Congenital anomalies and anatomical variations of the IVC are relatively rare,
varying from 0.07% to 8.4% when associated with left renal vein variations.
IVC is divided into hepatic,
suprarenal,
renal and infrarenal segments,
which have different embryological origins (right vitelline,
right subcardinal,
right supracardinal,
and posterior cardinal veins) established from a sequence of vascular formations,
anastomosis,
and regressions between the 4th and 8th weeks of gestation.
Fig. 1: EMBRYOLOGICAL ORIGIN OF THE INFERIOR VENA CAVA
References: Hospital Alvorada/ Americas Serviços Médicos, São Paulo / Brazil
The most common spectrum of variants can be classified as pre-renal (continuation of IVC with the azygos / hemiazygos system),
renal (retroaortic left and renal circumaortic vein) and postrenal (circumcaval ureter,
transposition or left IVC and duplication of IVC),
and IVC absence which is considered the most extreme form of these anomalies.
The vitelline vein contributes to the hepatic segment of the IVC.
The suprarenal IVC is composed of a segment of the right subcardinal vein that does not recede.
The renal segment of the IVC is formed by the anastomosis between the right subcardinal and right supracardinal veins.
A segment of the right supracardinal vein persists as the infrarenal segment.
The embryonic veins also lead to the azygos,
hemiazygos,
and common iliac veins.
Fig. 2: SEGMENTATION AND EMBRYOLOGICAL ORIGIN OF THE INFERIOR VENA CAVA
References: Hospital Alvorada/ Americas Serviços Médicos, São Paulo / Brazil
MDCT is the most common imaging modality for initial evaluation of IVC variants and pathological findings. Abdominal imaging at 70-90 seconds after intravenous administration of contrast medium shows a uniform enhancement of the entire IVC.
MRI is another advanced imaging technique to evaluate the IVC,
which can be performed with or without contrast medium. Administration of the contrast medium through the bilateral pedis veins allows a direct and faster evaluation of the IVC,
in addition to the joint evaluation of the deep and superficial venous systems of the lower limbs.
Fig. 3: Magnetic Resonance Imaging (MRI) technics
References: Hospital Alvorada/ Americas Serviços Médicos, São Paulo / Brazil