Anat Sci Int DOI 10.1007/s12565-015-0277-y
A case of an additional right external iliac vein surrounding the right external iliac artery and lacking the right common iliac vein Shogo Hayashi • Munekazu Naito • Tomiko Yakura Toshimasa Kumazaki • Masahiro Itoh • Takashi Nakano
Received: 30 November 2014 / Accepted: 18 February 2015 Ó Japanese Association of Anatomists 2015
Abstract A case of an additional right external iliac vein lacking a right common iliac vein was found in an 84-yearold female cadaver during a dissection course at Aichi Medical University in 2014. The findings are reported and discussed from the embryological and clinical viewpoints. The right and left iliac venous systems were macroscopically observed with attention to the homonymous arteries and the inferior vena cava. In this cadaver, a preaortic external iliac vein originated from a right external iliac vein and drained directly into the inferior vena cava. The preaortic and right external iliac veins surrounded the right external iliac artery. In addition, the right internal iliac vein drained into the left common iliac vein, and the right obturator vein drained into the right external iliac vein. Our findings suggested that normal external iliac veins developed from the ventral limb of the iliac venous system in this case. Our case has clinical importance for surgical complications such as hemorrhages in pelvic operations, phlebography, and especially central venous cauterization of the right femoral vein. Keywords Cadaver dissection Iliac vein Inferior vena cava Obturator vein Preaortic iliac venous confluence
S. Hayashi (&) M. Itoh Department of Anatomy, Tokyo Medical University, 6-1-1, Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan e-mail: [email protected]
M. Naito T. Yakura T. Nakano Department of Anatomy, Aichi Medical University, 1-1, Yazakokarimata, Nagakute, Aichi 480-1195, Japan T. Kumazaki Department of Health and Sports Management, Osaka University of Health and Sport Sciences, 1-1, Asashirodai, Kumatori-cho, Sennan-Gun, Osaka 590-0496, Japan
Introduction Normally, the inferior vena cava (IVC) is formed by the union of the bilateral common iliac veins (CIVs) posterior to the right common iliac artery (Babu et al. 2014). Variations of the IVC and iliac venous system are common and important both clinically and embryologically. One of the rarest variations is known as the preaortic iliac venous confluence, or the marsupial vena cava, in which the iliocaval junction is located anterior to the right common iliac artery or the aortic bifurcation (Babu et al. 2014; Baldridge and Canos 1987; Ruemenapf et al. 1998). In the abdomen, such variations of the positional relationship of the IVC branch are well known as the retroaortic left renal vein. The median incidence of a retroaortic left renal vein was 1.7 % in cadavers and 2.2 % in clinical subjects (Yi et al. 2012), whereas the number of previously reported cases of preaortic iliac venous confluences is less than 20 (Babu et al. 2014). Furthermore, the median incidence of a circumaortic left renal vein (also called the ‘‘circumaortic venous ring’’ or ‘‘renal collar’’) was 7.0 % in cadavers and 1.8 % in clinical subjects (Yi et al. 2012), whereas only two cases with right common iliac arteries surrounded by iliac veins have been reported (Babu et al. 2014; Tagliafico et al. 2007). In this report, we present the previously unreported case of an additional right external iliac vein (EIV) surrounding the right external iliac artery with the right EIV, with other associated pelvic venous variations.
Case report An 84-year-old female cadaver was used for a dissection course at Aichi Medical University in 2014. No
S. Hayashi et al.
external diameters of the right EIV and IIV were approximately 14.3 and 8.0 mm, respectively. The right CIV was absent, whereas a communicating vein was found behind the right internal iliac artery (Fig. 1b, c). This vein originated from the right IIV at 33 mm inferior to the iliocaval junction, ascended obliquely posterior to the right internal iliac artery, and inserted into the right EIV 28 mm inferior to the iliocaval junction. The diameters of the communicating vein were 3.8 mm at the origin and 2.2 mm at the insertion. In addition, the right obturator vein drained into the right EIV at 7 mm inferior to the insertion of the communicating vein (Fig. 1b, c). The narrow venous branch of the superior vesical vein also drained into the obturator vein. No variation was found in the left iliac venous system excluding the right IIV draining into the left CIV. The
macroscopic evidence of abdominal or perineal surgery was observed either on the surface or in the abdominal and pelvic cavity. We observed and recorded the right and left iliac venous systems, paying close attention to their positional relationships with homonymous arteries and IVC. The additional right EIV originated from the right EIV 45 mm inferior to the iliocaval junction and ran ventrally to the right external iliac artery so as to surround it with a right EIV, and it drained directly into the IVC at the ventral aspect of the iliocaval junction (Fig. 1a, c). The iliocaval junction was located at the level between the L5 and S1 vertebrae. The external diameters of the additional right EIV were approximately 5.0 mm at the origin and 5.3 mm at the insertion. The length of the additional right EIV was 60 mm. The right internal iliac vein (IIV) flowed into the left CIV at the iliocaval junction. At these ends, the
CI A CIA CI V
EI EI A V
AEIV IIV IIA
Fig. 1 Photographs and schematic drawing of the present case. a General representation of the abdominal and pelvic vessels. The right external iliac vein (EIV) branched to the narrower additional right external iliac vein (AEIV). The AEIV inserted immediately superior to the iliocaval junction. b Closeup representation of right pelvic vessels. The right internal iliac vein (IIV) drained into the left common iliac vein (CIV) and the right EIV drained directly into the inferior vena cava (IVC). The right CIV was absent, whereas a communicating vein (CV) conjoined the right EIV and ipsilateral IIV. The right obturator vein (OV) drained into the right EIV. The right OV also communicated with the superior vesical vein (SVV) with the narrow communicating branches (black star). c Schematic drawing. Ao abdominal aorta, CIA common iliac artery, EIA external iliac artery, IIA internal iliac artery, FN femoral nerve, IMA inferior mesenteric artery, OA obturator artery, ON obturator nerve, OvV right ovarian vein
Additional external iliac vein
diameter of the left CIV was 18.1 mm at the iliocaval junction. No communicating vein was found between the left EIV and ipsilateral IIV.
