Glomerulonephritis is a group of kidney diseases that involve inflammation or damage to the tiny filters inside your kidneys, called glomeruli. These small but vital structures are responsible for cleaning your blood, and when they become damaged, your kidneys may struggle to remove waste and excess fluid from your body. The condition can appear suddenly or develop gradually over time, and while some people experience no symptoms at all, others may notice changes in their urine or swelling in their face and legs.

What Is Glomerulonephritis?

Glomerulonephritis, often shortened to GN, refers to a collection of kidney diseases that affect the glomeruli. Each of your kidneys contains roughly one million of these tiny filtering units, which are made up of clusters of tiny blood vessels called capillaries. When blood flows through a glomerulus, these small vessels act like a sieve, allowing water, minerals, nutrients, and waste products to pass through while keeping larger molecules like proteins and red blood cells in your bloodstream. The filtered fluid then continues through the rest of the kidney structure, where the body reclaims what it needs and converts the remaining waste into urine.^[1]

In glomerulonephritis, something goes wrong with this filtering system. The glomeruli become inflamed or damaged, often because the immune system mistakenly attacks healthy kidney tissue. This damage disrupts the normal filtering process, potentially allowing blood and protein to leak into the urine while also preventing the kidneys from properly removing waste products from the bloodstream. The term encompasses many different conditions with various causes, but they all share this common feature of glomerular injury.^[5]

The disease can appear in two main forms. Acute glomerulonephritis comes on suddenly, often after an infection, and may resolve with treatment or even on its own in some cases. Chronic glomerulonephritis develops slowly over months or years and tends to cause progressive damage to the kidneys. Some people experience an acute episode first and then develop chronic disease years later. The distinction between these forms is important because it affects both the approach to treatment and the long-term outlook for kidney function.^[2]

Epidemiology: How Common Is This Condition?

Understanding how frequently glomerulonephritis occurs can be challenging because it encompasses many different diseases with varying patterns of occurrence. The condition can affect people of all ages, though certain types are more common in specific age groups or populations. While exact global statistics are difficult to determine, glomerulonephritis represents an important cause of kidney disease worldwide, contributing to both temporary kidney problems and long-term kidney failure.^[5]

One particular form of the disease, acute post-streptococcal glomerulonephritis, provides a useful example of how patterns have changed over time. This type develops after a throat or skin infection with streptococcal bacteria. In the United States and other developed countries, the incidence of post-streptococcal glomerulonephritis has decreased significantly in recent decades, likely due to improved living conditions and better access to antibiotics for treating strep infections. However, it remains a concern in developing countries where these infections are more common and less likely to receive prompt treatment.^[5]

Interestingly, while streptococcal-related cases have declined, glomerulonephritis associated with Staphylococcus aureus infections has increased in the United States and other developed nations. This shift reflects changing patterns of infection and possibly the aging population, as older adults are more vulnerable to staph infections. The disease can also appear as part of systemic conditions like lupus or diabetes, which means its occurrence patterns often mirror those of the underlying diseases.^[5]

Children can develop glomerulonephritis, particularly the acute form following infections. In pediatric cases, the disease often appears after a strep throat or upper respiratory infection, typically manifesting one to two weeks after the initial illness. The condition is also seen in association with rare inherited disorders, though these genetic forms are uncommon overall.^[13]

Causes: What Leads to Kidney Filter Damage?

