Introduction
In humans, majority of the population possess single renal artery for each kidney. The renal artery proper divides into anterior and posterior division close to the hilum of kidney.1 But rarely early division of renal artery is found very close to aorta. In small percentage of population, accessory renal artery is present along with renal artery proper. The accessory renal artery commonly originates from the abdominal aorta, superior or inferior to the renal artery.1 The accessory renal artery enters through the hilum or directly into the pole of the kidney.2
Generally, segmental arteries enter the hilum of kidney. Rarely they enter the poles of kidney directly. Ureteropelvic junction obstruction causing hydronephrosis was noted in the presence of lower accessory polar arteries due to its location anterior to the ureter.1 Extra renal calyces i.e, major calyces being present outside the kidney, is a rare entity. It was commonly associated with other urogenital abnormalities such as ectopic kidney, bifid ureter, horseshoe kidney. Only 20 cases were reported worldwide.3 The knowledge of the variations of renal arteries is significant when dealing with the renal transplantation, repair of abdominal aorta aneurysm, angiography.4
Case Report
During routine undergraduate dissection of an adult male cadaver, the posterior abdominal wall contents were explored and multiple variations were observed involving the renal arteries and pelvicalyceal system. They are described below.
a. Left kidney – Accessory renal artery
b. Right kidney – Early division of renal arteries
c. Both kidneys – Upper polar arteries
d. Both kidneys – Extrarenal calyces
Left kidney – Accessory renal artery
On the left side, two renal arteries originated as the left renal artery (LRA) and left accessory renal artery (LARA), as shown in Figure 1 D,E and Figure 2 A. Accessory renal artery (LARA) originated from the aorta, 5 mm above the origin of LRA, crossed LRA anteriorly and travelled inferolaterally and entered the hilum, measuring 8 cm in length.
Figure 1
Photographs of the variations in renal arteries and pelvicalyceal system; A: Early division of right renal artery; B: Two upper polar arteries (RUPA1, RUPA2) are seen entering upper pole. Extrarenal calyces of the right kidney held with forceps – Upper and lower major calyces (RUC, RLC); C: Cut section of right kidney showing renal pyramids and minor calyces; D: Accessory renal artery on the left (LARA). Two polar arteries (LUPA1, LUPA2) are seen entering upper pole; E: Extrarenal calyces of the left kidney– Upper, middle and lower major calyces (LUC, LMC, LLC); F: Cut section of left kidney showing renal pyramids and minor calyces.
Right kidney – Early division of renal arteries
On the right side, single right renal artery (RRA) originated from the aorta at the same level as LARA. Just after coursing for 1.4 cm from aorta, renal artery (RRA) bifurcated into anterior and posterior divisions. The early division is shown in Figure 1 A,B and Figure 2 A.
Both kidneys – Upper polar arteries
On the left side, LRA after passing about 3 cm, trifurcated into two upper polar arteries (LUPA1 AND LUPA2) and posterior segmental artery (LPSA), measuring 1 cm, 2 cm, 3 cm in length respectively. LUPA1 and LUPA2 entered the upper pole of kidney. On the right, RRA’s anterior division gave branch of an upper polar artery (RUPA1), measuring 1.5 cm that entered the upper pole. RRA’s posterior division gave another branch of upper polar artery (RUPA2), measuring 5 mm that entered the upper pole. The polar arteries are displayed in Figure 1 A,B,D,E.
Figure 2
Schematic illustrations of the variations in renal arteries and pelvicalyceal system; A: Right kidney: Early division of right renal artery, anterior division trifurcating into RUPA1, RMSA, RLSA, posterior division bifurcating into RUPA2, RPSA. Left kidney: Accessory renal artery on the left (LARA) and left renal artery trifurcating into LUPA1, LUPA2, LPSA; B: Presence of bilateral polar arteries and altered arrangement of structures at the hilum of right kidney and left kidney; C: Extrarenal calyces of right kidney and left kidney
Table 1
Morphometric details of kidneys and associated structures
[i] RUPA1–right upper polar artery 1, RMSA–right middle segmental artery, RLSA–right lower segmental artery, RUPA2–right upper polar artery 2, RPSA–right posterior segmental artery, RUC–right upper major calyx, RLC–right lower major calyx, LARA–left accessory renal artery, LUPA1–left upper polar artery 1, LUPA2–left upper polar artery 2, LPSA–left posterior segmental artery, LUC–left upper major calyx, LMC–left middle major calyx, LLC–left lower major calyx.