Discussion To the best of our knowledge, this is the first reported case of an additional right EIV surrounding the right external iliac artery. In addition, two additional venous variations were found in the present case, i.e., the right IIV draining into the left CIV and the obturator vein draining into the right EIV. Lotz and Seeger (1982) reported that large venous channels connected the right IIV and left CIV in two patients among 100 epidural venograms reviewed for the presence of anatomic variations of the iliac venous system. Morita et al. (2007) also reported that the prevalence rate of IIV anomalies detected using multidetector computed tomography (CT) in 63 patients was 30.2 %, and a right IIV draining into the left CIV was noted in 7 patients (11.1 %). Gilroy et al. (1997) reported that the occurrence of an obturator vein draining only into the external iliac venous system was 9–10 %. Embryologically, the abdominal veins inferior to the renal veins are developed mainly by pairs of anteromedial subcardinal veins and posterolateral supracardinal veins (Baldridge and Canos 1987; Nagashima et al. 2006) (Fig. 2). In the abdomen, the retroaortic left renal vein is explained by the abnormal partial persistence of these embryonic veins. Some researchers have argued that the preaortic iliac venous confluence probably represents the persistence of the ventral limb of the circumumbilical venous ring, which surrounds the future common iliac arteries on each side, and regression of the dorsal limb of the venous ring (Babu et al. 2014; Baldridge and Canos 1987; Nagashima et al. 2006; Ruemenapf et al. 1998) (Fig. 2). On the contrary, the additional right EIV in our case ran along the lateral aspect of the IVC. In addition, the right EIV and left CIV ran posterior to the arteries completely until its insertion. Therefore, although the communicating vein in the present case may be considered homologous to the normal left CIV, the embryological origin of the additional right EIV must be different from the preaortic veins in preaortic iliac venous confluence cases (Fig. 2). The findings in the present case may help to resolve some hitherto unknown aspects of the development of the iliac venous system. The knowledge of pelvic venous variations is important in pelvic surgeries in which the dissection of these vessels and the knowledge of their course will be considered in the prophylaxis of the vascular lesions or the interpretation of pelvic imaging using either CT or magnetic resonance imaging (MRI) (Baldridge and Canos 1987; Cardinot et al.
Fig. 2 Schematic drawing of the relationship between IVC development and variations of iliac veins. The IVC is formed by the connection of the right supracardinal vein (Sub), right supracardinal vein (Sup), and communication between the Sub and Sup (Com). Normally, the left Sub and Sup disappear except for the supracardinal communion, which persists as the left CIV. In the previous cases of preaortic iliac vein confluence (PIVC), subcardinal communication persists and inserts on the left (medial) side of the IVC. In the present case of the additional right external iliac vein (AEIV), it runs and inserts on the right (lateral) side of the IVC. RV renal vein
2006). The IIV and EIV are frequently manipulated by interventions in the pelvis such as retroperitoneal lymphadenectomy, anastomosis during a kidney transplant, hypogastric neurectomy, and hysterectomy (Cardinot et al. 2006). In our complicated case in particular, the risks of surgical complications such as hemorrhages in pelvic operations are likely higher. In addition, considering the phlebography and especially central venous cauterization of the right femoral vein in our case, the catheter may pass through a preaortic course, resulting in accidental perforation or puncture of iliac vessels. This risk is considered substantially greater than in an individual with a preaortic iliac venous confluence. Recent advancements in CT and MRI will contribute to the reduction of these clinical risks and to the identification of additional pelvic venous variations.
S. Hayashi et al. Acknowledgments The authors wish to thank Drs. Hitoshi Oishi, Yuki Ozawa, Yusuke Ohmichi, Mika Ohmichi, Keiichi Ohta and Ken Asamoto for their constructive suggestions and comments. Conflict of interest
The authors declare no conflict of interest.
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