Scimitar -Venolobar Syndrome

Clinical History

A 22 year old female was admitted with cough not responding to antibiotics. There was no significant past medical history. A chest radiograph was undertaken and showed volume loss. MR study and subsequent pulmonary artriogram were performed to rule out any cardiac or vascular anomalies explaining the shortness of breath.

Imaging Findings

Chest radiograph shows volume loss in the right hemithorax and mediastinal displacement to the right (Fig 1). There is no obscuration of right heart border or right hemidiaphragm to explain a lobar collapse or presence of mass as the cause of volume loss.

MR Arteriogram confirms radiographic suggestion of volume loss with heart occupying right hemithorax (dextrocardia). There is compensatory expansion of left lung. Paucity of arterial vasculature on the right suggests hypoplasia. Aorta and inferior vena cava are normally positioned (Fig 2).

MR Venogram shows heart occupying right lower hemithorax and small right pulmonary venous confluence converging towards right atrium (fig 3). High-density contrast reaches the posterior portion of right atrium directly from the right pulmonary veins (fig 4).

Selective right pulmonary arteriogram shows right lower lobe arterial hypoplasia (fig 5). Venous phase shows short right pulmonary venous confluence draining directly into right atrium (fig 6).

Discussion

Imaging studies confirmed asymptomatic venolobar syndrome also known as scimitar syndrome but in this case the term "venolobar syndrome" is probably more appropriate to use.

In Scimitar or Venolobar Syndrome [1], the two main components are lobar agenesis, aplasia, or hypoplasia and an abnormal draining pulmonary vein usually into the systemic circulation or right side of the heart. There are other minor associations (as this is a congenital anomaly), which are present to a varying degrees like dextrocardia, congenital heart disease (e.g. ASD, VSD, tetralogy of Fallot, PDA) / accessory diaphragm, diaphragmatic hernia/bronchiectasis/horseshoe lung/vertebral anomalies /genitourinary tract abnormalities [2, 3].
Left sided scimitar syndrome although described in the literature, is very rare [1]. The common differentials being hypoplastic lung (not associated with abnormal venous drainage) and Macleod syndrome (without cardiovascular anomalies and ipsilateral transradiancy) [4].

This case shows the main components of the syndrome i.e. lobar hypoplasia and abnormal venous drainage (direct drainage into right atrium being uncommon amongst reported cases) and the only minor association was azygos continuation of the IVC. There were no significant associated anomalies which is not surprising considering presentation in adulthood.

The common differentials include anomalies originating from broncho-pulmonary structures especially in a paediatric age group [5].

Presentation in childhood is usually symptomatic and associated with other congenital anomalies, while presentation in adulthood is usually an incidental finding or associated with less severe anomalies [4].

Treatment is tailored to associations and symptoms.

Differential Diagnosis List

Final Diagnosis

Venolobar/ Scimitar Syndrome

URL:	https://www.eurorad.org/case/11167
DOI:	10.1594/EURORAD/CASE.11167
ISSN:	1563-4086