When the Kidney’s Filters Become Inflamed
Blood or protein showing up in a urine test can sometimes be the first indication that the kidneys’ filtering structures are under stress. These filters, called glomeruli, normally help remove waste while keeping blood cells and important proteins in circulation. When inflammation disrupts that process, the effects can range from subtle laboratory changes to swelling, high blood pressure, or declining kidney function.
At Nephrology Associates of Northern Illinois and Indiana (NANI), patients in Berwyn and North Chicago, Illinois, and Bergen, New Jersey, may undergo evaluation when urine findings or kidney function tests suggest a glomerular disorder. Because glomerulonephritis can develop for several different reasons, understanding the pattern of inflammation is an important part of determining what the test results may mean.
Glomerulonephritis Is a Broad Term
Glomerulonephritis is not one single disease. It describes inflammation involving the glomeruli, but that inflammation can develop for different reasons.
Some forms are related to autoimmune conditions in which the immune system mistakenly attacks kidney tissue. Others may develop after infections or as part of a disease affecting multiple organs. Conditions such as IgA nephropathy, lupus nephritis, anti-GBM disease, and certain forms of vasculitis can all involve glomerular inflammation.
Because the causes vary, the treatment also varies. The first step is determining what is producing the inflammation and how much it is affecting kidney function.
Learning more about kidney disease can help patients understand why glomerular disorders are evaluated differently from kidney problems caused primarily by obstruction, inherited cysts, or other structural concerns.
Blood and Protein May Appear in the Urine
A healthy glomerulus normally keeps blood cells and most proteins out of the urine. Inflammation can disrupt this filtering barrier.
One possible finding is hematuria, or blood in the urine. Sometimes the urine looks pink, red, brown, or tea-colored. In other cases, the amount of blood is too small to see and is found only through laboratory testing.
Proteinuria can also occur. When protein levels become high enough, urine may look unusually foamy. Significant protein loss may contribute to low albumin levels in the blood and swelling in the legs, feet, hands, or around the eyes.
Blood or protein in the urine does not automatically mean someone has glomerulonephritis. Both findings have other possible causes, which is why additional evaluation is needed.
Symptoms Can Vary Widely
Some people with glomerular inflammation have few noticeable symptoms, particularly early in the condition. Others develop more obvious changes.
Possible signs and findings include:
- Blood in the urine
- Foamy urine caused by protein loss
- Swelling in the legs, feet, hands, or around the eyes
- High or worsening blood pressure
- Reduced urine output
- Fatigue or weakness
- Unexpected weight gain from fluid retention
- Rising creatinine or declining eGFR
The severity of symptoms does not always match the severity of kidney injury. A person may have important laboratory abnormalities without feeling particularly ill.
How Kidney Function May Be Affected
Inflamed glomeruli may become less effective at filtering waste and fluid from the blood. If enough filters are affected, serum creatinine may rise and estimated glomerular filtration rate, or eGFR, may fall.
The speed of this change varies. Some glomerular diseases progress slowly over months or years. Others can cause a rapid loss of kidney function and require urgent evaluation.
Reviewing kidney function measurements alongside urine findings helps the healthcare team determine whether the inflammation is primarily causing blood or protein leakage, reducing filtration, or doing both.
Trends are particularly important. A stable eGFR over time suggests a different situation from a rapid decline accompanied by worsening urine abnormalities.
What Causes Glomerular Inflammation?
The immune system is involved in many forms of glomerulonephritis.
In IgA nephropathy, immune deposits containing immunoglobulin A accumulate in the glomeruli and trigger inflammation. Lupus nephritis occurs when systemic lupus erythematosus affects the kidneys. ANCA-associated vasculitis can inflame small blood vessels, including those in the glomeruli.
Anti-GBM disease involves antibodies that attack a structural component of the kidney filters and may also affect the lungs. Some infections can also trigger glomerular inflammation.
In some situations, determining the exact cause requires specialized testing because several diseases can produce similar symptoms and urine findings.
How Glomerulonephritis Is Evaluated
Evaluation generally begins with blood and urine testing.
A urinalysis can identify blood, protein, and other findings that suggest glomerular injury. Urine protein measurements may help determine how much protein is being lost.
Blood tests commonly include creatinine and eGFR. Additional testing may look for autoimmune antibodies, complement levels, infections, or other markers that could point toward a specific cause.
Kidney ultrasound may be used to assess kidney size and structure. Imaging cannot diagnose most glomerular diseases by itself, but it can help rule out certain structural problems.
When the diagnosis remains uncertain or treatment depends on knowing the exact disease pattern, a kidney biopsy may be recommended. A biopsy allows a small piece of kidney tissue to be examined under a microscope and can help identify the type and severity of glomerular injury.
Why a Kidney Biopsy May Matter
Different glomerular diseases can produce similar laboratory results. Two patients may both have blood and protein in the urine but have very different underlying conditions.
A biopsy can show patterns of inflammation, immune deposits, scarring, and other microscopic changes that help distinguish among diseases.
This information may also influence treatment. Some inflammatory conditions respond to medications that suppress the immune system, while others require treatment of an infection, management of blood pressure and proteinuria, or another targeted approach.
A biopsy is not required for every patient. The nephrologist weighs the potential information it may provide against the risks and whether the result is likely to change management.
Treatment Depends on the Underlying Cause
There is no universal medication for glomerulonephritis.
Some patients need treatments that reduce immune-system activity, such as corticosteroids or other immunosuppressive medications. Others may need treatment directed at an infection or another underlying condition.
Blood pressure management is also important. Certain blood pressure medications can reduce pressure inside the glomeruli and may help lower protein loss.
Diuretics may be prescribed when fluid retention causes swelling. Dietary sodium reduction may also help with blood pressure and edema.
Following individualized kidney protection strategies can support the broader treatment plan by addressing blood pressure, medication use, nutrition, and other factors that influence long-term kidney health.
Monitoring After the Diagnosis
Even when treatment is working, follow-up testing remains important.
Urine protein, blood in the urine, creatinine, eGFR, blood pressure, and symptoms may all be monitored over time. The frequency depends on the specific diagnosis and how active or stable the condition appears.
Some forms of glomerulonephritis may improve and remain quiet. Others can relapse, meaning inflammation returns after a period of improvement. Certain conditions may gradually lead to chronic kidney disease because inflammation leaves behind permanent scarring.
Regular follow-up helps the healthcare team distinguish between active inflammation and lasting damage, which can affect decisions about treatment.
Looking at the Whole Pattern
Glomerulonephritis is best understood as inflammation affecting the kidney’s filtering units rather than as one specific diagnosis. Blood or protein in the urine, swelling, high blood pressure, and changing kidney function can all provide clues, but laboratory findings must be interpreted together.
The underlying cause, speed of progression, amount of protein loss, biopsy findings, and response to treatment all influence long-term care.
For patients in Berwyn and North Chicago, Illinois, and Bergen, New Jersey, NANI provides nephrology evaluation for glomerular and other kidney conditions. Identifying why the kidney filters are inflamed can help guide testing, treatment, and monitoring with greater precision.
Sources
Kidney Disease: Improving Global Outcomes Glomerular Diseases Work Group. (2021). KDIGO clinical practice guideline for the management of glomerular diseases. Kidney International.
Flores-Mendoza, G., Sansón, S. P., Rodríguez-Castro, S., & Paniagua, R. (2018). Glomerulonephritis: An update. Medicina Clínica.
Couser, W. G. (2016). Basic and translational concepts of immune-mediated glomerular diseases. Journal of the American Society of Nephrology.
