IgA nephropathy, also known as Berger’s disease, is a kidney condition where an immune system protein called immunoglobulin A (IgA) builds up within the kidney’s filtering units. These filtering units, known as glomeruli, normally remove waste and excess fluid from the blood. When IgA deposits accumulate in the glomeruli, they cause inflammation and damage. This hinders the kidneys’ ability to filter blood effectively, impacting overall kidney function.
Initial Diagnostic Clues and Tests
The initial signs of IgA nephropathy often appear subtly, and some individuals might not experience noticeable symptoms for years. Common indicators that prompt a medical visit include visible blood in the urine, which may appear pink, dark brown, or cola-colored, especially after a respiratory infection. Foamy urine, signaling the presence of protein, and swelling in areas like the hands, feet, ankles, or face, can also suggest kidney involvement.
When these symptoms arise, a doctor will order non-invasive tests to assess kidney health. A urinalysis is a first step, detecting microscopic blood cells or protein in the urine. Blood tests measure serum creatinine levels, a waste product that increases when kidney function declines. From this, an estimated glomerular filtration rate (eGFR) can be calculated, indicating how well the kidneys are filtering waste. While these initial tests can confirm kidney stress or damage, they cannot specifically diagnose IgA nephropathy.
The Definitive Diagnostic Procedure
A kidney biopsy is the definitive procedure to confirm IgA nephropathy. It involves obtaining a small tissue sample from a kidney for microscopic examination. The biopsy is performed using a thin needle guided through the skin over the kidney, often with ultrasound imaging for precise placement.
A kidney biopsy is the only definitive diagnostic method because it allows doctors to visually identify characteristic IgA deposits within the glomeruli. Without this direct microscopic confirmation, it is not possible to distinguish IgA nephropathy from other kidney conditions that might present with similar initial symptoms or test results. A nephrologist, a doctor specializing in kidney diseases, or an interventional radiologist performs this procedure. The tissue sample is then sent to a pathologist for detailed analysis, which takes several days to a week for full results.
Interpreting Biopsy Results and Disease Staging
Once the kidney tissue sample is obtained, a pathologist examines it under a microscope to confirm the presence of IgA deposits and assess the extent of kidney damage. This microscopic evaluation goes beyond merely confirming the diagnosis; it provides details about the disease’s severity and potential progression. The MEST-C score is a standardized classification system used by pathologists to categorize these biopsy findings and guide treatment decisions.
Each letter in the MEST-C score represents a specific finding within the kidney tissue. “M” stands for mesangial hypercellularity, indicating an increased number of cells in the mesangium, the central part of the kidney’s filters. “E” signifies endocapillary hypercellularity, referring to swelling and extra cells inside the glomeruli’s capillary loops. “S” represents segmental glomerulosclerosis, denoting scarring in specific portions of the filtering units.
“T” indicates tubular atrophy and interstitial fibrosis, which is scarring and shrinkage in the kidney tissue surrounding the filters. A higher score in this category correlates with poorer kidney function. The “C” component refers to crescents, crescent-shaped structures in the glomeruli indicating severe injury. The presence and extent of these crescents indicate more aggressive disease activity. This comprehensive scoring system helps doctors understand the disease’s current state and predict its likely future course, informing personalized treatment plans.
Ruling Out Other Conditions
The kidney biopsy differentiates IgA nephropathy from other conditions that might initially appear similar. Many other kidney diseases or systemic conditions can cause symptoms like blood or protein in the urine, making it challenging to pinpoint the exact cause without a biopsy. For example, lupus nephritis, a kidney inflammation associated with lupus, or membranoproliferative glomerulonephritis, another form of kidney filter inflammation, can present with overlapping symptoms.
IgA vasculitis, formerly known as Henoch-Schönlein purpura, is another condition that can mimic IgA nephropathy, especially in children, as it also involves IgA deposits. However, IgA vasculitis presents with additional symptoms like skin rashes, joint pain, and abdominal pain, which are not characteristic of IgA nephropathy alone. The kidney biopsy provides a detailed look at the specific patterns of immune deposits and tissue damage unique to IgA nephropathy, ensuring the most appropriate treatment can be planned.