PMC8948481_01
Plain frontal chest radiograph demonstrates a well-defined lucency 
in the left lower lobe medially with a curvilinear outline resembling an 
inferior accessory lobe and fissure. The right lung appears smaller than 
the left, but the heart is normally positioned.
AJTCCM-27-4-138-fig1.jpg
PMC8948481_01_AJTCCM-27-4-138-fig1.jpg
F1
The right lung  appeared smaller than the left, but the heart was normally positioned  (Fig. 1). 
Axial multidetector computed tomography (MDCT) on lung 
window demonstrates an isthmus of basal lung in continuity with the 
right lung, extending across the midline between the heart anteriorly 
and the aorta and vertebral body posteriorly. There is a distinct pleural 
interface between the isthmus and the left lung.
AJTCCM-27-4-138-fig2.jpg
PMC8948481_01_AJTCCM-27-4-138-fig2.jpg
F2
Coronal oblique reconstructions demonstrating vascular supply, bronchial supply, and the scimitar vessel.
. (A) Coronal oblique reconstruction 
using maximum intensity projection (MIP) with a slab thickness of 7 mm, demonstrating the arterial origin of the vessels arising from the right 
inferior pulmonary artery branches extending across the midline to supply the isthmus of lung. . (B) Coronal oblique reconstruction using minimum 
intensity projection (MinIP) with a slab of 5 mm, demonstrating a small attenuated bronchial branch from the right lung extending across the 
midline to supply the isthmus which has air-trapping.. (C) A contrast-enhanced coronal oblique maximum intensity projection (MIP) reconstruction 
on mediastinal window demonstrates the enhancing curvilinear structure ascending from the right lung base (scimitar vein) joining a second 
peripheral venous structure before entering the superior vena cava at its entry into the right atrium.
AJTCCM-27-4-138-fig3.jpg
PMC8948481_01_AJTCCM-27-4-138-fig3.jpg
F3
The arterial supply was from the right lung  branches (Fig. 3A) and there was a clearly defined pleural separation  from the left lung (the presumed 'isthmic fissure'). There  were, however, some significant associated venous abnormalities  in the form of a scimitar-type vessel, which ascended from the  right lung base peripherally to join another scimitar-type vessel  descending from union of two superior segmental intervertebral  veins, to enter the superior vena cava as it feeds into the right atrium  (Fig. 3C).