Anatomical Study of the Rare Left Renal Vein Anomaly

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Jan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5729267/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Introduction: Due to its length, the left renal vein (LRV) is generally idyllic in renal transplantation surgical procedures. As such, understanding the course and attributes of the LRV, including whether it is pre-aortic or not, is essential for surgeons and other healthcare professionals, such as physicians. The understanding of these aspects is crucial in preventing unexpected fatalities and hemorrhage resulting from surgical procedures. Nevertheless, a limited number of clinical anatomy studies have focused on the anatomical variations of the LRV compared to the renal arterial systems. Often, the anatomical anomalies and variations of the renal veins are overlooked by radiologists, even as such variations and anomalies are indicative of the operation course and type, including vascular surgical procedures. Therefore, this study aims to evaluate and describe rare LRV anomalies and variations. Macroscopic dissections of 8 human donors (6 males and two females) were conducted to realize this objective. The specimens were acquired from various body donation services and university dissection rooms. All the specimens studied were reported as having died from causes unrelated to this study. Results: This study's findings have demonstrated the existence of different LRV anomalies, which met the criteria for classification into four key categories. Type I anomaly was the most prevalent, closely followed by Types III, II, and IV. Nonetheless, the Type IV LRV anomaly has been acknowledged to be the most infrequent. In the present study, the prevalence/incidence rate of LRV Type I, Type II, Type III, and Type IV anomalies was disclosed to be 6.6%, 1.6%, 3.3%, and 0%, respectively. The present study found no Type IV LRV anomaly in the donors studied. Conclusion: Understanding the rare LRV anomalies and variations is essential as it improves the understanding of clinical events. A pre-operative computed tomography (CT) scan is vital to ensure the safety of any surgical procedure conducted in the retroperitoneal region and to avert possible fatalities and hemorrhage during renal surgeries. Left Renal Vein (LRV) Left Renal Vein anomalies Left Renal Vein Variations retroaortic LRV (RALRV) circumaortic LRV (CALRV) Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Background/Introduction Currently, there are limited reports on the various LRV variations and anomalies, which have been mainly attributed to errors in embryological development. The venous variations and anomalies found within the retroperitoneal region have significant clinical implications, primarily in relation to retroperitoneal surgical procedures, staging of testicular tumors, and caval filter placement. Furthermore, they should be accorded special consideration in instances that involve extensive dissections of the venous systems, including lymphadenectomy, as well as cases requiring venous system reconstruction, transplantations, and cancer invasion of the venous system, including cases of renal cancer with vascular extension [ 1 , 2 ]. Renal vein development is a crucial aspect of the intricate developmental process of the inferior vena cava (IVC). The developmental process of the renal veins begins during the fourth week after conception and concludes by the eighth week. An immense network comprising three pairs of parallel veins is involved in communication and includes the posterior cardinal, supracardinal, and subcardinal veins [ 3 ]. Through the persistence and regression of such veins, the formation of four IVC segments occur, including the hepatic part, from the hepatic sinusoids and hepatic vein; the pre-renal vein, from the right sub-cardinal vein; renal part, from the anastomosis between the supracardinal and subcardinal veins; and the post-renal part, from the right subcardinal vein. The IVC development is often marked by the supracardinal and subcardinal channels of anastomotic communications, as they form the collar of veins surrounding the aorta. Typically, the ventral portion of the circumaortic collar persists as a standard left renal vein (LRV). However, when the collar’s dorsal portion persists, the LRV is often posterior to the aorta and develops into a retroaortic left renal vein (RALRV). Still, the venous collar or circumaortic left renal vein (CALRV) has been attributed to the intersupracardinal and subsupracardinal anastomoses, as well as the persistence of the LRV’s dorsal limb [ 5 ]. Further, the renal veins are formed from the persistence of the anastomosis of the subcardinal and supracardinal veins. The significant anomalies of the IVC include IVC duplication, IVC transposition (left-sided IVC), retroaortic left renal vein (RALRV), circumaortic left renal vein (CALRV), and the absence of the hepatic segment of the IVC [ 6 ]. Both the RALRV and CALRV are attributable to the persistence of the embryonic LRV’s dorsal limb alongside the persistence of the renal collar or intersupracardinal anastomosis’ dorsal arch. Nevertheless, in RALRV, regression of the ventral arch occurs to enable the single renal vein to pass posteriorly to the aorta. It is also noteworthy that LRV is reported in approximately 0.3–3.7% of the population, even as RALRV has been reported in only 0.5–6.8% [ 7 ]. The congenital venous anomalies found within the retroperitoneal space are relatively rare and are typically considered asymptomatic in normal contexts; however, they have clinical significance due to the potential complications that may emerge if left unrecognized [ 8 ]. Normally, the LRV is approximately three times longer compared to the RRV (7.5 cm versus 2.5 cm), which is the underlying reason for the preference for the left kidney as a donor for live donor nephrectomy. Moreover, the LRV might be double, with one vein passing posteriorly and the other passing anteriorly to the aorta before joining the inferior vena cava (IVC) [ 3 ]. This is often referred to as renal collar persistence. When the anterior LRV is absent, a single retroaortic LRV develops [ 3 ]. The development of the renal vein between the 4th and 8th weeks of intrauterine life is considered an aspect of an intricate IVC developmental process. The process involves three parallel vein pairs, including the supracardinal veins, subcardinal veins, and posterior cardinal veins. Several existing clinical studies focusing on the left renal vein have been based on various radiological modalities, including CT-guided angiography, MRI, MDCT, and ultrasound, despite a limited number of anatomical studies having been conducted. This study was conducted due to its significant importance in embryology, morphology, surgery, and clinical applications. In this regard, the formation of the renal veins is facilitated by the persistence of the supracardinal veins' anastomosis [ 9 ]. It is vital that the surgeons understand the LRV’s course and if it is pre-aortic or not to avoid unanticipated hemorrhage or fatality. Surgically, the LRV anatomical variants, including the circumaortic (CLRV) and retroaortic (RLRV) courses, are of immense significance. Diverse topographical and morphological RLRV possibilities might occur. The LRV anomalies have been classified into four distinct types: Types I, II, and IV retroaortic veins and Type III circumaortic veins [ 7 ]. Thus, in a Type I LRV anomaly, the LRV’s ventral pre-aortic limb is missing, and the dorsal retroaortic limbs persist, joining the IVC in a normal position [ 7 ]. Consequently, a Type II LRV anomaly arises from the obliteration of the LRV ventral pre-aortic limb, even as the remainder of the dorsal limb becomes the RLRV [ 7 ]. In this regard, the LRV is found at the L4 and L5 levels and connects the ascending lumbar vein and the gonadal vein before joining the IVC. Additionally, Type II variation has been classified as a venous collar or CALRV due to the persistence of the LRV dorsal limb alongside the subsupracardinal or intersupracardinal anastomoses [ 7 ]. If the smaller retroaortic vein, which empties into the IVC, is considered, then it is highly likely that the prevalence of CALRV might be as high as 16% [ 5 ]. Consequently, in Type IV, the LRV’s ventral pre-aortic limb is missing. In contrast, the remaining dorsal limb becomes the RLRV, which inferiorly and obliquely courses to connect with the left common iliac vein. The other non-categorized LRV anomaly might involve the supernumerary actual veins of the kidney and the later venous confluences [ 5 ]. The Type I RLRV characteristically connects to the IVC in an orthotropic position, even as Type II RALRV connects with the IVC at the L4-L5 level [ 7 ]. Still, the Type IV RALRV vein connects with the left common iliac vein. Still, Type III LRV or CALRV anomaly comprises both the retroaortic and pre-aortic components [ 7 ]. The four types of LRV variants and anomalies are indicated in Fig. 1 below. In anatomy, fewer studies have focused on the renal venous system than the arterial system. Radiologists and other healthcare professionals have often overlooked the anomalies and variations of the renal veins. Such variations typically indicate the type and course of surgical