Renovascular hypertension (RVH) refers to hypertension caused by the stenosis of the main trunk or branches of one or both renal arteries and accounts for approximately 1–3% of all hypertension cases.
Etiology and Pathophysiology
The most common cause of renovascular hypertension is atherosclerosis, followed by Takayasu's arteritis and fibromuscular dysplasia. Less common causes include congenital renal artery abnormalities, acute renal artery embolism, renal artery aneurysm, renal arteriovenous fistulas, transplant kidney rejection, radiation arteritis, and similar conditions.
Atherosclerosis frequently occurs in men over the age of 50 and can affect one or both sides. Takayasu's arteritis often occurs in young women, with lesions primarily in the aorta and involvement of one or both renal arteries, commonly near the renal artery orifice. Fibromuscular dysplasia is more common in children or young individuals. Stenosis of the renal artery reduces renal blood flow, stimulating the juxtaglomerular cells and macula densa, which promotes the synthesis and release of renin. This subsequently activates the renin-angiotensin-aldosterone system, leading to an increase in blood pressure.
Clinical Manifestations
Common symptoms include headache, dizziness, palpitations, chest tightness, visual impairment, nausea, and vomiting, which are typical features of hypertension. The following characteristics are frequently observed:
- Hypertension often develops in individuals younger than 30 years old (more common in females) or older than 50 years old (more common in males).
- Long-standing hypertension may suddenly worsen or may occur acutely, with a short disease course and rapid progression.
- Blood pressure remains difficult to control even when treated with 2–3 antihypertensive medications.
- Pain may be experienced in the lower back or flank region, with vascular bruits audible in the upper abdomen in over half of patients.
- Impaired renal function may be present.
- Takayasu's arteritis patients often do not have a family history of hypertension.
Diagnosis
Diagnoses focus primarily on the exclusion of other forms of secondary hypertension, including renal parenchymal hypertension. Physical examinations may reveal severe hypertension, abdominal bruits (in both systolic and diastolic phases), hypertensive retinopathy (grades III–IV), and signs of systemic atherosclerosis.
Imaging Studies
Doppler ultrasound is recommended as the first-line screening method for renovascular hypertension. The affected kidney is often smaller than the healthy kidney, with stenotic segments of renal vessels displaying a narrowed blood flow channel, elevated flow velocity, and increased resistance index.
Renal artery angiography is considered the gold standard for confirming renovascular hypertension and serves as a prerequisite for surgical treatment. It can visualize the abdominal aorta, renal arteries, their branches, and the parenchymal phase, identifying abnormalities such as lesions at the renal artery orifice or stenosis/occlusion of the renal arteries and their branches.
Spiral CT angiography is suited for evaluating proximal renal artery stenosis. Magnetic resonance angiography (MRA) demonstrates high sensitivity and specificity for detecting renal artery stenosis and, because it does not require iodine-based contrast agents, is appropriate for patients with iodine allergies.
Radionuclide renography identifies renal functional impairment associated with renovascular hypertension, which may manifest as reduced or absent renal function. In some cases, when collateral circulation forms, the renogram may appear entirely normal. Dynamic imaging of the kidneys using radionuclides can show delayed perfusion and radioactive peaks in affected kidneys, with lower radionuclide uptake compared to the healthy kidney.
Blood Tests
Plasma Renin Activity Assay
Approximately 80% of individuals with significantly increased peripheral plasma renin activity are diagnosed with renovascular hypertension. Plasma renin activity may also be assessed via catheterization of the renal veins and inferior vena cava above and below the renal vein orifices. When renin activity in the affected kidney's renal vein is higher than that of the unaffected side, the renin activity ratio may further confirm diagnosis and assist in evaluating post-surgical outcomes and prognosis.
Angiotensin Blockade Test
Oral administration of 25 mg captopril results in increased plasma renin activity and a decrease in blood pressure, providing supporting evidence for a diagnosis of renovascular hypertension.
Treatment
The goals of treating renovascular hypertension are to control or reduce blood pressure, restore adequate renal blood flow, and improve renal function. Treatment primarily involves interventional or surgical approaches, though outcomes may be suboptimal in patients with extensive systemic vascular disease.
Interventional Therapy
Percutaneous transluminal angioplasty (PTA) is most suitable for fibromuscular dysplasia. It is also indicated for unilateral atherosclerotic renal artery stenosis (non-calcified and non-occlusive), Takayasu’s arteritis, recurrent stenosis after PTA, and anastomotic stenosis following surgery.
Percutaneous endovascular stent placement is a technique used for specific cases of renal artery stenosis.
Surgical Therapy
Vascular Reconstruction
Multiple techniques are available, each with unique characteristics. Common procedures include renal artery endarterectomy, resection and anastomosis of the stenotic segment, vascular wall reconstruction, and bypass surgery.
Autotransplantation
Autotransplantation of the kidney is primarily applied in cases of severe abdominal aorta-renal artery orifice stenosis caused by Takayasu’s arteritis, particularly when the abdominal aorta is extensively diseased.
Nephrectomy
Careful consideration is required. It may be performed when the affected kidney has lost significant function and the contralateral kidney is of normal size and function.