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Operative Management of Coexistent Aortic Disease and Horseshoe Kidney
Operative Management of Coexistent Aortic Disease and Horseshoe Kidney Cynthia K. Shortell, MD, Ethan L. Welch, MD, Kenneth Ouriel, MD, Richard M. Green, MD, and James A. DeWeese, MD, Rochester, New York
The presence of horseshoe kidney in conjunction with abdominal aortic disease significantly increases the technical difficulty of aortic reconstruction. Preservation of the renal blood supply and collecting system during the surgical procedure is the goal of operative management. The pertinent issues that remain unresolved include the need for specific preoperative studies, the optimal operative approach and the safety of isthmus division. From 1979 to 1994 eight patients with horseshoe kidney underwent operative intervention for aortic disease. Five men and three women who had a mean age of 66 years underwent seven reconstructions for aneurysmal disease and one for aortoiliac occlusive disease. All operations were elective and the transperitoneal approach was used in all cases. In the patients with aneurysmal disease the mean maximal aortic diameter was 7.3 cm. The mean preoperative serum creatinine value was 1.1 mg/dl. Preoperative identification of horseshoe kidney was accomplished in all seven patients with aneurysmal disease but not in the patient with occlusive disease. The anomaly was correctly identified by CT scan in seven of seven (100%) patients, arteriography in two of eight (25%) patients, ultrasonography in two of seven (29%) patients, and renal scan in one patient. In the three patients who underwent intravenous pyelography (IVP) the caliceal system was demonstrated to be completely separate from the isthmus. Renal artery anomalies were present in six (75%) patients; in three (50%) these anomalies could be not visualized on the preoperative arteriogram. Renal revascularization was accomplished by a variety of techniques, including reimplantation of multiple (one patient) and single (four patients) renal arteries and branch grafting to an individual renal artery (one patient). Isthmus division was required in three patients. Seven patients had no postoperative elevation in the serum creatinine level including the three patients in whom the isthmus was divided. One patient had postoperative renal failure requiring permanent hemodialysis; this patient had massive intraoperative blood loss due to technical difficulties unrelated to the horseshoe kidney. There were no perioperative deaths. Preoperative identification of horseshoe kidney is best accomplished by CT scanning. Arteriography and IVP should be performed routinely to evaluate the arterial and caliceal anatomy. Arteriography frequently fails to identify anomalous circulation; the transperitoneal approach affords the best opportunity to identify these anomalies intraoperatively. Preoperative IVP allows identification of the renal collecting system, facilitating safe division of the isthmus if necessary. (Ann Vasc Surg 1995;9:123-128.)
From the Department of Surgery, University of Rochester School of Medicine and Dentistry, and Rochester General Hospital' Rochester, N.Y. Presented at the Nineteenth Annual Meeting of the Peripheral Vascular Surgery Society, Seattle, Wash., June 5, 1994. Reprint requests: Cynthia K. Shortell, MD, 1415 Portland Ave., Rochester, NY 14621.
Horseshoe kidney is the most c o m m o n form of renal fusion and ectopy, occurring in approximately 0.25% of the population) "2 As with aneurysmal disease, m e n are affected more often than women. Coexistence of horseshoe kidney and aortic disease requiring operative intervention is a rare event, ~but w h e n it does occur it significantly 123
Annals of Vascular Surgery
124 Shortell et al.
increases the technical difficulty of aortic reconstruction. Developmentally the anomaly occurs between 4 and 6 weeks' gestation, after entrance of the ureteral bud into the renal blastema. At this time the two renal masses are in close proximity and any disruption of the usual anatomic relationships resulting in contact between these structures may cause them to fuse. 1 This event occurs well in advance of renal rotation and migration; hence these processes are affected as well. The collecting systems are located anteriorly, and the kidneys themselves are usually located more inferiorly than usual and their ascent is halted by the inferior mesenteric artery. If crossed fused ectopia occurs, the ureters enter the bladder contralateral to the position of the renal mass of origin since the renal masses are located on the side opposite that of their initial embrologic position. 1 The precise shape of the horseshoe kidney varies but generally it comprises two renal masses located on either side of the midline and fused medially. The fusion is most often at the lower poles of the renal masses, anterior to the aorta. Occasionally, however, the isthmus may be formed by fusion of the superior poles, may be extremely broad, or may be located posterior to the aorta. 1 The isthmus itself consists of varying amounts of renal parenchyma2; it may be a fibrous band or it may contain significant functioning renal tissue and rarely caliceal elements. Renal arterial anomalies are the norm, occurring in 60% to 80% of patients. 3~ Most patients have main renal arteries to each kidney arising in the usual position, with or without accessory arterial supply to the primary renal masses or isthmus arising from the aneurysm itself or from either or both iliac arteries. ~-~ The anterior position of the horseshoe kidney isthmus and the potential for anomalies of the arterial and collecting systems create technical challenges at the time of aortic repair. Optimal management is dependent on accurate preoperative diagnosis and preservation Of the collecting system and all renal arteries. This study attempts to identify the most accurate diagnostic procedures and the optimal surgical approach and also tries to determine the safety of isthmus division.
