Illustrated Encyclopedia of Human Anatomic Variation: Opus II: Cardiovascular System

Renal Vascular Pedicle, continued.

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed

J: Right, arteries: A single renal artery whose hilar branches attain an anterior position. Veins: A single renal vein in which a triangular hiatus occurs; through this orifice passes the right internal spermatic artery; from the latter arise suprarenal arteries, before and after the contributing artery passes through the hiatus.

K: Right, arteries: Two renal arteries, transverse in course; their branches reach the extreme ends of the renal hilus. The superior one is retrocaval, supplies the superior extremity; the inferior one is antecaval, gives off 3 hilar branches. The internal spermatic artery arises from the superior one of the 2 renals, passes through a cleft at the caval end of the internal spermatic vein. A ureteric artery leaves the lowermost hilar branch. From the superior renal artery; near its aortic origin, arises a short stem which divides into inferior phrenic and supernumerary renal artery, the latter piercing the parenchyma of the superior extremity. From both renal and phrenic subdivisions come suprarenal branches. Veins: A single large renal vein with a terminal hiatus transmitting the spermatic artery.

L: Right, arteries: A single renal artery from which arises a common stem for an inferior phrenic (with suprarenal twigs) and a suprarenal artery. From one of the hilar branches is derived an inferior suprarenal artery. The internal spermatic artery, of high aortic origin, passes obliquely downward and lateralward, at first in retrocaval course; emerging through an hiatus formed by the subdivision of the renal vein as the latter reaches the vena cava, it descends into the pelvis.

M: Veins: The double inferior vena cava is divided to a position superior to the point of entrance of the renal veins. Into the channel of the right side the renal vein is received; into the left, the left renal veins are received.

N: Left, arteries: A major renal artery and a supernumerary, the latter descending to perforate the lower extremity of the kidney (passing around the suprarenal vein and crossing the renal vein anteriorly); from the point of perforation an accessory vein emerges, the 2 vessels thus producing a minute supernumerary "hilus," the vein joins the internal spermatic before entering the renal. Veins: A single renal vein, retroaortic in course. Into this is received, on its cranial aspect, a suprarenal vein; the latter receives in turn a phrenic vein. Into the renal vein is received a common channel formed by the internal spermatic and the polar tributaries.

O: Right, arteries*- Three renal arteries which enter the hilus and kidney substance in the order of their origin (i.e., do not cross). The upper and middle area postcaval, the lower, antecaval, in position. A spermatic branch arises from the lowermost of 3, and is accompanied by the corresponding vein (which hooks over the lower renal artery). Veins: A single renal vein occurs, the superior tributary of which lies anterior to the upper artery, the lower and middle tributaries posterior to the hilar subdivisions of the intermediate artery. Ureter: Double throughout its course to the wall of the bladder.

P: Left, arteries: Double renal arteries from the inferior one of which the ovarian artery arises. Lumbar arteries are accompanied by communicating veins from the psoas major muscle, etc. Veins: One large renal vein which superiorly receives a single suprarenal vein, inferiorly, the 2 divisions of an ovarian vein. A second, or supernumerary, renal vein occurs; leaving the anterior surface of the inferior extremity, this vessel is one of 4 veins tributary to a short venous trunk which enters the inferior vena cava; in transverse course, it rests upon the psoas major muscle and the body of the fourth lumbar vertebra; it passes posterior to the ureter, ovarian vessels, abdominal aorta, and anterior to the sympathetic trunk and fourth lumbar artery. The lowermost of the 4 tributaries is a confluence of an anastomotic connection with the common iliac vein, and ureteric vein. The 2 intermediate tributaries of the short venous trunk are lumbar veins (here shown by removing a portion of the psoas major muscle.)

Three examples (Q, R, S) of persistent left caval vein were encountered in the course of 100 dissections by Davis et al, They are arranged in the order of decreasing caliber of the persistent, "anomalous" vessel. In each instance the caval vein connected the iliac with the renal.

Q: The large left inferior vena cava communicated with the fifth fourth, and third lumbar veins in its course to the renal, and also, received the internal spermatic vein.

R: The most caudally situated vein (fifth) of the lumbar series terminated in the left iliac near the point of origin of the caval vein; the third crossed to the "normal" inferior vena cava of the right side. The internal spermatic vein ended in the renal extremity of the left caval vein, the latter then being continued cranialward as the intermediate hemiazygos root.

S: The small, left inferior vena cava communicated with a regular caval vein of the right side through a third lumbar vein; as a paravertebral channel (represented in the thorax by the hemiazygos root), it was interrupted by connection with the caudal limb of a bifid renal vein. This point of renal connection was one of convergence of the lumbar, suprarenal, and thoracic (hemiazygos) vessels.

Conclusions
From a study of the renal vascular peclicles of 200 consecutive cadavers (400 sides), the following conclusions were provided by Pick and Anson:

There is a striking difference in frequency of occurrence, depending upon whether the figures are calculated on the basis of specimens or on that of sides.

Multiple renal veins are rare on the left side (occurring in only 2 of 200 cadavers; 1 per cent) while they are common on the right (54 of 194 sides. 27.8 per cent).

