When two or three blood pressure medications aren't controlling your numbers, the problem may not be your heart — it may be in your kidney arteries. A renal ultrasound can check for the narrowing that drives resistant hypertension.
If you're taking two or three blood pressure medications and your numbers are still elevated, you're not alone — and it's not necessarily a medication failure. Resistant hypertension often has a structural cause that standard medications simply cannot address on their own. One of the most overlooked is renal artery stenosis: narrowing in the arteries that supply the kidneys. When a kidney senses reduced blood flow, it releases hormones that drive blood pressure up — a self-perpetuating cycle that most antihypertensives can't break. A renal artery ultrasound checks for this in 30 minutes at your home.
THE ANSWER MAY BE IN YOUR KIDNEY ARTERIES
If 2–3 blood pressure medications aren't controlling your numbers, the problem might be in your kidney arteries, not your heart. A renal artery ultrasound checks for narrowing that drives resistant hypertension — at home, this week, without a referral.
Severely elevated blood pressure (systolic above 180 or diastolic above 120) is a hypertensive crisis and warrants immediate medical evaluation. Call your doctor or go to the emergency room. This page is intended for people managing chronic elevated blood pressure that is not reaching goal on medication.
When blood pressure resists medication, a secondary cause is often present. Here are the most important ones to evaluate:
The kidneys regulate blood pressure through a hormone system called the renin-angiotensin-aldosterone axis. When one or both renal arteries are narrowed by atherosclerotic plaque or fibromuscular dysplasia, the kidneys detect what they interpret as insufficient perfusion and respond by releasing renin. This triggers a hormonal cascade that raises blood pressure system-wide. The elevated pressure doesn't fix the underlying problem — it just keeps escalating. A renal artery duplex ultrasound can help identify abnormal flow velocities and pressure gradients in the kidney arteries that indicate significant stenosis.
Primary aldosteronism is a condition where one or both adrenal glands produce too much aldosterone — a hormone that causes the kidneys to retain sodium and water and excrete potassium. The result is elevated blood pressure that is typically resistant to treatment, often accompanied by low potassium levels. It is far more common than previously recognized and is estimated to account for up to 10–15% of resistant hypertension. Aldosteronism is diagnosed with blood tests, not ultrasound — but ruling out renal artery stenosis is an important step in the secondary hypertension workup.
Before assuming a structural cause, it's worth reviewing whether medications are being taken consistently and at the right times. Certain over-the-counter medications — particularly NSAIDs (ibuprofen, naproxen), decongestants, and some herbal supplements — can counteract antihypertensive effects. Missed doses, inconsistent timing, and drug interactions are common contributors to apparent medication resistance. These factors should be discussed with the prescribing physician alongside any structural workup.
Obstructive sleep apnea (OSA) is one of the most common and under-diagnosed contributors to resistant hypertension. During apneic events, oxygen levels drop and the sympathetic nervous system activates — repeatedly throughout the night — driving blood pressure up. Morning hypertension and difficulty controlling blood pressure despite multiple medications are hallmarks. OSA is diagnosed with a sleep study, not imaging, but awareness of the connection can accelerate diagnosis and treatment. CPAP therapy has been shown to reduce blood pressure in hypertensive patients with OSA.
Renal artery stenosis is the structural cause most efficiently screened with ultrasound:
Renal Artery Duplex Ultrasound · $397
Duplex ultrasound of the renal arteries evaluates blood flow velocity at the origin and throughout both kidney arteries. Significantly elevated velocities indicate stenosis that may be driving treatment-resistant blood pressure. The study is completely non-invasive, uses no radiation, and takes approximately 45–60 minutes at your home. Fasting for 6–8 hours beforehand improves image quality. The written report is available within 24–48 hours.
Note: Fasting for 6–8 hours before this study is recommended to reduce bowel gas interference with visualization of the abdominal vessels.
Learn about renal arterial ultrasound →Resistant hypertension is a time-consuming workup. Many patients on two or three antihypertensives who are not at goal have never had renal artery imaging — simply because the referral pathway to a vascular lab takes months to navigate.
BlackPoint Diagnostics can perform a renal artery duplex at your patient's home within the week. The written report is ready in 24–48 hours — formatted for specialist review and ready to accompany a nephrology or vascular surgery referral if indicated.
This allows you to either rule out renovascular disease quickly and move on to other secondary causes, or to have imaging evidence in hand before escalating the workup — without adding weeks to the timeline.
How to send a patient →Traditional Path
BlackPoint Diagnostics
Uncontrolled blood pressure is not a benign waiting game. Every year of poorly controlled hypertension contributes to heart failure, stroke risk, and kidney damage. Identifying and addressing a structural cause like renal artery stenosis can make the difference between a patient who needs four medications and one who returns to goal on two.
Emanuel Papadakis, RDCS, RVT, comes to your home with hospital-grade portable ultrasound equipment. For the renal artery duplex, fasting for 6–8 hours beforehand is recommended — bowel gas in the abdomen can obscure the renal arteries, and an empty stomach significantly improves image quality. Water is fine.
You lie comfortably on your back. Ultrasound gel is applied to the abdomen and the transducer is moved to locate the aorta and the origin of both renal arteries. Blood flow velocity is measured at the origin and within each renal artery. The study evaluates both kidneys and can also provide a general assessment of kidney size and structure.
The study takes approximately 45–60 minutes and is completely painless with no radiation. Emanuel provides a verbal summary before leaving and the formal written report is delivered within 24–48 hours.
The report documents flow velocities, renal-to-aortic ratios, and any findings suggestive of stenosis — in a format ready to share with your primary care physician, nephrologist, or vascular specialist.
Hypertension that remains above goal on three or more medications is called resistant hypertension. Common secondary causes include renal artery stenosis (narrowed kidney arteries), primary aldosteronism (excess adrenal hormone), and obstructive sleep apnea. A renal artery duplex ultrasound can help determine whether kidney artery narrowing may be contributing to treatment-resistant blood pressure.
Renal artery stenosis is narrowing of the arteries that supply blood to the kidneys. When a kidney detects reduced flow, it releases renin — triggering a hormonal cascade that raises systemic blood pressure. Because the mechanism is driven by the kidney's response to reduced perfusion, standard blood pressure medications often cannot overcome it without first addressing the underlying narrowing.
Fasting for 6–8 hours before the study is recommended. Bowel gas in the abdomen can obscure the renal arteries, and an empty stomach significantly improves image quality. Water is permitted. Continue taking your regular blood pressure medications as scheduled unless instructed otherwise by your physician.
Yes. BlackPoint Diagnostics does not require a physician referral. You can book directly online and we come to your home in Southern Maine. The written report is delivered within 24–48 hours and can be shared with the physician managing your blood pressure to help guide next steps in the workup or treatment plan.
Southern Maine · Mobile Service · No Referral
A 45-minute renal artery ultrasound at your home can determine whether kidney artery narrowing is behind your resistant blood pressure — results in 24–48 hours, no referral required.
Book Your Renal Artery ScanRenal Artery Duplex $397 · No Referral · Southern Maine
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