Renal anomalies in aortic surgery: Contemporary results

Renal anomalies in aortic surgery: Contemporary results GianLuca Faggioli, MD, Antonio Freyrie, MD, Alessandro Pilato, MD, Monica Ferri, MD, Tiziano Curti, MD, Oreste Paragona, MD, and Massimo D’Addato, MD, Bologna, Italy

Objective. The purpose of this study was to evaluate technical problems and results of surgical treatment of aortic disease associated with major renal anomalies. Study design. Renal anomalies observed during aortic procedures performed over a 19-year period were reviewed. Type of renal anomaly, diagnostic procedures, preoperative renal function, technique of vascular reconstruction, and management of the anomalous kidney were considered and correlated with perioperative and long-term results. Results. Eighteen patients (1.1%) with major renal abnormalities were found in our experience with more than 1650 aortic procedures. Of these, 10 involved horseshoe kidneys and 8 ectopic kidneys (3 pelvic, 3 lumbar, and 2 crossed ectopias). All elective cases were evaluated with computed tomography, urography, and angiography. Aortic reconstruction was performed in 17 patients for aortic aneurysm (1 urgent repair for rupture) and in 1 patient for obstructive disease. Surgical access was anterior transperitoneal in 16 patients and retroperitoneal/thoracoabdominal in 2. In 8 patients, reimplantation of 1 or both renal arteries was necessary. Division of the renal isthmus was necessary in 3 patients with horseshoe kidney. The perioperative mortality rate was 0%. Renal function was normal at discharge in all patients. At long-term follow-up (median, 5 years; range, 1 to 19 years) neither renal nor aortic complications were detected. In 15 of 17 patients, the aneurysm was confined to the abdominal aorta. Conclusion. Although infrequent, renal anomalies encountered during aortic surgery can be effectively treated with accurate diagnosis and preoperative planning. (Surgery 2003;133:641-6.) From the Department of Vascular Surgery, University of Bologna, Italy

RENAL ANOMALIES ENCOUNTERED in aortic surgery lead to specific technical problems. Several congenital abnormalities are described in the literature and can all be stratified in 2 categories: the horseshoe kidney and the ectopic kidney. Horseshoe kidney is the most frequent anomaly and occurs in 0.1% to 0.25% of aortic operations. It is characterized by medial fusion of the 2 kidneys anteriorly or occasionally posteriorly to the aorta.1-4 The isthmus may be simple fibrotic tissue or, less frequently, highly vascularized renal parenchyma5 (Fig 1). Each renal body usually has its own collecting system, with the ureter on the appropriate side. In some instances, the fusion is not limited to the isthmus but involves the 2 kidneys totally, resulting in a single renal mass with variable dimension and shape, usually located in front of the aorta (disc, pancake, or shield kidney).6 Ectopic kidney is a less frequent anomaly (0.2% to 0.03%),1,7,8 with variable locations, as Accepted for publication February 16, 2003. Reprint requests: Dr GianLuca Faggioli, Department of Vascular Surgery, University of Bologna, Policlinico S. Orsola, Via Massarenti 9, 40138 Bologna, Italy. © 2003 Mosby Inc. All rights reserved. 0039-6060/2003/$30.00 + 0 doi:10.1067/msy.2003.156

reported in the Table (Figs 2 and 3). Although it is usually unilateral, bilateral ectopia has also been described.9 Crawford et al10 reported a single case of ectopic kidney over 17 renal anomalies encountered during aortic surgery. In ectopic kidneys, the fusion phenomena of the horseshoe kidneys is not present.11-15 Renal anomalies are usually asymptomatic with a normal renal function. However, their occurrence in patients undergoing aortic reconstruction leads to particular technical problems because of the variety of possible arterial, venous, and renal malformations. We therefore reviewed our experience with the open approach to such patients with the aim of providing a contemporary standard for operative results. METHODS All patients with renal anomalies associated with abdominal aortic aneurysm or obstructive disease treated surgically since 1981 were retrospectively evaluated. For each patient, the usual epidemiologic data (gender, age, race, risk factors for atherosclerosis), type of renal anomaly, type of aortic disease (aneurysm versus obstructive disease), and preoperative renal function were catalogued. The intraoperative data taken into consideration included: type SURGERY 641

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Fig 1. Angiography (A) and artist interpretation (B) of abdominal aortic aneurysm with horseshoe kidney, with parenchimatous isthmus fed by isthmic artery.

