Project – Anatomical Variations of the Renal Arteries and Their Clinical Implications: A CT Angiographic Study at LUTH

CHAPTER ONE

INTRODUCTION

1.1 Background to the Study

The kidneys are highly vascularized retroperitoneal organs whose normal function depends on an adequate and uninterrupted arterial blood supply. Each kidney is usually supplied by a single renal artery arising laterally from the abdominal aorta, typically around the level of the first and second lumbar vertebrae. After entering the renal hilum, the renal artery divides into segmental branches that supply relatively defined vascular territories within the kidney. However, the apparently simple textbook pattern does not represent the full spectrum of renal arterial anatomy, as additional renal arteries, early arterial branching, polar arteries and variations in the origin and course of the renal arteries are frequently encountered. A comprehensive understanding of this anatomy is therefore important in anatomical education, diagnostic radiology, vascular surgery, urology and renal transplantation (Standring, 2021; Ozkan et al., 2006).

Renal arterial variations are believed to arise largely from the complex embryological development of the kidneys and their vascular supply. During development, the kidneys undergo ascent from the pelvic region toward their final abdominal position, accompanied by successive changes in their arterial supply. Persistence of vessels that would ordinarily regress can result in additional or accessory renal arteries. These vessels may enter the renal hilum or approach the superior or inferior pole of the kidney, where they may be described as polar arteries. Other developmental patterns may produce early division of the main renal artery or unusual arterial courses. Consequently, variations in renal arterial anatomy are not necessarily pathological abnormalities but represent developmental patterns that may have important clinical consequences (Standring, 2021; Satyapal et al., 2001).

The prevalence of renal arterial variations varies considerably between populations and according to the imaging or anatomical method used to identify them. In a large angiographic study of 855 patients, Ozkan et al. (2006) reported multiple renal arteries in 24% of individuals and bilateral multiple renal arteries in 5%, while early division occurred in 8% of cases. Similarly, Çınar and Türkvatan (2016), using multidetector CT angiography in 504 patients, reported multiple renal arteries in 31.3% of participants and prehilar branching in 6.5%. These findings demonstrate that additional renal arteries and variant branching patterns are relatively common and that their prevalence may differ substantially between study populations.

Computed Tomography Angiography (CTA) has become an important non-invasive technique for evaluating renal vascular anatomy because it provides high-resolution visualization of the renal arteries, their origins, number, branching pattern and course. Multidetector CTA permits multiplanar and three-dimensional reconstruction of vascular structures and can identify vascular configurations that may be difficult to appreciate on conventional imaging. Çınar and Türkvatan (2016) demonstrated that MDCT angiography could effectively characterize multiple renal arteries, early branching and renal vascular variations, while Mihaylova et al. (2023) similarly used multidetector CT to demonstrate substantial variation in renal arterial anatomy in an adult population. These findings support CTA as an appropriate method for systematic assessment of renal arterial variations in living individuals.

Among the most frequently encountered renal arterial variants are accessory or multiple renal arteries. These vessels may enter through the renal hilum or directly supply the superior or inferior pole. Their presence is clinically important because renal arteries are end arteries, and an accessory artery may supply a discrete portion of renal parenchyma. During renal transplantation or partial nephrectomy, failure to identify an additional renal artery may result in inadequate perfusion, inadvertent vascular injury or ischemic damage to part of the kidney. A systematic radioanatomical study by Bordei et al. and subsequent imaging studies have emphasized the clinical importance of recognizing multiple renal arteries before renal intervention. More recently, Bolla et al. (2026) reported multiple renal arteries in a substantial proportion of CTA examinations and emphasized that knowledge of these variants is important for renal surgery and endovascular procedures.

The clinical importance of renal arterial variations is particularly evident in kidney transplantation. Living-donor nephrectomy requires detailed preoperative assessment of the renal vascular pedicle because the number, origin, course and branching pattern of renal arteries influence surgical planning and vascular reconstruction. In a Nigerian kidney-transplant population, Sani et al. (2022) reported renal arterial configuration variations in 50% of living kidney donors, including accessory renal arteries and early arterial branches. The study emphasized that accurate understanding of renal vascular anatomy is essential for safe donor nephrectomy and preservation of graft function. This Nigerian evidence demonstrates that renal arterial variants are common in the local population and reinforces the need for radiological identification before renal transplantation.

