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Journal of the Anatomical Society of India

Horseshoe Kidney With Multiple Renal Arteries And Extrarenal Calyces-A Case Report

Author(s): Vaniya V.H.

Vol. 53, No. 2 (2004-07 - 2004-12)

B. J. Medical College, Ahmedabad,

Abstract:

Vascular pattern of horseshoe kidney is quite interesting. During routine dissection practice a horseshoe kidney was found in a male cadaver. Both the kidneys were joined at their lower poles by an isthmus in front of third and fourth lumber vertebrae. The part of fusion called the isthmus consisted of renal tissue. In the present case multiple renal arteries arising from the abdominal aorta at different levels were observed, which entered the horseshoe kidney. Four entered the right kidney, three entered the left kidney and the isthmus was supplied by an independent special branch originated from the distal aorta at the site of its bifurcation. The hilum of each kidney opened anteriorly and the ureters passed anterior to the connecting bridge and entered the urinary bladder normally. Pelvicalyceal system was found medial to the ureters. All the major calyces on both sides and few minor calyces on the left side were found extrarenal in position. Inferior mesenteric artery was running anterior to the isthmus making a deep groove on it. Such vascular malformation is of immense surgical importance especially during surgery of abdominal aorta (aneurysm) .

Key words: horseshoe kidney, multiple renal arteries, extrarenal calyces

Introduction:

Less than 0.3% of the general population have horseshoe kidneys and are seen in approximately 1 out of 300 pyelographies Dees (1941), Allen (1951) and Lowsley (1952). Horseshoe kidney is found in 1:1000 necropsies and more common in men Mann et al (1995). Papin's (1928) autopsy study of 139 horseshoe kidneys served as the basis for a classification system consisting of three groups. Group 1 kidneys have normal renal arteries and account for 20% of all horseshoe kidneys; Group 2 kidneys have three to five renal arteries and account for 66% of cases; Group 3 have more than five renal arteries and account for 14%, Pepin (1928) and Townsend (2002). The vessels may have varied origin from the aorta at the level of the T12 to the internal iliac artery at the lower levels. The total number of vessels may vary from 4 to 7 and the vessel size from 2 mm to 8 mm, Olsson and Wholey (1964). The present report is on a case of horseshoe kidney with multiple renal arteries and extrarenal calyces found during routine dissection.

Case Report:

The present report describes a case of malformation of the kidney of the type known as horseshoe kidney found in approximately a 55 years old male cadaver used for students dissection practice. Both the kidneys were joined at their lower poles by an isthmus located in front of third and fourth lumber vertebrae. The connecting bridge was well-developed, measured about 37 mm x 43 mm size and consisted of renal tissue. The maximum widths of right and left kidneys were 42 mm and 46 mm respectively. Hilum of each kidney opened anteriorly and ureters passed anterior to the connecting bridge and entered the urinary bladder normally. No other obvious external or internal malformation was found. Pelvicalyceal system was found medial to the ureters. All major calyces on both sides and few minor calyces on the left side were found outside the renal parenchyma. Both right and left renal veins opened in to the inferior vena cava and were found normal. Inferior mesenteric artery was running anterior to the isthmus making a deep groove on it (Fig.1).

Multiple renal arteries originating from the abdominal aorta at different vertebral levels were observed (Fig.2). At the level of L1 vertebra two separate renal arteries originated from the right side of the aorta measuring 3 mm and 2 mm diameter passing behind inferior vena cava and entered the upper part of right hilum. At the same vertebral level one left renal artery of 5 mm diameter originated from the left side of abdominal aorta and divided in to three terminal branches before it entered into the upper part of left hilum. At the level of L2 vertebra one artery of 2 mm diameter originated from right side of aorta, passed in front of inferior vena cava and entered the middle of the right hilum. At the level of L3 vertebra pair of renal arteries having the diameter of 3 mm each originated from the aorta just behind the upper part of isthmus and entered the lower segments of kidneys more near their junction with the isthmus from back. Below the isthmus at the level of L5 vertebra two arteries originated from the front of the bifurcation of the aorta. Out of these one artery having diameter of 3 mm entered directly the lower part of anterior surface of the isthmus, while another artery having 2 mm diameter divided in to two terminal branches before it entered into the lower pole near the left hilum.