Table. Classification of renal ectopia (modified from Hollis et al 11) Type

Location

Pelvic

Opposite sacrum, distal to aortic bifurcation In iliac fossa, opposite sacral promontory Above iliac crest, adjacent to L2 vertebra Below diaphragm, near T10 vertebra Total or partial location in chest, above diaphragm Ectopic kidney located on opposite side from its ureteral insertion 1. With fusion 2. Without fusion 3. Solitary crossed ectopia 4. Bilaterally crossed ectopia

Lumbar Abdominal Cephalad Thoracic Crossed ectopia

of surgical access (anterior versus retroperitoneal), correlation of intraoperative findings with diagnostic images, fate of the renal isthmus when present, reimplantation of renal arteries, and perioperative mortality and morbidity. RESULTS In the period of the study, 17 men and 1 woman, – ± standard deviation) of 67 ± 6 years, with an age(x with renal anomalies associated with aortic disease

were surgically treated. Renal anomalies were diagnosed before surgery, with both angiography and computed tomography, in all patients but 1, in whom repair of a ruptured aneurysm was performed emergently. Surgical technique was tailored on the basis of the specific anatomy encountered; the surgical approach was anterior transabdominal in 16 patients and retroperitoneal/thoracoabdominal in 2. The latter cases were type IV thoracoabdominal aneurysms. Ten patients had a horseshoe kidney, and 8 an ectopic kidney. In the latter group, there were 3 ectopic pelvic kidneys, 3 ectopic lumbar kidneys, and 2 crossed renal ectopias (with one “L” kidney; Fig 4). Surgical technique: horseshoe kidney (10 patients). The approach was anterior transabdominal in 9 cases and thoracoabdominal/retroperitoneal in 1 case with a type IV thoracoabdominal aneurysm according to Crawford’s classification. As assessed with contrast enhanced computed tomography and intraoperative inspection, the isthmus was fibrotic in 6 patients; in 3 of the patients, it was divided because grafting was not otherwise possible despite wide mobilization of the isthmus itself. In 4 patients, the isthmus was vascularized by an isthmic artery emerging anteriorly form the aorta below the neck of the aneurysm. This artery was reimplanted in the aortic graft in all but 1 case, in which the origin of the artery was at the level of the aortic bifurcation and remained distal to the distal aortic anastomosis.

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Fig 2. Angiography (A) and artist interpretation (B) of abdominal aortic aneurysm with ectopic lumbar kidney, with renal arteries originating from aortic bifurcation and right common iliac artery.

Fig 3. Angiography (A) and artist interpretation (B) of abdominal aortic aneurysm with crossed renal ectopia. Kidney fed by right renal artery is located on left, below left kidney.

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these 2 patients. Renal function was normal at discharge in all 18 patients. Therefore, dialysis was not necessary in any patient. The perioperative mortality rate was 0%. Late follow-up, carried on at yearly intervals, revealed no complications at a median of 5 years (range, 1 to 19 years).

Fig 4. Artist interpretation of abdominal aortic aneurysm with crossed renal ectopia. Two kidneys are fused together and are in part in front of aorta, with characteristic “L” shape.

Surgical technique: pelvic kidney (8 patients). The approach was anterior transabdominal in 7 patients and thoracoabdominal/retroperitoneal in 1 patient with a type IV thoracoabdominal aneurysm. The ectopic renal artery was reimplanted into the graft in 5 cases (with associated endarterectomy in 1), and in the other 3, its origin was distal to the site of the distal anastomosis. Although reimplantation was unnecessary in these 3 patients, in 2 the origin of the artery was stenotic and therefore endarterectomized. Perioperative results. Intraoperative perfusion with cold Ringer’s solution of 1 or more renal or accessory renal arteries was performed in 6 patients. In all other patients, the cross-clamp time was less than 40 minutes and no renal protection system was used. In the latter group, renal function temporarily worsened in 2 patients, with creatinine levels up to 2 mg/dL and 1.9 mg/dL. Renal clamping time was respectively 38 and 36 minutes in

DISCUSSION Surgical indications for aortic reconstruction for aneurysm depend on parameters such as aneurysm diameter, patient age, and comorbidities. In general, renal anomalies do not preclude aortic surgery, although they require special preparation and alteration of operative approach. Preoperative computed tomography reliably detects renal anomalies. The horseshoe kidney and the ectopic kidney share the feature of an anomalous rotation during the ascent to the natural position. Normally, the kidney rotates inward and the collecting system ends up posterior to the vascular structures. With horseshoe and ectopic kidneys, several rotation anomalies instead may occur, leading to a final position of the collecting system anterior to the vessels or to the renal body. The degree of fusion, time of occurrence of the fusion itself, and degree of rotation determine the final shape of the kidney. The arterial system is anomalous in 80% of such patients.16,17 The possible anatomic variants are summarized in Table I. Horseshoe kidneys typically have multiple arteries arising form the aorta. In the ectopic kidney, the number of renal arteries is fewer; however, in 25%, major renal arteries arise from the iliac vessels.11,18 Anomalies of the venous system are also frequent and variable, with the possibility of accessory multiple veins. When a renal anomaly is suspected, angiography is mandatory to identify the vessels supplying the kidneys and the isthmus. Small branches or accessory renal arteries in anomalous positions may be misdiagnosed as other visceral or lumbar arteries. Late films after the arteriography should be obtained during the renal excretory phase to visualize the ureters and possible anomalies in their number and position.10 Surgical dissection should identify every arterial branch to the kidney. Despite this identical embriogenic pathogenesis, substantial differences exist in the surgical approach to aortic disease in the presence of horseshoe kidney or ectopic kidney. With horshesoe kidneys, the most important consideration is the surgical approach to the aorta, avoiding the renal isthmus and identifying the anomalous renal arteries, whereas with ectopic kidneys, the main consideration is protection of the kidney from ischemia.