operations, especially in vascular surgeries. Thus, preoperative venous anatomy description using multi-detector computed tomography (MDCT) angiography is essential for examining arterial anatomies. However, most recent anatomical studies focusing on renal vascular variations have indicated that anatomical variations and anomalies of the renal veins are comparatively smaller than those of the various renal arteries [ 10 , 11 ]. In this regard, it has been acknowledged that there is only one instance of renal vein anatomic anomalies in the literature [ 10 ]. Despite the widespread definition of the accessory renal artery, the definition of the accessory renal vein has remained primarily unknown to clinicians and radiologists. Regardless, the acknowledgment of such anatomical variation is especially useful and vital in surgical procedures, as well as general surgery. In this regard, this study seeks to describe the increasingly rare anatomical anomalies and variations of the left kidney. We believe that this study will make a significant contribution to the existing literature. Material and Methods As stated earlier, this study aims to evaluate and describe rare LRV anomalies and variations. This study employed a macroscopic dissection method to examine kidney regions in 30 well-embalmed human donors. The processing of the donors was primarily conducted by freezing, which occurred 24 hours prior to post-mortem, followed by subsequent storage at a temperature of -27°C until the time of dissection. The researchers did not employ any fixation treatment on any of the specimens used. Moreover, it is noteworthy that the human donors used in this study comprised individuals who died from various causes unrelated to the study. All the bodies were donations from university dissection rooms and different body donation services, and the dissection was performed at the Embryology and Anatomy Department of the University of Nairobi’s School of Medicine. To conduct the study, the researchers opened the abdominal cavities using a cruciform incision that traversed the entire thickness of the anterior abdominal wall. In addition to the flaps being reflected, a systematic removal of abdominal viscera was conducted, following the guidelines outlined in the Cunningham manual for Practical Anatomy [ 12 ]. The renal veins were identified, which involved tracing the kidney’s hilum until its termination within the inferior vena cava (IVC). Additionally, the renal vein’s tributaries were traced to their origins. Results Among the observations made in this study include the view that, in 2 (6.6) of the donors, rather than assuming its usual course at the front of the aorta, the LRV took a retroaortic course and subsequently opened into the vena cava, as illustrated in Fig. 6 below. Furthermore, we observed that the termination level occurred at the L3-4 junction in one of the donors, as illustrated in Fig. 7 below. Furthermore, we observed that the LRV tributaries, including the suprarenal vein and testicular vein, had typical terminations and courses. However, additional anomalies were observed in 1 (3.3%) donor, including the left testicular vein joining the left renal vein (LRV) and dividing into two veins of nearly equal caliber after a shorter course. One of the two veins was observed to have passed at the front of the aorta. In contrast, the other one passed at the back, with termination occurring at much lower levels, as illustrated in Fig. 8 , within the inferior vena cava rather than the circumaortic left renal vein. The prevalence rates of the anomalies in the LRV observed in the studied donors are presented in Table 1 below. s. no Variation type Number of cases Percentage (%) 1 Type I: retroaortic LRV 2/30 6.6 2 Type II: retroaortic LRV 1/30 3.3 3 Type III: circumaortic LRV 1/30 3.3 Furthermore, among the 30 human donors studied, we observed that 6 (20%) were reported to have standard textbook renal vein patterns. In the other 9 (30%) donors, a broader array of anatomical variations was observed. From the developmental perspective, four types of renal vein variations have been identified in this study: retroaortic, supernumerary, plexiform, and circumaortic veins. Thus, the supernumerary left renal vein, an extra vein originating from the kidney’s hilum and draining into IVC, was noted in only one donor. Consequently, 10 (33.3%) donors were reported to have supernumerary right renal veins, with 9 (30%) donors having single right supernumerary renal veins and 1 (3.3%) donors having double right supernumerary renal veins, which we consider a rare anomaly. Furthermore, regarding the retroaortic left renal vein (LRV), we observed that 1 (3.3%) donor had an LRV that coursed dorsally to the aorta before draining into the inferior vena cava (IVC). Normally, in its course, the LRV joins the left suprarenal vein and the left ovarian vein. This study also recognized the circumaortic left renal veins in 1 (3.3%) case. Thus, in one case, an increasingly significant retroaortic limb was observed, more pronounced than the preaortic limb, which also obliquely passed downward to drain into the IV at the L3 level. Additionally, it was noted that the circumaortic left renal vein received two suprarenal veins. Consequently, the pre-aortic limb was observed to be smaller and horizontally oriented, coursing anteriorly to the aorta to drain into the IVC at the level of the kidney’s hilum. It was also observed to receive a testicular vein alongside a supra-renal vein. Consequently, in the second case, it was observed that the circumaortic LRV’s retroaortic limb was mainly a division of the LRV and had a comparatively smaller diameter. It was also noted that the retroaortic limb drained into IVC at the L3 level. Still, the pre-aortic segment was more pronounced in terms of size, even though it had a typical drainage pattern and received the gonadal and suprarenal veins. Lastly, a plexiform LRV was also noted in two donors. The plexiform LRV entails an infrequent variation in which the LRV, following its emergence from the kidney’s hilum, divides further, developing a network, and later reconnects to form a single renal vein. This results in the formation of two hiatuses and the emergence of the left gonadal artery from the left accessory renal artery, which then courses across the lower hiatus. Discussion Although several studies conducted on LRV, including clinical and RCT studies, have made use of various radiological modalities, including Multi-Detector Computed Tomography (MDCT), CT angiography, and Magnetic Resonance Imaging (MRI), a limited number of anatomical studies, as noted before, have been conducted on LRV anomalies. Therefore, this anatomical study has been conducted to assess and describe the rare LRV anomalies, as we believe that this will inform prospective surgical procedures and ensure safety while reducing the potential incidence of hemorrhage and death that might occur in instances of anomalies and variants. Among the notable critical anomalies found in the IVC are the transposition of the Left IVC, IVC duplication, retroaortic Left Renal Vein (LRV), and circumaortic Left Renal Vein (LRV), as well as the non-existence of the IVC’s hepatic portion [ 6 ]. During IVC development, the supracardinal and subcardinal channels often form anastomotic communications, leading to the formation of a vein encircling the aorta. Moreover, in normal LRV anatomy, the ventral segment of the circumaortic collar remains the normal LRV. Nonetheless, in instances where the collar’s dorsal segment persists, the LRV assumes a posterior course relative to the aorta, leading to the development of the retroaortic left renal vein (RLRV). Still, the development of the circumaortic left renal vein (CALRV) occurs in instances where there is intersupracardinal and subsupracardinal persistence alongside the LRV’s dorsal limb [ 5 ]. The anatomic prevalence rates of LRV anomalies have been found to vary. For instance, in their study focusing on anatomic prevalence rates, Satyapal et al. evaluated 1008 cases and reported that anomalies of the RLRV and CALRV occurred concurrently at rates of 0.5% and 0.3%, respectively [ 13 ]. Furthermore, a similar CT-based study conducted by Trigaux et al. and involving 1014 specimens disclosed that the incidence rate of RLRV and CALRV anomalies were reported as 1.8% and 4.4%, respectively [ 14 ], even as Özgül disclosed a prevalence rate of 4.4% for CALRV and 1.8% for RLRV based on 433 CT specimens [ 15 ]. The RLRV has also been described as a vein coursing posteriorly to the aorta, as opposed to coursing anteriorly, while the CALRV has been described as the periaortic venous ring [ 16 ]. In this regard, the general incidence rates of RLRV and CALRV are approximated to vary from 0.3 to 1.9% and 1.5 to 8.7%, respectively [ 16 ]. The anomalies of the RLRV and CALRV veins are attributable to aspects that include the persistence of embryonic structures, such as the renal collar’s dorsal arch and the embryonic left renal vein’s dorsal limb, through the anastomosis of the intersupracardinal vein. In instances of RLRV, the regression of the ventral arch results in the development of a single renal vein that courses at the aorta’s posterior, even as CLRV has both the posterior and anterior components, with an approximated prevalence