Exceedingly rare incidence of a double inferior vena cava (IVC) with azygos continuation of left IVC

Abstract

Key clinical message: Because of the complex embryonic origin of the abdominal venous structures, IVC and azygous systems can show numerous and even previously unreported anatomical variations and anomalies. Also, evaluating major vascular structures should not be dismissed in non-contrast-enhanced CT as it can provide valuable information about these structures.

Abstract: Double IVC is a rare occurrence of IVC anatomical variations and congenital anomalies. Herein, we discuss a case of a very rare type of double IVC that has not been reported in the literature before. A non-contrast-enhanced CT study was performed for a 34-year-old patient who visited our ER to evaluate for urolithiasis, during which two IVCs were noted. Each renal vein joined the ipsilateral IVC at a perpendicular angle. Unusually, the right IVC was formed from the confluence of both left and right common iliac veins (CIV), and the left IVC-Instead of crossing the midline at the renal veins level and reuniting the right IVC-cranially contributed to the azygos vein formation and caudally joined the left CIV. Also, there were some small communicating veins between the two IVCs and the left gonadal vein was slightly dilated before suggesting a reflux from the left renal vein (LRV). A complimentary doppler ultrasound exam confirmed the diagnosis and revealed a left-side varicocele. Although rare cases of hemiazygos continuation and interiliac connections of left-side IVC in the cases of double-IVC have been reported previously, a complete confluence of CIVs is rare. The main differential diagnosis is retro-aortic left renal vein (RLRV) type IV which seems to have an oblique course. Radiologists and surgeons should expect previously unreported variations in the vena cava system. Furthermore, reviewing the main abdominal vasculature should not be dismissed in non-contrast CT exams.

Keywords: azygos continuation of left IVC; case report; double inferior vena cava; left renal vein; left‐side inferior vena cava.

FIGURE 1

Axial planes of non‐contrast‐enhanced Abdominopelvic CT at different levels. Images were cropped for better visualization of retroperitoneal vascular structures. from cranial to caudal: (A) at the level of T12 vertebra. Azygos vein (white arrow) and aorta (AA) (B) at the level of L1 vertebra. There is a communicating horizontal venous structure (black arrow) crossing the midline between aorta and vertebral body, connecting the left IVC to the azygos vein in image A. Right IVC (RIVC) (C) at the level of L1‐L2 intervertebral disc through the renal veins (RV). The left renal vein does not cross anterior to the abdominal aorta and superior mesenteric artery (*) as it's expected to. (D) at the level of L3 vertebra. There is an additional venous structure (white blocked arrow) left to the abdominal aorta which was identified as left IVC. A slightly prominent left gonadal vein (curved arrow) and ureter stone can also be seen. (E) at the level of L3 vertebra just below image D. On careful evaluation, small communications (black blocked arrow) between left and right IVCs are visible crossing anterior to the vertebral bodies. (F) at the level of L4 vertebra right after abdominal aorta bifurcation into common iliac arteries (bidirectional curved arrow) (G) at the level of L5 vertebra through common iliac veins (arrowheads). The left IVC has already joined the left CIV.

FIGURE 2

Coronal reconstructions of non‐contrast‐enhanced Abdominopelvic CT at different levels. Images were cropped for better visualization of retroperitoneal vascular structures. (A) coronal plane through anterior aspects of lumbar vertebrae. Left renal vein (between arrowheads) connects to the left IVC (*) at a right angle. There is a superior 8 mm segment (dotted line) of left IVC above the confluence of the LRV that contributes to azygos vein formation via a horizontal communicating vein (between blocked arrows) that crosses anterior to the L1 vertebra. Posterior aspects of left kidney (LK) and aorta (AA) are also shown. (B) Another coronal plane 1 cm anterior to image A, demonstrating most of the right IVC (RIVC), left IVC route (****), their communications (arrows), and left IVC's connection to the left CIV.

FIGURE 3

Operator assisted 3D reconstruction of main retroperitoneal vasculature with 3D slicer application version 5.0.2. Aorta (red); right renal vein, right IVC and common iliac veins (dark blue); azygos vein, accessory hemiazygos vein, communication between azygos and left IVC, left renal vein, left IVC, its three visible communications to the right IVC and joint of the left IVC with left common iliac vein (cyan); right and left gonadal veins, with the later joining distal of the left renal vein (green). Right (R), left (L) and posterior (P) sides of the image are labeled. superior segment of the left IVC (arrow) above the confluence of the left renal vein is marked. Note the mostly vertical course of the left IVC and its perpendicular angle to left renal vein.

FIGURE 4

Doppler ultrasound study of the abdomen. (A) Transverse plane through the abdomen at an infrarenal level showed three retroperitoneal vascular structures. Right IVC (RIVC), abdominal aorta (AA), and left IVC (LIVC) are demonstrated. Left IVC shows the same flow direction as the abdominal aorta. (B) Longitudinal plane through the left IVC (LIVC) again, showing craniocaudal flow direction.

FIGURE 5

Scrotal Doppler study demonstrating enlarged left pampiniform plexus veins compatible with varicocele.