Right double inferior vena cava with a retrocaval ureter and preaortic iliac venous confluence: A case report with embryological considerations

Abstract

With advances in diagnostic imaging, congenital anomalies of the inferior vena cava are being increasingly detected incidentally in asymptomatic patients. Double inferior vena cava is a relatively well-known anomaly, with an estimated prevalence rate of 0.2%–3%. In contrast, right double inferior vena cava—in which two inferior vena cava run parallel on the right side of the abdominal aorta—is extremely rare, with only a handful of reported cases. In this case, the spatial relationship between the two inferior vena cava—which was lateral-to-medial immediately below the renal veins—changed to dorsal-to-ventral at the level of the pelvic inlet. From an embryological perspective, we discuss the spatial relationship between the two inferior vena cava, drawing on previous reports.

Introduction

The inferior vena cava (IVC) is formed through the development, regression, anastomosis, and replacement of three pairs of cardinal veins, the posterior cardinal, subcardinal, and supracardinal veins [[1], [2], [3]]. It is believed that abnormal persistence or regression during this developmental process gives rise to congenital IVC anomalies. While the term “duplicated IVC” typically refers to a configuration in which an IVC runs on each side of the abdominal aorta, a right double IVC is an extremely rare variant in which two infrarenal IVCs run parallel on the right side of the aorta [1,[4], [5], [6], [7], [8], [9], [10]].

A retrocaval (circumcaval) ureter is described as arising from a remnant of the right posterior cardinal vein, with the ureter running posterior to the IVC [[1], [2], [3], [4], [5], [6], [7], [8], [9], [10]]. While right double IVCs have been reported both with and without a retrocaval ureter, both types are associated with an anomaly known as the preaortic iliac venous confluence, in which the left common iliac vein runs anterior to the terminal aorta or iliac artery [1,[4], [5], [6], [7], [8], [9], [10]]. We present a case of right double IVC with a retrocaval ureter and preaortic iliac venous confluence, and discuss the imaging findings, embryological considerations, and clinical significance of this type of anomaly.

Case report

The patient was an 80-year-old man who presented with lower gastrointestinal hemorrhage. A dynamic abdominal contrast-enhanced CT scan was performed. The CT images revealed active diverticular hemorrhage in the ascending colon, and an emergency colonoscopy confirmed spontaneous hemostasis. The CT scan also incidentally revealed a right double IVC with a retrocaval ureter and preaortic iliac venous confluence. Approximately 10 mm caudal to the confluence of the right renal veins, two IVCs of nearly equal diameter were found running parallel to one another in a medial–lateral configuration on the right side of the abdominal aorta (Figs. 1a–b, g, h). In the caudal region, the two IVCs shifted to a ventral–dorsal orientation, with the lateral IVC positioned ventrally and the medial IVC dorsally (Figs. 1c-e). The ventral IVC ran ventrally to the right common iliac artery and became confluent with the left common iliac vein and right internal iliac vein, while the dorsal IVC became confluent with the right external iliac vein. At the pelvic level, a partial anastomosis was observed between the right internal iliac vein (IIV) and right external iliac vein (EIV) (Figs. 1f, i). The right ureter passed between the ventral and dorsal IVCs and deviated towards the ventral IVC side at the caudal end (Figs. 1d, g, h). A 7 mm stone was observed in the lower right ureter, accompanied by mild hydronephrosis. The mild hydronephrosis was caused by the stone, and no evidence of hydronephrosis due to a retrocaval ureter was found. The right gonadal vein drained into the ventral IVC (Figs. 1g, h). Based on the above, this patient was diagnosed as having a right double IVC with a retrocaval ureter and preaortic iliac venous confluence.

Fig. 1.

Contrast-enhanced CT images and 3D reconstruction images. (a) At the level of the right renal vein. (b) Just below the level of the renal veins, two IVCs run parallel to each other in a medial-lateral configuration. (c) At the level of the lower pole of the right kidney. (d) The retrocaval ureter (yellow arrowhead) is clearly visualized. (e) Preaortic iliac venous confluence. (f) At the intrapelvic level, an anastomosis (light blue arrowhead) is observed between the right external iliac vein and the right internal iliac vein. (g) 3D image, anteroposterior view. (h) 3D image, right anterior oblique 45° view. (i) 3D image, right anterior oblique 135° view.

