Aortic aneurysm, infrarenal

Jeffrey Lipshitz, MD Van R. Bohman, MD Patricia Pierce, MD Jennifer Mixdorf, RDMS

Address correspondence to Jeffrey Lipshitz, MD The Perinatal Center, 3196 Maryland Pkwy, Suite 209, Las Vegas, NV 89109-2313. Ph: 702-732-9332; Fax 702-732-4472

Synonyms: None.

Definition: A balloon-like swelling in the wall of the aorta.

Prevalence: Rare.

Etiology: Uncertain. May reflect a deficiency of iron-hematoxylin-reactive elastin in the aortic wall1.

Pathogenesis: Unknown.

Associated anomalies: Tuberous sclerosis2, arterial infection, giant-cell aortoarteritis, autoimmune connective disease, Kawasaki"s disease, Ehler"s-Danlos syndrome of Marfan"s syndrome, other forms of noninflammatory medial degeneration, arterial dysplasias, congenital idiopathic factors3.

Differential diagnosis: Arterio-venous malformation.

Prognosis: Good, in absence of other anomalies.

Recurrence risk: Unknown.

Management: No changes in the prenatal care; surgery after delivery.

MESH Aneurysm, aorta ICD9 747.2 CDC 747.270


Conventional realtime ultrasound has proved useful in detecting fetal morphologic abnormalities in utero. This case demonstrates the importance of color flow to further evaluate any cystic structures found. Congenital aortic aneurysms are rare, and this is the first known case diagnosed in utero.

Case report

A 27-year-old G1P0 woman was referred to our center for evaluation of a cystic area seen in the fetal pelvis on a prior ultrasound. The patient"s family history was significant in that the patient"s mother had a vascular pelvic tumor removed as a child secondary to tuberous sclerosis. The patient had not been formally investigated for tuberous sclerosis but had no obvious manifestations of the disease. Sonography revealed a 28-week male fetus whose size was consistent with menstrual dates. Normal amounts of amniotic fluid were present. The survey of the fetal anatomy showed no anomalies other than a polylobulated hypoechoic mass in the lower abdomen. This mass measured 18 x 18 x 13mm and was located superior to the fetal bladder and inferior to the kidneys (fig. 1).




Figure 1: Several views of the aortic aneurysm. Note the normal aorta above and the normal IVC. There is no evidence of dilatation of the cava or hydrops.


Color flow Doppler proved this to be vascular in nature, with marked turbulence and no jet into the inferior vena cava (fig. 2).


Figure 2: Axial and longitudinal views of the aneurysm, with color Doppler.

The pulse-wave Doppler demonstrates a diastolic flow similar to that of the descending aorta. This patient was scanned periodically during gestation to watch for any signs of cardiac failure or hydrops, which were never found. Aneurysmal dilatation of the aorta and arterio-venous malformation were considered in the differential diagnoses; however, as there were no signs of right-heart overload or failure, no evidence of high diastolic flow as would be expected in an arteriovenous fistula and no IVC jet was ever seen, it was felt that an aneurysm was the most likely diagnosis. At 39 weeks gestation, a healthy 3,430g male infant was delivered by cesarean section. Apgar scores were 8 and 9 at 1 and 5 minutes. The infant was taken to the neonatal unit for observation and testing. Of interest, the infant"s fibrinogen count dropped to 0 during the first day of life. Postnatal angiography confirmed the diagnosis of aortic aneurysm, with a suspected small aneurysm also found in the proximal left internal iliac artery. The lesion was successfully resected on the 7th day of life, utilizing aneurysmal wall and no grafts in this repair. This aneurysm measured 40x30mm at resection (fig. 3). The aneurysm was filled with clot, which was thought to be the etiology of the hypofibrinogenemia on the first day of life. At this writing, the infant is well and without sequelae.

Figure 3: Frame from the operating room video showing the dissection of the aneurysm.


An aortic aneurysm is an abnormal dilatation of the luminal wall of the aorta with bulging or ballooning of the vessel.


Aneurysms of the aorta are rare in the very young, and infrarenal aneurysms are even less common4. No aortic aneurysms of this type have been accurately diagnosed in utero preceding this patient.


The presence of color flow Doppler easily differentiates a vascular lesion from any of the cysts that might have occurred in the region (mesenteric, ovarian, renal...). In addition, the differential diagnosis between an arteriovenous fistula and an aneurysm can be made by the different type of flow in the two lesions. In an arteriovenous fistula, one would expect high diastolic flow due to the shunting. Conversely, in an aneurysm, the lesion is exposed to the same resistance as the rest of the vessel, and a low diastolic flow or a flow similar to that of the aorta is expected. Further, due to the poor cardiac reserve of the fetus, shunting lesions (chorioangioma, vein of Galen aneurysm, angioma of the liver) present rapidly with right-sided overload and failure. This is not expected to be found in aneurysms. A more difficult problem may arise when more than one vessel is involved. In this particular case, the question of arteriovenous malformation could not be excluded because the aortic aneurysm was bulging around the inferior vena cava.


If no other anomalies exist, routine prenatal management need not be altered. Postnatal management: Surgical excision is indicated after stabilization to avoid complications from rupture. Coagulopathy is another potential complication that should be assessed.


Prognosis may depend on the age at which this anomaly is detected, its size and location. Authors have reported a poor outcome for young patients that become symptomatic before a diagnosis is made.5


1. Tilson MD: Histochemistry of aortic elastin in patients with non specific abdominal aortic aneurysmal disease. Arch Surg 123:503-5, 1988.

2. Rolfes DB, Towbin R, Bove KE: Vascular dysplasia in a child with tuberous sclerosis. Pediatr-Pathol 3:359-73, 1985.

3. Sarkar R, Coran AG, Cilley RE, et al: Arterial aneurysms in children: clinicopathologic classification. J Vasc Surg 13:47-56; 1991

4. Roques X, Choussat A, Bourdeaud"hui A, et al: Aneurysms of the abdominal aorta in the neonate and infant. Ann Vasc Surg 3:335-40, 1989.

5. Lobe TE, Richardson CJ, Boulden TF, et al: Mycotic thromboaneurysmal disease of the abdominal aorta in preterm infants: its natural history and its management. J Pediatr Surg 27:1054-9, 1992.

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