of between 0.3% and 3.7%, and 0.5% and 6.8% of individuals, concurrently [ 6 , 17 ]. Furthermore, the RLRV has been categorized into two distinct forms: Type I, which refers to the orthotropic retroaortic renal vein, and Type II, which involves the single LRV descending renal hilum and coursing posteriorly to the aorta at the L4-L5 junction and subsequently joining the ovarian or testicular veins together with the ascending lumbar vein before joining the IVC [ 18 ]. The CLRV has been described in numerous studies as referring to the third type of RLRV, characterized by two distinctive veins that course posteriorly and anteriorly to the aorta and subsequently join the IVC [ 17 , 18 ]. Although very rare, the fourth type of LRV has been reported and involves the LRV draining into the iliac vein after receiving tributaries [ 19 ]. Among the most common urological symptoms associated with LRV anomalies is hematuria, with the highest prevalence in Types II and IV, and it is also highly prevalent in Type I in RLRV [ 20 ]. Additionally, in an MDCT angiography-based study comprising 1860 participants with various urological symptoms, including flank pain, hematuria, and left gonadal varicocele, four distinct critical types of LRV anomalies were mainly identified and classified based on their appearances [ 21 ]. Thus, Type I (RLRV) entails a vein that connects to the IVC in an orthotropic point; Type II involves RLRV connecting to the IV at an L4-L5 intersection; Type III entails the collar/circumaortic LRV; and Type IV involves RLRV linking up with the left iliac vein [ 20 ]. The study further revealed that the concurrent incidence of LRV Type I, LRV Type II, LRV Type III, and LRV Type IV was 3.6%, 1.4%, 1.2%, and 0.9%, respectively [ 18 , 21 , 22 ]. Nonetheless, for our study, the use of MDCT was unnecessary as the study did not focus on urological diseases and symptoms, and donors were utilized to study LRV anomalies. Of the donors studied, it was observed that LRV anomalies, specifically LRV Type I, LRV Type II, LRV Type III, and LRV Type IV, occurred in 2 (6.6%), 1 (3.3%), 1 (3.3%), and 0 (0%) specimens, respectively. The LRV anomalies prevalence rates were low, given that the study has disclosed that Type I RLRV had a 6.6% incidence rate of linking up with IVC in an orthotopic position while Type II LRV had an incidence rate of between 3.3% of linking up with the IVC at L4-L5, and the circumaortic LRV also had an incidence rate of between 3.3%. Similar to the findings of our study, which indicated a low incidence rate of retroaortic left renal vein (LRV), a cadaveric study conducted in Colombia with a total of 156 specimens observed that two specimens (1.3%) had a retroaortic course, and one specimen (0.6%) [ 23 ]. In this regard, the observed lower incidence rate of circumaortic and retroaortic left renal vein (LRV) variations may be attributable to morphological trends in the Colombian Mestizo population. Furthermore, the findings of our study have been corroborated and are consistent with those of studies conducted by Baptista et al. [ 24 ] and Satyapal et al. [ 13 ]. Additionally, a limited number of retroaortic LRVs have been observed in various Japanese studies, including a cadaveric study comprising 203 specimens, where only one specimen (0.49%) had a retroaortic LRV [ 25 ]. Similarly, studies conducted by Izumiyama, Horiguchi, and Okamoto in Japan have indicated incidence rates of 0.75% and 0.74%, respectively [ 26 , 27 ]. Such observed lower incidence rates of RALRV have been linked to factors that include racial differences. Still, in an instance involving a healthy hypertensive middle-aged male individual with a left-side varicocele alongside symptoms that include palpitations and giddiness, even no hematuria, which refers to the nutcracker phenomenon (posterior), was disclosed by the CT scan within the course of his labile HTN workup. The case has, therefore, placed substantial emphasis on the significance of the RALRV in the differential diagnosis of labile hypertension [ 28 ]. Adequate and timely diagnosis has, for this reason, been recommended as this will ensure that there are no unnecessary investigations. Additionally, Deschepper initially described “Nutcracker syndrome” or LRVHTN in 1972 [ 29 ] through the definition of LRV with renal venous HTN development, whose backward transmission to the parenchyma may lead to different symptoms [ 28 ]. There is an increased diversity regarding the nutcracker phenomenon and compression mechanism, with vein trapping found within an aortic-mesenteric space resulting from aneurysmal aorta dilatation or the anterior nutcracker phenomenon being the most frequent type [ 29 ]. In such instances, the RALRV or CALRV gets compressed between the vertebral body and the aorta and is referred to as the posterior nutcracker. The nutcracker and poster nutcracker phenomenon have varying clinical features, including chronic pelvic congestion and asymptomatic micro-hematuria [ 30 ]. The predominant symptom is Hematuria, which is attributable to the rupture of thin-walled varices into the collecting systems caused by an increase in venous pressure. The other widespread symptom is pain [ 31 , 32 ]. Renal infarcts and congested kidneys resulting from the posterior nutcracker phenomenon might additionally cause bacterial localization and the subsequent formation of abscesses. Further, aortic thrombosis has been acknowledged as a major complication resulting from sepsis and infections [ 30 ]. In neonatal cases, renal abscesses and septicemia caused by the nutcracker phenomenon have been documented [ 30 ]. Although such anomalies are generally asymptomatic, the rupture of the Abdominal Aortic Aneurysm (AAA) into the retroaortic left renal vein (LRV) results in a distinctive symptom marked by an incessant abdominal bruit, left flank pain, and abdominal pain with a related pulsatile mass [ 33 , 34 ]. The performance of proximal graft anastomosis and proximal aorta exposure pose substantial technical challenges, particularly in relation to IVC and renal vein anomalies and variations. Aortic clamping becomes possible below and above the retroaortic left renal vein (LRV) Type I [ 35 ]. Consequently, Arslan et al. reported RLRV prevalence rates of 1.7% in men and 1.6% in women following an examination of 1,125 abdominal CT scans [ 36 ]. Furthermore, the study revealed that nine individuals had varicocele, suggesting that the RLRV might be a potential etiologic factor underlying the development of varicocele [ 36 ]. Nevertheless, a study involving 149 patient participants with varicocele alongside 137 control patients disclosed that 13 patients (8.7%) presented with RLRV, while three control patients (2.2%) also presented with RLRV. The study's findings have indicated a considerably higher incidence rate of RLRV in individuals with varicocele than in the control group patients [ 37 ]. Comparing the four types of LRV anomalies is a key challenge, given that most studies have only reported on Types I and III LRVs. While some studies have only described Type I LRV anomaly, Type IV has been infrequently reported. However, our study observed Types I, II, and III LRV anomalies, even as Type IV was not observed. Conclusion In summary, although the LRV anomalies have been categorized into four types, they can be classified into two main classes: the circumaortic and the retroaortic LRV types. In this regard, it has been noted that the retroaortic left renal vein (LRV) may be further divided into three distinct types based on the termination level in relation to the inferior vena cava (IVC). The differences in the incidence rates of the LRVs are amongst the highly notable features that different studies have disclosed, attributed to racial differences. Therefore, understanding the LRV anomalies is essential for radiologists, anatomists, and surgeons, as they may pose life-threatening and fatal situations during surgical operations within the retroperitoneal regions if left unaddressed. Moreover, knowing the LRV variables will enable better comprehension of potential clinical events. Therefore, in instances of surgical operations within the retroperitoneal region, the performance of preoperative CT is recommended, as this aids in ensuring safer surgical procedure outcomes. Declarations Ethics approval and consent to participate (IRBC/1942/24) Consent for publication (Authors have offered their consent for publication) Availability of data and materials (Authors) Competing interests (Not applicable) Funding (Not applicable) Authors' contributions—YA conceptualized and designed the study, carried out the primary anatomical analysis, and prepared the methodology. YA drafted and revised the manuscript with the assistance of MMJ, who also provided critical revisions for significant intellectual content. Consequently, MMJ assisted in designing the study and made substantial contributions to the development of the research objectives. Jointly, YA and MMJ collected data through detailed anatomical dissections and recorded observations. YA also supervised the data collection and analysis process and reviewed and approved the final manuscript. YA and MMJ also jointly conducted the literature review and provided critical insights into contextualizing the findings, in addition to participating in the analysis and interpretation of the study results. Acknowledgements (Not applicable) References Verma M, Pandey NN, Ojha V, Kumar S, Ramakrishnan S. Developmental anomalies of the inferior Vena Cava and its tributaries: What the radiologist needs to know. Indian Journal of Radiology and Imaging. 