Both kidneys – Extrarenal calyces
On the left kidney, three major calyces – left upper calyx (LUC), left middle calyx (LMC), left lower calyx (LLC) joined to form renal pelvis outside the hilum, 1 cm away from the medial border of kidney. On the right side, the two major calyces – right upper calyx (RUC), right lower calyx (RLC) combined to form renal pelvis outside the hilum, 1 cm away from the medial border of kidney. The extrarenal calyces are observed in Figure 1 B,D, Figure 2 C. The cut section of kidney showed renal pyramids and formation of minor calyces which united as major calyces. The pelvis was not observed in the cut section of kidney.
The details of morphometry observed in relation to kidneys and associated structures is given in Table 1.
Discussion
The metanephric kidney in the kidney is initially sacral in position, which ascends cranially to level of L2 by the time embryo length is 13 mm. The blood supply for the ascending kidney is provided by the arteries in the vicinity, such as middle sacral and common iliac arteries. In the third month of intrauterine life, the definitive renal artery is visible, arising from the caudal most of the three suprarenal arteries. Therefore, accessory or additional renal arteries at the hilum or the poles were regarded to be persistent mesonephric or lateral splanchnic arteries.1 The early division of renal artery is supposed to be due to delayed contact between factors in mesenchyme of blood vessel and the factors in metanephros.5 The embryological basis for extrarenal calyces was due to the premature branching of ureteric bud even before it comes into contact with the metanephric blastema.6 It was supposed to be due to a discrepancy in the rate of growth between the metanephric tissue and the ureteric bud. The rapid development of ureteric bud compared to slow growth of the metanephric tissue can result in extrarenal calyces.7
The early division of renal artery is a significant finding in selecting the renal transplantation donor making the person ineligible. Accessory renal arteries are observed to cause high rates of renal graft failure. They are also important in abdominal aortic aneurysm repair and renal artery denervation for resistant hypertension.8, 9, 10 Hydronephrosis can occur due to accessory renal artery compressing over the ureter.11 Clinically, it has been observed that the upper polar arteries arising from the renal arteries are aligned much vertically leading to polar infarction and high chance of graft failure due to renal vascular thrombosis.4 The extrarenal calyces is a very rare entity associated with ectopic kidney, bifid ureter and other congenital anomalies. They were either incidental findings or found during workup for PUJO (pelvi-ureteric junction obstruction).7 Extrarenal calyces can be damaged during urologic surgeries accidentally. They can also give a false appearance of hydronephrosis on retrograde pyelography.3
Conclusion
In the present case, right kidney showed early branching of renal artery and left kidney showed accessory renal artery. Two polar arteries were seen on each kidney entering the upper poles. Extra renal calyces, a very rare entity, were noted on both the kidneys. The knowledge of early division of renal artery benefits the clinicians in decision-making with regards to renal transplantation donor suitability and prevention of inadvertent injuries to the accessory renal arteries during aortic aneurysm surgeries. The understanding about extra renal calyces is significant in correct interpretation of pyelogram and to prevent accidental damage during urologic surgeries.
Ethical Approval
The cadaver in which the variation was found are the bodies obtained through voluntary donation or unclaimed bodies. During donation, acceptance has been obtained for using the cadaver for academic purpose and research including for publication. But the data so obtained, is being shared in de-identified manner. Hence, no separate approval was obtained, as it is case report.
Authors' Contributions
Akhil J: Dissection, data collection, literature search and manuscript writing. Stephen PC: Literature search, manuscript editing. Sontakke YA: Project development, image illustrations, manuscript editing, data analysis. Hottigoudar SY: Project development, manuscript editing, data analysis. All authors approved the final manuscript.
Acknowledgements
Image courtesy: Dr Yogesh Sontakke. The authors would like to thank Dr Ambiga Raman for the assisting in the dissection and photography. The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed. Results from such research can potentially increase mankind's overall knowledge that can then improve patient care. Therefore, these donors and their families deserve our highest gratitude.
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