Organ With Vital Functions The Kidney

Published Date: 02 Nov 2017

Introduction

As an organ with vital functions, the kidney is involved

together with the hypothalamus, the hypophysis, the

suprarenal gland and the skin within the adjustment of the

discharges of water, catabolic and other soluble substances

not only as an effector but also as a secretory territory of

some local factors that control the processes within its

compartments. Regarding the renal surgery, modern

methods try to preserve the organ, at least partially if not

totally, considering its significant role within the human

body functions. The importance of the kidney is highlighted

by the fact that it has the largest blood supply

within the human body and the renal arteries are the largest

branches of the aorta in relation to the volume of the organ

that they supply. Delmas [7] use to say that ‘‘in order to

clarify the problem of kidney segmentation and its variation

it is advisable that first you study the vascular variations’’.

Similar to other regions of the human body at the

renal level, the anatomical research is directly related and

oriented upon the surgical needs. Indeed, the systemic

study of the renal vessels undergoes an unprecedented momentum closely related to partial nephrectomy procedures.

Among these researches, the most commonly used is

renal angiography, which shows numerous variations of the

traject, branching or collateral and terminal distribution of

the renal arteries. Referring to this, Larget [14] said: ‘‘the

impression that you have in front of a cliche´ of renal

arteriography is of infinite variety and the first move is to

deter, because no other arterial distribution may be compared

with the multiple modes of termination of the renal

artery’’. The arteries of the superior renal segment show a

large degree of morphologic variability regarding their

origin and number and also their supplied renal territory.

These arteries are always multiple, usually one of them

being more constant and significantly larger, with the origin

from one of the primary trunks, anterior or posterior.

When originating from the aorta as supplementary renal

artery or from the trunk of the renal artery prior to its

terminal ramification, the artery of the superior segment

may be unique supplying both faces of the superior renal

pole. Rarely and mostly because of a smaller caliber or a

smaller supplied territory, it may have a limited significance

within the systematization of the renal blood supply.

In those situations apart from this artery, superior polar

arteries, anterior and posterior usually appear, originating

from the corresponding primary arterial trunks; so the

superior renal pole will receive 2–5 arteries that will

increase the difficulty of a superior polar nephrectomy with

multiple ligatures.

Materials and methods

We studied the arteries of the upper renal segment on 461

cases of which 262 were arteries on the right side (56.83%

of the cases) and 199 arteries on the left side (43.17% of

the cases). We used as study methods: dissection of fresh

and formalin preserved kidneys (159 cases), injection of

contrast medium (barium sulfate), followed by radiography

of the injected samples (28 cases) and injection of plastic

(Technovit 7143) followed by corrosion with NaOH (68

cases). We also examined 21 MRI and 185 renal angiographies,

of which 99 were common (simple) and 86 were

CT angiography. We assessed the origin of the arteries that

supply the upper renal segment, the traject, the caliber, the

collateral and terminal branching and the supplied

territories.

Results

The superior pole of the kidney receives branches both for

its anterior and posterior faces, which in most cases are

multiple branches: 2–5 branches on both the sides of the

upper pole. Among them a big branch always occurs, the

main artery of the upper segment, both anteriorly and also

posteriorly.