2022 Sep;32(03):355-364. Indira CK, Arunkumar KG. Embryological and surgical considerations of an absent infra-renal part of the inferior vena cava and the left renal vein. Asian Journal of Medical Sciences. 2020 Sep 1;11(5):83-86. Anjamrooz SH, Azari H, Abedinzadeh M. Abnormal patterns of the renal veins. 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Nutcracker syndrome: an update on current diagnostic criteria and management guidelines. European journal of vascular and endovascular surgery. 2017 Jun 1;53(6):886-894. Lizama L, Bran S, Kuestermann S, García-Gallont R. Renal vein thrombosis due to posterior nutcracker syndrome. Methodist DeBakey Cardiovascular Journal. 2020 Oct;16(4): e5. Adela Văcăroiu I, Dragoş D, Tănăsescu MD, Ghenu I, Tulin A, Ştiru O, Mihai A, Balcangiu-Stroescu AE, Timofte D, Ionescu D. Nutcracker Syndrome an Anatomic Variant. Romanian Journal of Functional & Clinical, Macro & Microscopical Anatomy & of Anthropology/Revista Româna de Anatomie Functionala si Clinica, Macro si Microscopica si de Antropologie. 2021 Apr 1;20(2). Hsieh CL, Tiao WM, Chou YH, Tiu CM. Retroaortic left renal vein: three case reports. Journal of Medical Ultrasound. 2012 Jun 1;20(2):115-118. Wei ZJ, Zhu X, Yu HT, Liang ZJ, Gou X, Chen Y. Severe hematuria due to vesical varices in a patient with portal hypertension: a case report. World Journal of Clinical Cases. 2021 Jun 6;9(18):4810. Gabrielli R, Rosati MS, Siani A, Marcucci G. Preoperative evaluation of retroperitoneal venous system anomalies during abdominal aortic aneurysm rupture. Interactive cardiovascular and thoracic surgery. 2011 Feb 1;12(2):278-280. Mulcaire-Jones JP, Bailly DK, Frank DU, Verma AR, Barney BJ, Siefkes HM. Spontaneous aortic thrombosis in neonates: a case report and review of literature. Cardiology in the Young. 2020 Jan;30(1):95-99. Shindo S, Kubota K, Kojima A, Iyori K, Ishimoto T, Kobayashi M, Kamiya K, Tada Y. Anomalies of inferior vena cava and left renal vein: risks in aortic surgery. Annals of vascular surgery. 2000 Jul; 14:393-396. Arslan H, Etlik Ö, Ceylan K, Temizoz O, Harman M, Kavan M. Incidence of retro-aortic left renal vein and its relationship with varicocele. European radiology. 2005 Aug; 15:1717-20. Karazincir S, Balci A, Görür S, Sumbas H, Kiper AN. Incidence of the retroaortic left renal vein in patients with varicocele. Journal of Ultrasound in Medicine. 2007 May;26(5):601-604. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 06 Apr, 2025 Reviews received at journal 31 Mar, 2025 Reviewers agreed at journal 31 Mar, 2025 Reviews received at journal 31 Mar, 2025 Reviewers agreed at journal 31 Mar, 2025 Reviews received at journal 31 Mar, 2025 Reviewers agreed at journal 31 Mar, 2025 Reviewers invited by journal 30 Mar, 2025 Submission checks completed at journal 28 Mar, 2025 First submitted to journal 27 Mar, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5729267","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":436544625,"identity":"654246a6-9e70-4581-8f1c-44158d5fc491","order_by":0,"name":"Yasser Alharbi","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA80lEQVRIiWNgGAWjYBACNgbGBmYom/EBkODhI6SFH0kLswFICxshLZINQKUwGyUg9hIABjeSmz8XttnZy7f3Pqv8mmMnw8bA/PDRDbxaEtukZ7YlJ244c9zstuy2ZKDD2IyNcwhoYeZtY04wkEhjuy25jRmohYdNGp8W+xuJzZ952+rt5ec/YyuW3FZPWAvQlgZp3rbDjA032NgYP247TISWMw/bpHnOHQf6JY1ZmnHbcR42ZkJ+OZ7++DNPWTUwxI4xfvy5rdqen7354WN8WhgEEoDRDo0LZh4wiU85CPAfABJ/IGzGH4RUj4JRMApGwYgEAEXJRhtwFg2OAAAAAElFTkSuQmCC","orcid":"","institution":"Umm Alqura University","correspondingAuthor":true,"prefix":"","firstName":"Yasser","middleName":"","lastName":"Alharbi","suffix":""},{"id":436544626,"identity":"981c4380-b302-457c-9fe6-85fc1d35d324","order_by":1,"name":"Mustafa M. Jan","email":"","orcid":"","institution":"Umm Alqura University","correspondingAuthor":false,"prefix":"","firstName":"Mustafa","middleName":"M.","lastName":"Jan","suffix":""}],"badges":[],"createdAt":"2024-12-29 09:23:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5729267/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5729267/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":79746969,"identity":"37d7e869-3b2a-43bc-b02d-175ba42343b0","added_by":"auto","created_at":"2025-04-02 08:54:44","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":70308,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eNormal renal vascularity illustration \u003c/em\u003e[4]\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5729267/v1/4777bf98432c67e0be5a76a8.png"},{"id":79746975,"identity":"8d1effdc-5e3f-432a-8eec-d8fa5ee27c25","added_by":"auto","created_at":"2025-04-02 08:54:44","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":301289,"visible":true,"origin":"","legend":"\u003cp\u003eLRV Type I\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eDiverse types of LRV anomalies: Type I is RLV, in which the LRV connects to the IVC in an orthotropic position; Type II entails the LRV joining the IVC at level L4-5; Type III is a circumaortic LRV; and Type IV entails the renal vein joining the left common iliac vein \u003c/em\u003e[4]\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5729267/v1/7db38d5b4cdacf6d2b18d02a.png"},{"id":79746977,"identity":"02f1cc90-a3d1-4bac-8c0f-a5f517649656","added_by":"auto","created_at":"2025-04-02 08:54:44","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":256234,"visible":true,"origin":"","legend":"\u003cp\u003eLRV Type II\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eDiverse types of LRV anomalies: Type I is RLV, in which the LRV connects to the IVC in an orthotropic position; Type II entails the LRV joining the IVC at level L4-5; Type III is a circumaortic LRV; and Type IV entails the renal vein joining the left common iliac vein \u003c/em\u003e[4]\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5729267/v1/dea2a67e1fec070266ea1969.png"},{"id":79746976,"identity":"5ea74e96-b19a-4437-ba81-0d040904814d","added_by":"auto","created_at":"2025-04-02 08:54:44","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":332231,"visible":true,"origin":"","legend":"\u003cp\u003eLRV Type III\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eDiverse types of LRV anomalies: Type I is RLV, in which the LRV connects to the IVC in an orthotropic position; Type II entails the LRV joining the IVC at level L4-5; Type III is a circumaortic LRV; and Type IV entails the renal vein joining the left common iliac vein \u003c/em\u003e[4]\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5729267/v1/65cb0f48b4671444de2d0592.png"},{"id":79749489,"identity":"3cc86680-1130-40c6-933b-956e9733c1b2","added_by":"auto","created_at":"2025-04-02 09:10:45","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":262326,"visible":true,"origin":"","legend":"\u003cp\u003eLRV Type IV\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eDiverse types of LRV anomalies: Type I is RLV, in which the LRV connects to the IVC in an orthotropic position; Type II entails the LRV joining the IVC at level L4-5; Type III is a circumaortic LRV; and Type IV entails the renal vein joining the left common iliac vein \u003c/em\u003e[4]\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5729267/v1/88eafaea4beca3b11449651f.png"},{"id":79747782,"identity":"f5b48b68-7eb8-407d-a339-74c8304f44e1","added_by":"auto","created_at":"2025-04-02 09:02:45","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":367884,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eType I Retroaortic LRV\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003ea.\u003c/em\u003e \u003cem\u003eInferior vena Cava (blue arrow) b. Abdominal Aorta (green arrow) c. Retroaortic LRV (orange arrow)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5729267/v1/3e6607589b1bbab3191b4e4d.png"},{"id":79749490,"identity":"d3f39b74-adff-4588-978a-a23b30e69341","added_by":"auto","created_at":"2025-04-02 09:10:45","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":368238,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eType II Retroaortic LRV—Type II\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003ea.\u003c/em\u003e \u003cem\u003e\u0026nbsp;Inferior Vena Cava (blue arrow) b. Abdominal Aorta (orange arrow) c. Retroaortic LRV opening into IVC (green arrow)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5729267/v1/2f40b6ecd816da87c7f0cacd.png"},{"id":79750280,"identity":"4d13a098-02b7-4637-b60c-2e4338b44ae3","added_by":"auto","created_at":"2025-04-02 09:18:45","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":330380,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eType III circumaortic LRV\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003ea.\u003c/em\u003e \u003cem\u003eInferior vena cava (indicated by the blue arrow); b. Abdominal aorta (indicated by the orange arrow); c. The pre-aortic limb of the circumaortic left renal vein (indicated by the green arrow; d. LRV (indicated by the black arrow); e. Retro-aortic limb of circumaortic LRV (indicated by the yellow arrow)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-5729267/v1/98e02f81cf1c31a462077e3c.png"},{"id":79751737,"identity":"f3392514-d6fa-42b4-bd43-87e57548f4a5","added_by":"auto","created_at":"2025-04-02 09:26:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2872563,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5729267/v1/0255570c-c74e-4a95-b959-a72f27a7ec76.