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Keywords:

  • Aorta;
  • kidney;
  • midaortic syndrome;
  • middle aortic syndrome;
  • renovascular hypertension;
  • transplantation

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Case Report
  5. Discussion
  6. Disclosure
  7. References

Midaortic syndrome (MAS) is a rare condition characterized by stenosis of the aorta and often involving renal and visceral arteries. Current therapies include medical management of associated hypertension, and interventional procedures such as angioplasty or surgical bypass. We report a 2-year-old female with severe MAS who was initially treated with angioplasty and stents in both her aorta and superior mesenteric artery (SMA). Due to the presence of long segment stenoses, her renal arteries were not amenable to surgical reconstruction and she rapidly progressed to Stage V chronic kidney disease. The patient underwent bilateral nephrectomy and renal transplantation using a donor thoracoabdominal aorta allograft to provide inflow for the kidney as well as to bypass the nearly occluded aorta. The donor SMA was used to bypass the native SMA stenosis. Postoperatively, the patient had normalization of four limb blood pressures. She weaned from five anti-hypertensive agents to monotherapy with excellent renal function. This is the first reported case of thoracoabdominal aortic bypass using allograft aorta to address MAS. This approach allowed for successful kidney transplantation with revascularization of the mesenteric, and distal aortic circulation using allograft conduit that will grow with the child, obviating the need for repeated interventional or surgical procedures.


Abbreviations
MAS

midaortic syndrome

SMA

superior mesenteric artery

Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Case Report
  5. Discussion
  6. Disclosure
  7. References

Midaortic syndrome (MAS) is a rare entity characterized by stenosis of the lower thoracic and/or abdominal aorta. Most patients present in childhood with severe hypertension related to associated renal artery stenosis. At the time of presentation, renal function may be quite variable. Visceral arteries may be involved and result in feeding intolerance or rarely intestinal ischemia. The majority of MAS cases are idiopathic. Other etiologies of MAS include inflammatory aortitis, Williams syndrome, neurofibromatosis, fibromuscular dysplasia and atherosclerosis. Long-term hypertension in children may lead to renal insufficiency, left ventricular hypertrophy and heart failure. Current treatments for MAS include aggressive hypertension management, percutaneous angioplasty and stent placement, as well as patch aortoplasty or surgical bypass using synthetic grafts. The use of synthetic grafts is most reasonable in those children who have nearly completed their major growth spurt. However, the need for future growth in small children makes the use of stents or synthetic grafts suboptimal in this patient population. In this case report we demonstrate the feasibility of using an aortic allograft to perform a thoracoabdominal bypass while also performing a renal transplant and mesenteric arterial bypass. This approach offers a novel strategy to treat small children with severe forms of MAS.

Case Report

  1. Top of page
  2. Abstract
  3. Introduction
  4. Case Report
  5. Discussion
  6. Disclosure
  7. References

The patient is a female born at 32 1/7 weeks gestation with a birth weight of 1512 g at an outside institution. She was admitted to the neonatal intensive care unit and found to be hypertensive by day-of-life (DOL) 1 with systolic blood pressures in the 90–100 mmHg range. She was started on hydralazine and enalapril by DOL 4. By DOL 6 she developed acute kidney injury, with oliguria and elevated serum creatinine. Nuclear medicine renal scan (MAG-3) demonstrated minimal uptake in the left kidney and no uptake in the right kidney. By DOL 14, the patient had a serum creatinine of approximately 6 mg/dL and was initiated on peritoneal dialysis. Echocardiogram revealed left and right ventricular hypertrophy. Ultrasound and magnetic resonance angiogram demonstrated abdominal aortic stenosis below the origin of the superior mesenteric artery (SMA) with poorly defined renal artery anatomy. Eventually her renal function improved enough to allow discontinuation of peritoneal dialysis on DOL 57. She continued to have severely compromised renal function with a serum creatinine of 2.0 mg/dL (estimated GFR ∼ 10 mL/min 1.73 m2 as calculated using the original Schwarz formula). The patient was then transferred to our medical center for further management. At the time of presentation, she was on propranolol, clonidine, isradipine, and furosemide for blood pressure control.

Percutaneous interventions

At 3 months of age, right heart catheterization revealed good systolic and diastolic function and an aortogram revealed a 10–15 mmHg gradient between her transverse aortic arch and the abdominal aorta at the level of the iliac bifurcation. The origins of the renal arteries were occluded and were reconstituted via collateral vessels originating from the celiac and SMA trunks. The celiac trunk itself was stenotic with a 50 mmHg gradient. The origin of the SMA was also severely narrowed. At this time the celiac trunk was balloon dilated with the aim of improving renal perfusion. The patient underwent five subsequent catheterization procedures (Table 1) with repeat dilatation and stenting of either the aorta or the SMA (Figure 1). During this period, the patient demonstrated intermittent feeding intolerance that would resolve following SMA dilation. She also experienced escalating blood pressure and diminished renal function during periods of SMA re-stenosis, both of which would also improve following SMA dilation.

