Renal artery stent thrombosis as a complication of percutaneous renal artery revascularization and stent placement

Abstract

We present the case of a 46-year-old man with bilateral renal artery stenosis and a previous stent placed on the left renal artery who presented with a hypertensive emergency with flash pulmonary edema and acute-on-chronic renal failure. A renal angiogram revealed extensive thrombosis and in-stent restenosis, which were treated with thrombectomy, angioplasty, and stenting. Our case highlights the importance of careful patient selection for renal artery stenting and close monitoring post-stenting due to the risk of serious complications.

KEY POINTS

• Careful patient selection is essential for percutaneous transluminal renal angioplasty and stenting for renal artery stenosis, as the procedure benefits a limited subset of patients and has a risk of serious complications.

• After stenting, close follow-up is essential to ensure medication compliance and monitoring for the development of complications, and a high index of suspicion is needed to avoid a delay in diagnosis.

CME

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CASE SUMMARY

A 46-year-old man presented with left lower quadrant abdominal pain and vomiting. He had a history of recurrent hypertensive crises, smoking, chronic kidney disease, and bilateral renal artery stenosis (RAS). Nine months before the current presentation, he had been admitted to the hospital for acutely worsening renal failure and hypertensive urgency. His creatinine peaked at 5.6 mg/dL from a baseline around 2.0 mg/dL. At that time, he underwent a renal artery Doppler ultrasound, which was concerning for left RAS: the mid left renal artery velocity was 262 cm/s, and the left renal artery to aortic velocity ratio was 3.4. The resistive indices for the left renal artery were as follows: superior 0.4, mid 0.6, and inferior 0.7. The left kidney size was 11.2 cm and the right kidney was 9.4 cm. A renal angiogram showed total proximal occlusion of the right renal artery and 90% stenosis in the proximal segment of the left renal artery at the bifurcation of the upper and middle main branches, for which the patient underwent balloon angioplasty and placement of a bare metal stent with good effect (Figure 1a). After the procedure, his blood pressure improved and his creatinine down-trended to 3.70 mg/dL at the time of discharge. He was advised to continue dual antiplatelet therapy with aspirin and clopidogrel for 3 months, followed by aspirin monotherapy long term. He was advised to continue ambulatory blood pressure monitoring and repeat blood work as an outpatient, but unfortunately the patient was lost to follow up until his current presentation to the emergency department.

Figure 1.

Selective renal angiography. (a) The initial angioplasty and stenting of the left renal artery stenosis at the bifurcation of the upper and middle branches several months prior to the index hospitalization. (b) Angiography performed during the index hospitalization demonstrating ostial occlusion of the left renal artery with residual clot burden despite aspiration thrombectomy. (c) Angiography performed during the index hospitalization after the patient was maintained on anticoagulation, showing improved flow following anticoagulation and suboptimal expansion of in-stent restenosis treated with balloon angioplasty. The large polar artery to the superior portion of the left kidney was severely stenosed and likely occluded after angioplasty. The vessels’ origin can be seen faintly filling in panel C, the left image with poor anterograde flow; in the post angioplasty image on the right, there is no flow.

At the time of the current presentation, he reported that he had stopped taking his medications, including antihypertensives and aspirin, for the last 3 months. On admission, he was hypertensive to 218/146 mm Hg and hypoxemic, requiring supplemental oxygen. Physical examination revealed jugular venous distension, bibasilar lung crackles, and a mildly tender left lower abdomen. A chest radiograph showed bilateral pulmonary edema. A transthoracic echocardiogram was performed at this time and showed severe left ventricular hypertrophy with an interventricular septum diameter of 1.5 cm. The left ventricular ejection fraction was also reduced, in the range of 45% to 50% with diffuse hypokinesis. Doppler parameters were consistent with restrictive physiology, indicating decreased left ventricular diastolic compliance. The patient was treated with noninvasive positive pressure ventilation, continuous antihypertensive infusions, and diuretics with modest improvement. During the first 2 days of hospitalization, his blood pressure showed some improvement, and he was transitioned to oral antihypertensives. His creatinine, however, worsened from 2.9 mg/dL at presentation to 3.3 mg/dL in the first 2 days of hospitalization and further rose to 7.9 mg/dL on the fifth day of hospitalization, with sharply declining urine output, and renal artery restenosis was suspected.

Renal artery Doppler was performed; however, there was limited Doppler evaluation of the kidneys secondary to difficulty with breath-hold, and there was no evidence of elevated velocities. A renal angiography revealed flush occlusion of the left renal artery due to widespread thrombosis involving the main to distal branches with possible in-stent restenosis. Multiple rounds of aspiration thrombectomy were performed with the Penumbra device. Following this, the patient underwent percutaneous transluminal renal angioplasty (PTRA) followed by placement of a Synergy Megatron drug-eluting stent to the proximal-ostial left renal artery (Figure 1b, Supplement Video 1) due to concern for in-stent restenosis. The patient still had a large residual clot burden and required anticoagulation.

