There are numerous anatomical forms and variations of IVC abnormalities:
Absence of the IVC
Complete absent of the entire IVC or of only the infrarenal IVC is the rarest congenital anomaly.
It occurs when the three paired venous systems (subcardinal,
supracardinal and postcardinal systems) fail to develop properly; however,
perinatal venous thrombosis and atrophy have also been suggested as possible etiologies.
Absence of IVC may be accompanied by symptoms of venous insufficiency in the lower limbs or idiopathic deep vein thrombosis.
These conditions lead to the formation of collateral pathways,
so prominent lumbar colateral vessels may be a finding,
which can be mistaken for paraspinal masses.
Duplication of the IVC
Double IVC has a prevalence of 0.2 %-3 %.
There are two inferior vena cava on both sides of the abdominal aorta.
It is caused by persistence of both the left and right supracardinal veins.
The left infrarenal IVC joins the ipsilateral renal vein and leads to the right suprarenal IVC.
There may be important differences in size between both veins (Figure 6,
7).
It may be confused in imaging studies with paraaortic lymphadenopathy.
In case of indication of IVC filter,
two filters,
one in each inferior vena cava,
will be required.
Left-sided IVC
Left-sided IVC is caused by the regression of the right supracardinal vein,
with abnormal persistence of the left supracardinal vein.
It as a prevalence of 0.2%–0.5%.
The left-sided IVC courses cranially to the left of the abdominal aorta,
joins with the left renal vein,
and drains into a normal suprarenal IVC (Figure 8,
9). A left-sided IVC can cause difficult central venous access during interventional procedures.
Duplication with azygos continuation of IVC
Interruption of the IVC with azygous continuation results from failed formation of the right subcardinal-hepatic anastomosis,
with consequent atrophy of the subcardinal vein (suprarenal IVC) .
The infrarenal IVC continues as the azygous vein,
returning to the heart through the superior vena cava.
In cases of left IVC,
the infrarenal IVC continues as the hemiazygos vein and subsequently into the azygos vein (Figure 10).
The hemiazygos vein may also drain directly into the coronary sinus through a persistent left-sided superior vena cava or into the left brachiocephalic vein through the accessory hemiazygos vein.
The azygos or hemiazygos veinsare enlarged to accommodate increased flow,
and could be misinterpret as retrocrural adenopathy,
and a prominent azygos and superior vena cava confluence as a right paratracheal mass.
Drainage through the hemiazygos vein may simulate a left-sided mediastinal mass or,
in the event of accessory hemiazygos drainage,
an aortic dissection.
Associated situs anomalies are present in many of these cases.
Preoperative knowledge of this anomaly is important in planning cardiopulmonary surgery.
Circumaortic left renal vein
Normally,
the left renal vein is derived from the intersubcardinal anastomosis,
which course anterior to the aorta.
Persistence of both the intersupracardinal and intersubcardinal veins results in a circumaortic venous ring,
with one vein coursing anterior,
and the other posterior to the aorta and caudal with respect to the preaortic vein (Figure 11). Their identification is relevant for nephrectomy surgical planning.
On rare occasions,
it can lead to a nutcracker phenomenon (compression of the retroaortic renal vein),
with periureteric varices,
hypertension,
and hematuria.
It may also associate recurrent varicocele.
Retroaortic left renal vein
The left renal vein is unique and has a retroaortic path (Figure 12).
It is due to the persistence of the intersupracardial vein,
with regression of the intersubcardinal vein.
Its prevalence ranges from 1.7-3.4%.
Like the circumaortic left renal vein,
it can lead to varicocele and nutcracker phenomenon.
Retrocaval ureter
In normal situation,
the infrarenal IVC is formed by the right supracardinal vein,
located posterior and medial to the ureter.
But in this condition,
the infrarenal IVC develops from the right posterior cardinal vein,
which lies anterior and lateral to the ureter.
The ureter,
usually situated on the right side,
courses posterior to the IVC and descends to the right of the aorta.
This condition may lead to compression of the ureter,
and subsequent hydronephrosis or recurrent urinary tract infections.
The diagnosis can be made at intravenous urography or CT,
which shows the abnormal course of the proximal ureter as it projects over or medial to the lumbar pedicles on frontal images with proximal hydronephrosis.