Glomerular disease refers to a group of conditions that damage the kidneys’ filtering units, called glomeruli, which are responsible for cleaning the blood. When impaired, the kidneys cannot effectively remove waste and excess fluid from the body, leading to significant health issues. The management of glomerular disease focuses on addressing the damage to prevent further complications.
The Role of Glomeruli in Kidney Function
Within each kidney are approximately one million microscopic filtering units called nephrons, and each nephron contains a glomerulus. The glomerulus is a cluster of tiny blood vessels that acts as a sieve. As blood passes through, pressure pushes water, waste products, and solutes through a filtration membrane into a collecting tubule. This process cleans the blood of waste and excess fluid that become urine.
The glomerular filtration barrier is highly selective, allowing small waste molecules and fluid to pass through while blocking larger components like red blood cells and proteins. In a single day, the kidneys filter about 150 quarts of blood, reabsorbing most of the fluid back into the body. This continuous filtration allows the kidneys to maintain a healthy balance of water, salts, and minerals in the blood.
Causes and Risk Factors
The origins of glomerular disease are categorized as primary or secondary. Primary glomerular diseases begin directly within the kidneys, sometimes for unknown (idiopathic) reasons. Common forms include IgA nephropathy, where antibody deposits build up in the glomeruli, and focal segmental glomerulosclerosis (FSGS), which is characterized by scarring.
Secondary glomerular diseases develop from other systemic conditions. Diabetes is a leading cause, as high blood sugar levels can strain the glomeruli over time and lead to diabetic nephropathy. Autoimmune disorders like systemic lupus erythematosus (SLE) can also cause the immune system to attack the glomeruli, resulting in lupus nephritis.
Infections can also trigger glomerular disease. Post-streptococcal glomerulonephritis occurs after an infection like strep throat, where excess antibodies lodge in the glomeruli and cause damage. Certain viral infections, including HIV and hepatitis B and C, are also known to cause inflammation and scarring in the kidneys. Genetic factors can play a part, as with Alport syndrome, a hereditary condition that damages blood vessels in the glomeruli.
Recognizing the Symptoms
The initial signs of glomerular disease often appear in the urine. One common symptom is proteinuria, or excess protein in the urine. When the glomeruli are damaged, they can no longer prevent protein from leaking out of the blood, which can cause the urine to appear foamy.
Another sign is hematuria, or blood in the urine. This occurs when damaged glomeruli allow red blood cells to escape from the bloodstream. The urine may take on a pink, red, or cola-colored appearance. This indicates the kidney’s filtering barrier is compromised.
Fluid retention (edema) is another common symptom. When protein is lost from the blood, the body’s ability to manage fluid balance is disrupted, causing swelling in the hands, ankles, feet, or face. Over time, kidney damage can also lead to high blood pressure (hypertension) as the organ’s ability to regulate fluid is impaired.
Diagnostic Process
Confirming a diagnosis involves several evaluations, starting with laboratory tests. A urinalysis is often the first step, as it can detect protein and red blood cells, which are indicators of glomerular damage.
Blood tests assess kidney function by measuring waste products in the blood, like creatinine and blood urea nitrogen (BUN). Elevated levels suggest the glomeruli are not filtering waste. These tests also calculate the glomerular filtration rate (GFR), a precise measure of how well the kidneys are working.
While urine and blood tests indicate a problem, a kidney biopsy is often required for a definitive diagnosis. A small sample of kidney tissue is removed with a needle and examined under a microscope. This examination reveals the specific type and extent of damage, which helps determine the most effective treatment.
Approaches to Treatment and Management
Treatment for glomerular disease is tailored to the specific cause and aims to slow kidney damage and manage symptoms. If the disease is secondary to a condition like diabetes or high blood pressure, managing the primary disorder is the focus. Blood pressure medications like ACE inhibitors and ARBs are prescribed to reduce pressure inside the glomeruli and decrease protein leakage.
For diseases caused by an overactive immune system, such as lupus nephritis or IgA nephropathy, treatments may include immunosuppressive drugs. Corticosteroids like prednisolone are often used to reduce inflammation. In more severe cases, other medications that suppress the immune system, such as mycophenolate mofetil or cyclophosphamide, may be necessary.
Dietary and lifestyle adjustments are also part of management. Reducing sodium intake helps control blood pressure and fluid retention. Doctors may also recommend limiting dietary protein to decrease the workload on the kidneys. Diuretics may be prescribed to help the body eliminate excess fluid.