MATERIALS AND METHODS The hospital records of the eight patients with horseshoe kidney w h o underwent abdominal aortic reconstruction for aneurysmal or occlusive
disease between 1979 and 1994 were reviewed. Late follow-up data w h e n available were obtained from the attending surgeons. The five men and three w o m e n had a mean age of 66 years (median 60 years, range 60 to 80 years). Comorbid conditions included coronary artery disease in four (50%) patients, hypertension in four (50%), and a history of cigarette smoking in three (38%). None of the patients was diabetic. Seven (88%) patients h a d aneurysmal disease of the infrarenal aorta including two with bilateral iliac aneurysms as well. The mean aneurysm size was 7.3 cm (median 7.5 cm, range 5 to 9.5 cm). One patient had aortoiliac occlusive disease. All operative procedures were performed electively. The transperitoneal approach was used exclusively. A variety of preoperative studies were performed including CT scan (seven patients), arteriography (eight patients), intravenous pyelography (IVP; three patients), ultrasonography (seven patients), and renal perfusion scan (one patient).
RESULTS The diagnosis of horseshoe kidney was made preoperatively in all seven patients with aneurysmal disease and was recognized at operation in the patient with occlusive disease. This correlates with the use of CT scans; that is, all patients with aneurysmal disease underwent CT scanning, which identified the horseshoe kidney in every one of them (Fig. 1). The patient with occlusive disease, however, did not undergo preoperative CT scanning. Arteriography was performed in all patients and correctly identified the anomaly in two (25%). Ultrasound imaging was accurate in two of seven (29%-) patients in w h o m it was performed and renal scanning was accurate in the one patient w h o was evaluated using this modality. In the three patients w h o underwent W P , the caliceal system was correctly identified as being separate from the isthmus (Fig. 2). Renal artery anomalies were present in six (75%) patients; in three (50%) of them the anomalous blood supply was identified on the preoperative arteriogram (Fig. 3). Both of the patients with normal renal arterial anatomy underwent tube graft repair of an abdominal aortic aneurysm; in one of them this was accomplished without isthmus division, whereas in the other patient division of the isthmus was deemed necessary. In the patients with abnormal renal anatomy there were two predominant patterns of
Vol. 9, No. 1 1995
Management of coexistent aortic disease and horseshoe kidney
125
Fig. 1. CT scan with intravenous contrast demonstrating horseshoe kidney draped over the midportion of the abdominal aortic aneurysm. The isthmus contains significant functioning renal parenchyma.
Fig. 2. Intravenous pyelogram demonstrating absence of caliceal tissue within the isthmus of the horseshoe kidney.
Fig. 3. Intra-arterial aortogram demonstrating aberrant renal artery originating from the anterior surface of the aortic aneurysm.
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anomaly: patients in group 1 had normally positioned right and left main renal arteries with additional accessory vessels, whereas patients in group 2 had a normal left main renal artery but an abnormally positioned right main renal artery. Three of the four patients in group 1 had accessory renal arteries originating from the body of the aneurysm, which were reimplanted onto the graft. In one patient the button of tissue reimplanted consisted of a single accessory renal artery, in the second patient a button including the inferior mesenteric artery and a single accessory renal artery was reimplanted, and in another a button of four accessory renal arteries was reimplanted. Two patients in group 1 required isthmus division. The patient with occlusive disease had an accessory right renal artery originating from the distal aorta; this patient underwent end-toside aortobifemoral bypass grafting with creation of a proximal anastomosis above the level of the accessory renal artery and isthmus preservation. The two patients in group 2 had a single aberrant main right renal artery originating from the anterior surface of the aneurysm; they were managed with a tube graft and reimplantation of the right renal artery onto the graft in one and a jump graft with end-to-end anastomosis to the right renal artery in the other. Seven patients, including the three in w h o m division of the isthmus was required, had no significant postoperative increase in serum creatinine; in these patients the mean preoperative and postoperative values were 1.1 mg/dl and 1.0 mg/dl, respectively. Only one patient experienced any increase in creatinine (from 1.0 mg/dl preoperatively to 1.1 mg/dl) postoperatively. One patient whose preoperative serum creatinine level was 1.2 mg/dl developed renal failure in the immediate postoperative period and has required permanent hemodialysis. This patient suffered a massive intraoperative hemorrhage due to technical difficulties involving the proximal aortic anastomosis unrelated to the presence of the horseshoe kidney. The isthmus was not divided in this patient. There were no perioperative deaths or significant perioperative morbid events except for the patient with postoperative renal failure. Six patients are alive and well at 12 years, 4 years (two patients), 1 year (two patients), and 1 m o n t h postoperatively. Two patients including the one with postoperative renal failure were lost to follow-up.
