Duplicated left renal vein with aberrant inferior drainage to left common iliac vein: A rare anomaly of left renal vein

Abstract

Anatomical variations of the renal veins, such as duplicated renal veins, are usually asymptomatic and frequently discovered incidentally on imaging. While clinically silent, recognizing these anomalies is of paramount importance for surgical planning and avoiding diagnostic errors. We report the case of a 66-year-old man who presented to the emergency department with a persistent cough and exertional dyspnea. The patient had no significant past medical history, and physical examination and laboratory tests were unremarkable. To evaluate his respiratory symptoms, a triphasic contrast-enhanced computed tomography (CT) scan was performed. Although no acute thoracic pathology was found, the imaging incidentally revealed a duplicated left renal vein. An accessory vein originating from the lower pole of the left kidney, coursing inferiorly and draining into the left common iliac vein at the level of the inferior vena cava (IVC) bifurcation, visualized as a patent vessel in all contrast phases. No other abdominal or vascular anomalies were observed. This case highlights that duplicated renal veins can be incidentally detected on CT scans performed for unrelated, non-abdominal indications. Accurate radiologic identification and documentation of such venous variants are essential to prevent misdiagnosis (such as mistaking the vessel for a retroperitoneal mass or lymph node) and to avoid perioperative complications in future retroperitoneal, vascular, or urological procedures.

Introduction

One of the most common yet underrecognized types of vascular anomaly in the practice of clinical medicine and the diagnostic radiology is anatomical variations of the renal veins. In normal anatomy, each kidney is normally emptied by one renal vein which runs at the renal hilum into the inferior vena cava. However, there can be a variety of variations, including multiple renal veins, accessory venous branches, circumaortic venous rings, retroaortic courses because of complicated embryologic development of the subcardial and supracardial venous systems. These differences are caused by the presence of the persistence, retreat, or anastomosis of the primitive venous pathways in the embryo stage [1,2].

The incidence of variants of renal venous is variable with the populations and imaging modalities. Very large meta-analysis data of tens of thousands of subjects demonstrate that several renal veins take place in about 2–5% of people, and other versions of venous pathway and bridging arrangements have fluctuating occurrences [1]. These results prove the existence of vascular variations as not exceptionally rare and emphasize the importance of increased clinical vigilance.

CTA and contrast-enhanced multidetector computed tomography (MDCT) offer high-resolution views of the renal vascularity and can therefore be incidentally discovered even when the imaging is ordered on different clinical reasons. A number of radiologic reports indicate that regular abdominal CT scans have the ability to manifest abnormal venous anatomy, such as multiple and circum aortic veins, and retroaortic courses, among others [3,4].

The renal venous variations are rather numerous and despite the fact that most of them are not clinically present, their identification is essential in terms of diagnostic interpretation and their safety in terms of a procedure. Radiologic practice: The missed recognition or reporting of a venous variant can result in a misinterpretation of retroperitoneal anatomy, vascular pathology misdiagnosis, or unexpected findings of the interventional process. Comparing contrast-enhanced imaging with conventional methods, the former yields much better diagnostic results and provides a higher degree of anatomical definition [5].

Surgically, the specifics of the anatomy of the renal vein are extremely essential before surgery like nephrectomy, renal transplantation, paraaortic lymphadenectomy and retroperitoneal surgery. The risk of accidental injury, major bleeding, a prolonged operating period, and surgical technique alteration may be elevated, and undetected anomalous veins may lead to these conditions. Case reports and surgical review have highlighted the potential of unidentified venous variants to make operative dissection difficult, particularly in operating with minimal invasiveness or laparoscopic surgery where there is a paucity of tactile feedback (case report literature review) [6].

Considering the growing popularity of cross-sectional imaging in the contemporary clinical process and the extensive scope of the surgical procedures with the use of the retroperitoneal space, the detailed awareness and proper reporting of variations in renal veins is the key to ensuring patient safety. The case included in this report involves the incidental finding of renal vein variation in an elderly patient and the implications of the same on the clinical and surgical implications of the topic within the existing literature.

Embryology of the renal veins and inferior vena cava

The definitive IVC and renal veins develop during the 4th–8th gestational weeks from three paired systems: posterior cardinal (precursor of common iliac veins), subcardinal (suprarenal IVC), and supracardinal veins (infrarenal IVC) [1,9]. An inter-subcardinal anastomosis anterior to the aorta (ventral limb) and an inter-supracardinal anastomosis posterior to the aorta (dorsal limb), connected by sub-supracardinal anastomoses, form the renal collar around the aorta by the 8th week [9,10]. Normally, the dorsal limb regresses, leaving a single preaortic left renal vein. Persistence of the dorsal arch results in retroaortic vein (2.1%), both arches in circumaortic (3.2%), and two sub-supracardinal channels in duplicated vein [2].

