INTERVENTIONAL PEDIATRIC CARDIOLOGY

Endovascular Stent Placement for Management of Total Renal Artery Occlusion in a Child

Chi Di Liang, MD, *Chiung Jen Wu, MD, *Chih Yuan Fang, MD, **Sheung Fat Ko, MD
Chi Di Liang, MD, *Chiung Jen Wu, MD, *Chih Yuan Fang, MD, **Sheung Fat Ko, MD
Percutaneous transluminal angioplasty (PTA) has been recognized as a safe, simple and effective alternative to operation for the management of renal artery stenosis (RAS). However, major complications such as complete arterial occlusion and renal parenchymal perforation may ensue and usually require surgical intervention.1 In this report, we present a case of total renal artery occlusion as a complication of previous PTA in an 8-year-old boy. After a successful balloon angioplasty and stent implantation, his renal artery was kept patent. To the best of our knowledge, this is the first pediatric case of total renal artery occlusion after unsuccessful PTA, followed by successful revascularization by PTA and stent implantation. Case Report. An 8-year-old boy was referred to our hospital due to intractable hypertension. A diagnosis of renovascular hypertension due to left RAS (Figure 1) was made at another institution 3 months earlier. PTA was performed to dilate the stenosis, but failed; hypertension persisted after the procedure. He was treated with angiotensin-converting enzyme inhibitor with poor response. On admission, the patient’s blood pressure was 210/140 mmHg. The pulse was symmetric between upper and lower extremities. His renal function was normal. A chest radiograph demonstrated cardiomegaly and prominent aorta. An electrocardiogram showed left ventricular hypertrophy with ST-T changes. Echocardiography revealed hypertrophy of the interventricular septum and left ventricular free wall. Renal ultrasonography demonstrated a size discrepancy between the right and left kidneys (right, 10.9 x 4.6 cm; left, 8.1 x 4.3 cm). The proximal left renal artery was not visualized. PTA was planned and a standard percutaneous femoral artery approach was used. The aortography demonstrated total occlusion of the left renal artery and a collateral artery arising from the descending aorta to supply the superior pole of the kidney (Figure 2). After localizing the occluded area, a floppy-tip, 0.014´´ coronary guidewire (ACS, Guidant Corporation, Santa Clara, California) was pushed through and traversed the point of narrowing. A 3.5 mm balloon catheter (Boston Scientific/Scimed, Inc., Maple Grove, Minnesota) was used to dilate the stenosis, but the lesion was too tough to dilate under low pressures (3–4 atmospheres). When high pressures (16–18 atmospheres) were applied, the balloons ruptured twice. Therefore, we used rotational atherectomy followed by insertion of a cutting balloon catheter (InterVentional Technologies (IVT) Europe Ltd., Letterkenny, County Donegal, Republic of Ireland) to try to break and dilate the lesion. Subsequently, a 4 mm balloon catheter (Boston Scientific/Scimed, Inc.) was inserted and dilatation was again performed, but the stenosis was still present (Figure 3). Further dilatation with a 4.5 mm balloon (Schneider, Bülach, Switzerland) was performed until disappearance of the waist was attained. Finally, after detailed discussion with vascular surgeons and pediatricians, it was decided to deploy a 20-mm long, 6-mm wide Wallstent (Boston Scientific/Scimed, Inc.) vascular stent via an 8 French endovascular sheath in order to prevent elastic recoil after balloon dilatation. During the procedure, 4,000 units of intravenous heparin were administered. There was no pressure gradient across the stenosis after stent placement, although there was minimal residual stenosis. Repeat angiography demonstrated that the stent was in the correct position and completely expanded. However, there was mild intimal dissection of the renal artery (Figure 4). The patient was discharged one day after the procedure and received ticlopidine 250 mg/day for 2 weeks and aspirin 100 mg/day for 3 months. The blood pressure returned to 110/80 mmHg 3 months later. The electrocardiogram demonstrated normal sinus rhythm without ST-T changes; chest radiograph revealed regression of cardiomegaly and echocardiography revealed no hypertrophy of left ventricle at the 6-month follow-up exam. Hypertension has not recurred since, and the patient has remained free of symptoms for 12 months without medication. Discussion. Potential complications from PTA include