Scimitar Syndrome

What is the diagnosis? • Xray of the Week

Figure 1. What is the diagnosis?

Figure 2. Frontal chest radiograph reveals a curvilinear radiopaque tubular structure paralleling the right cardiac border (red arrows) —the classic “scimitar vein.”

Figure 3. (Contrast-Enhanced CT): Coronal images demonstrate the anomalous right pulmonary vein (red arrows) draining into the inferior vena cava (yellow arrows), confirming the diagnosis.

Scimitar Syndrome

(Congenital Pulmonary Venolobar or Hypogenetic Lung Syndrome)

Definition & Epidemiology

Scimitar Syndrome is a rare congenital condition characterized by partial anomalous pulmonary venous return (PAPVR), where pulmonary veins from the right lung drain into systemic veins—most commonly the inferior vena cava. The condition derives its name from the characteristic curvilinear vascular shadow on chest radiography, which resembles a scimitar sword. The estimated incidence is approximately 1–3 per 100,000 live births [1,12].

Imaging Findings

On chest radiography, the hallmark finding is a vertically oriented, curved opacity along the right cardiac border representing the anomalous pulmonary vein, the “scimitar sign.” Associated features may include right lung hypoplasia, dextroposition of the heart due to reduced right lung volume, and sometimes systemic arterial supply to the right lower lobe. These findings, although classic, are variably present and require confirmatory cross-sectional imaging. [2,3,10,13].

Contrast-enhanced CT better delineates the anomalous venous drainage, confirms the connection to the IVC, and demonstrates associated anomalies—such as right pulmonary artery hypoplasia, anomalous systemic arterial supply from the aorta, bronchial anomalies and atrial septal defects, which frequently coexist. [3,16,11].

Clinical Relevance & Classification

Two clinical variants exist: the infantile form, which often presents with pulmonary hypertension, heart failure, and more complex anatomy; and the adult/adult-variant form, frequently asymptomatic and diagnosed incidentally in adulthood [5,12].

Conclusion

Scimitar Syndrome is a rare but distinctly recognizable congenital anomaly on chest imaging. Familiarity with the CXR scimitar sign and adjunct CT findings is critical for accurate diagnosis, appropriate surgical referral, and procedural planning.

References

1. Dupuis C, Charaf LA, Brevière GM, Abou P, Rémy-Jardin M, Helmius G. The "adult" form of the scimitar syndrome. Am J Cardiol. 1992;70(4):502-507. doi:10.1016/0002-9149(92)91198-d

2. Roehm JOF, Jue KL, Amplatz K. Radiographic features of the scimitar syndrome. Radiology. 1966;86(5):856-859. https://doi.org/10.1148/86.5.856

3. Canter CE, Martin TC, Spray TL, Weldon CS, Strauss AW. Scimitar syndrome in childhood. Am J Cardiol. 1986;58(7):652-654. doi:10.1016/0002-9149(86)90296-1

4. Masrani A, McWilliams S, Bhalla S, Woodard PK. Anatomical associations and radiological characteristics of scimitar syndrome on CT and MR. J Cardiovasc Comput Tomogr. 2018;12(4):286-289. https://doi.org/10.1016/j.jcct.2018.02.001

5. Konen E, Raviv-Zilka L, Cohen RA, et al. Congenital pulmonary venolobar syndrome: spectrum of helical CT findings with emphasis on computerized reformatting. RadioGraphics. 2003;23(5):1175-1184. https://doi.org/10.1148/rg.235035004

6. Berrocal T, Madrid C, Novo S, Gutiérrez J, Arjonilla A, Gómez-León N. Congenital anomalies of the tracheobronchial tree, lung, and mediastinum: embryology, radiology, and pathology. RadioGraphics. 2004;24(1):e17. https://doi.org/10.1148/rg.e17

Kevin M. Rice, MD is the president of Global Radiology CME and is a radiologist with Cape Radiology Group. He has held several leadership positions including Board Member and Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator. He was once again a semifinalist for a "Minnie" for 2021's Most Effective Radiology Educator by AuntMinnie.com. He has continued to teach by mentoring medical students interested in radiology. Everyone who he has mentored has been accepted into top programs across the country including Harvard, UC San Diego, Northwestern, Vanderbilt, and Thomas Jefferson.

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