Azygos continuation of the IVC

IncidenceThe reported incidence of the this anomaly of interrupted IVC with azygous / hemi-azygous continuation is estimated to be 0.6-2 % of patients with congenital heart diseases and less than 0.3 % in otherwise normal individuals ^{1 2 3}.

This anomaly results from failure of right sub-cardinal-hepatic anastomosis with atrophy of right sub-cardinal vein and shunting of blood from supra-cardinal-sub-cardinal anastomosis to cranial portion of supra-cardinal vein (retro-crural azygos vein) ².

Imaging findings include: hepatic veins drain into right atrium. Renal veins drain into azygous (or hemi-azygous). This anomaly usually occurs with a right infra-renal IVC with azygos/hemi-azygos continuation ⁽⁴⁾, but it may also occur with other two variants:

(1) Left infra-renal IVC with azygos/hemi-azygos continuation ⁵ (as in this case). 

(2) Double infra-renal IVCs with two possibilities: EITHER both IVCs join at the renal level and continue as azygos vein) ⁶ OR (the right IVC continues as the azygos vein and the left one continues as the hemi-azygos vein) ⁷.

The clinical importance of this anomaly is in misinterpretation as right para-tracheal mass or retro-crural adenopathy, in being associated with heterotaxy syndromes and other congenital heart diseases and in pre-operative knowledge of the anatomy prior to planning cardio-pulmonary bypass and to avoid difficulties in catheterizing the heart ^{8 9}.