Note: Red, ventral inferior vena cava; blue, dorsal inferior vena cava; light blue, anastomotic vessel between the right internal and external iliac veins; yellow, right ureter; green, right gonadal vein; purple, pararenal/suprarenal inferior vena cava.

Discussion

The development of the IVC involves a complex process in which three pairs of cardinal veins, namely, the posterior cardinal, subcardinal, and supracardinal veins, undergo repeated development, regression, anastomosis, and replacement [[1], [2], [3], [4], [5], [6], [7], [8], [9], [10]]. The IVC consists of four segments: the hepatic, suprarenal, renal, and infrarenal segments. It is known that the hepatic segment originates from the vitelline vein, the suprarenal segment from the right subcardinal vein, the renal segment from the subcardino-supracardinal anastomosis and the subcardino-posterior cardinal anastomosis, and the infrarenal segment from the right supracardinal vein; the iliac veins are known to originate from the posterior cardinal vein [[1], [2]]. Disruption of the balance between persistence and regression of these veins at any stage of this developmental process results in congenital IVC anomalies [[1], [2], [3], [4], [5], [6], [7], [8], [9], [10]]. Double IVCs with an IVC on both sides of the infrarenal aorta are relatively common, occurring in about 0.2%–3% of the population [3]; however, a right double IVC, with two IVCs running parallel on the right side of the aorta, is extremely rare [1,[4], [5], [6], [7], [8], [9], [10]].

Two types of right double IVC have been reported, and the difference between them lies in whether or not they involve a retrocaval ureter. This difference has been believed to be determined by which two of the three pairs of cardinal veins have persisted [4,6,7].

First, as a report on right double IVC “without” a retrocaval ureter, Nagashima et al. reported five cases of a right double IVC without a retrocaval ureter [4]. All the five cases of right double IVC reported by them were associated with a preaortic iliac venous confluence, but with no anastomosis between the ventral IVC - iliac veins (Rt. IIV, Lt. IIV, and Lt. EIV) and dorsal IVC - the right EIV. The preaortic iliac venous confluence can be explained by persistence of the ventral portion of the circumumbilical venous rings (the cardinal collateral [C.C.] region in Fig. 2) in the composite model proposed by McClure et al. [[1], [2],9]. Furthermore, in regard to the absence of anastomosis between the right EIV and right IIV, atrophy of the posterior cardinal vein possibly led to atrophy of the subcardino-posterior cardinal anastomosis and dorsal portion of the right side of the circumumbilical venous ring (Fig. 2), resulting in non-persistence of the anastomosis between the right IIV (which drains into the ventral IVC) and right EIV (which drains into the dorsal IVC) [[1], [2],9]. The right double IVCs in the five cases reported by Nagashima et al. were represented by the presence of two IVCs located in a ventral-dorsal configuration immediately below the renal veins [4], which differed from the configuration observed in our case, in which the vessels transitioned from a lateral-medial configuration to a ventral-dorsal configuration as they moved caudally. Based on the above and the developmental analysis of right double IVCs reported by Nagashima et al., it can be inferred that the ventral IVC originates from the right subcardinal vein and drains blood from the iliac veins (Rt.IIV, Lt.IIV, and EIV) via the ventral portion of the circum-umbilical venous ring, and that the dorsal IVC originates from the IVC derived from the supracardinal vein and drains blood from the Rt.EIV (Fig. 2).

Fig. 2.

Composite diagram of embryologic development of the inferior vena cava, based on the embryological models created by editing McClure [1] and Shindo [9].

Abbreviations: C.C., cardinal collateral vein, ventral portion of the circumumbilical venous ring; Subc.Pc.Anast., subcardino-posterior cardinal anastomosis; Subc.Sprc.Anast., subcardino-supracardinal anastomosis; P.Hep., pars hepatica of vena cava posterior; P.Subc., pars subcardinalis of vena cava posterior; Int.Sprc.Anast., intersupracardinal anastomosis; Int.Subc.Anast., intersubcardinal anastomosis.

