Acute glomerulonephritis is a sudden inflammation of the tiny filters in your kidneys, called glomeruli. When these delicate structures become swollen and damaged, your kidneys struggle to clean your blood properly, which can lead to visible changes in your urine and swelling throughout your body.
Understanding Acute Glomerulonephritis
Acute glomerulonephritis is a type of kidney disease that develops quickly, often over days or weeks. Inside each of your kidneys, there are roughly a million tiny filtering units called glomeruli. These are clusters of microscopic blood vessels that work continuously to remove waste products and excess fluid from your blood. This filtered material becomes urine, which carries waste out of your body.[1]
When acute glomerulonephritis occurs, these glomeruli become inflamed and irritated. The inflammation damages their delicate structure, causing them to leak substances that should stay in your bloodstream—like proteins and red blood cells—into your urine. At the same time, the damaged filters cannot remove waste and fluid as efficiently, leading to a buildup of both in your body.[2]
Many people with acute glomerulonephritis don’t notice symptoms right away. In fact, about half of those affected experience no warning signs at all. The condition might only be discovered when a routine urine test reveals blood or protein where none should be.[7]
This condition differs from chronic glomerulonephritis, which develops slowly over months or years. Acute glomerulonephritis appears suddenly, and while many cases improve with proper treatment, some people may later develop the chronic form years after their initial episode.[1]
Epidemiology
The pattern of acute glomerulonephritis has shifted significantly in recent decades. Historically, acute poststreptococcal glomerulonephritis—which develops after a streptococcal infection like strep throat—was the most common form. This type typically affects children between the ages of 2 and 10 years.[7]
In recent years, the incidence of poststreptococcal glomerulonephritis has declined in the United States and other developed countries. This reduction likely reflects improved access to antibiotics and better treatment of streptococcal infections before they can trigger kidney inflammation. However, the disease remains more common in developing regions where access to healthcare may be limited.[3]
Interestingly, while streptococcal cases have decreased, glomerulonephritis associated with staphylococcal infections has increased. This shift is largely due to the rise of antibiotic-resistant Staphylococcus aureus infections, which have become more prevalent in healthcare settings and communities.[3]
Acute glomerulonephritis progresses to chronic kidney disease in about 30% of adults who develop the condition. Children generally have better outcomes than adults, with fewer long-term complications.[3]
Causes of Acute Glomerulonephritis
Acute glomerulonephritis develops when the glomeruli become inflamed, usually because of an immune system reaction. The body’s defense system, which normally fights off infections and foreign substances, sometimes mistakenly attacks the kidney’s filtering units. This immune response causes inflammation and damage to the glomerular tissue.[3]
One of the most well-known triggers is a bacterial infection with streptococcus, the same bacteria that causes strep throat or skin infections. When acute glomerulonephritis follows a streptococcal infection, it’s called acute poststreptococcal glomerulonephritis. This form typically appears more than one week after the person has recovered from the initial infection, such as a throat or skin infection.[13]
Other bacterial infections can also lead to acute glomerulonephritis. Staphylococcus and pneumococcus bacteria are known culprits. Additionally, bacterial endocarditis—an infection of the heart valves—can trigger kidney inflammation as a complication.[1]
Viral infections represent another important cause. Viruses such as hepatitis B, hepatitis C, and HIV can lead to glomerular inflammation. Even common childhood illnesses like chickenpox have been associated with acute glomerulonephritis. Parasitic infections, including malaria, can also trigger the condition.[7]
Sometimes, the inflammation results from autoimmune disorders, where the immune system attacks the body’s own tissues. Systemic lupus erythematosus (commonly called lupus) is one such condition that can affect the kidneys. Other immune-related causes include Anti-GBM disease (formerly called Goodpasture syndrome), which affects both the lungs and kidneys, and IgA nephropathy, where abnormal antibodies build up in the kidneys.[1]
Rare diseases that cause blood vessel inflammation—known as vasculitis—can also lead to acute glomerulonephritis. These include granulomatosis with polyangiitis, microscopic polyangiitis, and Henoch-Schönlein purpura.[1]
Risk Factors
Not everyone who develops a strep throat infection or other triggering condition will go on to develop acute glomerulonephritis. However, certain factors can increase the likelihood of developing this kidney disease.[1]
