Roentgen Ray 1997
uhrad.com - Chest Imaging Case of the Day
Case #2
by: Robert Gilkeson, M.D.
Mark Sands, M.D.
Diagnosis: Scimitar Syndrome.
Fig. 2A: Chest radiograph shows dextrocardia, a hyperlucent
right lung, and small right pulmonary artery. A small, abnormal
draining vein is seen overlying the right lower lobe (arrow).
Fig. 2B and 2C.
Fig. 2D and 2E
Fig. 2F
Fig. 2B - 2F: A contrasted chest CT with soft tissue windows show a small right pulmonary artery (2B),
and abnormal draining vein entering the IVC (2C, 2D) (arrows.) The lung windows show a small, bilobed
right lung (2E), an abnormal bronchial branching pattern, and bronchiectasis of the upper lobe (2F).
Discussion: The patient is a 53 year old patient with a history of radiation treatment for Stage I breast cancer, who presented to her physician with the history of persistent cough and sputum production. Her clinical history included the diagnosis of "dextrocardia" and chronic "URI symptoms." A chest radiograph (Fig. 2A) confirmed shift of the mediastinal structures to the right and a small right hemithorax. Closer evaluation revealed a small right pulmonary hilum, a relatively hyperlucent right lung, absence of the right minor fissure, and a tubular opacity within the right lower lobe. A spiral CT of the thorax (Fig. 2B-2E) confirmed the mediastinal shift, the bilobed right lung and an anomalous bronchial branching pattern in the right lung. The tubular opacity was found to represent an abnormal draining vein from the right lower lobe terminating in the supradiaphragmatic IVC. Evaluation of the right upper lobe showed cystic bronchiectasis(Fig. 2F).
The "scimitar syndrome" is a rare complex of disorders which have been variously called pulmonary venolobar syndrome [1], hypogenetic lung syndrome, and right pulmonary artery syndrome. First described by Cooper and Chassinat in 1836, Halasz first coined the term "scimitar syndrome" to refer to the appearance of the abnormal draining vein, which he likened to the shape of a Turkish sword.[2] The classic components of the scimitar syndrome is abnormal venous drainage of the affected lung, dextrocardia, and systemic arterial supply to the affected lung.[3] The right lung is affected in the vast majority of cases, and there is a slight female predominance, with scattered reports of familial cases. Incidence is estimated to be between 1-3/100,000 births [4] Symptoms can vary widely, and while many patients are asymptomatic, some patients, as seen in this case, suffer from repeated pulmonary infections.
The constant feature of the scimitar syndrome is the abnormal draining vein, and it is usually seen draining a part or all of the involved hypogenetic lung. Its course is variable, and while it usually drains into the infradiaphragmatic IVC, drainage into the right atrium, hepatic veins, portal or azygous vein has been reported[4]. While this abnormal draining vein does represent a left to right shunt, the shunt fraction is generally less than 2:1. In a study of over 100 such patients, the pulmonary artery pressure was normal in 85% and only slightly greater than normal in the remaining patients.[4] In some cases, ligation or coil embolization of the draining vein has been effective in symptomatic patients.[5] There are reports of pulmonary venous anomalies that can mimic the scimitar vein, most commonly a "wandering" pulmonary vein that eventually drains into the left atrium.[6]
Along with the abnormal scimitar vein, there is a spectrum of abnormalities of the tracheobronchial tree. There is often abnormal lobation, and the right lung may be bi- or unilobed. The right bronchus is often hyparterial and abnormally long. There are associated abnormalities of the trachea, and tracheal stenoses and diverticula are common. While the incidence of bronchiectasis in one series was 5%, it is frequently seen in the symptomatic population. Abnormal systemic arterial supply to the lung is common, though it is often difficult to demonstate.[7] There is a 25% incidence of congenital heart disease in these patients. Secundum type ASDs are the most common abnormality, and tetralogy of Fallot, ventricular septal defects, and patent ductus arteriosus[4] have been reported. Accessory or bilobed hemidiaphragm are also associated with the scimitar syndrome. It is important to recognize that the scimitar syndrome can mimic other conditions such as hypoplastic lung and Swyer James, and that identification of the scimitar vein is not possible in all cases. While angiography has been traditionally used for definitive diagnosis, noninvasive imaging with CT scan and cine MRI [8] may noninvasively identify the pertinent vascular structures that define this syndrome.
References:
1. Tomsick TA, Mosener SE, Smith WL Jr. The congenital venolobar syndrome
in three successive generations. J Assoc Canada Radiol 1976;27:196-199.
2. Halasz NA, Halloran KH, Liebow AA. Bronchial and arterial anomalies with drainage
of the right lung into the inferior vena cava. Circulation 1956;14:826-846.
3. Partridge JB, Osborne, JM, Slaughter RE. Scimitar etcetera-the dysmorphic right lung.
Clinical Rad 1988;39(1):11-9.
4. Dupuis, C, Charaf, LAC et al. The "adult" form of the scimitar syndrome. Amer J Cardiol.
70: 502-507,1992.
5. Schramel FM, Westerman CJ et al. The scimitar syndrome:clinical spectrum and sugical
treatment. European Respiratory J 1995;8(2):196-201.
6. Kanemoto N Sugiyama T et al. A case with pseudo-scimitar syndrome:"scimitar sign"
with normal pulmonary venous drainage. Japanese Circulation Journal 1987; 51(6):642-646.
7. Godwin JD and Tarver RD Scimitar syndrome: four new cases examined with CT.
Radiology;1986:159:15-20.
8. Baran R. Kir A, et al. Scimitar syndrome:confirmation of diagnosis by a noninvasive technique
(MRI). European Radiology 1996; 6(1):92-4, 1996.
Return to Day #3
Submitted by:
Robert C. Gilkeson, M.D.
Mark Sands, M.D.