Variations result from persistence of structures that normally regress:

• •Persistence of the dorsal inter-supracardinal arch alone → retroaortic left renal vein (0.5–3.4% prevalence) [1].
• •Persistence of both ventral and dorsal arches →circumaortic left renal vein (1.5–8.7%) [1].
• •Persistence of two separate subsupracardinal channels at the renal hilum → duplicated left renal vein [12].

Aberrant caudal drainage to the ipsilateral common iliac vein, as in our patient, is the rarest subtype. This pattern was first described by Brancatelli et al. (2000) as a retroaortic left renal vein joining the left common iliac vein [12] and subsequently defined embryologically by Kawai et al. (2016) [11]. In these reports, the cranial (normal) left renal vein derives from the ventral inter-subcardinal arch, while the caudal accessory vein derives from persistence of the caudal left subsupracardinal anastomosis and the left supracardinal vein itself, with maintenance of its embryonic connection to the left posterior cardinal vein. Since the left posterior cardinal vein is the direct precursor of the left common iliac vein, the accessory vein retains an embryonic pathway from the lower pole of the kidney to the pelvis, coursing inferiorly and draining into the left common iliac vein at the level of the IVC bifurcation (L4–L5), as observed in our case and in the recent anatomical case report of Balawender et al. (2022) [10].

Case presentation

On January 24, 2026, a 66-year-old man came to the emergency department of Faghihi Hospital complaining of persistent cough and exertional dyspnea. He never had any previous medical history, previous surgeries, or frequent medication. He denied smoking, drinking, and relevant family disease history. Vital signs were normal, and physical examination had no abnormal cardiopulmonary or abdominal observations. Laboratory tests were normal.

A contrast-enhanced computed tomography (CT) chest and abdomen was done to investigate his respiratory complaints. Although the scan showed no acute pathology in the chest to account for his symptoms, it did show an incidental anomaly. He was found to have a duplicated left renal vein, which originated from the inferior pole of the left kidney. The accessory vein tracked down and drained directly into the left common iliac vein at the level of inferior vena cava (IVC) bifurcation (Fig. 1).The extra vein was clearly seen and patent on all phases of the contrast injection. No other abdominal, organ or vascular anomalies were identified.

Fig. 1.

Post-contrast abdomen CT scan. (A) The arrow demonstrates the main left renal vein draining to the IVC on the axial image. (B) The arrow indicates the aberrant accessory left renal vein draining to the left common iliac vein on the axial image. (C) The arrow represents the aberrant accessory left renal vein draining to the left common iliac vein on the coronal image. (D) The arrow displays the aberrant vein joining the lower pole of the left kidney on the coronal image.

Discussion

Renal venous variations are developmental vascular defects that develop as a result of the complex embryologic development of inferior vena cava and its tributaries. Renal venous system forms out of subcardinal and supracardial venous systems and may have variants like doubled renal veins, additional accessory venous channels or abnormal drainage.

The occurrence of multiple renal veins is anatomical and radiologic study variable but has been estimated to be found in about 2–5 percent of individuals with higher incidences being reported on the right [[3], [4]]. Although these variants carry a relatively low prevalence, they are clinically relevant as they can be incidentally discovered due to the cross-sectional imaging conducted under unrelated reasons [5].

In the case in point, a duplicated renal vein was accidentally revealed during contrast-enhanced CT which was conducted to assess the respiratory symptoms. An accessory vein originating from the lower pole of the left kidney, coursing inferiorly and draining into the left common iliac vein at the level of the IVC bifurcation, visualized as patent in all contrast phases. No vascular or abdominal anomalies expected. This throws a major radiologic point into the limelight: although the radiologic test is ordered with non-abdominal indicators, a thorough systematic examination of the entire field of view must be undertaken in order to identify clinically significant incidental findings.

Important diagnostic implications are associated with the recognition of such variants. Unidentified renal venous abnormally can be mistaken with pathological features like lymphadenopathy, vascular malformations or retroperitoneal masses especially when the imaging planes are not horizontal or the contrast timing is not optimal [[5], [6]]. Consequently, multiplanar reconstruction and contrast-enhanced imaging are significant in proper identification.

