Infra-renal abdominal aorta agenesis: a case report with emphasis on MR angiography findings.

The purpose of this study is to report a case of infra-renal aorta agenesis with emphasis on the MR angiography (MRA) findings. A 66-year-old woman presented with urinary complaints. Pelvic and abdominal ultrasound showed hydronephrosis secondary to ureteral lithiasis; the distal portion of the abdominal aorta was not identified. Abdominal CT showed that the infra-renal portion of the abdominal aorta was apparently absent. MRI and MRA demonstrated that, after the origin of the renal arteries, the abdominal aorta spontaneously terminated in two lumbar hypertrophic arteries. In addition, MRA showed a dilated superior mesenteric artery that formed a vascular loop, which continued posterior and inferiorly towards the posterior pelvic region. In this region, it bifurcated and formed internal iliac branches, which were responsible for the arterial supply of the pelvis. In conclusion, MRA allows for precise evaluation of patients with infra-renal abdominal aorta agenesis. Although it is a rare entity, radiologists should be able to recognize it in ultrasound, CT and MRI studies.