Learn About Kidney Disease and Its Progression

What Kidney Disease Is and How It Develops

The kidneys are two bean-shaped organs about the size of your fist. They sit on either side of your spine, just below the rib cage. These organs work constantly to filter waste from your blood and create urine. When your kidneys are healthy, they remove about 120 to 150 quarts of blood daily to produce roughly 1 to 2 quarts of urine containing waste and extra water.

Kidney disease happens when the kidneys lose their ability to filter waste properly. This occurs gradually over time in most cases. The medical term is chronic kidney disease, or CKD. Unlike some illnesses that appear suddenly, kidney disease typically develops slowly, sometimes over years or even decades. Many people do not realize they have kidney disease because they feel fine and have no symptoms.

Your kidneys filter waste through tiny structures called nephrons. Each kidney contains about one million nephrons. When these nephrons become damaged, they cannot be repaired or replaced. As more nephrons stop working, the kidneys must work harder with the remaining ones. Eventually, if enough nephrons are damaged, the kidneys cannot keep up with filtering waste, and harmful substances build up in your blood.

Kidney disease affects approximately 15% of American adults, according to the Centers for Disease Control and Prevention. This means about 37 million people in the United States have some degree of kidney disease, though many do not know it. The disease is more common in people over 65 years old and in those with diabetes or high blood pressure.

Understanding how kidney disease develops is important because early detection can slow or stop its progression. Regular blood and urine tests can reveal kidney damage before you experience any symptoms. If you have risk factors like diabetes, high blood pressure, a family history of kidney disease, or are over 60, talking with your doctor about kidney screening is worthwhile.

Practical takeaway: Kidney disease usually develops without symptoms, so regular screening through blood tests (checking creatinine and GFR levels) and urine tests is valuable if you have risk factors. Knowing your kidney function numbers helps you understand your health status.

Stages of Kidney Disease Progression

Kidney disease is divided into five stages based on how well your kidneys are working. Doctors measure this using a number called GFR, which stands for glomerular filtration rate. The GFR shows how many milliliters of waste your kidneys filter from your blood each minute. A normal GFR is 90 or higher.

Stage 1 kidney disease means your kidneys are functioning normally or near-normally, with a GFR of 90 or higher. However, there are signs of kidney damage, such as protein in your urine or a family history of kidney disease. At this stage, many people have no symptoms at all. The key during Stage 1 is to prevent further damage through managing conditions like high blood pressure and diabetes.

Stage 2 involves mild loss of kidney function, with a GFR between 60 and 89. Like Stage 1, people usually have no symptoms. Kidney damage is present but mild. During this stage, it is important to identify and treat the underlying cause of kidney disease. Managing blood pressure, controlling blood sugar if you have diabetes, and maintaining a healthy diet can slow progression significantly.

Stage 3 is divided into two parts: Stage 3a (GFR 45-59) and Stage 3b (GFR 30-44). This represents moderate loss of kidney function. Some people may begin to notice symptoms such as fatigue, swelling in the hands or feet, or changes in urination patterns. Kidney disease at this stage requires closer monitoring and may involve seeing a kidney specialist called a nephrologist.

Stage 4 means severe loss of kidney function, with a GFR between 15 and 29. Most people with Stage 4 kidney disease experience symptoms including fatigue, shortness of breath, difficulty concentrating, decreased appetite, and swelling. Planning for kidney replacement therapy, whether through dialysis or transplant, often begins at this stage. Many people meet with social workers and dietitians to prepare for upcoming treatment.

Stage 5 is end-stage kidney disease, or ESRD, with a GFR below 15. At this point, the kidneys are no longer able to filter waste adequately, and kidney replacement therapy is necessary. Most people with Stage 5 kidney disease begin dialysis or receive a kidney transplant. According to the National Kidney Foundation, about 37,000 people start treatment for kidney failure each year in the United States.

Practical takeaway: Knowing which stage of kidney disease you have helps you understand what to expect and what steps to take next. Regular monitoring and tracking your GFR over time shows whether your kidney function is stable or changing. Ask your doctor to explain your GFR number and what it means for your health.

Common Causes of Kidney Disease

Diabetes is the leading cause of kidney disease, responsible for about 30% of all cases in the United States. When blood sugar stays too high for years, it damages the blood vessels in the kidneys. This damage makes it harder for the kidneys to filter waste. Many people with diabetes do not realize their kidneys are being affected until significant damage has occurred. Regular monitoring is particularly important for anyone with diabetes.

High blood pressure is the second leading cause of kidney disease. High blood pressure damages the small blood vessels in the kidneys, reducing their ability to filter waste. This creates a difficult cycle: damaged kidneys often make blood pressure harder to control, which can damage the kidneys further. Managing blood pressure to goal levels, typically below 130/80 for people with kidney disease, can significantly slow kidney disease progression.

Glomerulonephritis is a group of diseases that cause inflammation of the kidney's filtering structures. Some forms develop suddenly after a strep infection, while others develop gradually without a clear cause. This condition can progress rapidly to kidney failure or may remain stable for years. Early treatment may slow or stop progression in some cases.

Polycystic kidney disease, or PKD, is an inherited condition where numerous cysts develop in the kidneys over time. These cysts replace normal kidney tissue and reduce kidney function. PKD typically progresses to kidney failure by age 50 or 60, though the timeline varies widely among individuals. People with PKD in their family history may benefit from genetic counseling and early screening.

Recurrent kidney infections and kidney stones can also lead to kidney disease. When infections damage kidney tissue repeatedly or when stones block urine flow for extended periods, scarring can result. Treating infections promptly and managing stone-forming conditions reduces this risk.

Other causes include autoimmune diseases like lupus, long-term use of certain pain medications (NSAIDs), obstruction of urine flow, and reduced blood flow to the kidneys from heart disease or severe dehydration. Some people develop kidney disease from a combination of factors rather than a single clear cause.

Practical takeaway: Understanding what caused your kidney disease helps guide treatment decisions. If you have diabetes or high blood pressure, managing these conditions carefully is one of the most important things you can do to protect your kidney function. If you do not know the cause of your kidney disease, ask your doctor for clarity—it may affect your treatment options.

Symptoms and Warning Signs

Early-stage kidney disease often produces no symptoms at all. This is why the condition is sometimes called a "silent" disease. Many people discover they have kidney disease by chance during a routine physical exam or blood test for another reason. However, as kidney disease progresses, symptoms become more noticeable.

Fatigue and weakness are among the most common symptoms people report. This occurs because damaged kidneys produce less of a hormone called erythropoietin, or EPO, which tells your bone marrow to make red blood cells. Without enough red blood cells to carry oxygen, your body feels tired. The fatigue from kidney disease can be severe enough to interfere with daily activities and work.

Swelling in the hands, feet, face, and around the eyes is another frequent symptom. This happens when the kidneys cannot filter excess water and salt, causing fluid to build up in tissues. Some people notice they cannot fit into their rings or shoes or that their face looks puffy. Swelling typically worsens as the day goes on and improves after lying down overnight.

Changes in urination patterns may indicate kidney problems. Some people urinate