Double retroaortic left renal vein

Double retroaortic left renal vein is a very rare entity that is usually clinically silent and detected incidentally at imaging, surgery, or autopsy.

The knowledge of anatomical variations helps the surgeon or interventionist to avoid complications during surgery and interventional procedures  and this entity is no exception. Though usually asymptomatic, this anomaly can rarely cause certain clinical symptoms and the knowledge of its existence can aid in the diagnosis.

Epidemiology

The incidence of a retroaortic left renal vein is reported to be ~2% . Occurrence of a double left renal vein is ~2.5 of this group.. Hence the combination of both can be assumed to be rare.

Clinical presentation

Usually it is an incidental finding at imaging, surgery, or autopsy. Possible symptoms include :

• hematuria
• left flank pain
• inguinal pain
• pelvic congestion syndrome

Pathology

The left renal vein originates from the primitive renal venous collar. The venous collar is formed by regression of the paired postcardinal veins. This process occurs around the eighth week of embryogenesis. Laterally, the venous collar is formed by paired dorsal and ventral primitive renal veins. These attach to the central ventral subcardinal and dorsal supracardinal veins which are paired. Variations are seen according to the persistence or regression of various parts of this system.

Radiographic features

The two renal veins are called the superior and inferior left renal vein:

• superior: traverses horizontally posterior to the aorta, draining into the inferior vena cava, near L2
• inferior: passes obliquely posterior to the aorta, joining the inferior vena cava, near L4