Renal arterial variations are also relevant to other surgical and interventional procedures, including nephrectomy, partial nephrectomy, renal artery interventions and procedures for renovascular hypertension. An accessory artery may have a different origin or course from the principal renal artery and may cross areas that are important during surgery. A precaval right renal artery, for example, may pass anterior to the inferior vena cava rather than following the more typical posterior course. Early branching may also shorten the available length of the main renal artery and consequently influence surgical clamping and vascular reconstruction. Therefore, preoperative identification of the renal arterial pattern is important for reducing vascular complications and improving procedural planning (Ozkan et al., 2006; Çınar & Türkvatan, 2016).

Population-specific investigation of renal arterial anatomy is particularly important in Africa because available anatomical data have historically been more limited than those from Europe, Asia and North America. A Kenyan anatomical study found additional renal arteries in 14.3% of cases and identified several patterns of renal arterial branching and polar supply, while a Nigerian CT study of 200 patients found arterial variations in 37% of the study population. More recently, a systematic review and meta-analysis of African studies involving 2,451 subjects reported accessory renal arteries in 19.7% of individuals and found that 13.9% of kidneys possessed accessory renal arteries. These findings demonstrate both the frequency of renal arterial variants and the importance of African-specific evidence when interpreting renal vascular anatomy (Wanjiku et al., 2010; Ugwu et al., 2018; 2025 African systematic review).

The Nigerian population presents a particularly relevant context for further investigation. Ugwu et al. (2018), in a CT study of 200 Nigerian patients, found that 50% had some form of renal vascular variation, with arterial variations accounting for 37%. Accessory renal arteries were the most common arterial variant, followed by early branching and precaval right renal arteries. A separate Nigerian study of living kidney donors also reported renal arterial variations in half of the examined donors. Although these studies provide important evidence, further assessment using CT angiographic images from major Nigerian tertiary hospitals can expand the available regional data and improve understanding of the frequency, laterality and patterns of renal arterial variations in the Nigerian population (Ugwu et al., 2018; Sani et al., 2022).

Lagos University Teaching Hospital (LUTH) provides an appropriate clinical environment for a radiological study of renal arterial anatomy because CT imaging is routinely used in the assessment of abdominal and vascular conditions. A systematic review of CT angiographic images can allow the number, origin, course, branching pattern and other anatomical characteristics of the renal arteries to be documented in living adults. Such information can contribute to anatomical knowledge and may be particularly useful for radiologists, urologists, vascular surgeons and transplant teams. Given the documented prevalence of renal arterial variants among Nigerian patients, an institution-specific study at LUTH can provide additional locally relevant information and contribute to improved recognition of these variants during clinical imaging and surgical planning (Ugwu et al., 2018; Çınar & Türkvatan, 2016).

1.2 Statement of the Problem

The renal arteries are commonly presented as paired vessels arising directly from the abdominal aorta and supplying each kidney through a relatively predictable pattern. However, radiological and anatomical studies have demonstrated that additional renal arteries, early branching, polar arteries and unusual arterial courses occur with considerable frequency. The discrepancy between the simplified textbook description and the vascular anatomy encountered in clinical practice creates an important challenge for radiologists and surgeons. Failure to recognize these variations before renal procedures may result in inadvertent vascular injury, incomplete renal perfusion or difficulties during vascular reconstruction (Ozkan et al., 2006; Çınar & Türkvatan, 2016).

A further problem is the considerable variation in the reported prevalence of renal arterial anomalies among different populations. Studies have reported multiple renal arteries in approximately one-quarter to one-third of individuals, while Nigerian studies have reported even broader variation depending on the population and study design. In a Nigerian population of 200 patients, Ugwu et al. (2018) found arterial variations in 37% of participants, while a Nigerian kidney-donor study reported renal arterial configuration variations in 50% of donors. These differences demonstrate that findings from one population cannot necessarily be generalized to another and create a need for additional population- and institution-specific radiological studies in Nigeria.