The causes of glomerulonephritis are diverse, and in many cases, doctors cannot identify a specific trigger. However, research has identified several important pathways through which the disease can develop. Understanding these causes helps guide both treatment and prevention efforts.^[2]

Infections represent one of the most common triggers for acute glomerulonephritis. When your body fights off certain bacterial, viral, or parasitic infections, the immune response can sometimes go awry and damage the kidneys. Strep throat, caused by group A streptococcal bacteria, is a classic example. After the initial throat infection resolves, some people develop kidney inflammation as their immune system creates antibodies that inadvertently attack the glomeruli. This typically occurs one to three weeks after the infection. Similarly, bacterial infections of the heart valves, called bacterial endocarditis, can trigger kidney damage. Viral infections including HIV, hepatitis B, and hepatitis C are also known to cause glomerulonephritis in some patients.^[2]

Autoimmune diseases, in which the immune system mistakenly attacks the body’s own tissues, are another important cause. Systemic lupus erythematosus, commonly called lupus, frequently affects the kidneys and can cause a specific form of glomerulonephritis called lupus nephritis. Other autoimmune conditions that can damage the glomeruli include anti-GBM disease (formerly known as Goodpasture syndrome), which affects both the lungs and kidneys, and various forms of vasculitis, which involve inflammation of blood vessels throughout the body. These include granulomatosis with polyangiitis (formerly Wegener’s disease), microscopic polyangiitis, and Henoch-Schönlein purpura.^[2]

Some kidney diseases have glomerulonephritis as their primary feature. IgA nephropathy, for instance, occurs when an antibody called immunoglobulin A builds up in the glomeruli, causing inflammation and damage. This is one of the most common types of glomerulonephritis worldwide. Other primary kidney diseases that affect the glomeruli include minimal change disease and focal segmental glomerulosclerosis, though these conditions involve different mechanisms of damage.^[5]

Certain cancers can also lead to glomerulonephritis. Multiple myeloma, Hodgkin’s and non-Hodgkin’s lymphoma, leukemia, and solid tumors such as lung, colon, and thyroid cancer have all been associated with kidney damage affecting the glomeruli. The exact mechanisms vary, but they may involve the immune system’s response to the cancer or substances produced by cancer cells.^[2]

In rare cases, glomerulonephritis runs in families, suggesting a genetic component. One example is Alport syndrome, an inherited condition that affects both men and women, though men are more likely to develop serious kidney problems. However, most cases of glomerulonephritis are not inherited.^[13]

Risk Factors: Who Is More Likely to Develop This Disease?

While anyone can develop glomerulonephritis, certain factors increase the likelihood that the disease will occur. Understanding these risk factors can help people and their healthcare providers stay alert for early signs of kidney problems.^[2]

A personal or family history of kidney disease is an important risk factor. If you have previously experienced kidney problems or if close relatives have had kidney disease, your risk of developing glomerulonephritis may be higher than average. This is particularly true for the rare genetic forms of the disease, but even non-inherited types can show some familial clustering.^[2]

People with autoimmune conditions face elevated risk because these diseases can directly attack the kidneys. Anyone diagnosed with lupus, vasculitis, or similar conditions should have their kidney function monitored regularly, as glomerulonephritis can develop even when the underlying autoimmune disease seems well-controlled.^[2]

Certain infections increase the risk, particularly strep throat and other streptococcal infections. While most people who get strep throat will not develop kidney complications, the risk exists, especially if the infection goes untreated. Bacterial endocarditis, HIV, and hepatitis infections also raise the risk of kidney damage. People who inject drugs or have other risk factors for these infections should be aware of this connection.^[2]

Exposure to certain medications and toxins has been linked to glomerulonephritis in some cases. While the sources do not specify which medications are most problematic, it’s always important to discuss potential kidney effects with your doctor when starting a new medication, especially if you already have risk factors for kidney disease. Similarly, certain toxic substances can damage the kidneys, though specific exposures vary.^[2]

Cancer patients, particularly those with blood cancers like lymphoma and leukemia or solid tumors, have an increased risk of developing glomerulonephritis. The cancer itself, rather than its treatment, appears to be the primary risk factor in many cases, though chemotherapy and other cancer treatments can also affect kidney function.^[2]

Symptoms: What Does Glomerulonephritis Feel Like?

