An estimated Glomerular Filtration Rate (eGFR) test result of 42 can raise questions about kidney health. This blood test measures how well your kidneys filter waste from your blood. Your kidneys contain millions of tiny filtering units called glomeruli, which clean the blood by removing toxins and excess water. The eGFR calculation estimates the volume of blood these glomeruli filter per minute, providing a snapshot of kidney function.
Interpreting an eGFR Result of 42
A normal eGFR value in adults is generally above 90 mL/min/1.73m², though this number can decrease with age. An eGFR of 42 mL/min/1.73m² indicates a moderate decrease in kidney function. This result places an individual in Stage 3b Chronic Kidney Disease (CKD).
CKD is categorized into five stages based on eGFR levels. Stage 3 represents a range between 30 and 59 mL/min/1.73m², with Stage 3b specifically including eGFR values from 30 to 44 mL/min/1.73m². At this stage, the kidneys have sustained moderate damage, and their ability to filter waste and extra fluid from the blood is impaired.
Potential Symptoms and Complications
Many individuals with Stage 3b CKD may experience few or no noticeable symptoms, often leading to its discovery through routine blood tests. When symptoms do appear, they are typically a result of waste products accumulating in the body. These can include:
- Persistent fatigue and weakness
- Swelling (edema) in the legs, ankles, or feet
- Changes in urination frequency or appearance
- Dry, itchy skin
- Trouble concentrating
- Muscle cramps
- Mild back pain
As kidney function declines, doctors will monitor for potential complications that can arise with Stage 3 CKD. These include:
- Development or worsening of high blood pressure
- Anemia (a reduced red blood cell count)
- Early signs of bone disease, where blood levels of calcium and phosphorus may become imbalanced
- Metabolic acidosis (a buildup of acid in the blood)
Common Causes of Reduced Kidney Function
Reduced kidney function, such as an eGFR of 42, often stems from underlying health conditions that gradually damage the kidneys. The two most frequent causes of chronic kidney disease are diabetes and high blood pressure. In diabetes, persistently high blood sugar levels can harm the tiny blood vessels within the kidneys’ filtering units, leading to impaired filtration and potential protein leakage into the urine. High blood pressure can damage and narrow the blood vessels that supply the kidneys, reducing blood flow and impeding their ability to remove waste and excess fluid.
Other conditions can also contribute to decreased kidney function. These include:
- Autoimmune diseases, such as lupus, which can cause inflammation that damages the kidney’s filtering units.
- Polycystic kidney disease, a genetic disorder leading to the growth of fluid-filled cysts in the kidneys.
- Physical obstructions in the urinary tract, like recurrent kidney stones or an enlarged prostate, which can block urine flow.
- Certain medications, including non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen, and some proton pump inhibitors (PPIs).
Management and Next Steps
Upon receiving an eGFR result of 42, the immediate next step involves a thorough discussion with a healthcare provider to understand the implications and develop a personalized management plan. The doctor will likely confirm the result and may order additional tests, such as a urine albumin-to-creatinine ratio (ACR) test, which measures protein in the urine and helps assess the extent of kidney damage. This combination of eGFR and ACR provides a more complete picture of kidney health.
The primary goal of managing Stage 3b CKD is to slow its progression and minimize further kidney damage.
Lifestyle Modifications
Lifestyle modifications play a significant role in achieving this. Controlling blood pressure, often targeting below 130/80 mmHg, and managing blood sugar levels for individuals with diabetes are important, as these conditions directly impact kidney health. Dietary changes are also frequently recommended, including reducing sodium intake to less than 2,000-2,300 mg per day to help manage blood pressure and fluid retention. Healthcare providers may also advise a moderate protein intake, around 0.8 grams per kilogram of body weight daily, and potentially restricting potassium or phosphorus if blood levels are elevated.
Medications and Monitoring
Avoiding nephrotoxic medications, particularly over-the-counter NSAIDs like ibuprofen, is recommended to prevent additional strain on the kidneys. Medications such as Angiotensin-Converting Enzyme (ACE) inhibitors (e.g., lisinopril) or Angiotensin Receptor Blockers (ARBs) (e.g., losartan) are frequently prescribed. These help protect the kidneys by relaxing blood vessels and reducing stress on the filtering units, even in individuals without high blood pressure. Regular follow-up appointments, often every 3-6 months, are necessary to monitor kidney function and adjust treatment as needed.