Variety in form of the renal peclicles, based on the number of constituent vessels, is greater on the right than on the left; this difference is owing to the fact that multiple renal veins are a rarity on the left, this variable being important on the right side only.

Based only on the number of vessels (and considering both sides) the renal pedicle in 39.0 per cent of the specimens (78 of 200) is composed bilaterally of 2 vessels. This type, therefore, represents merely a plurality of the specimens.

Classifying the renal peclicles on the basis of the number of constituent vessels, there are 6 different forms. The majority, 59.75 per cent (239 of 400 sides), are confined to 1 group, in which there are but 2 vessels in the pedicle. The highest number of vessels in any single pedicle is 8 (single instance, right side).

Bilateral equality in the total number of vessels in the peclicles occurs in 49.5 per cent of the cadavers (99 of 200). However, 39 per cent (78 of 200) of the specimens included in this group belong to the simplest type of pedicle (2 right and 2 left renal vessels); actually then, bilateral equality in the number of renal vessels is rare in the presence of supernumerary renal arteries or veins (10.5 per cent, 21 of 200 cadavers).

In 64.25 per cent (257 of 400) of the sides an equal number of arteries and veins occur in their renal pedicles. This feature is not, however, as important as it might seem, since symmetry of this kind encountered in 59.5 per cent (238 of 400) are sides with single artery and vein. In the presence of supernumerary renal arteries or veins equality is encountered in only 4.75 per cent (19 of 400 sides).

Single renal arteries and veins on both sides in the same specimen occur in 38.5 per cent of cadavers (77 of 200), whereas a single renal artery and vein make up the pedicle in 59.5 per cent of the sides (239 of 400).

Classifying specimens on the basis of the number of arteries and veins in the renal peclicles of the 2 sides, 27 different varieties of arrangement are encountered, none of which represent over 38.5 per cent of the total (77 of 200). Thus there is no majority group of specimens, the most common type merely representing a plurality.

Classifying sides, however, on the basis of the number of arteries and veins in the pedicles, there are 12 different types, but the most common is represented by the majority, 59.5 per cent (238 of 400).

Frequently, the so-called "normal" form represents a plurality rather than a majority of the cases, depending on whether the incidence is based upon a consideration of side or of specimen. Failure to distinguish between these methods of calculating frequency of occurrence of types accounts for the discrepant reporting, in the literature, of results obtained by other investigators; it also accounts for failure to detect significant differences between sides.

Differences between the renal pedicles, depending on side, are accounted for chiefly by adult asymmetry in the renal venous drainage - the basis for which is the developmental transformation of a symmetrical into an asymmetrical caval plan.

It is regularly stated that the right is longer than the left renal artery, the left renal vein longer than the right. While this is anatomically true, actually the surgical lengths of the pedicles (permitting free mobilization) are about equal; on the right side the lateral border of the vena cava offers a fixed point for the renal arteries, while on the left, the lateral border of the aorta acts in a similar manner. From the urological standpoint the difference in the length of the pedicles is more apparent than real.

While it is true that ligation of the large collaterals of the dorsum of the left renal vein, just lateral to the aorta, would free the vein more completely, the left renal arteries are short; therefore, such a procedure would be of little surgical benefit. On the right it would be necessary to liberate the renal arteries from the dorsum of the vena cava - a dangerous method of mobilization. Even if such a procedure were successful, the right renal veins, being short, would nullify the effect of securing greater freedom for the right renal arteries.

In some instances the presence of supernumerary vessels does not occasion a pronounced spreading of the renal pedicle; in others, vessels affect the entire abdominal portion of the aorta and the vena cava.

The pedicle is frequently complicated by the occurrence of arteries sent from the renal stems to the suprarenal gland or from a suprarenal arterial source to the kidney.

Additional renal veins, which occur less frequently than supernumerary arteries, often communicate, on the left side, with other visceral veins (suprarenal and spermatic or ovarian), with a retroaortic venous plexus, and with the left lumbar and hemiazygos veins. Not infrequently the regular vein passes in front of the aorta, the supernumerary vein behind, forming (between left kidney and vena cava) a circumaortic venous ring.

Capacious hiatuses occur in the renal veins, and more commonly on the right than on the left; since the hiatus usually transmits the internal spermatic or the ovarian artery, the gonadal vessel, in such instances, lies definitely in the field of urological surgery. Of surgical interest, also, are those specimens in which the gonadal vessel merely crosses the renal pedicle, and those in which the vessel follows the renal artery in transverse course before descending - on the left side, hooking around the suprarenal tributary of the renal vein. Spermatic or ovarian arteries may arise directly from the renal, thus being, proximally, a constituent of the pedicle.

Redrawn from Pick, J.W. and B.J. Anson. The renal vascular pedicle. An anatomical study of 430 bodyhalves. J. Urol. 44:411-434, 1940; and Davis, R.A., Milloy, F.J. Jr. and B.J. Anson. Lumbar, renal, and associated parietal and visceral veins based upon a study of 100 specimens. Surg. Gynecol. Obstet. 107:1-22, 1958.

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