Having a personal or family history of kidney disease makes you more vulnerable to glomerulonephritis. If close relatives have experienced kidney problems, your risk may be elevated. In rare cases, the condition can run in families due to inherited genetic factors.[1]
Recent or current infections increase risk significantly. Streptococcal infections of the throat or skin are particularly important risk factors, especially in children. Other bacterial infections, such as bacterial endocarditis, also raise the likelihood of developing kidney inflammation. Viral infections like HIV, hepatitis B, and hepatitis C are known to be associated with increased risk.[1]
People with autoimmune conditions face a higher risk of acute glomerulonephritis. Conditions like lupus, where the immune system attacks the body’s own tissues, can extend their effects to the kidneys. Those diagnosed with vasculitis—diseases that inflame blood vessels—also have an elevated risk.[1]
Certain medications and exposure to specific toxins can trigger kidney inflammation in susceptible individuals. While the sources don’t specify which medications or toxins, it’s important to discuss any concerns about your medications with your healthcare provider.[1]
Having certain types of cancer, such as multiple myeloma, can also increase the risk of developing glomerulonephritis. The relationship between cancer and kidney inflammation is complex and may involve the immune system’s response to the cancer itself.[1]
Symptoms of Acute Glomerulonephritis
The symptoms of acute glomerulonephritis can vary widely from person to person. Some individuals experience obvious signs that something is wrong with their kidneys, while others have no symptoms at all and only discover the condition through routine medical testing.[7]
One of the most noticeable symptoms is changes in urine. Blood in the urine, called hematuria, can make urine appear brown, pink, or red. This happens because damaged glomeruli allow red blood cells to leak into the urine. The urine might also look foamy or bubbly, which occurs when protein leaks into it—a condition called proteinuria. These visible changes often prompt people to seek medical attention.[1]
Swelling, medically known as edema, is another common symptom. This occurs because damaged kidneys cannot remove excess fluid from the body effectively. The swelling is often most noticeable in the face, especially around the eyes when you wake up in the morning. It can also affect the legs, ankles, feet, and hands. As fluid accumulates, you might notice that your shoes feel tighter or rings don’t fit as easily.[2]
Changes in urination patterns can occur. Some people urinate less frequently than usual, or produce smaller amounts of urine. Others might urinate more often. These changes reflect the kidneys’ impaired ability to regulate fluid balance properly.[1]
High blood pressure, or hypertension, frequently develops with acute glomerulonephritis. This happens because damaged kidneys cannot properly regulate the amount of salt and water in the body, leading to increased fluid volume in the blood vessels. High blood pressure might not cause obvious symptoms but can be detected during a medical examination.[2]
Shortness of breath can develop, particularly if fluid builds up in the lungs—a condition called pulmonary edema. This is a serious symptom that requires immediate medical attention. The shortness of breath often worsens when lying down and improves when sitting up.[1]
Other symptoms may include nausea, which can affect your appetite and lead to weight loss. Some people experience pain in their joints or abdomen. A rash might appear in certain types of glomerulonephritis, particularly those associated with vasculitis or immune system disorders. Fatigue and feeling generally unwell are also common.[1]
In rare cases, people develop jaundice, where the skin and whites of the eyes take on a yellowish color. This can occur if the underlying cause of glomerulonephritis affects the liver as well as the kidneys.[1]
Prevention
While not all cases of acute glomerulonephritis can be prevented, certain measures can reduce your risk of developing this condition, particularly when it’s related to infections.[9]
Prompt treatment of bacterial infections, especially streptococcal infections, is crucial. If you develop strep throat or a skin infection, seeking medical care early and completing the full course of prescribed antibiotics can help prevent the infection from triggering kidney inflammation. Early antibiotic treatment may prevent the development of the antibody response that leads to glomerulonephritis, although the evidence on this is not definitive.[9]
Treating close contacts of people with streptococcal infections may also help prevent the spread of infection and reduce the risk of developing acute poststreptococcal glomerulonephritis. If someone in your household has strep throat, others who have been exposed might benefit from evaluation by a healthcare provider.[9]
