Inferior renal polar artery and its surgical importance

Introduction Renal artery variations have gained importance in the last decade because of the widespread development in transplantation surgery. Variations in the renal vasculature are of importance not only for the surgeons, but for the radiologists, especially in the interventional radiological approaches. Post surgical complications and the risk of kidney loss is higher in the cases with multiple renal arteries when compared with the kidneys having a single renal artery. The aim of this study was to discuss the surgical importance of the inferior renal polar artery. Case report During routine dissection, a case of accessory right renal inferior polar artery was found. The main renal artery was arising from the aorta about 1.7 cm below the superior mesenteric artery extending laterally towards the hilum of the kidney. At about 1.3 cm below the origin of the inferior mesenteric artery from the anterolateral aspect of the aorta, an accessory renal artery measuring 5.1 cm in length, was seen coursing upwards, backwards and laterally and entered the right kidney through its lower pole. This inferior polar renal artery in our case passed superficial to the ureter and testicular vein on the right side and hence can lead to partial obstruction of ureter leading to hydronephrosis, or testicular vein predisposing to varicocele. Conclusion Surgeons should exclude the possibility of presence of such accessory renal arteries obstructing ureter or testicular vein prior to the surgical treatment of hydronephrosis and varicocoele. The awareness about the presence of such variations is important from the academic, surgical and radiological point of view.


Introduction
The knowledge of the variations of the renal artery has gained importance with the increasing numbers of renal transplants, vascular reconstructions, endoscopic surgeries and various surgical and radiological techniques.A single renal artery to each kidney is present in approximately 70% of individuals.The arteries vary in their level of origin and in their calibre, obliquity and precise relations 1 .
Accessory renal arteries are present in 30% of individuals, which are regarded as persistent embryonic lateral splanchnic arteries.Accessory (supernumerary) renal arteries usually arise from the aorta superior or inferior to the main renal artery and follow the main renal artery to the hilum of the kidney.Accessory renal arteries may also enter the kidneys directly, usually into the superior or inferior poles.It is important to be aware that accessory renal arteries are end arteries; consequently, if an accessory artery is damaged or ligated, the part of the kidney supplied by it will become ischemic.Rarely, accessory renal arteries arise from the coeliac or superior mesenteric arteries near the aortic bifurcation or from the common iliac arteries 1,2 .It is a misnomer to call such vessels as accessory; aberrant or even supernumerary, because they are not extra but essential, tissue-sustaining arteries without anastomoses between them, which correspond to the segmental branch of a single renal artery 3 .
This case describes the right inferior renal polar artery and associated clinical significance of the same.

Case report
During routine dissection, a case of right accessory renal polar artery was found at inferior pole in an adult male cadaver in the Department of Anatomy, Maulana Azad Medical College, New Delhi.We observed that at about 1.3 cm below the origin of the inferior mesenteric artery from the anterolateral aspect of the aorta, an accessory renal artery measuring 5.1 cm in length, was seen coursing upwards, backwards and laterally and entered the right kidney thorough its lower pole.This accessory right inferior renal polar artery was seen to be passing over the abdominal part of ureter and testicular vein.The main right renal artery was arising from the aorta about 1.7 cm below the superior mesentric artery extending laterally towards the hilum of the kidney.It passed behind the inferior vena cava and reached the near upper pole of the right kidney.The main right renal artery gave three branches; one branch passed in front and entered the kidney at its upper pole and the second branch ran posterior to the right renal vein and entered the hilum of the right kidney while the third branch entered the kidney between the upper pole and hilum of the right kidney (Figure 1).On the left side, a single renal artery was observed, which divided into segmental branches on reaching the

Discussion
Most of the abnormalities of renal artery are due to changing positions of the kidney as a part of its normal development and ascent.Knowledge of the embryology of the renal vasculature and structural development of the kidney is essential to the understanding of the multitude of anomalies that may occur.With the complex development of the kidneys through the three stages of pronephros, mesonephros and metanephros, and the migration of the kidney from the pelvis to the lumbar region, along with its longitudinal location and simultaneous acquisition of a vascular supply, there is reason to understand why the possibility for anomalous development in the kidney may be greater than for other organs within the body 4,5 .
The embryological explanation of these variations has been presented and discussed by Keibel F and Mall FP 6 .In an 18 mm foetus, the developing mesonephros, metanephros, suprarenal glands and gonads are supplied by nine pairs of lateral mesonephric arteries arising from the dorsal aorta.The 3rd to 5th pair of arteries give rise to renal arteries.Graves 7 accordingly described an artery arising from the aorta or main renal artery should be accessory and all other sources should be called aberrant artery.When these vessels enter the upper or lower pole of the kidney they are termed as 'polar arteries 8 .'Incidence of multiple renal arteries has been reported to be 20.2% on the right side and 19% on the left side 9 .There was much discrepancy regarding the side of accessory renal arteries, many authors have reported a higher frequency on the left side, others reported this variation to be more frequent on the right side 10 .Availability of a huge amount of data about the presence of multiple renal arteries, categorised as accessory, aberrant or additional, presence of extra renal arteries unilaterally or bilaterally, superior and inferior polar arteries, necessarily warrants the importance of a uniform and internationally acceptable nomenclature and classification of renal arteries.Other factors like genetic background, oxygenation and haemodynamic changes may also account for presence of an accessory renal artery.Recent reports have also associated galactosemia with renal vascular anomalies 11 .
Bordei P et al. 12 reported 54 cases, out of which six cases were bilateral.In about 28 cases, supplementary renal artery entered the kidney through the hilum, in 16 cases it was inferior polar, in five cases it was superior polar artery.In this study, we found accessory right renal artery on the right side entering the lower pole as inferior polar artery.On the left side, normal renal artery was found.Inferior polar renal artery in our case passed superficial to the ureter and testicular vein on the right side and hence can lead to partial obstruction of the ureter leading to hydronephrosis, or testicular vein predisposing to varicocoele.
Although it is very rare, fibromuscular dysplasia in an accessory renal artery can be responsible for renovascular hypertension.Selective renal angiography should be performed as the 'gold standard' test when renovascular intervention is considered.Every accessory renal artery is related to segmental arteries, so the risk of bleeding during urological Inferior renal polar artery and its surgical importanceSJ Patil*, S Mishra Clinical Anatomy *Corresponding author Email: drsachin6880@gmail.comDepartment of Anatomy, Maulana Azad Medical College, Bahadhur Shah Zafar Marg, New Delhi, India hilum of the left kidney.No other anomalies were observed in the posterior abdominal wall.