Discussion:

As the renal rudiments are ascending from the pelvic region to the loin, they normally remain entirely separate. They may however come in contact and adhere resulting in a horseshoe kidney usually connected at the lower poles, Decker and Plessis (1996). This U shaped kidney usually lies at the level of lower lumbar vertebrae, since its ascent is prevented by the root of the inferior mesenteric artery Moore and Dalley (1999). As they ascend, the fusion prevents normal rotation and each renal pelvis remains anterior to the kidney, Mohanty et al (2002). The calyceal system in the present case was extrarenal in position. The anomaly could be due to disparity resulting from slow development of metanephric tissue or a relatively rapid development of the ureteric bud permitting extrarenal development of the first or second order of the collecting system, Malament et al (1961) and Mohanty et al (2002).

Fig. 1. Horseshoe kidney showing anterior view

Missing Image

A-Aorta, RRA-Right renal artery, RARA-Rt. accessory renal artery. IVC-Inferior, vena cava, ARAI-Accessory renal artery to isthmus, LARA-Left Accessory renal artery, LRA-Left renal artery, SMA-Superior mesenteric artery., IMA-Inferior mesenteric artery, RRP-Rt renal pelvis, LRP-Lt renal pelvis, RU-Rt ureter, LU-Lt ureter, RCIA-Rt Common iliac artery, LCIA- Lt Common iliac artery

Fig. 2. Horseshoe kidney showing posterior view

Missing Image

A=Aorta, RRA=Right renal artery, RARA=Right accessory renal artery. IVC=Inferior vena cava, ARAI=Accessory renal artery to isthmus, LARA=Left Accessory renal artery, LRA=Left renal artery (L1-L5 Shows vertebral levels of renal arteries)

In general horseshoe kidney can be regarded, as far as the arteries are concerned as two separate kidneys, which either approximate or are continuous across the midline. Graves (1969) in his study of the arterial anatomy of the congenitally abnormal kidney by means of resin casts, described 6 basic patterns of the blood supply to the horseshoe kidney. In the present case, the arterial supply somewhat resembled to the Graves type H-S IIIc. However, the arterial arrangement of the present case had certain variations. Branches to the upper and middle segments on right side originated directly and independently from the aorta and were smaller in caliber, while on the left side they were the branches of main stem of single renal artery which originated from the left side of the aorta at L1 vertebral level and had a larger caliber. Lower renal segments and broad isthmus were supplied by paired vessels from either side of the aorta just behind the upper border of isthmus. They were also supplied by two other separate arteries which originated from distal aorta at the site of bifurcation below the isthmus of the kidney. These vessels arising from the aorta, below the isthmus of the kidney, are probably the posterior branches of the lower segmental artery, which have taken their origin from the nearest point along the aortic route from which their mesonephric ancestors arose. Embryology is significant in congenital abnormality of the renal arteries. The proximal origin of the segmental arteries of the kidney can be explained by reference to the account of the development of the mesonephric arteries by Felix (1912). Persistence of some mesonephric arteries could account for the variation of origin of the adult segmental arteries from the aorta.

Hitherto a widely held view has been that the normal kidney is supplied by a single renal artery which enters the hilum before it divides and that any additional artery entering the organ at one or other pole is necessarily an extra or aberrant source of supply to that provided by the main renal stem, Graves (1969). In earlier works Graves (1954, 1956) on study of these vessels by cast and arteriogram showed that these so called 'extra' or 'aberrant and anomalous' arteries were in fact normal segmental vessels whose origin was more proximal than usual, and that ligation or division of them would result in ischaemia of the segment of renal tissue, which they supplied. Such vascular malformation is of immense surgical importance especially during surgery of abdominal aorta (e.g.aneurysm). A horseshoe kidney is a problem in abdominal aneurysm surgery. In only 20% of these cases do the renal arteries arise normally. In the remaining cases there are 5 or more additional arteries arising from the aorta or iliac arteries, Papin (1928) and Decker & Plessis (1996), some of which originate from the aneurysm. In this situation, repair of the aneurysm with preservation of renal function may be difficult or even impossible, Townsend (2002). Division of these vessels may result in ischaemia of the kidney, as there is no collateral circulation between the renal segments even in extremes of variations, Graves (1969). Hence to preserve renal function renal arteries arising from the aneurysm should be preserved if possible and reimplanted quickly after aortic reconstruction, Townsend (2002).

References:

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