COMPARATIVE ANATOMY of the SUPERFICIAL VESSELS of the MAMMALIAN KIDNEY DEMONSTRATED by PLASTIC (VINYL ACETATE) INJECTIONS and CORROSION by DAVID KAZZAZ and WILLIAM M

[ 163 1

COMPARATIVE ANATOMY OF THE SUPERFICIAL VESSELS OF THE MAMMALIAN KIDNEY DEMONSTRATED BY PLASTIC (VINYL ACETATE) INJECTIONS AND CORROSION By DAVID KAZZAZ AND WILLIAM M. SHANKLIN Department of Histology, School of Medicine, American University of Beirut, Beirut, Lebanon In spite of the fact that considerable work has been done on the circulation in the kidney, little attention has been paid to its superficial vessels. Morison (1926), in his paper on the renal circulation, illustrated (figs. 3, 4 and 5) the superficial veins of the kidney of man, dog and cat, as revealed by the celluloid injection and corrosion method. He described highly developed stellate veins in the cat and poorly developed ones in man, but gave no description of the superficial veins in the dog. Trueta, Barclay, Daniel, Franklin & Prichard (1947) studied the intra- renal circulation by various techniques and gave a detailed description of both the arterial and venous systems. They described (p. 164) superficial veins forming large venous trunks underlying the capsule in the kidney of the cat and comparable, but less developed, systems in man and the dog. It was our purpose to study in some detail the superficial vessels of the mammalian kidney as seen after plastic injections and corrosion.

MATERIAL AND METHODS A comparative study was made of the kidneys of two human newborn infants, twenty-one dogs, eight cats, twenty-eight rats, seven guinea-pigs, two sheep, one cow and one hedgehog. The animals used were of various sex and weight. The kidneys of the dog and of the cat were prepared by the method used for the dog's heart (Kazzaz & Shanklin, 1950). The method was slightly modified in the case of the other animals used, in that heparinization was omitted. Vinyl acetate (Ward's Natural Science Establishment, Rochester, N.Y.), of different colours, was injected into the renal artery under a pressure of 250-500 mm. Hg and into the renal vein under a pressure of 200-320 mm. Hg. The specimens were corroded in 2-5 % pepsin and 4 0 % hydrochloric acid.

OBSERVATIONS AND DISCUSSION The veins constitute by far the largest component of the superficial vessels of the kidney. Three distinct patterns were observed in the arrangement of the superficial veins in the animals studied, and are typified by that found in the rat, the dog and the cat. All the superficial vessels described below were seen, in the injected but non-corroded specimen, to lie superficially under the capsule of the kidney. I. The superficial vessels in the rat (PI. 1, fig. 1). The superficial veins in the kidney of the rat constitute the simplest pattern found. They start under the capsule as spur-like projections, often with a bifurcation at their distal end, and pass 164 David Kazzaz and William M. Shanklin perpendicularly inwards through the cortex to join the interlobular veins, which in turn empty into the arcuate veins. None of the superficial veins passes for any considerable distance parallel to the surface of the kidney before turning inwards. Thus there is only one system of veins whereby the superficial and the deep veins empty into the arcuate veins before joining the renal vein. No arteries lie at the same level as or superficial to the superficial veins. The kidneys of the guinea-pig, cow, sheep and hedgehog have superficial veins .of this pattern. II. The superficial vessels in the dog (P1. 1, fig. 2). Here the veins are arranged in a stellate manner over the whole surface of the kidney. They converge to a number of central points and join together to enter the substance of the kidney perpendicularly and join the interlobular veins. The veins draining the medial side of the kidney are arranged in a fan-shaped manner and unite at the hilum to empty directly into the renal vein. This arrangement, however, is extremely variable. It may involve the veins near the hilum, or those over most of the kidney surface. There is an extensive anastomosis between all the superficial veins. In some cases we observed one or more arteries emerging from the cortex and dividing into three or four branches which ramified underneath the capsule. In a few specimens arteries emerged from one surface of the kidney, passed round the lateral border and re-entered the substance of the kidney on the opposite surface (P1. 1, fig. 2). Sometimes corresponding veins accompanied these arteries. Arteries of this kind were observed in the sheep and the cow. In one human kidney we found a single artery of this kind, while on the other side of the same subject there was a similarly arranged vein. The human kidney has a system of stellate veins, similar to those in the dog, which drain into the interlobular veins. The degree of anastomosis, however, is less extensive and the distance that each vein runs over the surface of the kidney before penetrating it is much shorter than in the case of the dog. Unlike the condition found in the dog, the veins draining the medial part of the human kidney do not empty directly into the renal vein. III. The superficial vessels of the cat's kidney (P1. 1, fig. 3). A still more highly developed system of superficial veins is present in the kidney of the cat. It consists of four to six veins on each surface, which start at the lateral border and pass medially. They are radially arranged and drain into the renal vein at the hilum. All along their course they are joined on each side by numerous superficial sub- capsular tributaries. From their deep surface many small veins pass perpendicularly inwards to join the interlobular veins, which in turn open into the arcuate veins. There are rich anastomoses between all the superficial veins in the cat as in the dog. From the above we conclude that the cat's kidney has two systems of veins-those that empty directly into the renal vein and those that join the arcuate vein before emptying into the renal vein. As in the rat, all the renal arteries lie deep to the superficial veins. Journal of Anatomy, Vol. 85, Part 2 Plate 1

KAZZAZ AND SHANKLIN-SUPERFICIAL VESSELS OF THE MAMMALIAN KIDNEY 'Superficial vessels of the mammalian kidney 165

SUMMARY Seventy pairs of kidneys of different mammals were injected with vinyl acetate and corroded with pepsin and hydrochloric acid. The superficial veins of the kidney showed three different patterns illustrated best by the rat, dog and cat. The veins in the rat start as spur-like projections and join the interlobular veins. The dog has a system of stellate veins which on the lateral side of the kidney drain into the interlobulars and on the medial side directly into the renal vein. The cat has radially arranged veins running along the surface of the kidney and emptying into the renal vein. Numerous tributaries join each side of the veins and deep veins connect them to the interlobulars. The human kidney has a system of stellate veins that drain into the interlobulars as in the dog, but they are not so well developed. The guinea-pig, cow, sheep and hedgehog show patterns similar to that of the rat. Rudimentary arteries, with or without corresponding veins, were observed coming up to the surface of the kidney and ramifying under the capsule in the dog, cow, sheep and in one human newborn. The writers are greatly indebted to Mr Khalil Samarah for assistance with the injections. REFERENCES KAZZAZ, D. & SHANKLIN, W. M. (1950). The coronary vessels of the dog demonstrated by colored plastic (vinyl acetate) injections and corrosion. Anat. Rec. 107, 43-59. MORIsoN, D. M. (1926). A study of the renal circulation, with special reference to its finer distribution. Amer. J. Anat. 37, 53-93. TRUETA, J., BARcLAY, A. E., DANIEL, P. M., FRANKLIN, K. J. & PRICHARD, M. M. L. (1947). Studie8 of the Renal Circulation, pp. 164-166. Oxford: Blackwell Scientific Publications.

EXPLANATION OF PLATE PLATE 1 Fig. 1. Kidney of the rat showing the superficial veins with spur-like projections. x 3-6. Fig. 2. Kidney of the dog showing stellate veins that on the medial part drain directly into the renal vein. Note the artery (thick) and vein (thin) passing round the lateral border of this kidney. x 1-8. Fig. 3. Kidney of the cat showing the radial arrangement of the superficial veins and the extensive anastomosis between them. x 2 6.