One of the challenges in diagnosing glomerulonephritis is that many people with the condition experience no symptoms at all, especially in the early stages or in mild cases. The disease is sometimes discovered incidentally during routine blood or urine tests performed for other reasons. When symptoms do occur, they can vary widely depending on whether the disease is acute or chronic and how severely the kidneys are affected.^[2]

Changes in urine appearance are among the most noticeable signs. Blood in the urine, called hematuria, can make urine look pink, brown, or even red, though sometimes the blood is only visible under a microscope. Urine may also appear foamy or bubbly, which happens when excess protein leaks through the damaged filters and into the urine. This is called proteinuria, and it represents one of the hallmark features of glomerular damage. Some people notice they are urinating less frequently than usual, or that the amount of urine they produce has decreased.^[1][2]

Swelling, medically termed edema, often appears in the face, especially around the eyes, and in the legs, ankles, and feet. This happens because damaged kidneys cannot properly remove excess fluid from the body, and because protein loss in the urine disrupts the normal balance of fluids between blood vessels and tissues. The swelling is typically more noticeable in the morning after lying down all night, and it may improve somewhat as the day progresses and gravity pulls fluid downward.^[1]

High blood pressure frequently develops in people with glomerulonephritis. The kidneys play a crucial role in regulating blood pressure, so when they’re damaged, blood pressure often rises. Some people may experience headaches, dizziness, or other symptoms related to elevated blood pressure, though hypertension itself often causes no noticeable symptoms until it reaches very high levels.^[2]

Breathing difficulties can occur, particularly if fluid accumulates in the lungs or if the disease has progressed to significantly impair kidney function. Shortness of breath may be worse when lying flat and might improve when sitting up. This symptom requires prompt medical attention.^[2]

General symptoms can include fatigue, nausea, loss of appetite, and weight loss. Some people develop a rash, particularly if the glomerulonephritis is associated with vasculitis or lupus. Joint pain and abdominal discomfort may also occur. In cases related to infections, fever might be present. Jaundice, a yellowing of the skin and eyes, can develop in some situations.^[2]

The pattern of symptoms can provide clues about the underlying problem. For instance, when glomerulonephritis develops after a strep infection, symptoms typically appear one to two weeks after the throat infection seemed to resolve. The sudden onset of dark urine and facial swelling in a child who recently had strep throat is a classic presentation that should prompt immediate medical evaluation.^[13]

Prevention: Can You Reduce Your Risk?

While not all cases of glomerulonephritis can be prevented, there are steps you can take to reduce your risk, particularly for forms of the disease that develop after infections or as complications of other conditions.^[9]

Preventing and treating infections promptly is one of the most important preventive measures. If you develop a sore throat, especially with fever and swollen lymph nodes, see a healthcare provider to determine whether you have strep throat. If strep is diagnosed, taking the full course of prescribed antibiotics as directed is crucial, even if you start feeling better before the medication is finished. This helps eliminate the infection completely and reduces the risk of complications including glomerulonephritis. Good hygiene practices, such as regular handwashing, can help prevent the spread of streptococcal and other infections.^[5]

For people with chronic conditions that can affect the kidneys, such as diabetes or lupus, careful management of the underlying disease is essential. This means working closely with your healthcare team, taking medications as prescribed, monitoring blood sugar levels if you have diabetes, and keeping all scheduled appointments. Regular screening for kidney problems allows for early detection and intervention before significant damage occurs.^[9]

Avoiding or minimizing exposure to substances that can harm the kidneys is another preventive strategy. This includes being cautious with medications known to affect kidney function and avoiding the use of intravenous drugs, which carry risks of infections like HIV and hepatitis that can damage the kidneys. If you must take medications with potential kidney effects, regular monitoring of kidney function can catch problems early.^[2]

Maintaining overall health through lifestyle measures supports kidney function. Not smoking is particularly important, as smoking worsens kidney disease and increases the risk of complications in people who already have glomerulonephritis. Maintaining a healthy blood pressure through diet, exercise, and medication if needed helps protect the kidneys. A diet low in salt can help control blood pressure and reduce fluid retention.^[9]

Vaccination can play a role in prevention. Because glomerulonephritis can make you more vulnerable to infections, and because infections can trigger or worsen the disease, staying up to date with recommended vaccines is important. This includes annual flu shots and pneumonia vaccines as recommended by your healthcare provider.^[9][18]

Pathophysiology: How Does Glomerulonephritis Damage the Kidneys?