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Anatomical Study of the Rare Left Renal Vein Anomaly","fulltext":[{"header":"Background/Introduction","content":"\u003cp\u003eCurrently, there are limited reports on the various LRV variations and anomalies, which have been mainly attributed to errors in embryological development. The venous variations and anomalies found within the retroperitoneal region have significant clinical implications, primarily in relation to retroperitoneal surgical procedures, staging of testicular tumors, and caval filter placement. Furthermore, they should be accorded special consideration in instances that involve extensive dissections of the venous systems, including lymphadenectomy, as well as cases requiring venous system reconstruction, transplantations, and cancer invasion of the venous system, including cases of renal cancer with vascular extension [\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eRenal vein development is a crucial aspect of the intricate developmental process of the inferior vena cava (IVC). The developmental process of the renal veins begins during the fourth week after conception and concludes by the eighth week. An immense network comprising three pairs of parallel veins is involved in communication and includes the posterior cardinal, supracardinal, and subcardinal veins [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e]. Through the persistence and regression of such veins, the formation of four IVC segments occur, including the hepatic part, from the hepatic sinusoids and hepatic vein; the pre-renal vein, from the right sub-cardinal vein; renal part, from the anastomosis between the supracardinal and subcardinal veins; and the post-renal part, from the right subcardinal vein.\u003c/p\u003e\n\u003cp\u003eThe IVC development is often marked by the supracardinal and subcardinal channels of anastomotic communications, as they form the collar of veins surrounding the aorta. Typically, the ventral portion of the circumaortic collar persists as a standard left renal vein (LRV). However, when the collar\u0026rsquo;s dorsal portion persists, the LRV is often posterior to the aorta and develops into a retroaortic left renal vein (RALRV). Still, the venous collar or circumaortic left renal vein (CALRV) has been attributed to the intersupracardinal and subsupracardinal anastomoses, as well as the persistence of the LRV\u0026rsquo;s dorsal limb [\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e]. Further, the renal veins are formed from the persistence of the anastomosis of the subcardinal and supracardinal veins. The significant anomalies of the IVC include IVC duplication, IVC transposition (left-sided IVC), retroaortic left renal vein (RALRV), circumaortic left renal vein (CALRV), and the absence of the hepatic segment of the IVC [\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e]. Both the RALRV and CALRV are attributable to the persistence of the embryonic LRV\u0026rsquo;s dorsal limb alongside the persistence of the renal collar or intersupracardinal anastomosis\u0026rsquo; dorsal arch. Nevertheless, in RALRV, regression of the ventral arch occurs to enable the single renal vein to pass posteriorly to the aorta. It is also noteworthy that LRV is reported in approximately 0.3\u0026ndash;3.7% of the population, even as RALRV has been reported in only 0.5\u0026ndash;6.8% [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eThe congenital venous anomalies found within the retroperitoneal space are relatively rare and are typically considered asymptomatic in normal contexts; however, they have clinical significance due to the potential complications that may emerge if left unrecognized [\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e]. Normally, the LRV is approximately three times longer compared to the RRV (7.5 cm versus 2.5 cm), which is the underlying reason for the preference for the left kidney as a donor for live donor nephrectomy. Moreover, the LRV might be double, with one vein passing posteriorly and the other passing anteriorly to the aorta before joining the inferior vena cava (IVC) [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e]. This is often referred to as renal collar persistence. When the anterior LRV is absent, a single retroaortic LRV develops [\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e]. The development of the renal vein between the 4th and 8th weeks of intrauterine life is considered an aspect of an intricate IVC developmental process. The process involves three parallel vein pairs, including the supracardinal veins, subcardinal veins, and posterior cardinal veins.\u003c/p\u003e\n\u003cp\u003eSeveral existing clinical studies focusing on the left renal vein have been based on various radiological modalities, including CT-guided angiography, MRI, MDCT, and ultrasound, despite a limited number of anatomical studies having been conducted. This study was conducted due to its significant importance in embryology, morphology, surgery, and clinical applications. In this regard, the formation of the renal veins is facilitated by the persistence of the supracardinal veins\u0026apos; anastomosis [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e]. It is vital that the surgeons understand the LRV\u0026rsquo;s course and if it is pre-aortic or not to avoid unanticipated hemorrhage or fatality.\u003c/p\u003e\n\u003cp\u003eSurgically, the LRV anatomical variants, including the circumaortic (CLRV) and retroaortic (RLRV) courses, are of immense significance. Diverse topographical and morphological RLRV possibilities might occur. The LRV anomalies have been classified into four distinct types: Types I, II, and IV retroaortic veins and Type III circumaortic veins [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e]. Thus, in a Type I LRV anomaly, the LRV\u0026rsquo;s ventral pre-aortic limb is missing, and the dorsal retroaortic limbs persist, joining the IVC in a normal position [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e]. Consequently, a Type II LRV anomaly arises from the obliteration of the LRV ventral pre-aortic limb, even as the remainder of the dorsal limb becomes the RLRV [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e]. In this regard, the LRV is found at the L4 and L5 levels and connects the ascending lumbar vein and the gonadal vein before joining the IVC. Additionally, Type II variation has been classified as a venous collar or CALRV due to the persistence of the LRV dorsal limb alongside the subsupracardinal or intersupracardinal anastomoses [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e]. If the smaller retroaortic vein, which empties into the IVC, is considered, then it is highly likely that the prevalence of CALRV might be as high as 16% [\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e]. Consequently, in Type IV, the LRV\u0026rsquo;s ventral pre-aortic limb is missing. In contrast, the remaining dorsal limb becomes the RLRV, which inferiorly and obliquely courses to connect with the left common iliac vein. The other non-categorized LRV anomaly might involve the supernumerary actual veins of the kidney and the later venous confluences [\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eThe Type I RLRV characteristically connects to the IVC in an orthotropic position, even as Type II RALRV connects with the IVC at the L4-L5 level [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e]. Still, the Type IV RALRV vein connects with the left common iliac vein. Still, Type III LRV or CALRV anomaly comprises both the retroaortic and pre-aortic components [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e]. The four types of LRV variants and anomalies are indicated in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e below.\u003c/p\u003e\n\u003cp\u003eIn anatomy, fewer studies have focused on the renal venous system than the arterial system. Radiologists and other healthcare professionals have often overlooked the anomalies and variations of the renal veins. Such variations typically indicate the type and course of surgical operations, especially in vascular surgeries. Thus, preoperative venous anatomy description using multi-detector computed tomography (MDCT) angiography is essential for examining arterial anatomies. However, most recent anatomical studies focusing on renal vascular variations have indicated that anatomical variations and anomalies of the renal veins are comparatively smaller than those of the various renal arteries [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]. In this regard, it has been acknowledged that there is only one instance of renal vein anatomic anomalies in the literature [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e]. Despite the widespread definition of the accessory renal artery, the definition of the accessory renal vein has remained primarily unknown to clinicians and radiologists. Regardless, the acknowledgment of such anatomical variation is especially useful and vital in surgical procedures, as well as general surgery. In this regard, this study seeks to describe the increasingly rare anatomical anomalies and variations of the left kidney. We believe that this study will make a significant contribution to the existing literature.