymptomatic and incidentally detected in course of radiological investigations, but an intermittent claudicatio has been reported in a young patient [2, 3]. Jain et al. reported a case of an intraoperative recognition of this anomaly, misdiagnosed in radiological work up for kidney transplantation [5]. Diagnosis of a retro-psoas iliac artery is easy both with angiography and cross-sectional imaging if the radiologist keeps in mind the normal course of the common and external iliac arteries. Recognition of this anomaly is mandatory not only in vascular surgery but even in non-vascular lumbar and pelvic operations to prevent an inadvertent haemorrhage [4, 5].
Differential Diagnosis List
Retro-psoas iliac artery
Persistent sciatic artery
Arterial dysplasia
