Little is known about the variable uterine veins and their draining into the internal iliac vein. This becomes relevant with the upcoming field of uterus transplantation. Detailed knowledge of the number and length of venous vessels is crucial for careful operation planning regarding the anastomosis location and dissection point. Using cadaveric donors, we extracted the pelvic organs and dissected the venous vessels starting from the inferior vena cava and ending at the uterine veins in the parametrium. We measured the length of the common iliac vein and the internal iliac vein until the first uterine vein’s orifice. The number of uterine veins and that of the parietal vessels were counted. We found a high variability of uterine vein numbers (1 to 7). A distinct plexus wasn’t reaching the internal iliac vein in most of the cases. The length of the internal iliac vein was measured with a mean of 38 mm.
Concluding, a suitable length for an anastomosis during uterus transplantation and sparing of a simultaneous y-graft extraction in cadaveric donation was found.
Keywords : Pelvic veins ; Uterine transplantation ; Uterine veins ; Y-graft
Abbreviations: V: Vein; A: Artery; SEM: Standard Error of The Mean; COM: Communis; Dext: Right; Sin: Left; Utx: Uterus Transplantation; IIV: Internal Iliac Vein; CIV: Common Iliac Vein; UV: Uterine Vein; EIV: External Iliac Vein; NS: Not Significant
Uterine vein anatomy is, until now, poorly described in the literature. Nevertheless, the emerging field of Uterus Transplantation (UTx) requires a profound knowledge of the pelvic vessels to locate adequate dissection locations along the Internal Iliac Vein (IIV) or The Uterine Vein (UV). This location should offer an extensive and anatomically constant vessel for easier anastomosis and improved blood flow without the risk of occlusion. The uterine arteries were discussed in literature by several teams and with many techniques in the past. Even being subjected to a slight variability, they mostly emerge from the internal iliac artery, either directly, from the umbilical or the inferior gluteal artery.  The Common Iliac Vein (CIV) and its tributaries were also described in the literature, and a high variance was seen in all studies. A radiological survey by Shin et al. describes 19 variations between the CIV and the internal and External Iliac Veins (EIV) on both sides.  The uterus drainage is described as draining the venous blood through three systems: The first system uses anastomoses with the ovarian veins. Thus, the upper part of the uterine blood flows into the inferior vena cava directly or indirectly via the renal vein. Secondly, the uterovaginal plexus is thought to drain the lower part of the uterus blood into the uterine veins. Finally, the uterine veins drain the majority of venous outflow and merge into the IIV via the so called periuterine plexus. The uterine venous plexus is formed directly around the uterus and drains into one or more uterine veins in the cervical region of the uterus.  These veins are being described as two inconsistent veins, depending on their position to the oelvic ureter: a superficial one and a much larger deep UV.  These veins, which have no valves, dilate significantly during pregnancy becoming high-volume veins and are crucial for a proper uterine blood flow.  No details are described regarding the number of UVs or the exact confluence point with the IIV.
Therefore, we decided to conduct an anatomical study, focusing on the IIV and determining UVs’ exact location and number. Moreover, we aim to characterise the often-cited “plexus uterinus” in more detail. To our knowledge, we are the first to describe the exact number and location of UVs’ inflow into the IIV in a cadaveric study.
Material and Methods
In this cadaveric study started in January 2020 and terminated in July 2022 we used human bodies donated to the Institute of Clinical and Functional Anatomy of the Medical University of Innsbruck. All body donors had given their written informed consent prior to death for their use for scientific and educational purposes. All cadavers were preserved using an arterial injection of a formaldehyde solution and immersion in phenolic acid and water for one to three months . The possibility of this solution causing morphological preservation artefacts can be denied. The bodies are a representative sample of the general female Austrian and German population at the age of death . We investigated eighteen pelvic specimens. Three hemipelvices had to be excluded because of preceding vessel damage, causing possible bias in number and length on this side. So, we studied 33 hemipelvices in total. All pelvic organs, including vasculature, were removed from the pelvic bone for an optimal overview. The veins were dissected from the bifurcation of the inferior vena cava as far as possible into the parametrial tissue (Figure 1A and Figure 1B). All side branches were dissected and rated as relevant when having a diameter of at least 3 mm. The length of the IIV was measured from the confluence of the IIV and EIV and the first vein diverging to the uterus. All UVs were counted, and the given anatomy was evaluated. Additionally, the number of parietal vessels leaving the IIV between the bifurcation and the first UV was noted. Many already published iliac vein variations were found during this dissection.  These were also noted. Three IIV had to be excluded from the statistical evaluation because of a doubled IIV (numbers 14-16 shown in Table 1).