Chronic Kidney Disease (CKD) is a progressive condition where the kidneys sustain damage over time, leading to a decline in their ability to filter blood. Tracking this decline is done through a staging system, which allows healthcare providers to monitor severity and plan interventions. Stage 3 of this disease represents a moderate loss of function and is a significant point where a diagnosis can profoundly influence a person’s long-term health trajectory. This stage is often considered a clinical midpoint, setting the focus on stabilization to prevent further progression.
Understanding Chronic Kidney Disease Stage 3
Chronic kidney disease is categorized based on the estimated Glomerular Filtration Rate (eGFR). The eGFR is calculated from a blood test that measures creatinine, alongside a person’s age, sex, and race. A normal eGFR is typically above 90 mL/min/1.73 m².
Stage 3 CKD is defined by an eGFR that falls between 30 and 59 mL/min/1.73 m², indicating moderate damage and a noticeable loss of filtering capacity. This stage is further divided into two sub-categories. Stage 3a is characterized by an eGFR of 45–59 mL/min/1.73 m², representing a mild to moderate reduction in function.
Stage 3b is defined by an eGFR ranging from 30 to 44 mL/min/1.73 m², indicating a moderate to severe loss of function. At this point, the kidneys are less able to remove waste and excess fluid, which can lead to complications like anemia, high blood pressure, and bone issues. Many people with Stage 3 CKD experience few or no noticeable symptoms.
Symptoms, if present, are subtle and non-specific, often including fatigue, swelling in the feet or ankles, and changes in urination frequency. The lack of overt signs emphasizes why routine screening is necessary for individuals with known risk factors. Early diagnosis allows for the implementation of strategies that slow the disease’s advancement.
Statistical Prevalence of Stage 3 CKD
Stage 3 CKD represents the most frequent stage of the disease among adults. Globally, studies estimate that about 7.6% of the population has Stage 3 CKD, though this figure is often an underestimation. In the United States, approximately 5.1% of adults have Stage 3 CKD, with prevalence rates significantly increasing with age.
Prevalence is higher in older adults, with about 20.1% of individuals aged 65 years or older in the U.S. having Stage 3 CKD. The lifetime risk for an adult in the U.S. to develop Stage 3a or higher is estimated to be approximately 59.1%.
A major concern is the high percentage of people who remain undiagnosed. Over 60% of people with laboratory results consistent with Stage 3 CKD do not have a formal diagnosis recorded in their medical records. Undiagnosed cases are common among older adults and those with existing conditions like diabetes or hypertension. This lack of diagnosis means many individuals miss the opportunity for early intervention that could slow disease progression.
Main Drivers of Kidney Damage
Most Stage 3 CKD cases stem from two prevalent systemic diseases: uncontrolled Type 2 Diabetes and high blood pressure (hypertension). These conditions gradually damage the tiny filtering units within the kidneys called nephrons. About one in three U.S. adults with diabetes also have CKD, making it the most frequent cause.
High blood glucose levels in diabetes damage the small blood vessels and filters, causing them to leak protein into the urine. Hypertension is the second most frequent cause, as elevated blood pressure strains and damages the blood vessels supplying the kidneys. This damage impairs the filtering system, which can raise blood pressure further, creating a cycle of decline.
Other factors also contribute to kidney damage:
- Autoimmune disorders like lupus.
- Genetic conditions such as Polycystic Kidney Disease.
- Recurrent kidney infections.
- Chronic inflammation of the kidney filters (glomerulonephritis).
- Long-term use of certain medications.
Addressing these underlying causes is the primary way to manage and stabilize Stage 3 CKD.
Next Steps After Diagnosis
Active management focuses on stabilizing kidney function and slowing progression. The first step involves rigorous control of underlying conditions, particularly keeping blood pressure and blood sugar levels within target ranges. Medications like Angiotensin-Converting Enzyme (ACE) inhibitors or Angiotensin Receptor Blockers (ARBs) are often prescribed because they help protect the kidneys and slow disease advancement.
Lifestyle adjustments are integral to the treatment plan and include dietary modifications. A kidney-friendly diet involves limiting sodium intake to help control blood pressure and reducing protein consumption, as excessive protein creates more waste products for the kidneys to filter. Patients are also advised to avoid Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) like ibuprofen, as these common pain relievers can directly worsen kidney damage.
Regular monitoring is necessary to track the disease, including frequent testing of eGFR and the urine albumin-to-creatinine ratio (uACR). Working with a kidney specialist, or nephrologist, becomes important at this stage to coordinate care and manage potential complications like anemia or bone disease.