DISCUSSION The rarity of horseshoe kidney occurring in combination with aortic disease has precluded the development of a standardized approach to diagnosis and treatment. In addition, the wide variety of arterial and collecting system anomalies associated with horseshoe kidney have frustrated attempts to determine optimal management. The development of a standardized approach requires that two key issues be addressed; the most accurate method of preoperative diagnosis must be identified and the preferred operative approach determined. Preoperative diagnosis of horseshoe kidney and identification of the attendant anomalies of the renal arterial and collecting systems are critical, as they enable the operative team to customize therapy according to the abnormalities identified. The CT scan is unequivocally the mainstay of diagnosis with regard to recognition of the presence of a horseshoe kidney. In our experience the CT scan is an extremely sensitive method for identifying a horseshoe kidney, confirming the findings of others. 2"6 Fortunately CT scans are routinely obtained preoperatively in patients with abdominal aortic aneurysm, obviating the need for an additional screening test to detect a rare abnormality. Once the horseshoe kidney has been identified, the anatomy of the renal arterial supply and the collecting system must be determined. It is most important to determine the location of the main renal arteries as well as the presence of anomalous vessels arising from the body of the aneurysm or from other sites such as the fliac arteries. IVP must be performed in all patients to delineate the course of the ureters and to determine whether or not caliceal tissue is contained within the isthmus. The latter is a rare finding 1 but impacts the operative plan if division of the isthmus is contemplated. Other diagnostic evaluations such as ultrasonography and renal scanning may be used as indicated in individual patients, but we have found them to be of limited value. With the advent of modern duplex techniques, however, ultrasonography is likely to be a more effective tool for the identification of aberrant renal arteries. The second issue of importance with regard to the management of coexistent aortic disease and horseshoe kidney concerns the preferred operative strategy; specifically, whether the retroperitoneal or transperitoneal approach represents the optimal means of access. The ideal operative ap-
Vol. 9, No. 1 1995
proach should have the following characteristics: (1) allow performance of the aortic (and iliac) repair with the best possible access to these structures, (2) afford the best opportunity to identify and preserve anomalous renal arterial vessels including those not seen on preoperative arteriography, (3) minimize the possibility of injury to functioning renal parenchyma, and (4) minimize the possibility of collecting system injury. With regard to exposure of the aorta and anomalous renal arteries, the transperitoneal approach is clearly optimal, particularly w h e n right iliac artery disease is present or when the indication for surgery is occlusive disease. The isthmus is readily mobilized away from the anterior surface of the aorta and the graft is placed underneath it. The search for anomalous renal arteries is facilitated by the direct visualization afforded by the anterior approach because of the highly variable nature of these vessels. For this reason identification of these vessels may be seriously jeopardized by the retroperitoneal approach; unlike the visceral vessels in the repair of a thoracoabdominal aneurysm, the anomalous renal arteries in a patient with horseshoe kidney are small, unpredictably located, and exhibit minimal backbleeding because of intra-aortic thrombus and lack of collateral blood flow. If additional exposure is required, medial visceral rotation can be employed. The retroperitoneal approach has been advocated by other authors 6 because it permits the surgeon to leave the isthmus intact in virtually all cases. At issue is whether the avoidance of isthmus division is an important goal in and of itself. If division of the isthmus is not associated with alterations in postoperative renal function or injury to the caliceal system, then adherence to this goal at the expense of improved operative exposure of the iliac and accessory renal vessels m a y be detrimental. In our experience division of the renal isthmus was not associated with loss of renal function, nor was preservation of the isthmus associated with normal postoperative renal function. Others have also reported on the safety of isthmus division. 2"3"~'79 The risks of postoperative renal failure and urinary fistula are cited as the primary argument against isthmus division, ~ but neither of these eventualities has been documented in the literature. 2"3's'7 We therefore advocate the transperitoneal approach in the majority of patients because it allows for optimal achievement of the goals of operative management with-