\u003c/p\u003e"},{"header":"Material and Methods","content":"\u003cp\u003eAs stated earlier, this study aims to evaluate and describe rare LRV anomalies and variations.\u003c/p\u003e \u003cp\u003eThis study employed a macroscopic dissection method to examine kidney regions in 30 well-embalmed human donors. The processing of the donors was primarily conducted by freezing, which occurred 24 hours prior to post-mortem, followed by subsequent storage at a temperature of -27\u0026deg;C until the time of dissection. The researchers did not employ any fixation treatment on any of the specimens used. Moreover, it is noteworthy that the human donors used in this study comprised individuals who died from various causes unrelated to the study. All the bodies were donations from university dissection rooms and different body donation services, and the dissection was performed at the Embryology and Anatomy Department of the University of Nairobi\u0026rsquo;s School of Medicine. To conduct the study, the researchers opened the abdominal cavities using a cruciform incision that traversed the entire thickness of the anterior abdominal wall. In addition to the flaps being reflected, a systematic removal of abdominal viscera was conducted, following the guidelines outlined in the Cunningham manual for Practical Anatomy [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The renal veins were identified, which involved tracing the kidney\u0026rsquo;s hilum until its termination within the inferior vena cava (IVC). Additionally, the renal vein\u0026rsquo;s tributaries were traced to their origins.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eAmong the observations made in this study include the view that, in 2 (6.6) of the donors, rather than assuming its usual course at the front of the aorta, the LRV took a retroaortic course and subsequently opened into the vena cava, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e6\u003c/span\u003e below.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003cp\u003eFurthermore, we observed that the termination level occurred at the L3-4 junction in one of the donors, as illustrated in Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e below.\u003c/p\u003e\n\u003cp\u003eFurthermore, we observed that the LRV tributaries, including the suprarenal vein and testicular vein, had typical terminations and courses. However, additional anomalies were observed in 1 (3.3%) donor, including the left testicular vein joining the left renal vein (LRV) and dividing into two veins of nearly equal caliber after a shorter course. One of the two veins was observed to have passed at the front of the aorta. In contrast, the other one passed at the back, with termination occurring at much lower levels, as illustrated in Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e, within the inferior vena cava rather than the circumaortic left renal vein.\u003c/p\u003e\n\u003cp\u003eThe prevalence rates of the anomalies in the LRV observed in the studied donors are presented in Table 1 below.\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable id=\"Taba\" border=\"1\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003es. no\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eVariation type\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNumber of cases\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePercentage (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eType I: retroaortic LRV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2/30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eType II: retroaortic LRV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eType III: circumaortic LRV\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eFurthermore, among the 30 human donors studied, we observed that 6 (20%) were reported to have standard textbook renal vein patterns. In the other 9 (30%) donors, a broader array of anatomical variations was observed. From the developmental perspective, four types of renal vein variations have been identified in this study: retroaortic, supernumerary, plexiform, and circumaortic veins. Thus, the supernumerary left renal vein, an extra vein originating from the kidney\u0026rsquo;s hilum and draining into IVC, was noted in only one donor. Consequently, 10 (33.3%) donors were reported to have supernumerary right renal veins, with 9 (30%) donors having single right supernumerary renal veins and 1 (3.3%) donors having double right supernumerary renal veins, which we consider a rare anomaly. Furthermore, regarding the retroaortic left renal vein (LRV), we observed that 1 (3.3%) donor had an LRV that coursed dorsally to the aorta before draining into the inferior vena cava (IVC). Normally, in its course, the LRV joins the left suprarenal vein and the left ovarian vein. This study also recognized the circumaortic left renal veins in 1 (3.3%) case. Thus, in one case, an increasingly significant retroaortic limb was observed, more pronounced than the preaortic limb, which also obliquely passed downward to drain into the IV at the L3 level. Additionally, it was noted that the circumaortic left renal vein received two suprarenal veins. Consequently, the pre-aortic limb was observed to be smaller and horizontally oriented, coursing anteriorly to the aorta to drain into the IVC at the level of the kidney\u0026rsquo;s hilum. It was also observed to receive a testicular vein alongside a supra-renal vein.\u003c/p\u003e\n\u003cp\u003eConsequently, in the second case, it was observed that the circumaortic LRV\u0026rsquo;s retroaortic limb was mainly a division of the LRV and had a comparatively smaller diameter. It was also noted that the retroaortic limb drained into IVC at the L3 level. Still, the pre-aortic segment was more pronounced in terms of size, even though it had a typical drainage pattern and received the gonadal and suprarenal veins. Lastly, a plexiform LRV was also noted in two donors. The plexiform LRV entails an infrequent variation in which the LRV, following its emergence from the kidney\u0026rsquo;s hilum, divides further, developing a network, and later reconnects to form a single renal vein. This results in the formation of two hiatuses and the emergence of the left gonadal artery from the left accessory renal artery, which then courses across the lower hiatus.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eAlthough several studies conducted on LRV, including clinical and RCT studies, have made use of various radiological modalities, including Multi-Detector Computed Tomography (MDCT), CT angiography, and Magnetic Resonance Imaging (MRI), a limited number of anatomical studies, as noted before, have been conducted on LRV anomalies. Therefore, this anatomical study has been conducted to assess and describe the rare LRV anomalies, as we believe that this will inform prospective surgical procedures and ensure safety while reducing the potential incidence of hemorrhage and death that might occur in instances of anomalies and variants.\u003c/p\u003e \u003cp\u003eAmong the notable critical anomalies found in the IVC are the transposition of the Left IVC, IVC duplication, retroaortic Left Renal Vein (LRV), and circumaortic Left Renal Vein (LRV), as well as the non-existence of the IVC\u0026rsquo;s hepatic portion [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. During IVC development, the supracardinal and subcardinal channels often form anastomotic communications, leading to the formation of a vein encircling the aorta. Moreover, in normal LRV anatomy, the ventral segment of the circumaortic collar remains the normal LRV. Nonetheless, in instances where the collar\u0026rsquo;s dorsal segment persists, the LRV assumes a posterior course relative to the aorta, leading to the development of the retroaortic left renal vein (RLRV). Still, the development of the circumaortic left renal vein (CALRV) occurs in instances where there is intersupracardinal and subsupracardinal persistence alongside the LRV\u0026rsquo;s dorsal limb [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe anatomic prevalence rates of LRV anomalies have been found to vary. For instance, in their study focusing on anatomic prevalence rates, Satyapal et al. evaluated 1008 cases and reported that anomalies of the RLRV and CALRV occurred concurrently at rates of 0.5% and 0.3%, respectively [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Furthermore, a similar CT-based study conducted by Trigaux et al. and involving 1014 specimens disclosed that the incidence rate of RLRV and CALRV anomalies were reported as 1.8% and 4.4%, respectively [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], even as \u0026Ouml;zg\u0026uuml;l disclosed a prevalence rate of 4.4% for CALRV and 1.8% for RLRV based on 433 CT specimens [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The RLRV has also been described as a vein coursing posteriorly to the aorta, as opposed to coursing anteriorly, while the CALRV has been described as the periaortic venous ring [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. In this regard, the general