Variations in ovarian vein morphology including partial and complete duplication and various drainage sites have previously been reported in the literature (Table 1). Ghosh and Chaudhury (2019) [1] performed dissections on 47 female cadavers and reported on the course and termination of the right and left ovarian veins with two cadavers found to have duplicated right ovarian veins draining separately into the IVC, one cadaver with a partially duplicated left ovarian vein that bifurcated 40 mm distal to its termination at the left renal vein, and one cadaver with a single right ovarian vein draining to the right renal vein. Forte et al. (2002) [9] performed dissection of a 75-year-old at death female cadaver and reported an incomplete left ovarian vein duplication with a unique anastomosis with an inferior polar renal vein. Ito and Ikeda (2018) [10] documented a rare case of double IVC and double right ovarian vein in an 81-year-old at death Japanese female cadaver with both right ovarian veins running parallel to one another and terminating separately at the right IVC and right renal vein. Dissections of the paraaortic region in 18 cadavers from Klemm et al. (2005) [11] reported a case of bifurcation of the left renal vein with each trunk receiving one of a pair of duplicated left ovarian veins. Sonje et al. [7] performed dissection of 30 cadavers and observed one case with two variations including a duplicated left ovarian vein and drainage of the right side—right ovarian vein joining the right renal vein.

Duplicated ovarian veins have also been reported in the literature from inspection of the ovaries and related structures in ovarian disorders. Abrantes et al. (2019) [12] presented a case of a duplicated right ovarian vein in a 34-year-old patient, 72 hours postpartum, with postpartum ovarian vein thrombosis. In outlining conservative management in three cases of placenta percreta, Barber et al. (2011) [13] reported one case of a 34-year-old woman with abdominal pain and fever 11 weeks after delivery and upon computed tomography angiography (CTA), a duplicated right ovarian vein that drained into the IVC, a dilated left ovarian vein, and an enlarged uterus were observed. Rao et al. (2017) [3] reported duplication of the right ovarian vein at the level of S1 through L3 vertebrae during routine computed tomography (CT) in a patient with recurrent menorrhagia and pelvic pain.

Duplication of the ovarian vein may be explained by embryological disturbances that occur between the 5th and 7th weeks of venous development [9]. Normal venous development follows the sequence of development, regression, anastomosis, and replacement of the posterior cardinal, subcardinal, and supracardinal veins [2, 3]. The gonadal veins—testicular or ovarian veins, emerge from the caudal portion of the subcardinal veins and drain into the supracardinal and subcardinal anastomosis. Normal right gonadal vein drainage into the IVC occurs from merging of the supra-subcardinal anastomosis and a portion of the subcardinal vein which are incorporated into the IVC. Normal drainage of the left gonadal vein occurs when the supra-subcardinal anastomosis forms part of the left renal vein [1-3, 7, 9, 10, 14]. A duplicated ovarian vein and other vascular variations including a duplicated IVC can result from changes in the venous developmental sequence such as persistent connections with the lower subcardinal veins and the ipsilateral sacrocardinal veins [9].

Several diagnostic imaging modalities have been successfully used to assess ovarian vein duplication. Abdominopelvic CT, multidetector CT (MDCT), and CTA have been the most frequently used for confirmation of duplicated ovarian veins [3, 13, 15, 16]. CT/CTA/MDCT can be used to visualize normal ovarian vein anatomy, its variations and disorders [15]. In a case with postpartum ovarian vein thrombosis, an abdominopelvic CT with iodine contrast identified a duplicated right ovarian vein [12]. A CTA scan of a 34-year-old woman eight weeks after delivery with complete placenta percreta and a uterine septum revealed an arteriovenous malformation and a duplicated right ovarian vein draining into the IVC [13]. Pelvic venography (phlebography) has also been used to visualize ovarian duplication and to perform therapeutic embolization of the duplicated vein to treat pelvic venous congestion syndrome [6]. Other imaging modalities including transabdominal or transvaginal ultrasound, color Doppler ultrasound, and magnetic resonance imaging have also been used to diagnose ovarian disorders [16-18].

Knowledge of variations of the ovarian veins is useful in performing laparoscopic procedures and understanding the relationship of certain vascular disorders to variations of venous development. Ovarian venous reflux contributes to pelvic pain in women and is a common therapy is pelvic vein embolization for treating pelvic congestion syndrome. Pelvic venous congestion syndrome can result from variations in the ovarian veins and their drainage [16]. Therefore, understanding of such variations can guide clinicians in successful embolization and prevent complications [1, 6]. During other laparoscopic procedures, knowledge of the frequency and variants in the vasculature can aid in preventing vascular injury from hemorrhage and avoid transfusion or conversion to laparotomy [11]. Prior identification of gonadal vein variants in patients can also allow for further planning of abdominopelvic surgeries by radiologists and gynecologists in order to reduce the chance of failure. The gonadal veins are also particularly useful for kidney transplantation and vascular reconstruction. These veins can assist in elongation of renal veins during transplantation [2, 8]. Duplication of the ovarian vein has multiple implications and its visualization and assessment help to establish a clearer understanding of the abdominopelvic venous anatomy. Lastly, the site of crossing of the gonadal veins anterior to the ureter is a known site of potential renal calculus location. Therefore, in cases of duplicated veins, two potential sites of obstruction might be identified.

Variations of the ovarian veins can impact imaging diagnosis, surgical procedures of the region, and can be related to clinical findings such as compression of the ureter. Therefore, a good working knowledge of such variants is important to the clinician who interprets imaging of the posterior abdominopelvic region of women and surgeons who operate in this region.