Renal hypertension, a cause of systemic hypertension, is the result of stenosis or occlusion in the renal artery/arteries and the subsequent under perfusion of one or both kidneys [1]. 90% of cases are caused by atherosclerotic renal artery stenosis (ARAS), which affects males above the age of 50 years while the remaining are secondary to fibromuscular dysplasia (FMD), which is commonly found in younger women [2] [3].

While some patients are asymptomatic, headache is the most frequent manifestation in others. Further complaints include emesis, visual disturbances, and changes in the mental status. If the patient has developed congestive heart failure, the clinical presentation consists of fatigue, dyspnea on exertion, peripheral edema, palpitations, and other associated symptoms [4]. Moreover, individuals with renal disease are likely to exhibit hematuria and edema [4].

There are numerous risk factors for renal hypertension such as malignant hypertension, progressive renal impairment, diastolic blood pressure greater than 120 mm Hg, hypertension unresponsive to multidrug therapy, and worsening blood pressure with diuretic use. Furthermore, hypertension accompanied by proteinuria and azotemia is another risk.

Patients with renal hypertension typically have a history of 1) a sudden increase in blood pressure, 2) onset of hypertension in the absence of risk factors, 3) worsening of previously controlled hypertension, 4) repeat episodes of pulmonary edema, 5) unprovoked hypokalemia, 6) generalized atherosclerosis in older individuals, and/or 7) smoking,

Complications

Sequelae include chronic hypertension, kidney disease, renal failure, heart failure, seizures, encephalopathy, coma, and even death. Also, end-organ damage is a concern especially in the setting of chronic kidney disease [5] [6].

Individuals with a clinical presentation or a history as described above warrant a full workup. The assessment consists of the patient's personal and family history, physical exam, and the appropriate studies.

Physical exam

The patient's blood pressure and other vitals must be assessed with the proper techniques in order to ensure accuracy. Very importantly, the patient should be examined carefully. One remarkable finding in nearly 50% of affected individuals is an abdominal bruit, especially when present during both diastole and systole [7] [8].

Target-organ effects of chronic hypertension should also be investigated. For example, patients with heart failure will exhibit peripheral edema and other cardiovascular signs while those with ophthalmologic manifestations will have retinal hemorrhages and retinopathy.

Laboratory tests

A complete blood count (CBC) and a complete metabolic panel (CMP), which includes electrolyte levels and renal function tests, are important components of the workup [4]. Fasting glucose and fasting lipid tests are indicated in children with chronic kidney disease, individuals with severely elevated blood pressures, and other groups as well [4]. To examine rare causes of hypertension, a 24-hour urine collection can be used to measure creatinine, electrolytes and other metabolites [4].

Imaging

Intra-arterial digital subtraction angiography (DSA) is currently recommended as the initial study in the assessment of renal artery stenosis, especially in patients with renal impairment. Along with DSA, renal arteriography is also the gold standard diagnostic technique.

Magnetic resonance angiography (MRA) offers critical information regarding the renal arteries, their branches, anatomic variants, distal stenosis, and any suspicious masses. One meta-analysis study reports that gadolinium-enhanced MRA is associated with a 97% sensitivity and 85% specificity for detection of renal artery stenosis [9]. Computed tomographic angiography (CTA) is also another technique used to diagnose stenosis.

Multidetector contrast tomography (MDCT) provides details about the renal artery and parenchyma of the kidneys as well nearby structures [10]. Another study is doppler ultrasonography, which allows for the evaluation of the anatomy and function of the renal arteries. This modality is associated with good sensitivity and specificity for detection of stenosis [11]. Additionally, a nuclear renal scan can be used to determine if a patient will benefit from surgery [12]. This test can be used with captopril for enhancement.

Treatment for renal hypertension aims to control blood pressure and address the underlying cause of the condition. Medications such as ACE inhibitors, angiotensin II receptor blockers, or calcium channel blockers may be prescribed to manage blood pressure. In cases where the narrowing of the renal arteries is significant, procedures like angioplasty or stenting may be performed to improve blood flow. Lifestyle changes, including a healthy diet, regular exercise, and smoking cessation, are also important components of managing renal hypertension.

The prognosis for individuals with renal hypertension varies depending on the severity of the condition and the effectiveness of treatment. With appropriate management, many patients can achieve good blood pressure control and reduce the risk of complications. However, if left untreated, renal hypertension can lead to serious health issues, including chronic kidney disease, heart attack, or stroke. Early detection and intervention are key to improving outcomes.

