Ronald E. Merrill About 770 words

Kidney failure is one of the most common complications of multiple myeloma. About half of myeloma patients experience kidney problems at some point in the course of the disease.

The kidneys excrete waste products from the body into the urine. In the process, they control the fluid balance of the body, and maintain the proper levels of electrolytes in the blood. They also produce certain hormones, including erythropoetin (EPO), which stimulates production of red blood cells.

Researchers disagree about the cause of "myeloma kidney." It appears that the light chains of the myeloma M-protein form complexes with other body proteins, creating "casts" which clog up the tubules of the kidneys. However, it has also been argued that the myeloma proteins are directly toxic to the kidneys. Hypercalcemia (high blood calcium level), which commonly occurs in myeloma, may also damage the kidneys.

The consequences of kidney failure are usually very serious. When the kidneys are not working, metabolic wastes build up in the body very quickly. Moreover, the kidneys are responsible for adjusting the level of potassium in the blood, and keeping it in a narrow range. (The values 3.5-5.3 meq/L are commonly used, but different clinical labs sometimes use slightly different standards.) Potassium plays a key role in maintaining a regular heartbeat. When the kidneys fail, potassium levels start to rise, until the heart simply stops. Thus kidney failure can result in death within days.

Fortunately, today kidney failure can be treated. Hemodialysis using an "artificial kidney" can clean the blood and adjust potassium levels. Nonetheless, kidney failure is a major cause of death for myeloma patients. Beyond the direct dangers, it can interfere with treatment of multiple myeloma. Many research protocols, especially for BMT, automatically exclude patients with kidney problems. Use of certain medications, notably melphalan, may be limited because the body can no longer excrete them. At minimum, kidney failure has a major impact on quality of life. Commonly patients with severe kidney failure, who cannot make urine, are put on fluid restriction, which is very unpleasant indeed.

Your physician will track your kidney function regularly using blood tests. Normally the levels of creatinine and urea (basic urea nitrogen or BUN) are used to judge kidney function. These compounds are taken to represent the complex mixture of waste products produced by the body. Creatinine should not exceed 1.1 mg/dL, BUN not more than 19. (Again, some labs may use different numbers or units.)

Unfortunately, these tests generally will not indicate trouble until it is too late. Healthy kidneys have a large safety factor; they are capable of processing about ten times as much waste as the body normally produces. So creatinine and BUN levels do not start to rise until the kidneys have been badly damaged and most of their function has been lost. Since kidney failure can appear rapidly--over a period of a few days--you can lose kidney function without warning between blood tests.

Symptoms of kidney failure include loss of appetite with nausea and vomiting, diarrhea, and lethargy and drowsiness. Obviously patients who are undergoing chemotherapy may expect these symptoms and not realize that they could indicate kidney problems! However, you should be alert for problems with urination, and signs of accumulation of fluids--especially swelling in the ankles or difficulty in breathing. If you encounter such symptoms, get medical attention immediately. Hours count.

Can myeloma kidney be prevented? There are some simple precautions the myeloma patient can and should take. Most important, beware of dehydration. Drink plenty of fluids--preferably around three liters per day. The kidneys, like a garbage disposal, are less likely to get clogged up if the waste is washed down with plenty of water. You should also check that your medications are not nephrotoxic (kidney-damaging). Many antibiotics (eg, gentamicin), analgesics (especially non-steroidal anti-inflammatories such as naproxen or ibuprofen), and contrast agents (used for X-rays or MRI scans) are nephrotoxic. Sometimes use of nephrotoxic drugs is unavoidable, but you should at least be aware of the dangers.

If prevention fails, you may still be able to recover some kidney function. Immediate use of a process called plasmapheresis can remove much of the M-protein from the blood, preventing or at least reducing further damage and giving the kidneys a chance to recover. Although myeloma kidney is usually irreversible and there is no effective treatment, in many cases the kidneys do heal by themselves, at least partially--sometimes in a few weeks, sometimes over several years.