Table 1. Summary of percutaneous vascular interventions
AgeFindingsIntervention
6 monthsSMA near occlusion, R iliac artery occlusionSMA dilatation
9 monthsRe-occlusion of SMA. Mid aortic severe narrowing1. SMA stent
  2. Aortic stent from above celiac to SMA take-off
14 months30 mmHg gradient across thoracic and abdominal aorta, occlusion of celiac trunk, SMA and aortic re-stenosisBalloon dilation of SMA origin and previously stented aortic segment
20 monthsRe-stenosis of abdominal aorta and SMABalloon dilation of SMA origin and previously stented aortic segment
24 monthsSMA re-stenosisBalloon dilation of SMA stent
27 monthsSMA obstructionBalloon dilation of SMA stent
image

Figure 1. Aortogram at the time of the fourth percutaneous intervention. Note the presence of stents in the aorta and the origin of SMA. Renal arteries and the celiac trunk are not visible due to occlusion at their origins. (SMA, short arrow; aorta, long arrow.)

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Despite the numerous percutaneous interventions, the patient continued to have severe hypertension with systolic blood pressures fluctuating between 100 and 180 mmHg. She required escalation in her antihypertension regimen, eventually requiring five medications (minoxidil 2.75 mg BID, isradipine 1.75 mg BID, clonidine 12.5 mcg TID, hydralazine 1 mg TID and propranolol 20 mg TID). The patient had a persistently diminished GFR with serum creatinine in the 1.8–2.3 mg/dL range. Given the medically refractory hypertension, persistent severe renal insufficiency, and increasing feeding intolerance the patient was referred for surgical management at 20 months of age.

Surgical approach

In considering the surgical management of this patient, the following issues needed to be addressed: (i) renovascular hypertension, (ii) abdominal aortic stenosis, (iii) SMA stenosis, (iv) celiac stenosis, (v) Stage V CKD. Since surgical renal salvage was not possible due to the presence of severe bilateral long segment stenoses, renal transplantation was deemed the best long-term option. Unfortunately, arterial inflow for the transplant via the distal aorta was not an option due to the severe aortic stenosis that had been unresponsive to repeated dilation and stenting. Therefore, an abdominal aortic bypass was proposed to provide adequate inflow for the renal allograft. Our experience with the use of donor thoracoabdominal aortic grafts as conduits for multivisceral transplantation prompted us to consider using the donor aorta as a bypass conduit at the time of transplant.

The patient was evaluated and listed for renal transplant. An appropriate size matched and blood group identical donor was identified after over 4 months on the waitlist. The donor was a 5-year old, 25 kg female who progressed to brain death following a motor vehicle accident. The right kidney was procured en bloc with the aorta from the level of the arch to the iliac bifurcation. The aortic segment also included about 5 cm of proximal SMA. The right renal vein and ureter were procured with the kidney in the standard fashion. The entire recipient operation was performed through an upper abdominal transverse laparotomy. Bilateral native nephrectomies were performed. The donor thoracic aorta was divided just above the celiac trunk for use as a free graft. After exposure of the recipient distal thoracic aorta via the diaphragmatic hiatus, the donor thoracic aorta was anastomosed in an end-to-side fashion to the recipient aorta above the level of the superior stent that was above the level of the celiac artery (Figure 2). The thoracic donor aortic graft was then tunneled posterior to the stomach, anterior to the pancreas, and through the transverse mesocolon to the left of midline. The kidney and en-bloc aorta-SMA graft were brought up to the table and the donor renal vein was anastomosed to the inferior vena cava. The supraceliac donor abdominal aorta was then anastomosed to the newly implanted donor thoracic graft supplying adequate inflow for the renal graft. The kidney was reperfused prior to using the distal donor abdominal aorta to complete the aorto-aortic bypass. We elected to perform an end-to-side anastomosis of the graft to the native aorta in order to minimize the risk of severe ischemia in case of graft thrombosis as well as to preserve as much of the spinal cord blood supply as possible. The donor SMA, which remained in continuity with the donor aortic graft, was used to bypass the stented segment of the recipient SMA (Figures 3 and 4). Cold ischemia time was 13 h and 14 min and the renal warm ischemia time was 23 min.

image

Figure 2. Coronal and sagittal CT of the abdomen demonstrating the positions of the aortic and SMA stents.

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image

Figure 3. Intraoperative photo depicting the aortic allograft (*), kidney allograft (K) and the donor SMA (arrow) following completion of anastomoses.

