Surgical anatomy of the pelvis for total pelvic exenteration with distal sacrectomy: a cadaveric study

Beyond Total Mesorectal Excision: Compartment-based Anatomy of the Pelvis Revisited for Exenterative Pelvic Surgery

OBJECTIVE

Magnetic resonance imaging-based subdivision of the pelvis into 7 compartments has been proposed for pelvic exenteration. The aim of the present anatomical study was to describe the topographic anatomy of these compartments and define relevant landmarks and surgical dissection planes.

BACKGROUND

Pelvic anatomy as it relates to exenterative surgery is complex. Demonstration of the topographic peculiarities of the pelvis based on the operative situs is hindered by the inaccessibility of the small pelvis and the tumor bulk itself.

MATERIALS AND METHODS

Thirteen formalin-fixed pelvic specimens were meticulously dissected according to predefined pelvic compartments. Pelvic exenteration was simulated and illustrated in a stepwise manner. Different access routes were used for optimal demonstration of the regions of interest.

RESULTS

All the 7 compartments (peritoneal reflection, anterior above peritoneal reflection, anterior below peritoneal reflection, central, posterior, lateral, inferior) were investigated systematically. The topography of the pelvic fasciae and ligaments; vessels and nerves of the bladder, prostate, uterus, and vagina; the internal iliac artery and vein; the course of the ureter, somatic (obturator nerve, sacral plexus), and autonomic pelvic nerves (inferior hypogastric plexus); pelvic sidewall and floor, ischioanal fossa; and relevant structures for sacrectomy were demonstrated.

CONCLUSIONS

A systematic approach to pelvic anatomy according to the 7 magnetic resonance imaging-defined compartments clearly revealed crucial anatomical landmarks and key structures facilitating pelvic exenterative surgery. Compartment-based pelvic anatomy proved to be a sound concept for beyond TME surgery and provides a basis for tailored resection procedures.

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.