After the procedure, urine output improved, and creatinine decreased from 7.9 to 4.0 mg/dL. He required ultrafiltration for volume removal and eventually hemodialysis when creatinine did not improve further. At this point, it was considered if there was any function in the right kidney, and if right-sided revascularization should be performed. A Mag-3 renal scintigraphy study was performed, which showed split renal function—76% to the left kidney and 24% to the right kidney—suggestive of right renal atrophy. It was felt that revascularization of the right renal artery may not be associated with recovery. Given the patient’s young age, a recanalization was attempted; however, several attempts using glidewire and angled glide catheter were unsuccessful. A follow-up left renal angiogram revealed significantly reduced thrombus burden but showed suboptimal expansion of in-stent restenosis, which was treated with PTRA (Figure 1c, Supplement Videos 2 and 3). At the time of discharge, his creatinine was around 2.6 mg/dL, with an estimated glomerular filtration rate of 20 mL/min/1.73 m². After this, the patient required outpatient hemodialysis for 2 months, and his renal function improved significantly, with baseline creatinine around 2.5 to 3.0 mg/dL and an estimated glomerular filtration rate of about 30 mL/min/1.73 m². Subsequently, he was taken off hemodialysis with return of kidney function.

CLINICAL QUESTIONS

1. Which of the following is/are absolute contraindications for the use of angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) as antihypertensives?

   1. Unilateral RAS

   2. Bilateral RAS or unilateral RAS to a solitary functioning kidney

   3. Both of the above

   4. None of the above

2. A 65-year-old man with a past medical history of hypertension and chronic kidney disease presents for evaluation of poorly controlled blood pressure despite being on three antihypertensive medications. He reports no recent changes in medication adherence, diet, or fluid intake. Physical examination is unremarkable, and serum creatinine is mildly elevated compared to previous measurements. A renal Doppler ultrasound is ordered to assess for possible renovascular hypertension. What Doppler ultrasound finding is most suggestive of hemodynamically significant RAS?

   1. Peak systolic velocity (PSV) < 100 cm/s

   2. Resistive index > 0.9

   3. Renal-aortic ratio > 3.5

   4. All of the above

Answers are provided at the end of the article.

DISCUSSION

Patients with unilateral RAS often develop increased glomerular filtration through the contralateral kidney, resulting in compensatory preservation of kidney function. Thus, clinical chronic kidney disease often results when RAS is bilateral or due to unilateral stenosis of a solitary functioning kidney.¹ However, hypertension can occur as a complication of both unilateral and bilateral RAS. The treatment of both unilateral and bilateral atherosclerotic RAS involves medical therapy with antiplatelet agents and lipid-lowering therapies as well as blood pressure control. Inhibitors of the renin-angiotensin-aldosterone system (RAAS) including ACE inhibitors and ARBs should be utilized as antihypertensives, as they have high efficacy in these patients.² A certain subset of patients with RAS benefits from revascularization with PTRA and stent placement. However, this carries a risk of in-stent restenosis and thrombosis and should only be performed after careful patient selection.

A meta-analysis that included seven randomized controlled trials and eight nonrandomized comparative studies comparing PTRA combined with medical therapy to medical therapy alone did not show a significant beneficial effect of PTRA in terms of clinical outcome.³ The largest of these trials was the Cardiovascular Outcomes in Renal Atherosclerotic Lesions trial, which also showed limited benefit of stenting in terms of preservation of renal function or mortality.⁴ However, most of these trials had certain limitations and did not include patients with severe RAS. Hence, PTRA and stenting are still routinely utilized based on the current guidelines for certain patients, such as those with refractory hypertension, recurrent flash pulmonary edema, bilateral RAS, or severe RAS in a solitary kidney, to delay the need for renal replacement therapy.⁵ Patients who undergo stenting should be on dual antiplatelet therapy for at least 3 months, should receive lifelong aspirin and a statin, and should avoid smoking. Close monitoring of blood pressure and renal function is essential for early diagnosis. Guidelines recommend baseline renal artery duplex ultrasound 1 month following renal stenting, followed by an annual ultrasound in asymptomatic patients.⁵ Studies have also shown renal ultrasound to correlate with contrast arteriography for the diagnosis of in-stent restenosis.⁶ Stent thrombosis and restenosis can occur despite best efforts, and a high index of suspicion is needed to avoid delay in diagnosis.

ANSWERS TO CLINICAL QUESTIONS

Question 1, d. The mechanism of hypertension in patients with RAS involves activation of RAAS due to renal hypoperfusion. In patients with RAS, RAAS-blocking agents such as ACE inhibitors or ARBs are considered first-line antihypertensives due to their efficacy.⁷ In patients with bilateral RAS or stenosis to a solitary functioning kidney, there is a risk of acute kidney injury; however, these agents are not contraindicated as long as the patient is carefully monitored. In fact, these agents are well tolerated in patients with bilateral RAS and reduce mortality, with one study showing that 78% of patients with bilateral RAS tolerated these agents.⁸

Question 2, c. An elevated renal-aortic ratio and elevated PSV are indicative of significant RAS on duplex ultrasound. A cutoff of renal-aortic ratio > 3.5 is a common threshold, while PSV thresholds of 180 to 200 cm/s are generally used, with some authors suggesting that higher thresholds > 300 cm/s to increase specificity.⁹ Resistive index is defined as (PSV − end diastolic velocity)/PSV. An elevated restrictive index > 0.80 is neither sensitive nor specific for detection of RAS, but some individuals report its value as a negative prognostic indicator for response to revascularization.⁹

Disclosure statement/Funding

The planners and faculty for this activity have no relevant financial relationships to disclose. The authors report no funding. The patient consented to publication of this case report.