Renal hypertension is primarily caused by the narrowing of the renal arteries, a condition known as renal artery stenosis. This narrowing can result from atherosclerosis, a buildup of fatty deposits in the arteries, or fibromuscular dysplasia, an abnormal growth of cells in the artery walls. Less commonly, renal hypertension may be caused by other conditions affecting the kidneys or their blood supply.

Renal hypertension is a relatively common condition, particularly among older adults and individuals with risk factors for atherosclerosis, such as high cholesterol, diabetes, or smoking. It is estimated that renal artery stenosis is present in about 1-5% of patients with hypertension. The prevalence increases with age and is more common in men than women. Fibromuscular dysplasia, another cause of renal hypertension, is more frequently seen in younger women.

The pathophysiology of renal hypertension involves the reduced blood flow to the kidneys due to narrowed renal arteries. This reduction triggers the kidneys to release hormones like renin, which leads to the production of angiotensin II, a potent vasoconstrictor that increases blood pressure. Additionally, the kidneys may retain more sodium and water, further elevating blood pressure. This complex interplay of hormonal and vascular changes contributes to the development and maintenance of high blood pressure in renal hypertension.

Preventing renal hypertension involves managing risk factors associated with atherosclerosis and maintaining overall cardiovascular health. Key preventive measures include adopting a heart-healthy diet low in saturated fats and sodium, engaging in regular physical activity, maintaining a healthy weight, and avoiding tobacco use. Regular monitoring of blood pressure and cholesterol levels can also help identify and address potential issues early.

Renal hypertension is a form of high blood pressure caused by reduced blood flow to the kidneys, often due to narrowed renal arteries. It can lead to serious health complications if not properly managed. Diagnosis involves a combination of clinical evaluation and imaging studies, while treatment focuses on controlling blood pressure and addressing the underlying cause. Lifestyle changes and medications play a crucial role in management, and early detection is key to improving outcomes.

If you have been diagnosed with renal hypertension, it's important to work closely with your healthcare provider to manage your condition. This may involve taking prescribed medications, making lifestyle changes, and attending regular follow-up appointments. Understanding your condition and actively participating in your treatment plan can help you maintain good blood pressure control and reduce the risk of complications. Remember to monitor your blood pressure regularly and report any new symptoms or concerns to your healthcare provider.

1. Dillon MJ. The diagnosis of renovascular disease. Pediatr Nephrol. 1997;11(3): 366–72.
2. Mehta AN, Fenves A. Current opinions in renovascular hypertension. Proc (Bayl Univ Med Cent). 2010;23(3): 246-9.
3. Safian RD, Textor SC. Renal-artery stenosis. N Engl J Med. 2001;344(6): 431–42.
4. National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. The Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents. Pediatrics. 2004;114(2): 555-76.
5. Mitsnefes MM, Daniels SR, Schwartz SM, Khoury P, Strife CF. Changes in left ventricular mass in children and adolescents during chronic dialysis. Pediatr Nephrol. 2001;16(4):318–23.
6. Mitsnefes MM, Kimball TR, Witt SA, et al. Left ventricular mass and systolic performance in pediatric patients with chronic renal failure. Circulation. 2003;107(6):864–68.
7. Kaplan NM. Renal vascular hypertension. In: Kaplan NM, Lieberman E, eds. Clinical hypertension. 7th ed. Baltimore: Williams & Wilkins; 1998; 301–21.
8. Pohl M. Renal artery stenosis, renal vascular hypertension, and ischemic nephropathy. In: Schrier RW, Gottschalk CW, eds. Diseases of the kidney. 6th ed. Boston: Little, Brown; 1997:1367–423.
9. Tan KT, van Beek EJ, Brown PW, et al. Magnetic resonance angiography for the diagnosis of renal artery stenosis: a meta-analysis. Clin Radiol. 2002;57(7): 617–24.
10. Tsai IC, Chen MC, Lee WL, et al. Comprehensive evaluation of patients with suspected renal hypertension using MDCT: from protocol to interpretation. AJR Am J Roentgenol. 2009;192(5): W245-54.
11. Strandness DE Jr. Duplex imaging for the detection of renal artery stenosis. Am J Kidney Dis. 1994;24(4):674–78.
12. Hartman RP, Kawashima A. Radiologic evaluation of suspected renovascular hypertension. Am Fam Physician. 2009;80(3):273-79.