horseshoe kidney ( hsk ) is the most common congenital abnormality of the kidney , occurring in 0.150.25% of newborns , with a male - to - female ratio of 2:1 . hsk is characterized by three anatomical anomalies : ectopia , malrotation and changes in vascular supply . fusion is usually at the lower poles resulting in the kidneys been caught at the level of the developing inferior mesenteric artery [ 2 , 3 ] . the isthmus that connects the lower renal poles in hsk may either be a fibrous band or contain functional parenchymal tissue . the co - existence of abdominal aortic aneurysm ( aaa ) and hsk is rare , occurring only in 0.12% of patients . the isthmus in hsk almost always lies over the aneurysm , making its exposure extremely difficult . moreover , the complex anatomical anomalies of the kidney and of its collecting system and arteries make the surgical repair of the aneurysm very challenging . we report a rare case of juxtarenal aaa associated with hsk , which was successfully repaired using transperitoneal approach with division of the renal isthmus . a 67-year - old man , with a known aaa of 4.42 cm , was found to have expansion of the aneurysm diameter to 5.40 cm after undergoing a 3-month surveillance ultrasound scan . the patient 's aneurysm was further investigated by a computed tomography angiography ( cta ) , which demonstrated a 5.50 cm juxtarenal aaa that was not suitable for endovascular aaa repair ( evar ) because of a severely angulated proximal neck . moreover , the cta demonstrated a hsk anterior to the abdominal aorta ( fig .  1 ) . following a multidisciplinary team discussion , an open repair with involvement of both vascular and urology surgeons was decided . , we identified a juxtarenal aaa and a hsk with both renal pelvises located medially . the renal isthmus closely lied over the aneurysm , and there was a small vein draining blood from the renal isthmus to the left renal vein , but no accessory artery supplying the renal isthmus was found ( fig .  2 ) . both ureters were identified and preserved . the left renal artery was identified and dissected free from the proximal neck of the aneurysm . provisional clamping of the left renal artery resulted in ischaemia of the left kidney and the renal isthmus , indicating that the arterial blood supply of the renal isthmus was from the left renal artery . considering the minimal gap between the aneurysm and the renal isthmus , we had concerns over controlling retrograde lumbar bleeding when the aneurysm is open ; therefore , we decided to divide the renal isthmus in order to facilitate exposure of the aneurysm . the left renal vein was preserved , and the vein draining the renal isthmus was divided and ligated . careful division of the renal isthmus over the aneurysm was carried out , and homeostasis was achieved . figure  2:(a ) hsk ( the isthmus ) , ( b ) the distal segment of aneurysm close to the iliac bifurcation , ( c ) the aneurysm neck , ( d ) the left renal vein and ( e ) the left ureter . ( a ) hsk ( the isthmus ) , ( b ) the distal segment of aneurysm close to the iliac bifurcation , ( c ) the aneurysm neck , ( d ) the left renal vein and ( e ) the left ureter . the aneurysm was repaired using a 20 mm dacron without the left renal artery reconstruction ( the graft was sutured obliquely so that the origin of the left renal artery was patent ) ( fig . figure  3:the divided renal isthmus and repaired aneurysm using a 20 mm dacron . the divided renal isthmus and repaired aneurysm using a 20 mm dacron . the post - operative recovery was uneventful , and the patient had stable renal function . the patient was mobile on day 3 after the operation and was discharged with good condition on post - operative day 5 . several surgical approaches have been used to repair aaa in patients with co - existent hsk . transperitoneal approach provides the best exposure to the aneurysm and kidney , however , the presence of the renal isthmus affects both surgical exposure and proximal aortic control . left retroperitoneal approach has the advantage of avoiding interference with the renal isthmus and urinary tracts ; however , access to the right iliac artery is limited . in our case , the endovascular approach was not suitable because the proximal neck of the aneurysm was severely angulated . division of the renal isthmus can be associated with increased risk of retroperitoneal urinary leaks , bleeding , infection and renal ischaemia . .   demonstrated successful division of the renal isthmus in 24 patients with aaa and co - existent hsk without any post - operative renal necrosis or urine leaks . however , they did not recommend routine division of the renal isthmus but did not hesitate to advise the division of the isthmus when it facilitates the operation . in our case , we had to divide the renal isthmus to facilitate exposure of the aneurysm . in fact , considering the substantial difficulty in exposing the aneurysm due to overlying isthmus , we had concerns over controlling retrograde lumbar bleeding when the aneurysm is open . suprarenal cross - clamping , especially if it is for longer than 30 min , has been shown to increase the serum creatinine by itself to > 200 mol / l regardless of the presence or absence of anatomic malformations . we had to use suprarenal cross - clamping ( over the left renal artery only ) for 22 min , which did not increase the post - operative creatinine significantly ( 118 mol / l ) . however , it should be taken into account that our patient had normal renal function before the operation , while an abnormal preoperative renal function is known to be an important indicator of poor prognosis in patients with aaa and co - existent hsk . moreover , we did not have to perform the renal artery reconstruction , which is often necessary in patients with aaa and co - existent hsk when temporary renal exclusion takes place . in fact , we avoided the left renal artery reconstruction by suturing the graft obliquely at the origin of the left renal artery . we reported a rare case of juxtarenal aaa associated with hsk , which was successfully repaired using transperitoneal approach with division of the renal isthmus . despite the potential complications , particularly renal insufficiency , associated with division of the renal isthmus and suprarenal cross - clamping of the abdominal aorta , in our case , post - operative period was uneventful and the patient 's recovery was satisfactory .
the co - existence of abdominal aortic aneurysm ( aaa ) and horseshoe kidney ( hsk ) is rare . 
 we report a 67-year - old man with an expanding juxtarenal aaa associated with a hsk . 
 the aneurysm had a severely angulated neck and contained a significant amount of mural thrombus . 
 the isthmus of hsk closely lied over the aneurysm , making its exposure extremely difficult . 
 the aneurysm was successfully repaired using transperitoneal approach with division of the renal isthmus and without any need for the renal artery reconstruction . despite the potential complications , particularly renal insufficiency , associated with division of the renal isthmus and suprarenal cross - clamping of the abdominal aorta , in our case 
 , post - operative period was uneventful and the patient 's recovery was satisfactory .