The posterior arteries of the superior renal segment

originate most frequently from the posterior terminal

branch of the renal artery (Fig. 2) as 1–3 arterial branches,

which even when they individually supply the posterior

face of the upper pole are smaller in caliber compared to

the antero-superior artery or arteries. In only eight cases

(1.73% of the cases) we assessed a posterior artery of

the upper segment larger than the anterior one. When the

anterior artery of the upper renal pole also supplies the

posterior face, the posterior branch of the renal artery

provides 1–3 branches for the superior pole, which, in the

end, will be blood supplied from both terminal branches of

the renal artery. In only 42 cases (9.11% of the cases) we

found that the terminal posterior branch of the renal artery

does not participate at all in the upper renal pole blood

supply, predominantly on the right side in 31 cases (6.72%

of the cases). In these cases, the blood supply of the posterior

face of the upper pole was provided only by the

anterior branch, larger in caliber and which ended by

bifurcation within an anterior and a posterior branch; more

often it appeared as an apical artery (that approaches the

upper renal pole outside the hilum). In the case of multiple

renal arteries, double or triple, the posterior arteries for the

superior renal segment may originate from a second or

even a third renal artery, when they are crossing one

another or give rise to the posterior branch of the renal

artery. In 11 cases (2.39% of the cases) the posterior artery

also supplied the anterior face of the upper renal pole, in

eight of them (1.73% of the cases) being the only source of

blood supply of the upper pole, while the anterior artery

was absent. In four cases (0.87% of the cases) the posterior

artery originated from the anterior branch of the renal

artery providing alone the blood supply of the posterior

face of the upper pole while the posterior terminal branch

of the renal artery did not supply the upper pole at all.

The anterior arteries of the superior segment have very

different origins (Fig. 1a–k) and participate frequently in

the blood supply of the posterior face of the upper pole,

especially when they originate from the trunk of the renal

artery or from the aorta; thus the superior pole is entirely

supplied, both anterior and posterior, from this artery.

In 190 cases (41.21% of the cases), the anterior arteries

of the superior segment originated from the anterior branch

of the renal artery; 109 samples were on the right (23.46%

of the cases) and 81 samples on the left (17.57% of the

cases). In 177 cases (38.39% of the cases) it appeared as a

collateral branch of this artery (Fig. 1a), 107 of them on the

right (23.21% of the cases) and 70 cases on the left

(15.18% of the cases). In only 13 cases (2.82% of the

cases) the anterior artery of the superior segment was a branch originating from the terminal division of the anterior

branch of the renal artery (Fig. 1b), three cases (0.65%

of the cases) on the right and ten cases (2.17% of the cases)

on the left. In those cases, usually the artery approached the

upper renal pole at the superior part of the hilum (proper

renal artery) and in few cases, the artery approached the

superior pole above the hilum through the medial border as

apical artery, more often when it was a terminal branch of

the anterior division of a renal artery that divided outside

the hilum.

In 73 cases (15.84% of the cases) the anterior artery of

the upper segment originated from the renal artery

(Fig. 1c), at different levels between its origin and its terminal

division, 44 cases on the right (9.54% of the cases,

Fig. 2) and 29 cases on the left (6.29%% of the cases,

Fig. 3). We did not assess a peculiarity of its origin related

to the origin of the inferior suprarenal artery. In these cases

the approach to the upper renal pole was performed

through the medial border above the renal hilum.

We assessed this artery as a terminal division of the

renal artery in 34 cases (7.38% of the cases, Fig. 1d), 16

cases on the right (3.47% of the cases) and 18 cases on the

left (3.91% of the cases). The approach of the upper renal

pole was performed in almost equal shares either through

the superior part of the renal hilum or through the medial

border of the superior pole.

We assessed the anterior artery of the superior renal pole

as originating from the posterior terminal branch of the

renal artery in 18 cases (3.90% of the cases, Fig. 1e), ten

cases on the right (2.17% of the cases, Fig. 4) and eight

cases on the left (1.73% of the cases). The approach of the renal parenchyma was performed either through upper part

of the renal hilum or through the inferior part of the medial

border of the superior renal pole.

In 138 cases (29.93% of the cases), the artery of the

superior renal segment originated from a supplementary

renal artery, double or triple, in 65 cases on the right (14.10% of the cases) and in 73 cases on the left (15.83%

of the cases). In 118 of them (25.60% of the cases), the

arteries distributed to the superior renal pole originated

from or represented themselves as a double renal artery, 57

cases on the right (12.37% of the cases) and 61 cases on the

left (13.23% of the cases). Among those, 74 cases (16.05%

of the cases) were collateral branch of the superior renal

artery (Fig. 1f), 35 cases on the right (7.59% of the cases)

and 39 cases on the left (8.46% of the cases). As terminal

branch of the superior renal artery we assessed 18 cases

(3.90% of the cases), ten on the right (2.17% of the cases)

and eight on the left (1.73% of the cases, Fig. 5), 13 of

them (2.82% of the cases) with the artery supplying only

the superior renal pole (Fig. 1g) as a proper superior polar

artery; five cases were on the right (1.09% of the cases) and

eight cases on the left (1.73% of the cases). The remaining

five cases presented an artery that did not supply the

superior segment only. In ten cases (2.17% of the cases),

the anterior artery of the superior renal pole originated

from the inferior renal artery, five cases on each side. In

those situations, the two renal arteries showed a crossed

traject, the superior one passing anterior to the inferior one.