Second, regarding case reports involving a right double inferior vena cava and a postvenous ureter, we can cite this case and the report by Ichikawa et al., both of which exhibited similar anatomical features [6]. Specifically, at the caudal end of the right renal vein confluence, two infrarenal IVCs of nearly equal diameter ran parallel to each other on the right side of the aorta in a medial-lateral configuration, and as they extended caudally, the medial-lateral configuration changed to a ventral-dorsal configuration. In addition, the ventral IVC ran along the ventral aspect of the right common iliac artery and drained blood from the right IIV and left CIV-IIV/EIV. The dorsal IVC drained blood from the right EIV, and partial communication was observed between the right EIV and proximal portion of the right IIV. The right gonadal vein drained into the ventral (lateral) IVC, and the ureter passed dorsally to the ventral IVC (Figs. 1a–f). From an embryological perspective, the findings in our case and the cases of right double IVCs described by Ichikawa et al. [6] suggest that the ventral IVC originates from the posterior cardinal vein and drains blood from the right IIV and left CIV-IIV/EIV via the ventral portion of the circumumbilical venous ring [[1], [2],9] (Fig. 2). Furthermore, because the posterior cardinal vein remained intact in these cases, it can be inferred that the anastomosis (between the right EIV and the right IIV) via the dorsal portion of the circumumbilical venous ring also remained intact (Fig. 2).

Regarding the spatial relationship of IVC in the two types of the right double IVC mentioned above (the right double IVC without and with a retrocaval ureter), Shin et al. have examined this based on the embryological spatial relationships of the three cardinal veins [4,[6], [7]]. In other words, since the cases reported by Nagashima et al. did not associate with a retrocaval ureter, it is thought that the subcardinal and supracardinal veins may have been retained in those cases; developmentally, these veins also exhibit a ventral-dorsal relationship [4]. On the other hand, based on the presence of a retrocaval ureter in the cases of right double IVC reported by Ichikawa et al. and in the present case, the ventral IVC most likely represents a remnant of the posterior cardinal vein; consequently, the dorsal IVC is thought to originate from a remnant of the supracardinal vein (or subcardinal vein), which is consistent with their lateral-medial relationship in the embryological stage [6].

There is some room for debate on the embryological analyses reported by Ichikawa et al. and the present case regarding whether the dorsal IVC originates from the supracardinal vein or subcardinal vein [[1], [2],6]. Considering this point in view of the composite model proposed by McClure et al. [[1], [2],9], if the dorsal IVC was derived from the subcardinal vein, the right circumumbilical venous ring would be expected to remain almost completely intact, resulting in a marsupial type [1,9], and a morphology in which the right EIV drains independently into the dorsal IVC is unlikely to occur.

In regard to the incidence, although there are a very small number of published reports of cases of right double IVC with a retrocaval ureter [1,[4], [5], [6], [7], [8], [9], [10]], uncertainties remain regarding the precise number of cases due to differences in the compilation of previously reported data and language regions. Therefore, we believe it is appropriate to describe this case modestly as “one of an extremely small number of cases.”

Conclusion

We report an extremely rare case of a right double inferior vena cava associated with a retrocaval ureter and preaortic iliac venous confluence. Based on findings, such as two IVCs running parallel to each other on the right side of the aorta in a medial-lateral configuration below the level of the renal veins and transitioning to a ventral-dorsal arrangement caudally, presence of a preaortic iliac venous confluence, the relationship between the ventral and dorsal IVCs and the iliac veins, and the presence or absence of anastomoses between the right EIV and IIV, we examined the embryological differences of this case from previously reported cases of right double IVC. Recognition of this anomaly might be important before retroperitoneal surgery, vascular and endovascular surgery.

Declaration of Generative AI and AI-assisted technologies in the writing process

During the preparation of this work, the author(s) used ChatGPT to assist with language editing and organization of the embryological explanation. After using this tool, the author(s) reviewed and edited the content as needed and take full responsibility for the content of the publication.

Patient consent

Written informed consent for publication of this case report and accompanying images was obtained from the patient.