Identifying kidney disease risk
Written by Dr. Harvey Kaufman, Senior Medical Director, Medical Informatics at Quest Diagnostics.
Our kidneys have many functions including filtering our blood. They filter many drugs and their metabolites from the blood to be removed from the body. Every day, our kidneys filter 240-300 pints of blood (a pint is the size of a unit of blood) and we generate approximately 2 pints of fluid waste. As we age, the function of our kidneys decline. Most of us function well enough into our old age and don’t need to be concerned about our declining kidney function. However, for 26 million Americans, kidney function declines to the point that the kidneys cannot filter blood effectively. This can be harmful to a person’s health in the following ways:
- Drug levels in the blood may become too low or too high due to improper filtration
- The level of vitamin D that is activated in the kidneys becomes low
- The level of a hormone produced in the kidneys that stimulates production of red blood cells also becomes low, leading to anemia
- The risk of heart disease increases as kidney function diminishes
When chronic kidney disease progresses to late stages, people affected need to prepare for end stage renal (renal is another word for kidneys) disease which may require dialysis or a kidney transplant.
Who gets chronic kidney disease?
The primary risk factors for chronic kidney disease are high blood pressure (hypertension), diabetes, and family history of chronic kidney disease. Guidelines from the National Kidney Foundation state that adults should be tested to identify their risk, and help prevent chronic kidney disease. The primary test is called creatinine, as measured from a blood specimen. Creatinine is generated from muscle so muscle mass affects test interpretation. Specifically, higher muscle mass is typically observed in younger adults than older adults, African Americans than non-African Americans, and men than women. To improve the relationship between the test and chronic kidney disease, an equation is used that adjusts for age, sex and race (African American or non-African American). The equation makes adjustments that reflect differences in muscle mass. The equation generates the estimated glomerular filtration rate (eGFR) that corresponds to levels of kidney function.
In national surveys, approximately 90% of people with chronic kidney disease are unaware they have the condition. A key reason is that most patients have no symptoms. The most common symptoms are non-specific and include fatigue, poor appetite, and difficulty sleeping. Nevertheless, the lack of awareness is shocking given how easy it is to assess kidney function. Once identified, additional evaluation is necessary to exclude other diagnoses and to confirm the presence of chronic kidney disease. Chronic kidney disease can be managed through diet, close management of associated conditions such as diabetes and high blood pressure, and adjustment of many medications. Kidney disease specialists (nephrologists) are experts in guiding patients and controlling and managing disease progression.
For decades, we focused on identification and management of high blood pressure (hypertension), diabetes, and high cholesterol. Physicians and public health experts agree that chronic kidney disease is appropriate to add to this list of common, actionable chronic medical conditions. It all starts with a commonly performed laboratory test that is more than a century old, creatinine. With identification and management of chronic kidney disease, more people will live longer, healthier lives.