In only three cases (0.65% of the cases) we found anterior

arteries of the superior segment originating from both

arteries (Fig. 1h), two cases on the right (0.43% of the

cases) and one case on the left side (0.22% of the cases).

In 20 cases (4.34% of the cases), the artery of the

superior renal segment originated from the triple renal arteries, eight cases on the right (1.73% of the cases) and

12 cases on the left (2.60% of the cases). Among those 20

cases, in nine samples (1.95% of the cases) the artery for

the superior renal pole was represented by the superior

renal artery that supplied the upper renal pole only

(Fig. 1i), as a proper superior polar artery that entered the

kidney through its medial border and supplied both of its

faces (Fig. 6). Three of those cases were on the right

(0.65% of the cases) and five cases on the left (1.08% of the

cases). Also in eight cases (1.73% of the cases), the artery

for the superior renal segment was represented by a terminal

or collateral branch of the superior renal artery

(Fig. 1j), four cases on each side (0.87% of the cases). In

only three cases (0.65% of the cases), one on the right side

(0.22% of the cases) and two on the left side (0.43% of the

cases), the artery for the superior segment originated from

the middle renal artery (Fig. 1k) which showed an inferior

traject or crossed posteriorly the superior renal artery.

In 28.42% of the cases (131 cases), the superior renal

segment was supplied by the two arteries that showed

similar or different origins.

Supplementary renal arteries, double or triple, that

supplied solely the superior renal pole were assessed in 22

cases (4.77% of the cases) and were described as arteries

for the superior segment with aortic origin. When the artery

for the superior renal segment originated from the aorta as

supplementary renal artery, from the vessel started the

inferior suprarenal artery, with the exception of five cases

when this artery started directly from the aorta above the

origin of the superior renal artery.

In 328 cases (71.75% of the cases), the anterior artery of

the superior renal pole also participated in the supply of the

posterior surface, 154 cases on the right (33.41% of the

cases) and 174 cases on the left (37.74% of the cases); in

eight cases (1.73% of the cases) it was missing, the supply

of the anterior face being performed by the posterior artery

that originated from the posterior terminal branch of the

renal artery.

In most of the cases, 453 cases (98.26%), the anterior

division was larger than the posterior one, sometimes with

differences between 0.2 and 0.3 mm.

Frequently, the anterior artery for the superior renal

segment provides branches for the antero-superior segment;

sometimes the artery for the antero-superior segment

also participated in the blood supply of the anterior

segment.

The superior polar artery showed a caliber between 0.3

and 0.6 cm; a larger caliber occurred when the artery

originated directly from the aorta or the renal artery.

The length of the artery for the superior renal segment

was larger when originating from the aorta or the renal

artery with dimensions between 3–8 cm on the right and

2–3 cm on the left. When the artery for the superior segment

originated from the terminal anterior renal branch, its

length was 1.5–2.5 cm on both the sides.

When originating from the renal artery or from one of its

branches, the arteries for the superior renal segment

showed a supero-lateral obliquely ascending traject, while

when originating from the aorta, the traject was more

horizontal.

Among the 461 evaluated arteries, 244 cases (52.93% of

the cases) approach the kidney above the renal hilum

(proper superior polar arteries), while the rest of 217 cases

(47.07% of the cases) the approach was performed at the

upper part of the renal hilum (apical arteries). 8% of those

showed a clear separation between the anterior and the

antero-superior segments, leading us to a total of 61% of

the cases with a clear delimitation for the blood supply for

the upper renal segment.

In 62 cases (13.45% of the cases) either the anterior

segmentary artery or one of its branches showed a penetrating

aspect entering the kidney through one of its faces,

more often the anterior one.

