Ultrasound Division, ASL Roma B, Rome, Italy.

Introduction

Ductus arteriosus is a large vessel that connects the pulmonary trunk to the descending aorta in fetal life. It maintains a short tubular shape, with a caliber that progressively increases with gestation until its size equals that of the descending aorta at term (10 mm) [1]. Its normal shape is straight, though it can present a mild or sharp tortuosity called S-shaped or kinking of ductus arteriosus. Benson et al showed that a markedly curved ductus arteriosus (defined as bending more than 90 degrees or having an S shape) was present in 35% of fetuses aged 32-38 weeks and in 56% of fetuses over 38 weeks of age [2,3]. Although there is one report showing that this is caused by tricuspid regurgitation and right heart dilatation (4), they point out that an S-shaped ductus arteriosus is common in normal fetuses, especially in the third trimester and other cardiac changes should not be attributed to this feature [2,3].

Here are presented 2 cases of S-shaped ductus arteriosus at 34 and 32 weeks in uncomplicated pregnancies.

Case1

Images 1- 6: 34 weeks;  Gray scale and color Doppler images showing S-shaped ductus arteriosus.

Case 2

Images 7-13: 32 weeks; Gray scale and color Doppler images showing S-shaped ductus arteriosus.

References

1. Alvarez L, Aranega A, Saucedo R et.al. Morphometric data on the arterial duct in the human fetal heart. In J Cardiol 1991;31:337-344.
2. Benson CB, Brown DL, Doubilet PM et.al. Increasing curvature of the normal fetal ductus arteriosus with advancing gestational age. Ultrasound Obstet Gynecol 1995;5:95-97.
3. Brown DL, Benson CB. The S-shaped ductus arteriosus. Letters to the editor. Ultrasound Obstet Gynecol 1995;6:372-74.
4. Mielke G, Peukert U, Krapp M et.al. Fetal and transient neonatal right heart dilatation with severe tricuspid valve insufficiency in association with abnormally S-shaped kinking of the ductus arteriosus. Ultrasound Obstet Gynecol 1995;5:334-337.