Vaccination can play a protective role. Because glomerulonephritis can make you more vulnerable to infections, staying current with recommended vaccines is important. The seasonal flu vaccine and the pneumococcal vaccine (which protects against pneumonia) are particularly recommended for people with kidney disease or those at risk.[10]
Smoking cessation is important for overall kidney health. Smoking can worsen kidney disease caused by glomerulonephritis and increases the risk of complications such as heart disease and stroke, which are more common in people with kidney problems. If you smoke, quitting can significantly improve your health outcomes.[10]
Managing chronic conditions that can lead to glomerulonephritis is essential. If you have an autoimmune disease like lupus, working closely with your healthcare team to keep the condition under control may help protect your kidneys. Similarly, managing conditions like diabetes and high blood pressure can reduce the overall burden on your kidneys.[11]
Being cautious about medication use is also important. Some medications can affect kidney function or trigger inflammation in susceptible individuals. Always discuss new medications with your healthcare provider, especially if you have a history of kidney problems or autoimmune disease. Avoid taking anti-inflammatory medicines such as ibuprofen and naproxen without medical guidance, as these can worsen kidney problems.[20]
Pathophysiology: How Acute Glomerulonephritis Affects Your Body
To understand what happens in acute glomerulonephritis, it helps to know how healthy kidneys work. Each kidney contains about one million nephrons, which are the functional units responsible for filtering blood. Inside each nephron is a glomerulus—a ball-shaped cluster of tiny blood vessels called capillaries. These capillaries have special walls with small pores that allow certain substances to pass through while keeping others in the bloodstream.[4]
In a healthy glomerulus, blood flows through these capillaries, and waste products, excess water, minerals, and other small molecules pass through the pores into a surrounding capsule. Large molecules like proteins and blood cells are too big to pass through and remain in the bloodstream. The filtered fluid then moves through the rest of the nephron, where the body reabsorbs needed substances like water, minerals, and nutrients, while waste and excess water become urine.[2]
Acute glomerulonephritis disrupts this finely tuned process. The condition typically involves the formation or deposition of immune complexes in the glomeruli. These are clusters made up of antibodies bound to antigens—substances that trigger an immune response. When these immune complexes lodge in the glomerular tissue, they activate inflammation.[3]
The inflammation causes the glomerular tissue to swell and become irritated. The walls of the capillaries thicken and the tiny pores become disrupted. This damage to the glomerular basement membrane—the protein meshwork that forms the filtration barrier—allows substances that should stay in the blood to leak through. Red blood cells and proteins escape into the urine, causing hematuria and proteinuria.[4]
At the same time, the inflamed and swollen glomeruli cannot filter blood as effectively. The reduced filtering capacity means the kidneys produce less urine, leading to oliguria (producing small amounts of urine). Waste products that should be removed from the blood begin to accumulate, causing azotemia—elevated levels of nitrogen-containing compounds in the blood.[3]
Because the kidneys are not removing excess fluid and salt effectively, these substances build up in the body. The retained fluid leaks out of blood vessels into body tissues, causing the visible swelling seen in the face, legs, and other areas. The excess fluid in the bloodstream increases blood volume, which raises blood pressure. In severe cases, fluid can even accumulate in the lungs, causing difficulty breathing.[3]
The severity of these changes varies from person to person. In mild cases, only a small number of glomeruli are affected, and the kidneys can still function reasonably well. In more severe cases, many or most glomeruli become inflamed and damaged, leading to significant impairment of kidney function.[3]
In some individuals, the inflammation progresses rapidly to a condition called rapidly progressive glomerulonephritis. In this severe form, most of the glomeruli are destroyed within a short time, leading to kidney failure. This occurs in about 1% of children and 10% of adults with acute glomerulonephritis.[7]
The body’s response to acute glomerulonephritis also involves changes beyond the kidneys. The buildup of waste products can cause symptoms throughout the body, including fatigue, nausea, and muscle cramps. The changes in fluid balance and blood pressure can strain the heart and blood vessels. In children and young adults, the body often has a remarkable ability to recover from acute glomerulonephritis, with many cases resolving completely. However, adults, particularly elderly individuals, may face more challenges in recovery and have higher rates of long-term complications.[9]