Kidney Function: GFR vs. Creatinine in Health Concerns

Glomerular filtration rate and kidney disease issues?

Hello Dr.
Wu: I am 180 cm tall and weigh about 71 kg.
Recently, for the past month, I have noticed persistent bubbles in my urine and have experienced increased urinary frequency (especially 2-3 hours after consuming sugary drinks) and nocturia.
I am concerned that this may indicate kidney disease or diabetes.
Last week, I visited the hospital and consulted a nephrologist, who ordered blood and urine tests.
The results showed that the routine urine analysis was normal, with no glucose or protein detected (-).
My uric acid level was 5.6 mg/dL, creatinine was 1.0 mg/dL, and fasting blood glucose was 102 mg/dL (reference range 70-100).
The doctor indicated that my urine protein levels were normal.
Regarding the slightly elevated fasting blood glucose, he suggested that I see a metabolic specialist for further evaluation.
I confirmed with the doctor whether my kidney function was normal, and he stated that based on the blood and urine test results, everything appeared to be fine.
He advised me to continue monitoring the bubbles and to maintain a light diet.
However, after researching online, I learned that creatinine levels alone cannot determine kidney function or the presence of kidney disease; the glomerular filtration rate (GFR) should be assessed.
I entered my creatinine value on the Kidney Foundation website (http://kidney.tsn.org.tw/) and calculated my GFR to be 88.41.
According to their staging table, this falls into stage 2 chronic kidney disease, which differs from what the doctor informed me last week, leaving me confused.
Given all this information, I would like to ask Dr.
Wu whether my condition indicates normal kidney function or if it suggests impaired kidney function (stage 2 chronic kidney disease).
Thank you for taking the time to clarify this for me.

Liu R, 30~39 year old female. Ask Date: 2016/01/12

Dr. Wu Jiyu reply Internal Medicine

Based on the data you provided, the physician's response is correct because the current formula for estimating glomerular filtration rate (GFR) is derived from international sources, while domestic scholars have been researching a formula specific to our population.
In summary, regular monitoring and controlling the three highs (such as your elevated fasting blood glucose levels) may result in a GFR of 90 ml/min/1.73m² or higher at your next check-up.
Thank you for your inquiry; the Nephrology Department at Changhua Hospital cares about your health.

Reply Date: 2016/01/12

More Info

Understanding kidney function is crucial, especially when interpreting lab results such as creatinine levels and estimated Glomerular Filtration Rate (eGFR). In your case, the recent lab results indicate a creatinine level of 1.0 mg/dL and an eGFR of approximately 88.41 mL/min/1.73 m². Let’s break down what these numbers mean and how they relate to your kidney health.

Creatinine and eGFR: What They Indicate
Creatinine is a waste product generated from muscle metabolism and is typically filtered out of the blood by the kidneys. The normal range for serum creatinine is generally between 0.6 to 1.2 mg/dL for adult males, although this can vary slightly depending on the laboratory. Your creatinine level of 1.0 mg/dL falls within the normal range, suggesting that your kidneys are effectively filtering this waste product from your blood.

The eGFR is a calculated estimate of how well your kidneys are filtering blood, based on your creatinine level, age, sex, and sometimes race. An eGFR of 88.41 mL/min/1.73 m² indicates that your kidney function is still within the normal range, as values above 60 mL/min are generally considered acceptable. However, eGFR values between 60 and 89 mL/min can indicate a mild decrease in kidney function, which is often classified as Stage 2 chronic kidney disease (CKD) if persistent.

Interpreting Your Results in Context
While your eGFR suggests a mild decrease in kidney function, it is essential to consider the context of your overall health. You mentioned experiencing symptoms such as foamy urine and increased frequency of urination, particularly after consuming sugary drinks. Foamy urine can sometimes indicate the presence of protein, but your urine tests showed no protein or glucose, which is reassuring. The absence of these substances suggests that your kidneys are functioning well in terms of filtering waste and maintaining proper balance.

The slight elevation in fasting blood sugar (102 mg/dL) does warrant further investigation, as it is above the normal range (70-100 mg/dL) and could indicate prediabetes. This condition can have implications for kidney health, as diabetes is a leading cause of kidney disease. It would be prudent to follow your doctor's advice and consult with a metabolic specialist to monitor your blood sugar levels and assess your risk for diabetes.

Next Steps and Recommendations
1. Monitoring: Continue to monitor your kidney function through regular check-ups. Given that your eGFR is currently at 88.41, it is essential to keep track of any changes over time. Regular blood tests for creatinine and urine tests for protein will help in this regard.

2. Lifestyle Modifications: Adopt a kidney-friendly lifestyle. This includes maintaining a balanced diet low in sodium and processed sugars, staying hydrated, and engaging in regular physical activity. These changes can help manage your blood sugar levels and support overall kidney health.

3. Follow-Up: Since you have experienced symptoms that concern you, and given the slight elevation in fasting blood sugar, it is advisable to follow up with your healthcare provider. They may recommend additional tests, such as an HbA1c test to assess your average blood sugar levels over the past few months, and possibly a referral to a nephrologist if there are further concerns about your kidney function.

4. Stay Informed: Continue to educate yourself about kidney health and the implications of your lab results. Understanding the significance of eGFR and creatinine levels can empower you to make informed decisions about your health.

In conclusion, while your current kidney function appears to be within a normal range, the context of your symptoms and slightly elevated blood sugar levels suggests that ongoing monitoring and lifestyle adjustments are essential. Engaging with your healthcare team will provide you with the best strategies for maintaining your kidney health and overall well-being.

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