Discussion

Considering the origin of the arteries for the superior renal

pole, we described two potential situations: most of the

cases, the origin was from the renal artery, 438 cases

(95.01% of the cases) with several variations above presented

and in only 22 cases with aortic origin as supplementary

renal artery, double or triple, that supplies the superior renal pole only (4.77% of the cases). We did not

encounter any artery for the superior segment originating

from a renal artery that emerged from a right common iliac

artery (high L2 aortic bifurcation in a horseshoe kidney, as

showed by Huang et al. [13]) on the left, the artery for the

superior segment originated from an accessory renal artery

that started from the aorta. Our percentage regarding the

aortic origin is significantly smaller than the ones from

literature [9, 10] describing 18.4% of the cases [16], with

12% of the cases [15], with 9% of the cases and [18] with

7.9% of the cases. Lippert and Pabst [15] describes the

artery for the superior pole as superior renal artery (double)

in 7% of the cases and [18] in 6.8% of the cases; we

describe this situation in only 2.82% of the cases of proper

superior polar arteries. Regarding the triple renal arteries,

Lippert and Pabst [15] described the superior renal artery

as a source for the upper segment in 2% of the cases and

[18] in 6.8% of the cases; we assessed this situation in

1.95% of the cases, closer to [15] 2.17% of the cases. As

collateral or terminal branches of a supplementary renal

artery, Lippert describes 2% of the cases of triple renal

arteries, while [18] assessed 15.8% of the cases for double

renal arteries and 2.6% of cases for triple renal arteries.

These authors do not quote the situation, the origin of the

artery for the superior segment from the inferior renal

artery (when double), from the middle renal artery (when

triple) or from both, an aspect that we encountered in

3.47% of the cases.

We found the origin of the anterior arteries of the

superior renal pole from the renal artery in 95.01% of cases

while Ferreira et al. [9, 10] described 81.6% of the cases

and Ecoiffier [8] in 100% of the cases, although he mentions

a possible aortic origin.

The origin from a single renal artery (15.84% of the

cases) is closer to Ferreira et al. [9, 10] 13.1% of the cases,

Lippert et al. [15] with 14% of the cases and Sampaio et al.

[18] with 14.3% of the cases, smaller than Callas et al. [2]

with 20% of cases and significantly smaller than Ecoiffier

[8] with 46% of the cases. The origin from the anterior

terminal branch of a single renal artery (41.21% of cases) is

similar to Ecoiffier [8] with 44% of the cases and much

smaller than Ferreira et al. [9, 10], with 65.7% of the cases.

Gre´goire [11] encountered this variation several times,

while Paturet [16] shows that the artery for the superior

segment, more often the inferior one, originates either from

the upper most branch of the anterior terminal branch of the

renal artery (Shoja et al. [20] describe a percentage of

22.5% of the cases) or directly from the renal artery (Shoja

et al. [20] describe a percentage of 1.2% of the cases).

The origin of the anterior artery of the superior segment

from the posterior terminal branch of the renal artery was

assessed in 3.90% of the cases while Ferreira et al. [9, 10]

found 2.8% of the cases and Ecoiffier [8] 10% of the cases.

For Gre´goire [11] the artery originated predominantly from

the posterior terminal branch, also stated by Testut [21]. As

a terminal branch of a single renal artery we assessed

7.38% of cases, compared to Lippert and Pabst [15] with

only 2% of the cases. Callas et al. [2] stated that the second

degree branches of the posterior terminal branch of the

renal artery usually ends in a tree like manner and give

birth to branches oriented anteriorly and a proper superior

polar artery that supplies the medial and median territory

above the hilum and 1–2 branches for the dorsal parenchyma

of this pole.

The posterior arteries of the superior segment originate,

most frequently, from the posterior terminal branch of the

renal artery, sometimes as an arcade oriented with an

infero-medial concavity, with collaterals starting from this

convexity (‘‘comb’’ teeth aspect) and with first 2–3 branches

dedicated to the superior pole [3]. When the posterior

branch does not supply the superior renal pole it ends by

bifurcation or trifurcation and when it gave birth to posterior

polar branches, they were smaller in number and

volume.