Management of coexistent aortic disease and horseshoe kidney
127
out jeopardizing the functional integrity of the horseshoe kidney. It must be recognized, however, that the presence of certain u n c o m m o n conditions may favor the use of the retroperitoneal approach. These include the presence of a "hostile" abdomen, pancake kidney, and thoracoabdominal aneurysm. In addition, if IVP demonstrates caliceal tissue within the isthmus, and the necessity for isthmus division is anticipated, the retroperitoneal approach should be considered. Based on these principles of management we have developed a strategy of operative management. Preoperatively all patients undergo abdominal CT scanning; this is usually w h e n the horseshoe kidney is identified. Once the diagnosis is made, arteriography and IVP are performed in all patients. The preferred operative approach is transperitoneal with rare exceptions. At operation the isthmus is mobilized off the anterior surface of the aorta, affording exposure of accessory branches to the isthmus and renal masses at this level. Care must be taken to reimplant all vessels supplying the kidney including small accessory vessels, inasmuch as the distribution of renal parenchyma supplied is unpredictable and ligation may result in necrosis of significant portions of the kidney. In addition, it is imperative that the surgeon search for arterial anomalies not identified on the arteriogram; in our experience and in that of other investigators, arteriography fails to detect these anomalies in 40% to 60% of cases. 2-4a~ The ureters are similarly identified and preserved. Aortic reconstruction is performed with intravenous infusion of mannitol prior to interruption of any renal blood flow. After completion of the proximal anatomosis, the anomalous renal arterial supply is reconstructed, usually by reimplantation using a button of aortic tissue. The distal anastomoses are completed and renal revascularizations are evaluated using Doppler imaging.
CONCLUSION The presence of horseshoe kidney in patients with aortic disease requiring operative intervention is best detected by means of CT scanning. In patients with occlusive disease the use of preoperative CT scans is not routine and the diagnosis may be missed. After the diagnosis of horseshoe kidney is made, preoperative arteriography and IVP are mandatory to delineate the anatomy of the
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arterial supply and collecting system, respectively. Arteriography, however, fails to identify anomalous circulation in a significant number of patients and the transperitoneal approach usually affords the best opportunity to recognize these vessels intraoperatively. With careful preoperative evaluation and preparation the isthmus can be divided with no adverse effects on renal function in the majority of patients.
REFERENCES 1. Bauer SB, Perlmutter AD, Retik AB. Anomalies of the upper urinary tract. In Walsh PC, ed. Campbell's Urology, 6th ed. Philadelphia: WB Saunders, 1992, pp 1357-1442. 2. Crawford ES, Coselli JS, Hazim JS, et al. The impact of renal fusion and ectopia on aortic surgery. J Vasc Surg 1988;8:375383.
Annals of Vascular Surgery
3. Sidell PM, Pairolero PC, Payne WS, et al. Horseshoe kidney associated with surgery of the abdominal aorta. Mayo Clin Proc 1979;54:97-103. 4. Bietz DS, Merendino KA. Abdominal aneurysm and horseshoe kidney: A review. Ann Surg 1975;181:333-341. 5. Connelly TL, McKinnon W, Smith RB III, et al. Abdominal aortic surgery and horseshoe kidney. Arch Surg 1980;115: 1459-1463. 6. O'Hara P J, Hakaim AG, Hertzer NR, et al. Surgical management of aortic aneurysm and coexistent horseshoe kidney: Review of a 31-year experience. J Vasc Surg 1993;17:940-947. 7. Tapper SS, Martin RS III, Edwards WH, et al. Ruptured abdominal aortic aneurysm and horseshoe kidney. South Med J 1990;83:224-226. 8. Scott R Jr, DeBakey ME, Mani P. Surgical correction of abdominal aortic disease in 8 patients with horseshoe kidney. J Urol 1969;102:21-26. 9. Starr DS, Foster WJ, Morris GC Jr. Resection of abdominal aortic aneurysm in the presence of horseshoe kidney. Surgery 1981;89:387-389. I0. Ezzet F, Dorazio R, Herzberg R. Horseshoe and pelvic kidneys associated with abdominal aortic aneurysms. Am J Surg 1977; 134:196-198.
