According to the CDC, more than 1 in 7 US adults are estimated to have chronic kidney disease (CKD). As many as 9 in 10 adults with CKD do not know they have it, and about 1 in 3 adults with severe CKD do not know they have CKD at all.
This is why it’s important to get tested for chronic kidney disease as an adult, especially if you have a history of chronic kidney disease in your family or you have had a kidney transplant.
Seeing a kidney disease specialist, or a nephrologist, is the first step to the assessment and treatment of CKD. Let’s dive deeper into understanding how a kidney doctor would test an individual for CKD.
Part 1: Measuring GFR
Aside from asking about your medical history, a kidney specialist will assess the glomerular filtration rate (GFR) of your kidneys. This measures the efficiency of the kidney’s primary function, which is to clear water-soluble waste products from the blood.
GFR is measured by how many milliliters of blood is cleaned by the kidneys in one minute. A blood test will measure creatinine (waste product) levels to calculate the estimated GFR (eGFR). The formula for this test accounts for body size as well.
A normal GFR is on average 100 - meaning 100 millimeters of blood cleaned per minute. But values as low as 60 can be considered normal given there are no other signs or symptoms of kidney disease.
However, the eGFR can be inaccurate when factoring in extremities of weight and muscle. For instance, a bodybuilder can have a falsely low eGFR due to much higher muscle mass.
There are five stages of kidney diseases in which a higher stage number means a lower eGFR result. The chart below also outlines what each stage means.
Chart from the American Kidney Fund. Read more here.
Part 2: Urine Test for Albuminuria
Measuring GFR may not be enough to identify mild kidney damage because they may appear normal or borderline normal. For these milder cases,a kidney performs a urine test for an albumin excretion.
Too much albumin in urine (albuminuria, also called proteinuria) is a sign of kidney disease. A urine test can also show abnormalities in urine sediment.
The three main stages of albuminuria are classified as A1, A2, and A3, ranging from normal, moderate, and severe. A normal protein level in urine is lower than 3mg/mmol. Anything higher than 30mg is considered severe.
Both GFR and albuminuria levels should be used together, rather than separately, to ensure a more accurate assessment of CKD. Additionally, the combined results can help a kidney specialist predict if you’re more likely to develop further complications.
The chart below outlines the intersective results of GFR and albuminuria categories. The higher the stages of each category, the higher the risk of CKD.
At what stage will I show signs or symptoms of chronic kidney disease?
Generally, patients with stages 1-3 of chronic kidney disease are asymptomatic. Stages 4-5 is when signs and symptoms become more prevalent.
What are the signs and symptoms of chronic kidney disease?
With stages 4-5, patients may experience endocrine/metabolic derangements of imbalances of water or electrolytes. They are likely to experience muscle weakness, loss of lean body mass, plus deficiency in energy and protein. This can lead to fatigue, headaches, and
In stage 5, the kidneys can start to alter how they handle salt and water, showing signs of peripheral edema, pulmonary edema, and hypertension. Although hypertension alone should not be considered a sign of kidney disease since it is seen in many people.
What is end stage renal disease (ESRD?)
End stage renal disease is what happens with stage 5 CKD (GFR of 15 ml/min or less). At this stage, the kidneys have lost nearly all their ability to function and eventually a patient will need dialysis or a kidney transplant to live.