By Ronald M. Goldin, MD

High blood pressure (hypertension) can be related to chronic kidney disease (CKD) in a number of ways. Hypertension can independently cause CKD, contribute to its development in the setting of other potential causes or even be the result of CKD, as is the case in patients with polycystic kidney disease. Regardless of the circumstances, hypertension is present in approximately 80 percent of patients with CKD.

Studies show that as kidney function worsens the likelihood that a patient will have hypertension increases. Furthermore, as in patients without kidney disease, the risk of having hypertension in CKD patients is increased with advancing age, higher body weight and in African Americans.

The relationship between CKD and hypertension can be explained by several factors. CKD can lead to salt retention and subsequent volume overload. This may or may not be accompanied by swelling (edema) along with increased blood pressure. In addition, failing kidneys appear to trigger increased activity of the sympathetic nervous system, causing something like an adrenaline surge. More advanced CKD can also lead to low blood count or anemia. The treatment may help to produce hypertension, depending on the resultant rise in the blood count.

Hormonal mechanisms also play an important role in the link between CKD and hypertension, primarily via the renin-angiotensin system. These hormones can be released in response to chronic damage and scarring of the kidneys, and can contribute to a patient’s hypertension by stimulating both salt retention, as well as constriction of blood vessels. Fortunately, medications known as angiotensin converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) now exist to help us try to control these undesirable actions.

Another hormone that may raise blood pressure and has increased quantities with advancing CKD is the parathyroid hormone (PTH). The PTH raises calcium in the blood, which can also cause tightening of the blood vessels, resulting in hypertension. Again, this effect can be at least partly regulated by medication, such as vitamin D, that lowers the PTH level.

A condition that can lead to CKD and hypertension is renal artery stenosis (tightening of the blood vessels supporting the kidneys). When narrowing becomes severe enough, the lack of blood flow can cause a loss of kidney function. If the blood supply to both kidneys is affected, or blood flow to a single functioning kidney, such as following the removal of a kidney due to cancer, is compromised, a patient will develop CKD. This reduction in blood flow triggers the renin-angiotensin system, causing hypertension. In cases of progressive kidney failure and/or uncontrollable hypertension, it may be worthwhile to consider a procedure to open the diseased blood vessel. However, these procedures can carry some risk and may not always achieve their goals. Therefore, they should be undertaken with caution and only after thorough discussion of risks and benefits with a kidney specialist.

Why is it important to control blood pressure once a patient has CKD? The answer is two-fold. First, study after study has shown better blood pressure control slows progression of CKD, thereby making it less likely a patient will require dialysis. Second, patients with CKD are more likely to die of cardiovascular disease than they are to require dialysis. In other words, lowering blood pressure will reduce the risk of heart disease, which for most patients with CKD, is more of an immediate threat than end-stage renal disease (ESRD).

Blood pressure goals for patients with CKD have been debated for years and are constantly in flux. One of the determining factors is the amount of protein a patient loses in his/her urine. Patients that lose a significant amount of protein in the urine are at somewhat higher risk, both for progressive kidney disease and heart disease. Currently, guidelines support a goal blood pressure less than 130/80 for all patients with CKD and less than 125/75 for those patients losing more than one gram of protein in the urine per day.

Treatment for hypertension in CKD patients can be divided into two categories: nonpharmacological and pharmacological. Neither is more important than the other. Medications are certainly essential in the treatment of hypertension, especially in CKD, but there are lifestyle changes patients can make that may have a just as profound impact on their blood pressure and general health.

Weight loss of as little as eight to 10 pounds can have a dramatic impact on blood pressure. Exercise must be an integral part of any successful weight loss program. Excessive alcohol intake is a clear risk factor for hypertension, and blood pressure can often be lowered without medication merely by reducing consumption of alcohol. The role of elevated salt intake as a risk for hypertension has been controversial, but it is likely that certain populations, such as the elderly, African Americans and patients with CKD, benefit from sodium restriction. Pharmacological therapy of hypertension is a subject that occupies entire textbooks. As new studies are released each year, the recommendations change to use the most desirable drug or combination of drugs. One now indisputable finding is most patients with CKD require more than one medication to achieve adequate control of blood pressure.

Two classes of medications have now emerged as leaders in hypertension treatment of CKD patients. They are the ACE inhibitors and ARBs. These medications counteract effects of the renin-angiotensin system. They have been shown to slow the progression of kidney disease in patients with and without diabetes. While especially effective in reducing protein loss in the urine, they will preserve kidney function even in patients that do not lose protein. They can even reduce the risk of death of patients already on dialysis, independent of their effects on blood pressure.

Other classes of medications are also very useful. Diuretics can eliminate salt excess and reduce volume overload, which can be a key component of hypertension in CKD. Beta-blockers work by stifling the “adrenaline surge” in CKD patients, helping reduce the risk of progressive kidney and heart disease. Calcium channel blockers are effective in patients with volume overload and can reduce protein loss in some patients.

Regardless of the medications or nonpharmacological methods used, evidence provides hope and motivation in showing that by achieving the recommended blood pressure goals, CKD patients can reduce their risk of needing dialysis or experiencing an adverse cardiovascular event, such as a heart attack or stroke.

Ronald Goldin, MD, is a nephrologist in the Fort Lauderdale/Plantation area of South Florida. He completed his fellowship at the University of Florida in Gainesville. He is a contributing author to the most recent edition of the Handbook of Nephrology and Hypertension. His specialized areas of interest include hypertension, dialysis and diabetic kidney disease.

This article originally appeared in the March/April 2005 issue of Kidney Beginnings: The Magazine, Vol. 4, No. 1.

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