The presence of horseshoe kidney in conjunction with abdominal aortic disease significantly increases the technical difficulty of aortic reconstruction. Preservation of the renal blood supply and collecting system during the surgical procedure is the goal of operative management. The pertinent issues that remain unresolved include the need for specific preoperative studies, the optimal operative approach and the safety of isthmus division. From 1979 to 1994 eight patients with horseshoe kidney underwent operative intervention for aortic disease. Five men and three women who had a mean age of 66 years underwent seven reconstructions for aneurysmal disease and one for aortoiliac occlusive disease. All operations were elective and the transperitoneal approach was used in all cases. In the patients with aneurysmal disease the mean maximal aortic diameter was 7.3 cm. The mean preoperative serum creatinine value was 1.1 mg/dl. Preoperative identification of horseshoe kidney was accomplished in all seven patients with aneurysmal disease but not in the patient with occlusive disease. The anomaly was correctly identified by CT scan in seven of seven (100%) patients, arteriography in two of eight (25%) patients, ultrasonography in two of seven (29%) patients, and renal scan in one patient. In the three patients who underwent intravenous pyelography (IVP) the caliceal system was demonstrated to be completely separate from the isthmus. Renal artery anomalies were present in six (75%) patients; in three (50%) these anomalies could be not visualized on the preoperative arteriogram. Renal revascularization was accomplished by a variety of techniques, including reimplantation of multiple (one patient) and single (four patients) renal arteries and branch grafting to an individual renal artery (one patient). Isthmus division was required in three patients. Seven patients had no postoperative elevation in the serum creatinine level including the three patients in whom the isthmus was divided. One patient had postoperative renal failure requiring permanent hemodialysis; this patient had massive intraoperative blood loss due to technical difficulties unrelated to the horseshoe kidney. There were no perioperative deaths. Preoperative identification of horseshoe kidney is best accomplished by CT scanning. Arteriography and IVP should be performed routinely to evaluate the arterial and caliceal anatomy. Arteriography frequently fails to identify anomalous circulation; the transperitoneal approach affords the best opportunity to identify these anomalies intraoperatively. Preoperative IVP allows identification of the renal collecting system, facilitating safe division of the isthmus if necessary. (Ann Vasc Surg 1995;9:123-128.)
From the Department of Surgery, University of Rochester School of Medicine and Dentistry, and Rochester General Hospital' Rochester, N.Y. Presented at the Nineteenth Annual Meeting of the Peripheral Vascular Surgery Society, Seattle, Wash., June 5, 1994. Reprint requests: Cynthia K. Shortell, MD, 1415 Portland Ave., Rochester, NY 14621.
Horseshoe kidney is the most c o m m o n form of renal fusion and ectopy, occurring in approximately 0.25% of the population) "2 As with aneurysmal disease, m e n are affected more often than women. Coexistence of horseshoe kidney and aortic disease requiring operative intervention is a rare event, ~but w h e n it does occur it significantly 123
Annals of Vascular Surgery
124 Shortell et al.
increases the technical difficulty of aortic reconstruction. Developmentally the anomaly occurs between 4 and 6 weeks' gestation, after entrance of the ureteral bud into the renal blastema. At this time the two renal masses are in close proximity and any disruption of the usual anatomic relationships resulting in contact between these structures may cause them to fuse. 1 This event occurs well in advance of renal rotation and migration; hence these processes are affected as well. The collecting systems are located anteriorly, and the kidneys themselves are usually located more inferiorly than usual and their ascent is halted by the inferior mesenteric artery. If crossed fused ectopia occurs, the ureters enter the bladder contralateral to the position of the renal mass of origin since the renal masses are located on the side opposite that of their initial embrologic position. 1 The precise shape of the horseshoe kidney varies but generally it comprises two renal masses located on either side of the midline and fused medially. The fusion is most often at the lower poles of the renal masses, anterior to the aorta. Occasionally, however, the isthmus may be formed by fusion of the superior poles, may be extremely broad, or may be located posterior to the aorta. 1 The isthmus itself consists of varying amounts of renal parenchyma2; it may be a fibrous band or it may contain significant functioning renal tissue and rarely caliceal elements. Renal arterial anomalies are the norm, occurring in 60% to 80% of patients. 3~ Most patients have main renal arteries to each kidney arising in the usual position, with or without accessory arterial supply to the primary renal masses or isthmus arising from the aneurysm itself or from either or both iliac arteries. ~-~ The anterior position of the horseshoe kidney isthmus and the potential for anomalies of the arterial and collecting systems create technical challenges at the time of aortic repair. Optimal management is dependent on accurate preoperative diagnosis and preservation Of the collecting system and all renal arteries. This study attempts to identify the most accurate diagnostic procedures and the optimal surgical approach and also tries to determine the safety of isthmus division.
