By Tejas Desai, MD, and Darina Stankeyeva, MD

After being diagnosed with chronic kidney disease (CKD), many patients feel they lose control over their health and cannot help protect their kidneys. This is not entirely true.

Understanding Kidney Function
Kidney function is the ability of kidneys to filter blood in order to rid the body of waste and toxins. The amount of blood the kidneys are able to filter in one minute, adjusted for body surface area, is a measurement of kidney function. This is how your doctor assesses kidney function to determine what stage of CKD you have. Creatinine, a naturally occurring chemical in the body, is used to measure kidney function. As kidney function decreases, the level of creatinine in the blood increases.

In addition to filtering the blood, the kidneys have other important roles:
1. They help control blood pressure.
2. Process vitamin D, which is needed for healthy bones in children and adults.
3. Help produce new red blood cells.

While kidney function decreases as we age, it can decrease at a faster rate in patients who already have CKD. The rate of progression of CKD depends on the cause of kidney disease (such as diabetes, lupus, etc.) and measures taken by the physician and the patient to slow its progression.

Kidney function is extremely important to the overall well-being of the body. Even in patients receiving dialysis, having any amount of kidney function is better than none at all, and leads to better survival.

Factors that affect progression of CKD and how they can be modified
There are many factors that play a role in the progression of CKD, some of which can be modified.

Modifiable factors:
1. Blood sugar control: Elevated levels of blood sugar are toxic to the kidneys and are the most common cause of kidney failure in North America. For patients with diabetes, better control of their blood sugar is associated with slower decline in kidney function [1, 2]. It is best to bring down hemoglobin A1c (measured in blood to assess blood sugar control over the course of three months) to less than 6.5 percent, but any reduction is beneficial.

2. Blood pressure control: Elevated blood pressure is known to accelerate CKD [1, 2, 3]. Blood pressure control in patients with kidney disease is often more difficult to control than in patients without CKD and frequently requires more than two medications. It is best to maintain blood pressure below 130/80.

3. Medications: In many kidney diseases, kidneys leak protein in the urine (called proteinuria). Higher amounts of protein in the urine often mean faster progression of kidney disease. Lower blood pressure decreases the amount of proteinuria, which is often achieved by using medications from the ACE-inhibitor and ARB classes (such as lisinopril or losartan, respectively) ^{[1, 4]}. Even in patients with normal blood pressure these medications are known to decrease the degree of proteinuria.

4. Anemia and cholesterol management: This has been studied with mixed results. Chronically diseased kidneys cannot aid in the production of red blood cells, leading to anemia ^{[1, 2]}. Some studies suggest anemia worsens kidney function even further. It is recommended the target red blood cell level (referred to as hemoglobin) be between 11 and 12. Direct effect of elevated cholesterol on progression of CKD is unclear at this time, but having lower cholesterol levels is beneficial for overall cardiovascular health.

5. Smoking: There is information from several studies that smoking is directly toxic to the kidneys and increases the amount of proteinuria. Stopping smoking slows down CKD progression rate as well as benefits overall cardiovascular health ^{[5, 6].}

6. Dietary modifications: Earlier it was believed strict low-protein diet would help slow the progression of CKD. At this time there is not enough evidence to recommend low protein diets for all patients with CKD. Sodium restriction, however, does help lower blood pressure, which in turn is known to slow CKD progression ^[6].

Non-modifiable factors:
Male gender - There is increased evidence kidney disease tends to progress faster in men with established kidney disease and high blood pressure.

Ethnicity - African-Americans have higher incidence of kidney disease and faster progression of CKD, which is in part related to higher incidence of diabetes and elevated blood pressure. Kidney function in patients with CKD usually declines gradually over time. However, here are some factors that can lead to acute drop in kidney function and are best avoided:

1. Radiocontrast dye used in imaging studies is toxic to the kidneys. When it cannot be avoided, its toxicity can be minimized by the use of intravenous hydration and medication called mucomyst ^{[1, 2]}.
2. Certain antibiotics form a class of aminoglycosides (amikacin, gentamicin) or an antifungal drug amphotericin can cause an abrupt decline in renal function ^{[1, 2]}.
3. Medications from the class of non-steroidal anti-inflammatory drugs (also known as NSAIDs, such as ibuprofen, naproxen, etc.), which are commonly sold over the counter for pain relief, are toxic to the kidneys, especially if taken over a long period of time and should be avoided in all patients with CKD ^{[1, 2]}.

The best step a patient can take to protect kidney function is to speak with their doctor about the above recommendations. While all recommendations may not apply to every patient, a detailed discussion with your physician can help set the path for healthy kidneys and improved quality of life.

References:
_{1.) Saweirs and Goddard. What are the best treatments for early chronic kidney disease? Nephrology, Dialysis, Transplantation 2007; 22 (9): ix31
2.) NKF KDOQI Guidelines
3.) Peterson JC, Adler S, Burkart JM et al. Blood pressure control, proteinuria and the progression of renal disease. The modification of diet in renal disease study. Ann Intern Med 1995; 123 754-762
4) Lea J, Greene T, Hebert L et al. The relationship between magnitude of proteinuria reduction and risk of end-stage renal disease. Results of the African American study of kidney disease and hypertension. Arch Intern Med 2005; 165: 947–953
5) British Cardiac Society BHS, Diabetes UK, HEART UK, Primary Care Cardiovascular Society, The Stroke Association. JBS 2: Joint British Societies’ guidelines on prevention of cardiovascular disease in clinical practice. Heart 2005; 91:v1–v52
6) Stengel B, Tarver-Carr M, Powe N et al. Lifestyle factors, obesity and the risk of chronic kidney disease. Epidemiology 2003; 14: 479–487}

Tejas Desai, MD, is a Nephrology Fellow in the Emory University Division of Nephrology. His academic interests focus on Internet-based medical education for physicians in-training and dialysis patients.

Darina Stankeyeva, MD, is a Nephrologist based in Atlanta, Georgia. 

This article originally appeared in the September 2009 edition of Kidney Beginnings: The Magazine.

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