incidence rates of RLRV and CALRV are approximated to vary from 0.3 to 1.9% and 1.5 to 8.7%, respectively [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe anomalies of the RLRV and CALRV veins are attributable to aspects that include the persistence of embryonic structures, such as the renal collar\u0026rsquo;s dorsal arch and the embryonic left renal vein\u0026rsquo;s dorsal limb, through the anastomosis of the intersupracardinal vein. In instances of RLRV, the regression of the ventral arch results in the development of a single renal vein that courses at the aorta\u0026rsquo;s posterior, even as CLRV has both the posterior and anterior components, with an approximated prevalence of between 0.3% and 3.7%, and 0.5% and 6.8% of individuals, concurrently [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFurthermore, the RLRV has been categorized into two distinct forms: Type I, which refers to the orthotropic retroaortic renal vein, and Type II, which involves the single LRV descending renal hilum and coursing posteriorly to the aorta at the L4-L5 junction and subsequently joining the ovarian or testicular veins together with the ascending lumbar vein before joining the IVC [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The CLRV has been described in numerous studies as referring to the third type of RLRV, characterized by two distinctive veins that course posteriorly and anteriorly to the aorta and subsequently join the IVC [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Although very rare, the fourth type of LRV has been reported and involves the LRV draining into the iliac vein after receiving tributaries [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Among the most common urological symptoms associated with LRV anomalies is hematuria, with the highest prevalence in Types II and IV, and it is also highly prevalent in Type I in RLRV [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAdditionally, in an MDCT angiography-based study comprising 1860 participants with various urological symptoms, including flank pain, hematuria, and left gonadal varicocele, four distinct critical types of LRV anomalies were mainly identified and classified based on their appearances [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Thus, Type I (RLRV) entails a vein that connects to the IVC in an orthotropic point; Type II involves RLRV connecting to the IV at an L4-L5 intersection; Type III entails the collar/circumaortic LRV; and Type IV involves RLRV linking up with the left iliac vein [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The study further revealed that the concurrent incidence of LRV Type I, LRV Type II, LRV Type III, and LRV Type IV was 3.6%, 1.4%, 1.2%, and 0.9%, respectively [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Nonetheless, for our study, the use of MDCT was unnecessary as the study did not focus on urological diseases and symptoms, and donors were utilized to study LRV anomalies. Of the donors studied, it was observed that LRV anomalies, specifically LRV Type I, LRV Type II, LRV Type III, and LRV Type IV, occurred in 2 (6.6%), 1 (3.3%), 1 (3.3%), and 0 (0%) specimens, respectively. The LRV anomalies prevalence rates were low, given that the study has disclosed that Type I RLRV had a 6.6% incidence rate of linking up with IVC in an orthotopic position while Type II LRV had an incidence rate of between 3.3% of linking up with the IVC at L4-L5, and the circumaortic LRV also had an incidence rate of between 3.3%.\u003c/p\u003e \u003cp\u003eSimilar to the findings of our study, which indicated a low incidence rate of retroaortic left renal vein (LRV), a cadaveric study conducted in Colombia with a total of 156 specimens observed that two specimens (1.3%) had a retroaortic course, and one specimen (0.6%) [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. In this regard, the observed lower incidence rate of circumaortic and retroaortic left renal vein (LRV) variations may be attributable to morphological trends in the Colombian Mestizo population. Furthermore, the findings of our study have been corroborated and are consistent with those of studies conducted by Baptista et al. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] and Satyapal et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Additionally, a limited number of retroaortic LRVs have been observed in various Japanese studies, including a cadaveric study comprising 203 specimens, where only one specimen (0.49%) had a retroaortic LRV [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Similarly, studies conducted by Izumiyama, Horiguchi, and Okamoto in Japan have indicated incidence rates of 0.75% and 0.74%, respectively [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Such observed lower incidence rates of RALRV have been linked to factors that include racial differences.\u003c/p\u003e \u003cp\u003eStill, in an instance involving a healthy hypertensive middle-aged male individual with a left-side varicocele alongside symptoms that include palpitations and giddiness, even no hematuria, which refers to the nutcracker phenomenon (posterior), was disclosed by the CT scan within the course of his labile HTN workup. The case has, therefore, placed substantial emphasis on the significance of the RALRV in the differential diagnosis of labile hypertension [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Adequate and timely diagnosis has, for this reason, been recommended as this will ensure that there are no unnecessary investigations.\u003c/p\u003e \u003cp\u003eAdditionally, Deschepper initially described \u0026ldquo;Nutcracker syndrome\u0026rdquo; or LRVHTN in 1972 [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] through the definition of LRV with renal venous HTN development, whose backward transmission to the parenchyma may lead to different symptoms [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. There is an increased diversity regarding the nutcracker phenomenon and compression mechanism, with vein trapping found within an aortic-mesenteric space resulting from aneurysmal aorta dilatation or the anterior nutcracker phenomenon being the most frequent type [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. In such instances, the RALRV or CALRV gets compressed between the vertebral body and the aorta and is referred to as the posterior nutcracker. The nutcracker and poster nutcracker phenomenon have varying clinical features, including chronic pelvic congestion and asymptomatic micro-hematuria [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. The predominant symptom is Hematuria, which is attributable to the rupture of thin-walled varices into the collecting systems caused by an increase in venous pressure. The other widespread symptom is pain [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Renal infarcts and congested kidneys resulting from the posterior nutcracker phenomenon might additionally cause bacterial localization and the subsequent formation of abscesses. Further, aortic thrombosis has been acknowledged as a major complication resulting from sepsis and infections [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. In neonatal cases, renal abscesses and septicemia caused by the nutcracker phenomenon have been documented [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Although such anomalies are generally asymptomatic, the rupture of the Abdominal Aortic Aneurysm (AAA) into the retroaortic left renal vein (LRV) results in a distinctive symptom marked by an incessant abdominal bruit, left flank pain, and abdominal pain with a related pulsatile mass [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The performance of proximal graft anastomosis and proximal aorta exposure pose substantial technical challenges, particularly in relation to IVC and renal vein anomalies and variations. Aortic clamping becomes possible below and above the retroaortic left renal vein (LRV) Type I [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Consequently, Arslan et al. reported RLRV prevalence rates of 1.7% in men and 1.6% in women following an examination of 1,125 abdominal CT scans [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Furthermore, the study revealed that nine individuals had varicocele, suggesting that the RLRV might be a potential etiologic factor underlying the development of varicocele [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Nevertheless, a study involving 149 patient participants with varicocele alongside 137 control patients disclosed that 13 patients (8.7%) presented with RLRV, while three control patients (2.2%) also presented with RLRV. The study's findings have indicated a considerably higher incidence rate of RLRV in individuals with varicocele than in the control group patients [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Comparing the four types of LRV anomalies is a key challenge, given that most studies have only reported on Types I and III LRVs. While some studies have only described Type I LRV anomaly, Type IV has been infrequently reported. However, our study observed Types I, II, and III LRV anomalies, even as Type IV was not observed.