MATERIALS AND METHODS The hospital records of the eight patients with horseshoe kidney w h o underwent abdominal aortic reconstruction for aneurysmal or occlusive
disease between 1979 and 1994 were reviewed. Late follow-up data w h e n available were obtained from the attending surgeons. The five men and three w o m e n had a mean age of 66 years (median 60 years, range 60 to 80 years). Comorbid conditions included coronary artery disease in four (50%) patients, hypertension in four (50%), and a history of cigarette smoking in three (38%). None of the patients was diabetic. Seven (88%) patients h a d aneurysmal disease of the infrarenal aorta including two with bilateral iliac aneurysms as well. The mean aneurysm size was 7.3 cm (median 7.5 cm, range 5 to 9.5 cm). One patient had aortoiliac occlusive disease. All operative procedures were performed electively. The transperitoneal approach was used exclusively. A variety of preoperative studies were performed including CT scan (seven patients), arteriography (eight patients), intravenous pyelography (IVP; three patients), ultrasonography (seven patients), and renal perfusion scan (one patient).
RESULTS The diagnosis of horseshoe kidney was made preoperatively in all seven patients with aneurysmal disease and was recognized at operation in the patient with occlusive disease. This correlates with the use of CT scans; that is, all patients with aneurysmal disease underwent CT scanning, which identified the horseshoe kidney in every one of them (Fig. 1). The patient with occlusive disease, however, did not undergo preoperative CT scanning. Arteriography was performed in all patients and correctly identified the anomaly in two (25%). Ultrasound imaging was accurate in two of seven (29%-) patients in w h o m it was performed and renal scanning was accurate in the one patient w h o was evaluated using this modality. In the three patients w h o underwent W P , the caliceal system was correctly identified as being separate from the isthmus (Fig. 2). Renal artery anomalies were present in six (75%) patients; in three (50%) of them the anomalous blood supply was identified on the preoperative arteriogram (Fig. 3). Both of the patients with normal renal arterial anatomy underwent tube graft repair of an abdominal aortic aneurysm; in one of them this was accomplished without isthmus division, whereas in the other patient division of the isthmus was deemed necessary. In the patients with abnormal renal anatomy there were two predominant patterns of
Vol. 9, No. 1 1995
Management of coexistent aortic disease and horseshoe kidney
125
Fig. 1. CT scan with intravenous contrast demonstrating horseshoe kidney draped over the midportion of the abdominal aortic aneurysm. The isthmus contains significant functioning renal parenchyma.
Fig. 2. Intravenous pyelogram demonstrating absence of caliceal tissue within the isthmus of the horseshoe kidney.
Fig. 3. Intra-arterial aortogram demonstrating aberrant renal artery originating from the anterior surface of the aortic aneurysm.
126
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anomaly: patients in group 1 had normally positioned right and left main renal arteries with additional accessory vessels, whereas patients in group 2 had a normal left main renal artery but an abnormally positioned right main renal artery. Three of the four patients in group 1 had accessory renal arteries originating from the body of the aneurysm, which were reimplanted onto the graft. In one patient the button of tissue reimplanted consisted of a single accessory renal artery, in the second patient a button including the inferior mesenteric artery and a single accessory renal artery was reimplanted, and in another a button of four accessory renal arteries was reimplanted. Two patients in group 1 required isthmus division. The patient with occlusive disease had an accessory right renal artery originating from the distal aorta; this patient underwent end-toside aortobifemoral bypass grafting with creation of a proximal anastomosis above the level of the accessory renal artery and isthmus preservation. The two patients in group 2 had a single aberrant main right renal artery originating from the anterior surface of the aneurysm; they were managed with a tube graft and reimplantation of the right renal artery onto the graft in one and a jump graft with end-to-end anastomosis to the right renal artery in the other. Seven patients, including the three in w h o m division of the isthmus was required, had no significant postoperative increase in serum creatinine; in these patients the mean preoperative and postoperative values were 1.1 mg/dl and 1.0 mg/dl, respectively. Only one patient experienced any increase in creatinine (from 1.0 mg/dl preoperatively to 1.1 mg/dl) postoperatively. One patient whose preoperative serum creatinine level was 1.2 mg/dl developed renal failure in the immediate postoperative period and has required permanent hemodialysis. This patient suffered a massive intraoperative hemorrhage due to technical difficulties involving the proximal aortic anastomosis unrelated to the presence of the horseshoe kidney. The isthmus was not divided in this patient. There were no perioperative deaths or significant perioperative morbid events except for the patient with postoperative renal failure. Six patients are alive and well at 12 years, 4 years (two patients), 1 year (two patients), and 1 m o n t h postoperatively. Two patients including the one with postoperative renal failure were lost to follow-up.
