A median sacral artery anterior to the iliocaval junction: a case report-anatomical considerations and clinical relevance for spine surgery

A case of double inferior vena cava with the connection to sacral venous plexus

Double inferior vena cava (IVC) is known as a variation in which the additional IVC is found on the left side of the abdominal aorta. Their developmental process has been well documented, but the venous development around the lumbosacral region is controversial. In the present double IVC case, the left IVC entered the left renal vein at the L2 level, and the renal veins on each side flowed into the right IVC at the L1 level. The internal and external iliac veins were merged at the S1 level on each side. Besides, a venous communication (3-mm-width) was found horizontally between the internal iliac veins near their origin at the S1 level. It had also an extra narrow branch (1-mm-width), which ran obliquely upward and reached the left IVC at the level of L5. The median sacral artery (MSA) ran at the ventral side of the horizontal communication but at the dorsal side of its extra oblique branch. These results suggest that the oblique branch is a remnant of the anastomosis between the right and left posterior cardinal veins. Furthermore, the horizontal vein corresponds to the sacral venous plexus, suggesting that the anastomosis can be formed between the IVC and sacral venous plexus.

Fetal median sacral artery anatomy study by micro-CT imaging

PURPOSE

The median sacral artery (MSA) is the termination of the dorsal aorta, which undergoes a complex regression and remodeling process during embryo and fetal development. The MSA contributes to the pelvic vascularization and may be injured during pelvic surgery. The embryological steps of MSA development, anastomosis formation and anatomical variations are linked, but not fully understood.

METHODS

The pelvic vascularization and more precisely the MSA of a human fetus at 22 weeks of gestation (GW) were studied using micro-CT imaging. Image treatment included arterial segmentations and 3D visualization.

RESULTS

At 22 GW, the MSA was a well-developed straight artery in front of the sacrum and was longer than the abdominal aorta. Anastomoses between the MSA and the internal pudendal arteries and the superior rectal artery were detected. No evidence was found for the existence of a coccygeal glomus with arteriovenous anastomosis.

CONCLUSIONS

Micro-CT imaging and 3D visualization helped us understand the MSA central role in pelvic vascularization through the ilio-aortic anastomotic system. It is essential to know this anastomotic network to treat pathological conditions, such as sacrococcygeal teratomas and parasitic ischiopagus twins (for instance, fetus in fetu and twin-reversed arterial perfusion sequence).