Understanding the mechanisms by which glomerulonephritis damages the kidneys requires looking at what happens at the microscopic level within these tiny filtering structures. The pathophysiology, or the abnormal changes that occur in the body during disease, involves complex interactions between the immune system, blood vessels, and kidney tissues.^[5]

In healthy kidneys, each glomerulus consists of three main layers working together to filter blood. The innermost layer is a fenestrated endothelium, meaning it has tiny holes that allow small molecules to pass through. The middle layer is the glomerular basement membrane, a meshwork of proteins that acts like a selective barrier. The outer layer contains specialized cells called podocytes, which have foot-like projections that wrap around the capillaries and help maintain the filtration barrier. Mesangial cells, located between the capillaries, provide structural support and help regulate blood flow through the glomerulus.^[5]

In glomerulonephritis, immune-mediated damage affects one or more of these structures. The most common mechanism involves the deposition of immune complexes—clusters of antibodies bound to antigens—in the glomeruli. These immune complexes can form either in the bloodstream and then get trapped in the kidney filters, or they can form directly in the kidney when antibodies attack components of the glomerular structure itself. Once deposited, these complexes trigger inflammation as the body attempts to clear them away.^[5]

The inflammation causes several problems. It damages the delicate filtration barrier, making it more permeable than it should be. This increased permeability allows proteins, which are normally too large to pass through, to leak into the urine. When protein levels in the blood drop because of this loss, fluid shifts out of the blood vessels and into surrounding tissues, causing swelling. The inflammation can also damage blood cells passing through the glomeruli, leading to blood appearing in the urine.^[4]

At the same time, the inflammatory process and the accumulation of cells and debris in the glomeruli can reduce the surface area available for filtration. This means less blood gets filtered, and waste products that should be removed begin to accumulate in the bloodstream. This accumulation of waste is called azotemia, and it can be measured through blood tests that check levels of substances like creatinine and blood urea nitrogen.^[5]

The reduced filtration also affects fluid and salt balance in the body. When the kidneys don’t filter properly, they may retain sodium and water, leading to increased blood volume. This extra fluid volume puts additional pressure on blood vessel walls, resulting in high blood pressure. The elevated pressure, in turn, can cause further damage to the already compromised glomeruli, creating a harmful cycle.^[4]

In some forms of glomerulonephritis, the damage primarily affects the podocytes rather than causing widespread inflammation. When these specialized cells are damaged, they cannot maintain the filtration barrier properly, leading to massive protein loss in the urine. This pattern is seen in conditions like minimal change disease, where the glomeruli may look almost normal under standard microscopy but show damage when examined with electron microscopy.^[5]

The disease can follow different patterns of injury that pathologists classify when examining kidney tissue under a microscope. Some forms are described as proliferative, meaning there is an abnormal increase in the number of cells in the glomeruli, whether these are inflammatory cells infiltrating from the blood or the kidney’s own cells multiplying in response to injury. Other forms are non-proliferative, showing damage without the prominent cellular increase. These patterns help doctors understand the specific type of glomerulonephritis and guide treatment decisions.^[4]

Without treatment, or in severe cases despite treatment, the ongoing inflammation and damage lead to scarring of the glomeruli, a process called glomerulosclerosis. Scarred glomeruli cannot filter blood at all. As more and more filtering units become scarred and non-functional, overall kidney function progressively declines. This can eventually lead to chronic kidney disease and, in the most severe cases, end-stage renal disease requiring dialysis or transplantation.^[5]