Renal disorder, commonly known as kidney disease, affects millions of people worldwide and occurs when the kidneys lose their ability to filter blood effectively. Understanding this condition is essential because early detection and proper management can significantly slow its progression and help maintain quality of life.

Epidemiology

Chronic kidney disease is remarkably common across the United States and around the world. More than one in seven American adults, or approximately 35.5 million people, are estimated to have chronic kidney disease, though most remain unaware of their condition. In fact, as many as nine out of ten people with chronic kidney disease don’t know they have it, and about 40 percent of those with severely reduced kidney function who are not on dialysis are unaware of their diagnosis.^[6][1]

Globally, kidney failure affects more than 750,000 people in the United States each year and around 2 million people worldwide. Kidney diseases rank among the leading causes of death in the United States. Every single day, approximately 360 people begin dialysis treatment for kidney failure. The condition shows no preference for gender in its basic occurrence, though certain risk factors may affect men and women differently. As people age, the risk for developing kidney disease increases, making it particularly concerning for older adults.^[5][6]

Causes

The root causes of kidney disease are varied, but two conditions stand out as the most common culprits. Diabetes and high blood pressure together account for the majority of chronic kidney disease cases. When diabetes remains unmanaged, elevated blood sugar levels can damage the tiny blood vessels in the kidneys over time, impairing their ability to filter waste effectively. Similarly, persistent high blood pressure puts constant strain on the delicate filtering units within the kidneys, gradually destroying their function.^[5][12]

Beyond these two primary causes, several other conditions can lead to kidney damage. Heart disease creates a bidirectional risk, as it can contribute to kidney problems while kidney disease itself increases the risk of cardiovascular complications. Some people inherit genetic conditions that affect kidney health, such as polycystic kidney disease, which causes cysts to form in the kidneys and gradually impair their function. Autoimmune diseases like lupus or IgA nephropathy can cause the body’s immune system to attack the kidneys, leading to inflammation and damage.^[1]

Structural defects in the kidneys, whether present from birth or developed later, can also interfere with normal kidney function. Acute kidney injuries, which develop quickly due to sudden events like severe infections, major surgery, or exposure to certain medications or toxins, can sometimes lead to permanent damage if not treated promptly. In some cases, the exact cause of kidney disease remains unknown even after thorough investigation.^[1]

Risk Factors

Several groups of people face higher odds of developing kidney disease based on their health conditions, family history, and lifestyle factors. Having diabetes or high blood pressure substantially increases your risk, as these conditions directly damage kidney structures over time. If you have heart disease, your kidneys are also at greater risk because the heart and kidneys work closely together to maintain overall health.^[6]

Family history plays a significant role in kidney disease risk. If close family members have experienced kidney disease, you carry a higher likelihood of developing it yourself, particularly if the family history includes genetic conditions affecting the kidneys. Age is another unavoidable risk factor, as the natural aging process can reduce kidney function and older adults face increased vulnerability to kidney damage.^[1]

Obesity adds to the burden on your kidneys by increasing the risk of diabetes and high blood pressure, the two leading causes of kidney disease. Smoking damages blood vessels throughout the body, including those in the kidneys, and can worsen existing kidney disease while interfering with medications designed to lower blood pressure. Excessive alcohol consumption also puts strain on kidney function. Certain medications, particularly nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, can harm the kidneys when used regularly or in high doses, especially in people who already have some degree of kidney impairment.^[11]

Symptoms

One of the most challenging aspects of kidney disease is that many people experience few or no symptoms during the early stages. The condition can silently cause damage even when you feel perfectly fine, which is why it’s often called a “silent disease.” However, as kidney function declines, various symptoms may begin to appear, affecting daily life and overall well-being.^[5][12]

Extreme tiredness or fatigue is one of the most common symptoms reported by people with declining kidney function. This exhaustion goes beyond normal tiredness and doesn’t improve much with rest. It occurs because damaged kidneys don’t produce enough of a hormone that signals the body to make red blood cells, leading to anemia, which is a condition where the blood lacks sufficient healthy red blood cells to carry adequate oxygen to tissues.^[5]

Changes in urination patterns often signal kidney problems. You might notice changes in how often you need to urinate, particularly waking up frequently during the night to use the bathroom. Some people see blood in their urine, while others notice their urine appears foamy or bubbly, which indicates protein leaking into the urine. In advanced kidney disease, the amount of urine produced may actually decrease as the kidneys lose their filtering capacity.^[8][19]

Swelling, medically termed edema, frequently develops in people with kidney disease. This puffiness typically appears around the ankles and feet first, but can also affect the hands, face, and other body parts. The swelling occurs because damaged kidneys cannot remove excess fluid from the body, causing it to accumulate in tissues. Some people experience weight gain related to this fluid retention.^[5]

Digestive symptoms commonly accompany kidney disease. Nausea and vomiting can become persistent problems, and many people lose their appetite or find that food tastes different, often metallic. These changes happen because waste products building up in the blood affect the digestive system and alter taste sensations. Confusion or difficulty concentrating, sometimes described as “brain fog,” can develop as toxins accumulate in the bloodstream. Other symptoms include persistent itching of the skin, muscle cramps, shortness of breath, and restless legs, particularly at night.^[5][8][19]

Prevention

While you cannot always prevent kidney disease, especially when genetic factors are involved, you can take concrete steps to protect your kidney health and reduce your risk significantly. These preventive measures focus on controlling the conditions that most commonly lead to kidney damage and maintaining overall health.^[6]

