INTRODUCTION
Variations in the ramification patterns of renal and testicular vessels have been reported in detail, particularly with respect to their possible number, origin, course, and termination [8, 20, 23, 25, 27]. However, such mutations sometimes occur simultaneously and in various combinations, and they may be accompanied by malformation in the kidney and urinary tract [1, 2, 9, 11, 13, 18, 21, 26, 28]. Compared to a single variation, the presence of multiple variations increases the risk of unexpected injury to the urogenital vessels during surgical procedures; therefore, a detailed description of combined variations is helpful to ensure safe surgery. Additionally, detailing possible variations in the urogenital vessels may facilitate the understanding of their developmental processes. Hence, we report herein a case of bilateral supernumerary renal arteries, retrocaval right testicular artery, retroaortic left renal vein, and duplicated right testicular veins and briefly reference their developmental process. To the best of our knowledge, this is the first report of such a combined variation.
CASE REPORT
We encountered combined variations in the renal and testicular vessels (Fig. 1) in an 87-year-old Japanese male cadaver (No. 1117) during routine educational gross dissection at the National Defense Medical College.
Two renal arteries were present on each side. The right superior and inferior renal arteries originated from the abdominal aorta at the levels of the L1 and L4 vertebrae, respectively (RRA1 and RRA2 in Fig. 1); the superior one entered the hilus of the right kidney, while the inferior one entered the inferior pole of the right kidney. On the left side, the superior and inferior renal arteries arose from the abdominal aorta at the level of the L1/L2 intervertebral disc and L4 vertebra, respectively, and entered the left kidney through the hilus (LRA1 and LRA2 in Fig. 1).
The right and left testicular arteries emerged from the abdominal aorta at the levels of the L2 and L3 vertebrae, respectively (RTA and LTA in Fig. 1). The right one advanced posteriorly to the inferior vena cava, proceeding towards the deep inguinal ring. Both testicular arteries crossed anteriorly to the ipsilateral inferior renal artery (Fig. 1).
The right renal vein drained into the inferior vena cava at the level of the L2 vertebra without any tributaries (not shown in Fig. 1). The left renal vein ran posteriorly to the abdominal aorta and opened into the inferior vena cava at the level of the L2 vertebra (LRV in Fig. 1); on the way to the inferior vena cava, the left renal vein was anastomosed with the bilateral first lumbar veins as well as the azygos and hemiazygos veins (AnB in Fig. 1B). The left testicular vein and suprarenal veins, which received the inferior phrenic vein (LTV, SRV in Fig. 1), joined and proceeded anteriorly to the abdominal aorta, below the origin of the superior mesenteric artery, opening into the inferior vena cava at the level of the L1/L2 intervertebral disc (Fig. 1) without any communication with the retroaortic renal vein.
The right testicular vein was duplicated (RTV1 and RTV2; Fig. 1). The lateral vein ascended along the right testicular artery and opened into the inferior vena cava at the angle between the right renal vein and inferior vena cava at the level of the L2 vertebra (RTV1 in Fig. 1). The medial vein ascended parallel to the lateral vein and opened into the inferior vena cava, slightly below the opening of the lateral testicular vein (RTV2 in Fig. 1).
DISCUSSION
The present case exhibited multiple vessel variations, including bilateral supernumerary renal arteries, a retrocaval right testicular artery, a retroaortic left renal vein, and duplicated right testicular veins. The combined variations identified in this study are herein reported for the first time.
The primitive kidney receives the mesonephric arteries, which are several pairs of lateral branches that emerge from the thoracic to lumbar region of the aorta (MeA in Fig. 2A) [4]. During development, the kidney ascends from the pelvic cavity to the upper abdomen; accordingly, the upper mesonephric arteries supply blood to the kidney instead of the lower mesonephric arteries [4]. Subsequently, the lower mesonephric arteries usually regress; however, some of them occasionally persist and may become an additional renal artery arising at a lower level than the orthotopic renal artery, as was observed in the present case (RA2 in Fig. 2D) [4].
Normally, the testicular artery is derived also from the lower mesonephric arteries (MeA in Fig. 2A) [4], and according to Terayama et al. [29], the course of the definitive right testicular artery changes according to the positional relationship between the mesonephric arteries and the inferior vena cava during their development (Fig. 2). The inferior vena cava is formed by the cranial portion of the right subcardinal vein, the right sub-supracardinal anastomosis, and the caudal portion of the right supracardinal vein (Fig. 2) [3, 7, 12, 19]. The right mesonephric arteries run dorsal to the right subcardinal vein (Fig. 2A) [29]. Thus, in the case of a right testicular artery derived from the mesonephric arteries passing cranially to the sub-supracardinal anastomosis, the right testicular artery possesses a retrocaval course, as in the present case (TA in Fig. 2D).
During development, a pair of subcardinal and supracardinal veins and the anastomotic branches between them surround the aorta (Fig. 2A) [3, 6, 7, 14]. The course and tributaries of the definitive left renal vein are determined based on the remaining obliteration patterns of the venous ring [3, 6, 7, 14]. Typically, the left renal vein is derived from the inter-subcardinal and sub-supracardinal anastomoses and receives blood from the left subcardinal vein, which forms the testicular and suprarenal veins (Fig. 2B). However, the retroaortic left renal vein is derived from the inter-supracardinal and left sub-supracardinal anastomoses (Fig. 2C) [3, 7, 12, 16]. According to previous reports, the retro-aortic left renal vein typically receives blood from the left testicular and suprarenal veins (Fig. 2C) [15, 17, 24]. Thus, the anastomosis between the primitive left renal vein and the left testicular and suprarenal veins remains similar to a normal pattern, even in the case of abnormal development of the left renal vein. However, in the present case, the retro-aortic left renal vein did not receive blood from the left testicular or suprarenal veins (Figs. 1 and 2D). Thus, the development in the present case may have differed from that reported previously. The primitive left renal vein, and the left testicular and suprarenal veins were connected through the left sub-supracardinal anastomosis, and the localised regression of this anastomosis may have caused the rare drainage pattern found in this case (Figs. 1 and 2D). The regression pattern of the sub-supracardinal anastomosis plays a key role in determining the course of the left renal vein [16]. Considering the present case, the regression pattern of the sub-supracardinal anastomosis may have additionally changed the drainage pattern of the left testicular and suprarenal veins.
The right testicular vein was formed by the right subcardinal vein located caudally to the sub-supracardinal anastomosis. Duplication of the right testicular vein, which was detected in the present case, may have been caused by duplication [22, 23] or dysplasia of the subcardinal vein [5, 30].
CONCLUSIONS
Herein, we reported a case with multiple variations in the renal and testicular vessels. The urogenital vessels are closely related to each other during development, which may partially contribute to the occurrence of combined variations, as in the present case. Detailed descriptions of possible combined variations are beneficial for performing safe renal and gonadal surgical procedures and for facilitating the understanding of their developmental processes.
ARTICLE INFORMATION AND DECLARATIONS
Acknowledgments
The authors sincerely thank those who donated their bodies to the anatomical research field. The results of this research will potentially increase humankind’s overall knowledge, which can improve patient care. Therefore, the donor and his family deserve the highest gratitude [8].
Conflict of interest
None declared.
