a 59-year - old man presented with liver cirrhosis and esophageal varix bleeding . a ct scan ( lightspeed qx / i , general electric co. , milwaukee , wi , usa ) with contrast media was performed and it incidentally revealed a horseshoe kidney with a well - enhanced isthmus and a 3-cm enhancing mass in the left part ( fig . the tumor was limited to the kidney , but its extension into the renal pelvis was not definite . digital subtraction angiography ( dsa ) via the right femoral artery route was performed under local anesthesia just before the embolization procedure . the dsa of the aorta showed that the horseshoe kidney was fed by a five - vessel supply that consisted of both the two normal main renal arteries , two aberrant vessels that were originating from the aorta and they entered both sides of the isthmus ( fig . 1b ) that entered the left side of the isthmus and it originated from the left common iliac artery . the dsa of the left renal artery demonstrated hypervascular tumor staining that was supplied by the anterior inferior segmental branch of the left main renal artery ( fig . although the portion of the tumor that had invaded the collecting systems could not be completely excluded , the decision was made to perform organ - preserving surgery or simple enucleation . catheterization was performed via a transfemoral approach with the use of the standard coaxial technique . a 5-f end - hole catheter ( cobra catheter , cook , bloomington , in , usa ) was introduced over a 0.035-inch guide wire ( termo ; radifocus , tokyo , japan ) to the left main renal artery . the feeding vessel to the tumor was catheterized with the use of a 3-f microcatheter ( renegade ; boston scientific , watertown , ma , usa ) and it was embolized superselectively with contour ( 355 - 500 microns , boston scientific international , la garenne colombes cedex , france ) ( fig . the contour granules were slowly and carefully injected ( to prevent reflux of the particles ) under fluoroscopic guidance before embolization with the use of a 0.018-inch - diameter tornado microcoil ( 3 mm to 2 mm , cook ) . a postembolization angiography shows a successful segmental embolization of the anterior inferior segment of the left part kidney , including the tumor ( fig . for the patient to undergo an effective and comfortable intervention , analgesic ( midazolam 2 mg , i.v . ; roche , fontenay - sous - bois , france ) and sedative ( fentanyl 60 micrograms , i.v . ; co. , hwasung , korea ) were administered just before the dsa to achieve moderate sedation . under general anesthesia the tumor site was a mild brown color and it was easily identified at the left side of the horseshoe kidney because of the previous renal artery embolization . the tumor was enucleated by repeated cuts with the use of an electrosurgical generator ( valleylab inc . , boulder , co , usa ) . the parenchymal bleeding was easily controlled by suture because of the previous renal artery embolization . upon examination of the gross specimen , the tumor showed as a well - circumscribed , bright yellow , solid mass measuring about 3 cm at its greatest diameter ( fig . the tumor was confined to the kidney and it proved to be a renal cell carcinoma , grade 2 ( fig . 1f ) . a follow - up ct scan with contrast media 33 days after the operation showed a parenchymal defect at the previous tumor site with some postoperative change ( fig . the horseshoe kidney is probably the most common of all renal fusion anomalies ( 3 ) . this anomaly consists of two distinct renal masses lying vertically on either side of the midline ; the masses are connected at their respective lower poles by a parenchymatous or fibrous isthmus that crosses the midplane of the body ( 3 ) . most of the malignant tumors arising in horseshoe kidneys are renal cell carcinomas , but transitional cell carcinomas , squamous cell carcinomas , wilm 's tumors , lymphomas , carcinoid tumors and sarcomas have also been reported ( 4 , 5 ) . it has been stated that the occurrence of renal cell carcinoma in horseshoe kidneys is no higher than in non - fused kidneys , but that the incidence of transitional cell carcinoma in horseshoe kidneys is higher , and this is conceivably due to the presence of chronic urinary tract infections ( 4 ) . the blood supply to the horseshoe kidney can be quite variable ( 3 ) . in 30% of the cases , it consists of one renal artery for each kidney ( 6 ) , but the blood supply may be atypical , with duplicate or even triplicate renal arteries supplying one or both kidneys ( 3 ) . the isthmus and adjacent parenchymal masses may receive a branch from each main renal artery , or they may have their own arterial supply originating from the aorta either above or below the level of the isthmus ( 3 ) . not infrequently , this area is supplied by branches from the inferior mesenteric artery , the common or external iliac arteries , or the sacral arteries ( 7 ) . in this case , the isthmus was receiving two arterial supplies that originated from the aorta at the level of the isthmus , and there was an additional arterial supply from the left common iliac artery ( fig . an aberrant vascular supply is one of the major anatomic features in horseshoe kidneys ; thus , the vascular supply can not be easily predicted on the surgical field . this is especially true when preoperative renal artery embolization is necessary and a part of the organ has to be removed due to malignant disease while the maximal amount of functioning renal tissue needs to be preserved . radical nephrectomy is the standard therapy for renal cell carcinoma ( 8) . in cases of neoplasm in a horseshoe kidney , however , there is a place for limited resection or heminephrectomy , with special attention being paid to the abnormal arteries and the renal pelvis ( 8) . preoperative superselective renal artery embolization helps to prevent excessive bleeding complications during organ - preserving surgery , it allows the preservation of a maximum amount of functioning renal tissue and it enables easy detection of the tumor site via the discoloration ; thus , simple enucleation is then feasible during the operation . in conclusion , preoperative superselective renal artery embolization can be an effective tool to facilitate organ - preserving surgery in a case of a horseshoe kidney with renal cell carcinoma .
only rarely is renal cell carcinoma encountered in a horseshoe kidney . 
 this is a case report on renal cell carcinoma in a horseshoe kidney , in which superselective renal artery embolization was performed preoperatively . 
 ct and digital subtraction angiography revealed a horseshoe kidney with a 3-cm tumor in the left side . 
 superselective renal artery embolization of the tumor was performed as a prerequisite procedure for the organ - preserving surgery of simple enucleation . 
 preoperative superselective renal artery embolization can be an effective tool to facilitate organ - preserving surgery in a horseshoe kidney .