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If you’re living with amyloidosis, chances are you’ve taken a urine test at some point. Most people urinate (pee) seven or eight times a day, and those trips to the bathroom can provide valuable information about your health. Urine tests are commonly used in medicine to help detect problems like infections, kidney disease, and diabetes.
For people with amyloidosis, urine tests that check for protein are especially helpful. Although they aren’t used to screen for amyloidosis itself, they play an important role in diagnosing and managing the condition.
In this article, we’ll explain why a doctor might order a urine test, which types of urine tests are used for amyloidosis, and what the results can reveal about how the disease is affecting your body.
Proteinuria (high levels of protein in the urine) can be an early sign of kidney problems. To understand why, let’s first look at how your body makes urine.
Urine is produced in your kidneys — two bean-shaped organs located in your lower back, on each side of your spine. Their job is to filter your blood, and every drop passes through them multiple times each day. The waste products, toxins, and extra fluid that get filtered out become your urine.
Normally, important substances such as proteins and red blood cells stay in your blood because they’re too large to pass through the kidney filters. That’s why healthy urine has little to no protein (and is clear or yellowish instead of red like blood).
Urine tests can detect protein that ends up in the urine. For people with healthy kidneys, urine contains less than 150 milligrams of protein per day. If test results show more than that, it’s a sign that something isn’t right with your kidneys. These tests are often done routinely during regular checkups to screen for health problems before they cause symptoms. A positive result for proteinuria means that you may have a kidney problem, but your doctor may want to run more tests to figure out what’s going on.
Amyloidosis is a rare disease caused by the buildup of abnormal proteins called amyloids. These proteins form amyloid fibrils (sticky clumps) that circulate through the bloodstream and get deposited in different parts of the body. Over time, these deposits can damage organs and make it harder for them to work properly. The three most common types of amyloidosis are:
A fourth type of amyloidosis, called dialysis-related amyloidosis, happens in people who have been on long-term dialysis for kidney failure. However, this type mostly involves bones, joints, and tendons, not the kidneys.
The kidneys are among the most common sites of amyloid deposits. The medical term for amyloidosis in your kidneys is “renal amyloidosis.” About two-thirds of people with AL amyloidosis have kidney involvement. AA amyloidosis can also affect the kidneys.
The buildup of amyloid protein clogs the kidneys’ glomeruli (tiny filters) and damages them. As the filters get damaged and stop working properly, protein begins to leak into the urine — one of the most common signs of amyloidosis. Studies show that about 97 percent of people with AA amyloidosis have over 500 milligrams of protein in their urine per day — more than triple the normal amount.
If your healthcare provider thinks you might have a kidney problem, they’ll likely order a urine test to check for proteinuria. You’ll pee in a cup to collect a sample of urine, and one or more types of tests will measure the amount of protein in the urine sample.
The dipstick test can be done at your doctor’s office. A thin plastic strip with a chemical-coated pad is dipped in the urine sample. If there’s protein in your urine, chemicals on the pad change color and indicate whether your protein levels are normal, borderline, or high. However, this test doesn’t measure the amount of protein in your urine.
The 24-hour collection test takes more time and effort, but it’s considered the gold standard for measuring protein in urine. You’ll empty your bladder as usual first thing in the morning. After that, you’ll collect all your urine for the next 24 hours, including the first time you pee the next morning, and keep it refrigerated or on ice.
Once your samples are collected, they’re sent to a lab to have the total amount of protein in your urine measured. This test gives the most accurate picture of how your kidneys are working.
The spot albumin-creatinine and spot protein-creatinine tests were developed as an easier alternative to the 24-hour test. For a spot test, you collect your urine just once at a specific time of day. These tests compare the amount of protein to creatinine, a waste product your body makes at a steady rate, and provide a good estimate of how much protein you lose in a day.
Spot tests are especially useful for tracking changes over time or when a 24-hour test isn’t practical.
If your doctor thinks you have renal amyloidosis, they may have you do more than one type of urine test to check for proteinuria. Since the 24-hour test is considered the most accurate method, it will likely be part of your testing plan. You may need to repeat these tests over time to get the clearest picture.
Finding protein in the urine doesn’t automatically mean that you have amyloidosis or even kidney disease. The amount of protein in your urine can be temporarily affected by other factors, including:
Be sure to tell your doctor if you’re taking medications or had any recent imaging tests. Certain drugs and imaging dyes can also interfere with the dipstick test.
If your healthcare provider finds a high protein level in your urine, the next step is to figure out why your kidneys are leaking protein. To confirm a diagnosis of renal amyloidosis, your doctor will likely recommend a kidney biopsy. This test involves taking a tissue sample from your kidneys and looking at it under a microscope to check for amyloid deposits.
Your healthcare team may also perform urine tests and blood tests to look for signs of amyloid. These tests include:
If you’re diagnosed with renal amyloidosis, urine testing will continue to be an important tool to help your healthcare team keep tabs on how you’re doing. The amount of protein in your urine helps your healthcare provider determine your stage of renal amyloidosis, assess how well your treatment is working, and track disease progression.
Studies show that a urine protein level over 5 grams of protein per day in people with AL amyloidosis is a risk factor for end-stage renal disease (kidney failure), which is a possible complication of kidney amyloidosis.
It’s important to follow your healthcare team’s instructions on urine testing. By staying on top of these tests and other recommended monitoring, you and your doctor can work together to manage your condition and protect your kidney health.
On MyAmyloidosisTeam, the social network for people with amyloidosis and their loved ones, members come together to ask questions, give advice, and share their stories with others who understand life with amyloidosis.
Have you been diagnosed with amyloidosis? Have you done urine testing to diagnose or manage renal amyloidosis? Share your experiences in the comments below, or start a conversation by posting on your Activities page.
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