Keeping your blood pressure under control stands as one of the most important protective measures. Healthcare providers generally recommend maintaining blood pressure below 140/90 mm Hg, though your doctor may set a different target based on your individual situation. For people with diabetes, controlling blood sugar levels is equally critical. Staying within your target blood sugar range as much as possible helps protect the small blood vessels in your kidneys from damage caused by elevated glucose levels.^[6][22]

Physical activity benefits kidney health in multiple ways. Regular exercise helps control blood pressure and blood sugar levels, both of which directly affect kidney function. The general recommendation is to aim for at least 150 minutes of moderate physical activity each week. This doesn’t mean you need to become an athlete; even activities like brisk walking, swimming, or gardening count toward this goal.^[6]

Making healthy food choices supports kidney health and overall wellbeing. A balanced diet rich in fresh fruits and vegetables, whole grains, and low-fat dairy products provides essential nutrients without overburdening your kidneys. Reducing salt intake is particularly important, with experts recommending less than 2,300 milligrams of sodium per day. Cooking at home with herbs and spices instead of salt, choosing fresh foods over processed ones, and reading food labels carefully can help you meet this goal. Limiting added sugars to less than 10 percent of daily calories also protects both kidney function and overall metabolic health.^[22]

If you smoke, quitting represents one of the most beneficial changes you can make for your kidneys. Smoking worsens kidney disease, damages blood vessels, and interferes with blood pressure medications. Managing alcohol consumption is also advisable, as excessive drinking can increase blood pressure and add extra calories that contribute to obesity. Maintaining a healthy weight through balanced eating and regular activity reduces the strain on your kidneys and lowers your risk of diabetes and high blood pressure.^[6][11]

Regular testing becomes essential if you fall into high-risk categories. Getting screened for kidney disease allows for early detection when interventions can be most effective. Blood and urine tests can reveal kidney problems before symptoms appear. Certain medications, particularly angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs), may be prescribed to protect your kidneys in addition to lowering blood pressure. Taking all prescribed medications as directed and avoiding over-the-counter pain medications like NSAIDs without consulting your doctor helps prevent medication-related kidney damage.^[6][22]

Pathophysiology

Understanding what happens inside the body when kidney disease develops helps explain why symptoms occur and why certain treatments are necessary. Your kidneys are bean-shaped organs, each about the size of your fist, located near the middle of your back on either side of your spine, just below your rib cage. Though small, they perform vital functions that keep your entire body in balance.^[5][12]

Inside each kidney lie about one million tiny filtering units called nephrons. These microscopic structures work constantly to clean your blood, removing waste products, toxins, and excess water, which then leave your body as urine. The kidneys filter all the blood in your body approximately every 30 minutes, processing about 200 quarts of blood daily to produce about 2 quarts of urine. Beyond waste removal, the kidneys perform several other essential jobs: they help control blood pressure, signal the body to produce red blood cells, activate vitamin D so your body can use it to maintain bone health, and balance the amounts of important minerals and electrolytes such as sodium, potassium, phosphorus, and calcium.^[3][6]

When kidney disease develops, it typically attacks the nephrons, causing progressive damage that impairs their filtering ability. Most kidney diseases cause this damage slowly over months or years, though acute kidney injury can occur rapidly over hours or days. As nephrons become damaged, they lose their ability to filter blood effectively. Waste products and toxins that should be removed begin to accumulate in the bloodstream, while substances the body needs, like protein, may leak into the urine and be lost.^[3]

The disease progresses through five stages based on how well the kidneys filter substances, measured by something called the estimated glomerular filtration rate (eGFR). A normal eGFR is above 90, indicating the kidneys are filtering efficiently. In Stage 1, the eGFR remains higher than 90, but there are signs of mild kidney damage. Stage 2 shows an eGFR between 60 and 89 with more evident damage, though the kidneys still function reasonably well. Stage 3 is divided into two parts: Stage 3a with eGFR between 45 and 59, and Stage 3b with eGFR between 30 and 44, both indicating mild to moderate loss of kidney function. Stage 4 represents severe loss of function with eGFR between 15 and 29. Stage 5, or end-stage kidney disease (ESKD), occurs when eGFR drops below 15, meaning the kidneys have failed or are very close to complete failure.^[5][12]

As kidney function declines, multiple body systems become affected. The kidneys can no longer remove enough fluid, leading to fluid buildup in tissues and potentially in the lungs, causing swelling and shortness of breath. They fail to balance electrolytes properly, which can result in dangerous levels of potassium that affect heart rhythm, or low levels of calcium that weaken bones. The accumulation of waste products in the blood causes the fatigue, nausea, confusion, and other symptoms people experience. Without adequate production of the hormone that stimulates red blood cell formation, anemia develops, contributing to fatigue and weakness. The inability to activate vitamin D properly affects bone health, and the disruption of blood pressure regulation can create a vicious cycle where high blood pressure both causes and results from kidney damage.^[6]

In the most advanced stage of kidney disease, the kidneys can no longer sustain life on their own. At this point, waste and fluid buildup becomes life-threatening without treatment. People with end-stage kidney disease require either dialysis, which is a treatment that artificially filters the blood using a machine or the body’s own tissues, or a kidney transplant to survive. Even with these serious consequences, many people with early to moderate chronic kidney disease can slow progression through proper management and never reach kidney failure.^[5][13]