DISCUSSION The rarity of horseshoe kidney occurring in combination with aortic disease has precluded the development of a standardized approach to diagnosis and treatment. In addition, the wide variety of arterial and collecting system anomalies associated with horseshoe kidney have frustrated attempts to determine optimal management. The development of a standardized approach requires that two key issues be addressed; the most accurate method of preoperative diagnosis must be identified and the preferred operative approach determined. Preoperative diagnosis of horseshoe kidney and identification of the attendant anomalies of the renal arterial and collecting systems are critical, as they enable the operative team to customize therapy according to the abnormalities identified. The CT scan is unequivocally the mainstay of diagnosis with regard to recognition of the presence of a horseshoe kidney. In our experience the CT scan is an extremely sensitive method for identifying a horseshoe kidney, confirming the findings of others. 2"6 Fortunately CT scans are routinely obtained preoperatively in patients with abdominal aortic aneurysm, obviating the need for an additional screening test to detect a rare abnormality. Once the horseshoe kidney has been identified, the anatomy of the renal arterial supply and the collecting system must be determined. It is most important to determine the location of the main renal arteries as well as the presence of anomalous vessels arising from the body of the aneurysm or from other sites such as the fliac arteries. IVP must be performed in all patients to delineate the course of the ureters and to determine whether or not caliceal tissue is contained within the isthmus. The latter is a rare finding 1 but impacts the operative plan if division of the isthmus is contemplated. Other diagnostic evaluations such as ultrasonography and renal scanning may be used as indicated in individual patients, but we have found them to be of limited value. With the advent of modern duplex techniques, however, ultrasonography is likely to be a more effective tool for the identification of aberrant renal arteries. The second issue of importance with regard to the management of coexistent aortic disease and horseshoe kidney concerns the preferred operative strategy; specifically, whether the retroperitoneal or transperitoneal approach represents the optimal means of access. The ideal operative ap-
Vol. 9, No. 1 1995
proach should have the following characteristics: (1) allow performance of the aortic (and iliac) repair with the best possible access to these structures, (2) afford the best opportunity to identify and preserve anomalous renal arterial vessels including those not seen on preoperative arteriography, (3) minimize the possibility of injury to functioning renal parenchyma, and (4) minimize the possibility of collecting system injury. With regard to exposure of the aorta and anomalous renal arteries, the transperitoneal approach is clearly optimal, particularly w h e n right iliac artery disease is present or when the indication for surgery is occlusive disease. The isthmus is readily mobilized away from the anterior surface of the aorta and the graft is placed underneath it. The search for anomalous renal arteries is facilitated by the direct visualization afforded by the anterior approach because of the highly variable nature of these vessels. For this reason identification of these vessels may be seriously jeopardized by the retroperitoneal approach; unlike the visceral vessels in the repair of a thoracoabdominal aneurysm, the anomalous renal arteries in a patient with horseshoe kidney are small, unpredictably located, and exhibit minimal backbleeding because of intra-aortic thrombus and lack of collateral blood flow. If additional exposure is required, medial visceral rotation can be employed. The retroperitoneal approach has been advocated by other authors 6 because it permits the surgeon to leave the isthmus intact in virtually all cases. At issue is whether the avoidance of isthmus division is an important goal in and of itself. If division of the isthmus is not associated with alterations in postoperative renal function or injury to the caliceal system, then adherence to this goal at the expense of improved operative exposure of the iliac and accessory renal vessels m a y be detrimental. In our experience division of the renal isthmus was not associated with loss of renal function, nor was preservation of the isthmus associated with normal postoperative renal function. Others have also reported on the safety of isthmus division. 2"3"~'79 The risks of postoperative renal failure and urinary fistula are cited as the primary argument against isthmus division, ~ but neither of these eventualities has been documented in the literature. 2"3's'7 We therefore advocate the transperitoneal approach in the majority of patients because it allows for optimal achievement of the goals of operative management with-
