To understand why blood pressure management matters so much with IgAN, it’s helpful to examine what happens inside the kidneys.
Kidney Damage Can Raise Blood Pressure
The kidneys contain tiny filtering units called glomeruli. Dr. Voora suggests thinking of glomeruli as microscopic mesh filters. These filters remove waste and excess fluid from your blood while keeping important substances, such as protein, from leaking out.
In IgAN, the body makes an abnormal form of immunoglobulin A (IgA), a protein that’s normally part of your immune defense. The immune system sees this abnormal IgA as a threat and creates antibodies to attack it, says Yasir Qazi, MD, a transplant nephrologist with Providence St. Joseph Hospital in Orange, California.
These antibodies attach to the abnormal IgA and create clumps that can become trapped in the kidney’s mesh filters, triggering inflammation and damage. As the damage progresses, the filters become less effective at removing excess fluid and sodium from the body, which can lead to high blood pressure.
At the same time, higher blood pressure means blood is pushing through the kidneys’ filters with greater force. Voora compares that force to a power washer hitting a delicate mesh screen. The added pressure can tear and damage the filters even further, increasing kidney damage, she says.
High Blood Pressure Can Cause Excess Protein in Urine
With high blood pressure, the specialized cells that support the glomeruli can also become damaged, Voora says. The walls of the tiny blood vessels inside the glomeruli can stretch and weaken as well. As a result, large protein molecules that normally belong in the bloodstream can leak into the urine, a condition known as proteinuria.
Proteinuria is a sign that the kidney filters are damaged. As the kidneys try to process and reabsorb protein leakage, more inflammation can develop, adding to the injury already caused by IgAN.
“High levels of protein leakage are the strongest indicator that the disease is active, the kidneys are under stress, and there is a higher risk of progression toward dialysis, if not addressed,” says Voora.
Kidney Scarring Can Occur
When the kidneys face continued stress from high blood pressure and inflammation, they try to repair the damage. One way they do this is by laying down scar tissue.
The problem is that once a filtering unit becomes scarred, known as glomerulosclerosis, it loses its blood supply and can no longer function properly, says Voora.
As more scarring occurs, the remaining healthy filters have to take over the workload. “To compensate, these healthy filters dilate and experience even higher blood pressure and filtration demands, leading to burnout and faster scarring,” Voora explains.
Meanwhile, the kidneys can also trigger the release of hormones that tighten blood vessels, which also raises blood pressure. Dr. Qazi says that this creates a cycle in which high blood pressure causes kidney scarring, and kidney scarring causes blood pressure to rise.
Breaking that cycle is one of the main goals of IgAN treatment.