Hypertensive Emergency in a Young Adult: Diagnosis of FMD by Renal Angiography But Not MRI/MRA

Hypertensive emergency (also referred to as malignant hypertension) is defined by the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) as severe elevation in blood pressure (> 180/120 mmHg) complicated by evidence of impending or progressive target organ dysfunction.¹ We report a previously healthy patient who presented with severe hypertension (252/160 mmHg), headaches, visual disturbances, papilledema and severe retinopathy. He had fibromuscular dysplasia (FMD) in the inferior branch of the left renal artery on angiography, which was not visualized on magnetic resonance angiography (MRA). His blood pressure markedly improved following balloon angioplasty. Hypertensive emergency has been reported in patients with FMD associated with renal artery dissection and/or aneurysm, but to the best of our knowledge has not been reported in uncomplicated FMD. This case further demonstrates that MRA is not a sufficient screening tool for renal artery pathology in patients with hypertensive emergency. Case Report. A 37 year-old male was admitted to the hospital with headache of 6 months’ duration that had worsened in the last week and was accompanied by blurry vision, dyspnea on exertion and weakness in his legs. He had no significant past medical history, was not taking any medications and had never been diagnosed with hypertension. Family history was remarkable for a mother with hypertension and a sister with migraine headaches. There was no history of alcohol or drug use. The patient’s brachial blood pressure was 252/160 mmHg with no significant difference between the arms. Examination by an ophthamology consultant showed Grade IV retinopathy including marked atrioventricular nicking and venous dilatation, cotton wool spots, large areas of choroidal ischemia, delayed vascular filling, blind spots and papilledema in both eyes. Electrocardiography displayed sinus rhythm, left ventricular hypertrophy by voltage criteria and repolarization abnormalities consistent with a strain pattern. Computed tomography (CT) and magnetic resonance imaging (MRI) of the brain showed no evidence of intracerebral masses, but increased signal abnormality within the pons, consistent with hypertensive encephalopathy, was present on the MRI. MRI/MRA of the abdomen showed normal kidney size, no renal or adrenal masses and normal renal arteries. Serum sodium (140 mmol/L), potassium (3.6 mmol/L), creatinine (1.1 mg/dL), and hematocrit (43%) were within normal limits. Evaluation for secondary causes of hypertension including serum aldosterone, serum cortisol, thyroid function tests, urine toxicology screen, urinanalysis, urine metnephrines and urinary VMA were unremarkable. Serum renin activity was 4.8 ng/ml/hour. Urinary levels of free catecholamines and epinephrine were undetectable, while urinary levels of norephrinephrine and dopamine were mildly elevated at 106 µg/24 hours (normal, Discussion. FMD is a noninflammatory, nonatherosclerotic vascular disease of small and medium-sized vessels that most frequently affects the renal arteries and extracranial cerebrovascular arteries.² This process is classified based on the predominant site of dysplasia in the arterial wall with medial dysplasia, which results in the “string of beads” appearance on angiography, being the most common form of fibromuscular dysplasia in adults. Thickened fibromuscular membranes are common, and interruption of these membranes by balloon angioplasty is thought to explain the resolution of translesional pressure gradients.³ The etiology of FMD is unknown, but smoking, genetic predisposition and hormonal changes are associated risk factors. Traditionally, the highest prevalence of FMD was in adult females of child-bearing age,² but recently it has been recognized increasingly in the elderly and in males.⁴ Renal artery FMD often causes minimal symptoms and thus the true incidence in the general population is unknown.² However, in cases of symptomatic FMD, hypertension is the most common presenting feature. FMD comprises less than 10% of cases of renal artery stenosis, with the most common cause of being atherosclerosis.⁵ Our patient meets the criteria for hypertensive emergency as defined by the JNC 7.¹ He presented with severe hypertension (252/160 mmHg), headaches, visual disturbances, papilledema and severe retinopathy. His blood pressure improved with medications and following balloon angioplasty of the left renal artery, and his symptoms and retinopathy resolved. He remains on 2 antihypertensive medications at moderate doses, and presumably has underlying essential hypertension. The presence of left ventricular hypertrophy by electrocardiography is consistent with chronic, untreated hypertension prior to his presentation with hypertensive emergency. Hypertensive emergency is thought to be potentially associated with any cause of hypertension6 and has been reported in patients with FMD associated with renal artery dissection and/or aneurysm, but to the best of our knowledge, has not been reported in uncomplicated FMD. We believe that his hypertensive emergency was caused by FMD for the following reasons: (1) there was the angiographic appearance of FMD in the left renal artery, along with a 20 mmHg translesional pressure gradient; (2) while our patient’s blood pressure improved with medical management, it remained elevated despite treatment with metoprolol, hydralazine and clonidine; (3) his blood pressure further improved following balloon angioplasty; (4) no secondary causes of hypertension were discovered despite an extensive evaluation; (5) his blood pressure is well controlled 18 months after the initial presentation. FMD was not demonstrated on renal MRA in this patient, consistent with published studies showing that FMD can be difficult to diagnose using this technology. The Renal Artery Diagnostic Imaging Study in Hypertension group reported that the sensitivity of MRA for renal artery stenosis from FMD, using angiography as a gold standard, was only 22% (with a specificity of 96%).⁷ Similarly, CT angiography was a specific, but not sensitive, imaging modality for diagnosing FMD, with a sensitivity of 28% and specificity of 99%. Atherosclerotic renal artery stenosis has been described in conjunction with hypertensive emergency,⁶ however cases of hypertensive emergency in patients with FMD have been described, but only in the presence of complications of FMD, including renal artery dissection and aneurysm.^8,9 Cases of hypertensive emergency with renal artery fibrodysplasia have been described in children with severe hyponatremia, hypokalemia and transient proteinuria, a condition known as hyponatremic-hypertensive syndrome (HHS).¹⁰ In our patient, there was no angiographic evidence of renal artery dissection or aneurysm. Hypertensive emergency is associated with end-organ damage to the central nervous system, retina, heart and kidneys, and early diagnosis and treatment are associated with reduced morbidity and mortality.^1,6 We present a case of FMD associated with hypertensive emergency. Renal angioplasty in this patient resulted in rapid improvement of blood pressure and symptoms. In the future, FMD should be considered in patients with hypertensive emergency, and angiography, rather than MRA or CT angiography, should be the diagnostic tool of choice to visualize the renal arteries.

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