Management of coexistent aortic disease and horseshoe kidney
127
out jeopardizing the functional integrity of the horseshoe kidney. It must be recognized, however, that the presence of certain u n c o m m o n conditions may favor the use of the retroperitoneal approach. These include the presence of a "hostile" abdomen, pancake kidney, and thoracoabdominal aneurysm. In addition, if IVP demonstrates caliceal tissue within the isthmus, and the necessity for isthmus division is anticipated, the retroperitoneal approach should be considered. Based on these principles of management we have developed a strategy of operative management. Preoperatively all patients undergo abdominal CT scanning; this is usually w h e n the horseshoe kidney is identified. Once the diagnosis is made, arteriography and IVP are performed in all patients. The preferred operative approach is transperitoneal with rare exceptions. At operation the isthmus is mobilized off the anterior surface of the aorta, affording exposure of accessory branches to the isthmus and renal masses at this level. Care must be taken to reimplant all vessels supplying the kidney including small accessory vessels, inasmuch as the distribution of renal parenchyma supplied is unpredictable and ligation may result in necrosis of significant portions of the kidney. In addition, it is imperative that the surgeon search for arterial anomalies not identified on the arteriogram; in our experience and in that of other investigators, arteriography fails to detect these anomalies in 40% to 60% of cases. 2-4a~ The ureters are similarly identified and preserved. Aortic reconstruction is performed with intravenous infusion of mannitol prior to interruption of any renal blood flow. After completion of the proximal anatomosis, the anomalous renal arterial supply is reconstructed, usually by reimplantation using a button of aortic tissue. The distal anastomoses are completed and renal revascularizations are evaluated using Doppler imaging.
CONCLUSION The presence of horseshoe kidney in patients with aortic disease requiring operative intervention is best detected by means of CT scanning. In patients with occlusive disease the use of preoperative CT scans is not routine and the diagnosis may be missed. After the diagnosis of horseshoe kidney is made, preoperative arteriography and IVP are mandatory to delineate the anatomy of the
128
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arterial supply and collecting system, respectively. Arteriography, however, fails to identify anomalous circulation in a significant number of patients and the transperitoneal approach usually affords the best opportunity to recognize these vessels intraoperatively. With careful preoperative evaluation and preparation the isthmus can be divided with no adverse effects on renal function in the majority of patients.
REFERENCES 1. Bauer SB, Perlmutter AD, Retik AB. Anomalies of the upper urinary tract. In Walsh PC, ed. Campbell's Urology, 6th ed. Philadelphia: WB Saunders, 1992, pp 1357-1442. 2. Crawford ES, Coselli JS, Hazim JS, et al. The impact of renal fusion and ectopia on aortic surgery. J Vasc Surg 1988;8:375383.
Annals of Vascular Surgery
3. Sidell PM, Pairolero PC, Payne WS, et al. Horseshoe kidney associated with surgery of the abdominal aorta. Mayo Clin Proc 1979;54:97-103. 4. Bietz DS, Merendino KA. Abdominal aneurysm and horseshoe kidney: A review. Ann Surg 1975;181:333-341. 5. Connelly TL, McKinnon W, Smith RB III, et al. Abdominal aortic surgery and horseshoe kidney. Arch Surg 1980;115: 1459-1463. 6. O'Hara P J, Hakaim AG, Hertzer NR, et al. Surgical management of aortic aneurysm and coexistent horseshoe kidney: Review of a 31-year experience. J Vasc Surg 1993;17:940-947. 7. Tapper SS, Martin RS III, Edwards WH, et al. Ruptured abdominal aortic aneurysm and horseshoe kidney. South Med J 1990;83:224-226. 8. Scott R Jr, DeBakey ME, Mani P. Surgical correction of abdominal aortic disease in 8 patients with horseshoe kidney. J Urol 1969;102:21-26. 9. Starr DS, Foster WJ, Morris GC Jr. Resection of abdominal aortic aneurysm in the presence of horseshoe kidney. Surgery 1981;89:387-389. I0. Ezzet F, Dorazio R, Herzberg R. Horseshoe and pelvic kidneys associated with abdominal aortic aneurysms. Am J Surg 1977; 134:196-198.