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, although the LRV anomalies have been categorized into four types, they can be classified into two main classes: the circumaortic and the retroaortic LRV types. In this regard, it has been noted that the retroaortic left renal vein (LRV) may be further divided into three distinct types based on the termination level in relation to the inferior vena cava (IVC). The differences in the incidence rates of the LRVs are amongst the highly notable features that different studies have disclosed, attributed to racial differences. Therefore, understanding the LRV anomalies is essential for radiologists, anatomists, and surgeons, as they may pose life-threatening and fatal situations during surgical operations within the retroperitoneal regions if left unaddressed. Moreover, knowing the LRV variables will enable better comprehension of potential clinical events. Therefore, in instances of surgical operations within the retroperitoneal region, the performance of preoperative CT is recommended, as this aids in ensuring safer surgical procedure outcomes.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eEthics approval and consent to participate (IRBC/1942/24)\u003cbr\u003eConsent for publication (Authors have offered their consent for publication)\u0026nbsp;\u003cbr\u003eAvailability of data and materials (Authors)\u003cbr\u003eCompeting interests (Not applicable)\u003cbr\u003eFunding (Not applicable)\u003cbr\u003eAuthors\u0026apos; contributions\u0026mdash;YA conceptualized and designed the study, carried out the primary anatomical analysis, and prepared the methodology. YA drafted and revised the manuscript with the assistance of MMJ, who also provided critical revisions for significant intellectual content. Consequently, MMJ assisted in designing the study and made substantial contributions to the development of the research objectives. \u0026nbsp; Jointly, YA and MMJ collected data through detailed anatomical dissections and recorded observations. YA also supervised the data collection and analysis process and reviewed and approved the final manuscript. YA and MMJ also jointly conducted the literature review and provided critical insights into contextualizing the findings, in addition to participating in the analysis and interpretation of the study results.\u003cbr\u003eAcknowledgements (Not applicable)\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eVerma M, Pandey NN, Ojha V, Kumar S, Ramakrishnan S. Developmental anomalies of the inferior Vena Cava and its tributaries: What the radiologist needs to know. Indian Journal of Radiology and Imaging. 2022 Sep;32(03):355-364.\u003c/li\u003e\n\u003cli\u003eIndira CK, Arunkumar KG. 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I., \u0026amp; Steinmetz, O. K. (2001). Incidence of major venous and renal anomalies relevant to aortoiliac surgery as demonstrated by computed tomography. \u003cem\u003eAnnals of vascular surgery\u003c/em\u003e, \u003cem\u003e15\u003c/em\u003e(6), 615-618.\u003c/li\u003e\n\u003cli\u003eBallesteros LE, Saldarriaga V, Ramirez LM. Morphologic evaluation of the renal veins: a study with autopsy material from Colombian subjects. Rom J Morphol Embryol. 2014 Jan 1;55(1):77-81.\u003c/li\u003e\n\u003cli\u003eBaptista-Silva JC, Ver\u0026iacute;ssimo MJ, Castro MJ, C\u0026acirc;mara AL, Pestana JO. Anatomical study of the renal veins observed during 342 living-donor nephrectomies. Sao Paulo Medical Journal. 1997; 115:1456-1459.\u003c/li\u003e\n\u003cli\u003eYoshinaga K, Kawai K, Kodama K. An anatomical study of the retroaortic left renal vein. Okajimas Folia Anatomica Japonica. 2000 Aug 21;77(2-3):47-52.\u003c/li\u003e\n\u003cli\u003eIzumiyama M, Horiguchi M. 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Interactive cardiovascular and thoracic surgery. 2011 Feb 1;12(2):278-280.\u003c/li\u003e\n\u003cli\u003eMulcaire-Jones JP, Bailly DK, Frank DU, Verma AR, Barney BJ, Siefkes HM. Spontaneous aortic thrombosis in neonates: a case report and review of literature. Cardiology in the Young. 2020 Jan;30(1):95-99.\u003c/li\u003e\n\u003cli\u003eShindo S, Kubota K, Kojima A, Iyori K, Ishimoto T, Kobayashi M, Kamiya K, Tada Y. Anomalies of inferior vena cava and left renal vein: risks in aortic surgery. Annals of vascular surgery. 2000 Jul; 14:393-396.\u003c/li\u003e\n\u003cli\u003eArslan H, Etlik \u0026Ouml;, Ceylan K, Temizoz O, Harman M, Kavan M. Incidence of retro-aortic left renal vein and its relationship with varicocele. European radiology. 2005 Aug; 15:1717-20.\u003c/li\u003e\n\u003cli\u003eKarazincir S, Balci A, G\u0026ouml;r\u0026uuml;r S, Sumbas H, Kiper AN. Incidence of the retroaortic left renal vein in patients with varicocele. Journal of Ultrasound in Medicine. 2007 May;26(5):601-604.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"artery-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Artery Research](https://arteryresearch.biomedcentral.com/)","snPcode":"44200","submissionUrl":"https://submission.springernature.com/new-submission/44200/3","title":"Artery Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Left Renal Vein (LRV), Left Renal Vein anomalies, Left Renal Vein Variations, retroaortic LRV (RALRV), circumaortic LRV (CALRV)","lastPublishedDoi":"10.21203/rs.3.rs-5729267/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5729267/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eIntroduction: \u003c/strong\u003eDue to its length, the left renal vein (LRV) is generally idyllic in renal transplantation surgical procedures. As such, understanding the course and attributes of the LRV, including whether it is pre-aortic or not, is essential for surgeons and other healthcare professionals, such as physicians. The understanding of these aspects is crucial in preventing unexpected fatalities and hemorrhage resulting from surgical procedures. Nevertheless, a limited number of clinical anatomy studies have focused on the anatomical variations of the LRV compared to the renal arterial systems. Often, the anatomical anomalies and variations of the renal veins are overlooked by radiologists, even as such variations and anomalies are indicative of the operation course and type, including vascular surgical procedures. Therefore, this study aims to evaluate and describe rare LRV anomalies and variations. Macroscopic dissections of 8 human donors (6 males and two females) were conducted to realize this objective. The specimens were acquired from various body donation services and university dissection rooms. All the specimens studied were reported as having died from causes unrelated to this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eThis study's findings have demonstrated the existence of different LRV anomalies, which met the criteria for classification into four key categories. Type I anomaly was the most prevalent, closely followed by Types III, II, and IV.\u003cstrong\u003e \u003c/strong\u003eNonetheless, the Type IV LRV anomaly has been acknowledged to be the most infrequent. In the present study, the prevalence/incidence rate of LRV Type I, Type II, Type III, and Type IV anomalies was disclosed to be 6.6%, 1.6%, 3.3%, and 0%, respectively.\u003cstrong\u003e \u003c/strong\u003eThe present study found no Type IV LRV anomaly in the donors studied.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e Understanding the rare LRV anomalies and variations is essential as it improves the understanding of clinical events. A pre-operative computed tomography (CT) scan is vital to ensure the safety of any surgical procedure conducted in the retroperitoneal region and to avert possible fatalities and hemorrhage during renal surgeries.\u003c/p\u003e","manuscriptTitle":"Anatomical Study of the Rare Left Renal Vein Anomaly","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-02 08:54:40","doi":"10.21203/rs.3.rs-5729267/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-04-06T23:38:50+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-01T03:43:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"9373262528628641577011308749970110453","date":"2025-04-01T03:34:38+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-03-31T21:24:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"174519904805504404559488407574846288811","date":"2025-03-31T18:38:18+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-03-31T12:13:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"140823217953991862686069753717632399938","date":"2025-03-31T11:50:57+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-03-30T14:00:46+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-03-28T07:27:26+00:00","index":"","fulltext":""},{"type":"submitted","content":"Artery Research","date":"2025-03-27T13:55:30+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"artery-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Artery Research](https://arteryresearch.biomedcentral.com/)","snPcode":"44200","submissionUrl":"https://submission.springernature.com/new-submission/44200/3","title":"Artery Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"63508481-bcb3-4f8c-9ef3-2adc5ff151b3","owner":[],"postedDate":"April 2nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-05-08T14:08:45+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-02 08:54:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5729267","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5729267","identity":"rs-5729267","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}