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Horseshoe kidney. Surgical technique is tailored to preserve the integrity of the renal parenchyma as much as possible. The approach to the aorta can be anterior transperitoneal or retroperitoneal. Both ways are described in the literature, but traditionally the anterior approach is the most frequently used.19-22 The anterior was the approach of choice in our series because often the right iliac artery was diseased and needed reconstruction. However, we believe that when arterial disease is limited to the aorta the retroperitoneal approach would avoid problematic dissection of anomalous renal structures.23,24 Clearly, this is not an issue in thoracoabdominal aneurysms; when a thoracoabdominal exposure is needed, the retroperitoneal approach to the abdominal aorta remains the route of choice. To obtain adequate aortic exposure, the isthmus can be either divided or excised. In some instances, 1 of the 2 renal bodies has been excised together with the isthmus. When the isthmus is divided, urinary leakage may occur. This event is rarely reported in the literature and is never associated with a fibrous isthmus.22 Division of the fibrotic isthmus was performed in 3 of our patients to obtain optimal aortic exposure, and no complications occurred. In contrast, division of an isthmus composed of renal parenchima may result in hemorrhage, ischemia of the adjacent renal tissue, or damage to the excretory system. Fortunately, in many patients, division of the isthmus is not necessary because it is sufficient to mobilize it anteriorly to place the aortic graft behind it. According to Crawford et al,10 when the isthmus is particularly large or in the presence of a pancake kidney, the retroperitoneal approach, with mobilization of the renal mass and its excretory system toward the right, is particularly advantageous because this approach avoids venous and renal anomalies and the renal arteries can be identified from the inside of the aneurysmal sack. On the other hand, in the presence of a small isthmus or when the right iliac artery has to be reached, the anterior transabdominal approach is usually preferred. Ectopic kidney. Although different approaches such as medial visceral rotation have been described in selected patients, the surgical approach is usually the anterior transperitoneal approach, which allows optimal visualization and control of the ectopic renal arteries usually emerging from the iliacs. Protection of renal tissue from the ischemia during aortic clamping and the position of the aortic graft are the main issues in these cases. Several techniques have been described for this purpose. The simplest is use of furosemide or

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mannitol before suprarenal aortic clamping, with subsequent aortic reconstruction and no other protective procedures. The problem with this approach is the limited time available for aortic reconstruction because renal ischemia should not be extended more than 30 to 40 minutes. Therefore, this method is feasible only in those patients in whom aortic reconstruction is simple and straightforward.8 Some authors reported use of a temporary (Gotttype) shunt, which allows renal perfusion during aortic clamping. However, problems have been reported with embolization or iatrogenic lesions created during shunt placement or removal.25,26 Other authors suggest the use of a temporary axillofemoral bypass, which allows the retrograde perfusion of the kidney during aortic clamping; this technique allows renal protection but requires additional operative time for adjunctive inguinal and axillary exposures.27,28 For this reason, this technique and use of extracorporeal circulation have not been adopted by most vascular surgeons.29 In complex cases, where renal protection is anticipated, cold Ringer’s lactate can be infused in the anomalous branches. This method appears to allow sufficient time to achieve aortic reconstruction (up to 90 minutes) without any adjunctive risks and was the method of choice in our patients. All anomalous renal arteries originating from the diseased aorta should be reimplanted in the graft; this is usually quite easy, although O’Hara et al23 report patients in whom it is necessary to graft the renal vessels because of the inadequate length after removal of the aneurysm. In our series, grafting was not necessary after adequate dissection of the renal vessels. Small arterial branches can be ligated with few consequences; however, any vessel greater than 2 mm in diameter should be preserved.23 When the location of the different structures is particularly altered or when an inflammatory aneurysm is present, preoperative placement of ureteral stents may be useful to aid their identification during the surgical dissection of the aorta and its branches.6,10 Although perioperative mortality is usually higher in these patients compared with uncomplicated aortic reconstructions, in our series this was not the case. In Crawford et al’s10 and O’Hara et al’s23 series, the operative mortality rates were 12% (2/17) and 16% (3/19), respectively. In the latter, preoperative renal failure was predictive for higher operative mortality. Major complications occurred in 29% of patients in the series reported from the Mayo Clinic.24 We believe that modern preoperative and operative strategies allow results comparable with those of simple aortic reconstruction.

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We thank Dr John J Ricotta, SUNY at Stony Brook, NY, for his extensive support during the preparation of the manuscript.

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