Callas et al. [2] describe some second degree branches

of the posterior terminal branch of the renal artery that

provide 1–2 divisions for the dorsal parenchyma of this

pole. Gre´goire [11] shows that, among the three terminal

branches of the artery of the superior segment that

approach the parenchyma, one is always posterior and

supplies the posterior face of the pole along the posterior

face of the renal pyramid.

The anterior arteries of the superior segment approach

the renal parenchyma either at the level of the medial

border of the superior pole (52.93% of the cases), named

proper superior polar arteries or at the level of the hilum

(47.07% of the cases), most often at its superior part,

named apical arteries. The proper polar arteries were more

frequent on the left side while the apical arteries occurred

mostly on the right. It is interesting to notice that some

authors [3, 11, 21, 22] stated the fact that the artery for the

superior segment approach the renal parenchyma on the

internal border of the pole closer to the margin of the sinus

without penetrating it.

In 13.45% of the cases, we assessed either an anterior

segmental artery or one of its branches that showed a

penetrating situation entering the kidney through one of its

faces, predominantly the anterior one. This aspect was also

described by Cordier et al. [5, 6] which presented a superior

polar artery that penetrated the superior pole on its

anterior face, a significant position in relation with the

superior segmentectomy.

The ending manner of the anterior arteries for the

superior segment is by bifurcation, in 62.69% of the cases,

or trifurcation 37.31% of the cases. In literature, the

bifurcation type ending is supported by Cordier et al. [5, 6] while Ferreira et al. and Gre´goire [9–11] assessed a more

frequent ending by trifurcation. Only Callas et al. [2]

described a ‘‘tree like’’ ending manner of the artery of the

superior segment. In 6.25% of the cases, Petru et al. [17]

described a gonadal artery originating from the artery of

the superior renal segment.

In 28.42% of the cases (131 cases), the superior renal

segment was supplied by two arteries that showed similar

or different origins. The second of these two arteries was

always smaller than the first one. For Cordier et al. and

Gre´goire [6, 11] the blood supply of the superior pole is

rarely provided by a single superior polar artery that

originated from the extrahilar segment of the renal artery.

According to Arvis and Guntz [1, 12], a second apical

artery (with ventral or dorsal intrahilar origin) or a superior

polar artery will always double the artery for the superior

pole. Frequently, these apical arteries originated from the

dorsal branch from the ventral branch, or from both (most

often), in a percentage of about 89% of the cases. We did

not encounter a renal arterial branch that supplies simultaneously

both renal poles as quoted by Shakeri et al. [19].

Conclusions

The morphology of the arteries for the superior renal segment

shows a significant degree of variability mostly in

what concerns the anterior ones, with regard to their origin

but also to their traject, dimensions, approach of the renal

parenchyma and supplied territory. In many cases differences

appear between the morphological characteristics on

the right and left side within the same individual, without

any degree of symmetry between them.

Frequently we encountered a clear delimitation of the

superior renal segment from the antero-superior one (in

more than 61% of the cases), a situation that allows a

relatively ease superior nephrectomy. This procedure is

more difficult when the arteries for the superior segment

participate in the blood supply of the antero-superior segment

also or the arteries of this latter one also supply the

superior segment, so the partial nephrectomy will involve

multiple vascular sutures. The partial nephrectomy is also

more difficult when the artery for the superior segment or

one of its branches penetrate the superior pole through its

anterior face, a situation also stated by Lippert et al. [15]

and Paturet et al. [15, 16] which mentioned the importance

of this variation in order to avoid the avulsion of the artery

during blind maneuvers on the renal pole. Thus, within

superior polar nephrectomy, most of the complications

involve the antero-superior artery, as long as the posterior

one shows a less variable morphology.

Within the evaluation of the terminal segmentary renal

branches, a significant importance is carried by the

angiographical examination, mostly the CTA, as mentioned

also by Clemente et al. [4].

We consider that the variability of percentage within the

literature and the differences between our results and those

of other authors in what concerns the morphology of the

artery of the superior renal segment may be attributed to

differences between the geographical area, to the number

of evaluated samples and also, as many authors stated, to

racial differences. Same time, the vascular variability

within the same geographical area may be the result of

environmental influences during organogenesis, influences

that may efficiently explain the differences in population

groups within the same geographical area but in different

moments in time.