vascular rupture from an oversized balloon, perforation of renal artery from the guidewire or catheter tip, and complete obstruction of the main renal artery after balloon dilatation. In the past, emergency surgery with nephrectomy was inevitable if complications occurred. In this case, although the renal artery was totally occluded, it still had the chance to be recanalized by a successful PTA. PTA is increasingly performed to dilate coronary artery occlusions in an effort to minimize infarction. Application of PTA in dilating renal artery occlusion is relatively rare.2,3 In kidney transplant recipients, total renal artery occlusion is not uncommon.4,5 However, total renal artery occlusion as a complication of PTA is rare.6 In this case, the collateral artery probably kept the kidney viable; thus, an elective PTA could be performed 3 months later. Since the hypertension was complicated by post-PTA renal artery occlusion and was intractable to angiotensin-converting enzyme inhibitor, PTA and stent placement might be a suitable therapeutic alternative in this patient. However, if the occluded renal artery cannot be recanalized by PTA, surgical revascularization or nephrectomy is inevitable. In this case, two major problems were encountered. First, it was very difficult to advance the balloon angioplasty catheter across the stenotic lumen. Second, the balloon catheter could not be inflated initially since the stenosis was very resistant. Before rotational atherectomy, the balloon catheters ruptured twice at high pressure. The stenosis showed elastic recoil and had waist appearance under subsequent angioplasty, which indicated that the stenosis was very tough. Therefore, sequential cutting balloon and stent implantation were required. A mild renal artery intimal dissection was observed immediately after stent implantation; this may have been due to vessel damage by previous PTA or by the cutting balloon. Renal angiography follow-up is mandatory in this patient. When technically feasible, PTA is usually the first choice in RAS. However, not all patients with RAS are good candidates for PTA, such as those with bilateral atheromatous stenosis, neurofibromatosis, stenosis at the ostium of the renal artery, or long-segment stenosis.6,7 In addition, there are two major unfavorable consequences of PTA. The first is marked arterial elastic recoil or arterial dissection. The second is restenosis. Percutaneously introduced vascular stents can improve the long-term results of angioplasty. Stent implantation has been safely and effectively applied for native renal artery stenosis after inadequate angioplasty or ineffective endarterectomy, and for ostial lesions of native renal arteries with nearly complete success.8,9 Vascular endoprostheses have gained clinical acceptance in the treatment of arterial occlusive disease.8–10 Percutaneous endoluminal stent procedures after resistant transplant renal artery stenosis or for ex novo treatment for severe anastomotic stenoses appear to be promising. The indications for stent placement were elastic recoil or dissection of the renal artery after angioplasty, or restenosis after initially successful balloon angioplasty.10 The advantages of the Wallstent are its longitudinal flexibility, inherent pliability, a low occlusion rate, and the characteristic of self-expansion.11 Stent placement provides effective nonoperative management of flow-compromising dissections induced by PTA, leading to reclosure. Long-term results with the stent were good; however, 11% of patients had stent restenosis.10 The restenosis is probably caused by myointimal proliferation, layered fibrin, organized thrombus, inaccurate positioning or underexpansion of the stent.9 In this case, the final outcome of the procedure was remarkable, and adequate renal arterial diameter and flow were attained. The patient’s blood pressure returned to normal within 3 months and he did not require further antihypertensive medication. In conclusion, endovascular stent placement for management of renal artery occlusion is effective. In our patient, the combination of balloon angioplasty and stent placement allowed reestablishment of perfusion and salvage of a severely threatened kidney. The favorable early and mid-term results suggest that repeat PTA and stent placement are effective treatments for total renal artery occlusion after prior unsuccessful balloon angioplasty.
References
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