Another major problem concerns the clinical consequences of unidentified renal arterial variants. Accessory arteries may supply specific renal segments, while inferior polar arteries may be closely related to the ureter and can have implications during renal surgery. Early arterial division can reduce the length of the main renal artery available for clamping or anastomosis, while unusual arterial courses may complicate surgical access. These anatomical considerations are particularly important during renal transplantation, partial nephrectomy, nephrectomy and endovascular procedures. Consequently, inadequate preoperative knowledge of renal arterial anatomy may increase procedural complexity and the risk of avoidable complications (Sani et al., 2022; Bolla et al., 2026).

Despite the clinical importance of renal arterial variations and the availability of CT angiography for their identification, there remains a need for additional contemporary data from Nigerian tertiary healthcare institutions. Existing Nigerian research has provided valuable evidence, but differences in sample populations, geographic locations, imaging protocols and study objectives mean that the available data do not necessarily provide a complete picture of renal arterial anatomy among patients undergoing imaging at LUTH. A systematic CT angiographic assessment at LUTH is therefore necessary to document the prevalence and patterns of renal arterial variations and to evaluate their potential clinical implications for renal surgery, transplantation and interventional radiology (Ugwu et al., 2018; Çınar & Türkvatan, 2016).

1.3 Aim of the Study

The aim of this study is to assess the anatomical variations of the renal arteries and determine their clinical implications using CT angiographic images at Lagos University Teaching Hospital (LUTH).

1.4 Objectives of the Study

The specific objectives are to:

1. Determine the prevalence and types of renal arterial anatomical variations observed on CT angiographic images at LUTH.
2. Assess the patterns of renal arterial variations according to laterality, including accessory renal arteries, early branching, polar arteries and other identifiable variations.
3. Determine the association between selected demographic characteristics, particularly age and sex, and the occurrence of renal arterial anatomical variations among the study population.
4. Evaluate the clinical implications of the identified renal arterial variations, particularly their relevance to renal transplantation, nephrectomy, partial nephrectomy and interventional radiological procedures.

1.5 Research Questions

The following research questions will guide the study:

1. What are the prevalence and types of renal arterial anatomical variations observed on CT angiographic images at LUTH?
2. What patterns of renal arterial variations occur on the right and left sides, including accessory renal arteries, early branching and polar arteries?
3. Is there a significant association between selected demographic characteristics, particularly age and sex, and the occurrence of renal arterial variations?
4. What are the clinical implications of the identified renal arterial anatomical variations?

1.6 Research Hypothesis

Null Hypothesis (H₀): There is no statistically significant association between selected demographic characteristics, particularly age and sex, and the occurrence of renal arterial anatomical variations among adults assessed using CT angiographic images at Lagos University Teaching Hospital.

1.7 Significance of the Study

The study will be significant to radiologists because it will provide information about the range and frequency of renal arterial configurations encountered on CT angiographic examinations at LUTH. Knowledge of common and uncommon renal arterial patterns can assist radiologists in accurately reporting vascular anatomy and identifying variants that may be important before surgical or interventional procedures.

The study will be particularly useful to urologists, transplant surgeons and vascular surgeons. Renal transplantation and renal surgery require accurate preoperative knowledge of the renal vascular pedicle. Identification of accessory arteries, polar arteries, early branching and unusual arterial courses can influence the choice of surgical approach, vascular clamping, arterial reconstruction and graft preparation. Evidence from Nigerian transplant imaging has demonstrated that renal arterial variations are common among potential kidney donors (Sani et al., 2022).

The study will also benefit interventional radiologists involved in renal vascular procedures. Detailed knowledge of renal arterial origin and branching patterns is important during procedures involving renal artery stenosis, embolization and other endovascular interventions. Recognizing variant vessels can help minimize the risk of incomplete treatment or inadvertent occlusion of arteries supplying functioning renal tissue (Çınar & Türkvatan, 2016).

