What Is Bence-Jones Proteinuria?

Bence-Jones proteinuria is the secretion of certain blood products, called Bence-Jones proteins, in the urine. A special test is required to identify them because the basic dipstick analysis used to quickly test urine in the lab is not sufficient. Medical providers may consider testing for Bence-Jones proteinuria if they believe a patient’s symptoms may be suggestive of a condition associated with kidney dysfunction. In most cases, large numbers of Bence-Jones proteins in the urine are indicative of a malignancy.

Healthy patients have functional kidneys that filter out a wide variety of blood products along with useful substances the body needs. Waste products are routed into the bladder for disposal in the urine. As kidney function starts to break down in people with medical problems, the ability to filter is compromised, and the kidneys start excreting more proteins. Urine testing can reveal the decline in function, and may include a visual inspection of the urine for cloudiness and discoloration, along with a dipstick check and more advanced testing.

Changes in urine chemistry like Bence-Jones proteinuria can be caused by problems with the kidneys or bladder, as well as other regions of the body. The kidneys act as one of the body’s waste processing systems and they can be an important indicator of overall health. If a problem develops in one or both kidneys, it can be a sign of a deeper medical problem.

Patients commonly develop Bence-Jones proteinuria when they have a cancer like multiple myeloma or Waldenstrom’s macroglobulinemia. In a thorough workup for a patient with suspected cancer, the doctor may request some kidney function testing to determine whether the cancer is putting stress on the kidneys or other organ systems. Treating the underlying cancer is the only way to address the proteinuria, and the strain on the kidneys can become a complicating factor when developing a treatment plan because some chemotherapy regimens are very harsh on the kidneys.

In some cases, Bence-Jones proteinuria has a different cause or is benign in nature. When it is identified in lab testing of a patient’s urine, the next step is usually additional testing to find out more about what is causing it. This can include blood tests, medical imaging studies of the kidneys, or biopsy samples. A complete patient history can also be helpful, as it may provide useful information about why the patient developed proteinuria. Medical providers can review the data to determine the diagnosis and make treatment recommendations.