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image

Figure 4. Illustration depicting aorto-aortic bypass, renal transplantation, and SMA bypass. Aortic stents are also depicted at the origins of the celiac and SMA trunks.

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Postoperatively, the patient had excellent renal allograft function with a decline in serum creatinine to 0.2 mg/dL. Immunosuppression included daclizumab and methylprednisone intraoperatively and maintenance tacrolimus (serum trough 10–12 ng/mL) and mycophenolate mofetil. Her feeding intolerance resolved by 2 weeks following transplant. At the time of discharge, her hypertension was well controlled on amlodipine 1 mg twice daily. On follow-up CT scan 6 months following transplant her SMA bypass was found to be occluded but the distal SMA was well perfused via inferior mesenteric artery collaterals. At 18-month follow-up, she continued to be normotensive on low dose amplodipine that we use routinely for renal protection in the setting of calcineurin inhibitor therapy. She continues to have satisfactory renal graft function with a serum creatinine of 0.8 mg/dL.

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Case Report
  5. Discussion
  6. Disclosure
  7. References

MAS is generally a disease of the young with a mean age at presentation of 14.3 years with no gender predilection [1]. Abdominal aortic coarctation accounts for 0.5–2% of all reported cases of aortic coarctation [2, 3]. In MAS, the narrowed segment most often involves the mesenteric and renal segments of the aorta [4]. Diffuse involvement of the aorta is seen in 12% of cases and the suprarenal region is affected in 11% of cases [4]. Renal artery involvement is seen in over 90% of cases of MAS. Renovascular hypertension is the most common presenting symptom of this syndrome. Severe neonatal cases have been described that are associated with significant morbidity and mortality [5, 6]. Medical management is directed at controlling hypertension, which if untreated can lead to hypertensive encephalopathy [7] or heart failure. Involvement of the SMA and celiac artery is seen in about one-third of the patients but the inferior mesenteric artery is rarely involved. The presence of intestinal angina is not very common [8]. The majority of patients will eventually require surgical intervention in order to treat refractory hypertension and improve renal, intestinal and lower extremity perfusion. In one review [1], surgical treatment included aorto-aortic bypass in the majority of patients (64%) with 40% undergoing renal revascularization as well. Aortic bypass was performed using synthetic grafts. Isolated renal vascularization was performed in only 15% and patch aortoplasty was used in 10% of cases.

Our patient had an unusually early presentation at DOL 1. The youngest previously reported patient with MAS presented at 19 days of age. She was found to have stenosis of the suprarenal and inter-renal segments of her aorta. She also had diffuse involvement of the renal arteries bilaterally as well as the orifices of both the celiac and SMA arteries. The renal arteries were not amenable to reconstruction or bypass and renal transplantation was indicated given her renal function. The use of PTFE or other synthetic graft material for the surgical treatment of MAS in adolescents and adults has been the standard approach [9-11]. However, the use of synthetic graft material in very young children is not ideal due to the lack of growth potential of the graft which will usually require future procedures to revise or lengthen the conduit as the child grows. If clinically feasible, many surgeons prefer waiting until children have nearly completed the majority of their linear growth before proceeding with surgical intervention [1, 12]. Percutaneous vascular dilation and stent placement has been utilized as an important strategy to dilate and maintain patency of the affected vessels. This can provide a bridge to definitive surgery, however, the surveillance and maintenance of stent patency usually requires numerous interventions.

Simultaneous kidney transplantation and vascular reconstruction has been previously reported in adult patients with aortic aneurysms or aorto-iliac occlusive disease [13]. In these cases, fresh aortic allograft was procured from the kidney donor and used to replace the recipient diseased vessels. Follow-up of up to 116 months demonstrated no evidence of allograft degeneration, aneurysm, or thrombosis. Based on published reports [14] as well as our own experience with using aortic grafts for multivisceral transplants, we do not anticipate a high likelihood of isolated rejection of the aortic conduit in this patient. However, we will continue to monitor the growth and the luminal diameter of the graft with periodic imaging studies.

We believe this is the first reported case of using fresh donor allograft aorta for aortic and SMA bypass in conjunction with renal transplantation for the surgical treatment of MAS. This approach may obviate the need for future procedures that are usually needed when prosthetic materials are used in growing children. Long-term follow-up will be necessary to determine if growth of the donor allograft aorta will match the growth of the recipient sufficiently to avoid the need for future graft revision. Since immunosuppression is necessary when fresh allograft vessels are used, this approach should only be considered in situations where the patient already requires an organ transplant.

Disclosure

  1. Top of page
  2. Abstract
  3. Introduction
  4. Case Report
  5. Discussion
  6. Disclosure
  7. References

The authors of this manuscript have no conflicts of interest to disclose as described by the American Journal of Transplantation.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Case Report
  5. Discussion
  6. Disclosure
  7. References