Surgical importance of renal venous variations is even more severe. Close understanding of the renal vasculature is vital before nephectomy, renal transplant, para-aortic surgery or retroperitoneal surgery. Unnoticed accessory or redundant veins could pose greater risks of intraoperative hemorrhage, vascular trauma, long surgery time or operative complexity in dissection, particularly in laparoscopic or minimal invasive procedures [4]. In this regard, the reporting of such variants, even accidentally, is critical in surgical planning and patient safety.

Anomalies of the left renal vein are not uncommon, but there are great variations among different variants. For example, Sutariya (2016) described a very rare case of a double retro-aortic left renal vein terminating at the left common iliac vein [7]. While the drainage of our patient's left renal vein was different (bifurcation of the IVC at origin of left common iliac vein), both cases highlight the variability in the drainage sites of duplicate left renal veins. It's essential to identify such unusual drainage points, as it goes against anatomical conventions.

- A recent report in the Journal of Clinical and Scientific Research (2025) by Chinta et al. [8] described a 50-year-old female with complex right-sided renal vascular variant incidentally discovered: an accessory right renal artery arising from the right common iliac artery and an accessory right renal vein draining into the left (contralateral) common iliac vein. The authors emphasized that such combined arterial and venous iliac-based variants are extremely rare but clinically silent, usually found incidentally on cross-sectional imaging performed for unrelated reasons. They concluded that 3D CTA is essential for accurate preoperative mapping and that failure to recognize such variants may lead to catastrophic bleeding during pelvic surgery. Their case differs from ours in laterality (right vs left), presence of arterial variant, and contralateral versus ipsilateral iliac drainage, yet it supports the same main message: awareness and documentation of iliac drainage patterns of renal veins are critical.

Most variations of renal venous do not present symptoms, but it is noteworthy that their occurrence is not devoid of consequences since in some cases, the change in the venous drainage patterns can affect renal hemodynamics or predispose to vascular compression phenomena. Even though no complications of this kind were recorded in this patient, the record of the anomaly is a good source of information that can be used during a clinical or surgical procedure.

The case highlights the need to identify and report renal venous variations that were incidentally identified during imaging studies. Proper characterization of these variants does not only help avoid diagnostic pitfalls, but also makes a direct contribution towards surgical safety and optimal clinical care.

Conclusion

Renal venous anatomical variants, including duplicated left renal veins, are increasingly detected as incidental findings due to the widespread use of cross-sectional imaging like contrast-enhanced CT. As demonstrated in this 66-year-old patient, these anomalies can be entirely asymptomatic and discovered during evaluations for unrelated thoracic complaints. It is crucial for radiologists to systematically assess the entire field of view and accurately document these venous variants, even when the primary indication for imaging is not abdominal. Recognizing a duplicated renal vein not only prevents its misinterpretation as a retroperitoneal mass or lymphadenopathy but also provides vital pre-operative anatomical mapping. Such documentation is essential to minimize the risk of severe vascular complications during any future surgical or interventional procedures involving the kidneys, inferior vena cava, or the retroperitoneal space.

Learning points

• 1.Duplicated left renal vein with drainage into the left common iliac vein is an rare anomaly.
• 2.Embryology: The anomaly results from persistence of the left supracardinal-suprasubcardinal channels and intercardinal anastomosis caudal to the normal renal collar, with regression of the orthotopic connection to IVC for the accessory lower-pole channel, leading to persistent drainage into the posterior cardinal-derived common iliac vein.
• 3.Consistent description is key: accessory vein originating from lower pole of left kidney, coursing inferiorly, draining into left common iliac vein at level of IVC bifurcation, patent in all phases.
• 4.Even on chest CT or non-abdominal indications where abdomen is partially included, radiologists must review the retroperitoneum to catch incidental vascular variants.
• 5.Clinical relevance: Prevents misdiagnosis as lymphadenopathy/retroperitoneal mass and is crucial to avoid hemorrhage during nephrectomy, transplantation, paraaortic lymphadenectomy, and aortoiliac surgery. Preoperative CTA with MIP/3D-VR is recommended.
• 6.Reporting template should include number of renal veins, origin (hilum vs polar), course (preaortic/retroaortic/circumaortic/inferior), drainage site, caliber, and patency.

Ethical approval

This study received ethical approval from the Shiraz University of Medical Sciences Research Ethics Committee.

Patient consent

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