Scimitar Syndrome

Radiologic Findings PA (Fig. 1A) and lateral (Fig. 1B) chest radiographs demonstrates a small right hilum and a small right lung with ipsilateral mediastinal shift. There is dextroversion or dextroposition of the cardiac silhouette. An arcuate tubular opacity courses towards the right cardiophrenic angle. Note that the right bronchus is hyparterial (Fig. 1A).     Diagnosis: Scimitar Syndrome

Differential Diagnosis

• Arteriovenous Malformation
• Intralobar Sequestration
• Mucoid Impaction /Bronchial Atresia
• Pulmonary Varix

Discussion

Scimitar syndrome is a rare congenital anomaly of the right lung and pulmonary vasculature of unknown etiology and is also known as pulmonary venolobar syndrome and hypogenetic lung syndrome. It characteristically involves the right lung and may be associated with a variety of cardiopulmonary anomalies. “Scimitar” is a descriptive term that refers to the curvilinear or arcuate course followed by the anomalous draining pulmonary vein, which has been likened to the shape of a Turkish sword called a scimitar. The anomalous vein(s) may drain all or only a portion of the right lung and typically drains into the inferior vena cava. In other cases the anomalous draining vein drains into hepatic circulation, azygos vein, coronary sinus or right atrium. Associated findings may include: hypoplasia of the right pulmonary artery, interruption of the IVC, duplication, eventration or partial absence of the right hemidiaphragm, and tracheal trifurcation. The hypogenetic right lung may also demonstrate anomalous segmentation, or bronchial branching.

 

Clinical Findings

Scimitar syndrome may be diagnosed in infancy because of the associated symptomatic congenital cardiovascular disease (25-50%). Associated congenital cardiac anomalies include: atrial septal defect, ventricular septal defect, patent ductus arteriosus, tetralogy of Fallot, coarctation of the aorta, hypoplasia of the left heart, and various endocardial cushion defects. Some patients may present with hemoptysis and/or recurrent pulmonary infection. Approximately 50% of patients are asymptomatic and diagnosed incidentally on chest radiography acquired for unrelated reasons. Women are slightly more often affected with a female-to-male ratio of 1.4:1.

 

Imaging Findings

Radiography

• Small right lung and hemithorax (Fig. 1A and 1B)
• Mediastinal shift to the right with dextroversion of the heart (Fig. 1A)
• Indistinct right cardiac border
• Blunted costophrenic angle
• Vertically-oriented curved tubular opacity (anomalous draining vein) in right inferior thorax coursing towards right cardiophrenic angle (Fig. 1A)
• Diminished right pulmonary vascularity (Fig. 1A)

MDCT / MRI

• Allows optimal visualization of the anomalous draining vessel and its course and
• drainage into IVC, hepatic circulation,  right atrium, or coronary sinus
• Non-invasive assessment of left-to-right shunts with velocity-encoded cine MRI

Treatment

• Asymptomatic patients without associated anomalies: Observation alone
• Symptomatic patients with significant shunts: Surgical correction, ligation or coil embolization
• Recurrent hemoptysis and pulmonary infection: Lung resection
• Correction of significant associated congenital cardiovascular disease

Prognosis

• Good in the absence of associated anomalies
• Dependent on the presence of  associated congenital heart disease and its severity

Selected Readings

1. Ferguson EC, Krishnamurthy R, Oldham SAA. Classic Imaging Signs of Congenital Cardiovascular Abnormalities. RadioGraphics 2007; 27: 1323-1334.
2. 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: 1175-1184.
3. Parker MS, Rosado-de-Christenson ML, Abbott GF. Anomalies of the Pulmonary Arteries and Veins. In: Teaching Atlas of Chest Imaging. Thieme, New York; 2006: 79-83.
4. Woodring JH, Howard TA, Kanga JF. Congenital Pulmonary Venolobar Syndrome Revisited. RadioGraphics 1994; 14: 349-369.