The study will be valuable to anatomists and medical educators by providing contemporary radiological evidence of renal arterial variation in a Nigerian population. CT angiography allows the vascular anatomy of living individuals to be demonstrated and can complement traditional cadaveric studies used in anatomy teaching.

The study will also contribute to Nigerian anatomical and radiological literature. Existing Nigerian research has documented a substantial prevalence of renal vascular variations, but further institution-specific studies are necessary to establish broader reference data. Findings from LUTH can be compared with previous Nigerian and international studies to determine similarities and differences in the distribution of renal arterial variants (Ugwu et al., 2018; Ozkan et al., 2006).

Finally, the study may provide a foundation for future research on renal vascular anatomy, renal transplantation, surgical outcomes and population differences in vascular morphology. The findings may also contribute to larger multicentre studies aimed at establishing more comprehensive Nigerian reference data for renal arterial anatomy.

1.8 Scope of the Study

The study will focus on the radiological assessment of anatomical variations of the renal arteries using CT angiographic images at Lagos University Teaching Hospital.

The study will assess the number, origin, course and branching patterns of the renal arteries. Particular attention will be given to accessory or multiple renal arteries, polar arteries, early branching, unusual arterial origins and other identifiable renal arterial variations.

The study will also examine the distribution of the identified variations according to laterality and selected demographic characteristics, particularly age and sex, where such information is available from the imaging records.

The clinical significance of the identified variations will be considered in relation to renal transplantation, nephrectomy, partial nephrectomy, renal vascular intervention and preoperative radiological assessment.

The study will focus specifically on the renal arteries and will not provide a comprehensive assessment of renal venous variations or other abdominal vascular anomalies except where such findings are necessary to describe the arterial anatomy or clinical context.

1.9 Operational Definition of Terms

Renal Artery: A major blood vessel arising normally from the abdominal aorta and supplying arterial blood to a kidney.

Renal Arterial Variation: Any anatomical difference in the number, origin, calibre, course, branching pattern or distribution of a renal artery from the commonly described single-artery configuration.

Accessory Renal Artery: An additional renal artery supplying a kidney in addition to the principal renal artery.

Multiple Renal Arteries: The presence of two or more arteries supplying one kidney.

Polar Artery: An additional renal artery that enters the kidney directly at its superior or inferior pole rather than through the main hilar region.

Superior Polar Artery: An additional renal artery supplying the upper pole of the kidney.

Inferior Polar Artery: An additional renal artery supplying the lower pole of the kidney.

Early Branching: Division of the main renal artery into major branches before the vessel reaches the renal hilum or within a relatively short distance from its origin.

Renal Arterial Origin: The anatomical point at which the renal artery arises, normally from the abdominal aorta.

Precaval Renal Artery: An anomalous right renal artery that passes anterior to the inferior vena cava.

Renal Hilum: The medial indentation of the kidney through which the renal vessels, ureter and associated structures enter or leave the organ.

Computed Tomography Angiography (CTA): A CT-based imaging technique using intravenous contrast material to visualize blood vessels and their anatomical relationships.

CT Angiographic Image: A cross-sectional or reconstructed CT image obtained during angiographic imaging and used to demonstrate arterial structures.

Laterality: The side of the body on which an anatomical structure is located, in this study referring primarily to the right or left kidney.

Renal Transplantation: Surgical transfer of a functioning kidney from a donor to a recipient with advanced renal failure.

Nephrectomy: Surgical removal of all or part of a kidney.

Partial Nephrectomy: Surgical removal of a portion of a kidney while preserving the remaining functioning renal tissue.

Clinical Implication: The potential relevance of an anatomical variation to diagnosis, surgical planning, treatment, prognosis or prevention of complications.

Anatomical Variation: A structural difference occurring naturally among individuals that does not necessarily represent disease.

Project – Anatomical Variations of the Renal Arteries and Their Clinical Implications: A CT Angiographic Study at LUTH