Diabetes and the Kidneys
Your kidneys do many things, but the most important are getting rid of products from your blood by excreting them in urine and maintaining a proper mineral and fluid balance in your body. In this way, your kidneys are a bit like a filter or sieve, keeping the right amounts of the good stuff in and getting rid of the things you don't need.There are a tremendous number of tiny blood vessels that feed the very small cavities in your kidneys, much like the many tiny blood vessels that feed the tissues in your eyes. The vessels in the kidneys have selective-size pores that allow certain molecules to fall into the cavities and be carried out with the urine while at the same time keeping needed molecules from leaving the body.
As your glucose levels remain elevated, advanced glycated end products (AGEs) build up in the walls of the blood vessels, ironically causing the vessels to become abnormally porous. In addition to AGEs, high blood pressure, nicotine use, and certain other conditions can damage the small blood vessels of the kidneys. As a result, protein molecules start leaking through the pores in the blood vessels and end up in the urine.
In the early stages of kidney disease, albumin, the major protein in your blood, begins to leak through the damaged vessels and into the urine at an abnormal rate. This condition is called proteinuria (or in the earliest stages, microalbuminuria, since only small amounts of protein appear in the urine). Normally, less than 30 micrograms (a microgram, or mcg, is one-millionth of a gram) of albumin are found in your urine on any given day. Results greater than 30 mcg indicate kidney damage.
As kidney disease progresses, the pores in the kidneys' blood vessels become larger due to damage, and more protein is lost. When the protein loss reaches 1,000 milligrams, or 1 gram, each day, you may notice puffiness in your ankles due to fluid buildup (edema). As the kidneys become less effective at filtering, waste products slowly begin to collect in the blood; this buildup can be measured and is called your serum creatinine level. As the creatinine level increases, so do the levels of other waste products, causing you to become nauseated and fatigued.
The waste buildup poisons the kidneys, harming their ability to make erythropoietin, a substance needed by your bone marrow to make oxygen-carrying red blood cells; you become anemic, which means your body's cells become starved for oxygen. At this point, your kidneys can no longer do their most basic job, and you require dialysis. Dialysis involves being hooked to a machine that removes the wastes from your blood.
But kidney disease and the slow deterioration of your body's filtering system do not need to happen. There are several things you can do to protect your kidneys and reduce the likelihood of kidney problems, prevent current problems from becoming worse, and even reverse problems that have started.
Get screened. Maintaining kidney health starts with yearly screening for microalbumin. This test looks for small amounts of protein in the urine that cannot be detected by the usual "dipstick" test done during routine urinalysis. (Note, however, that infection, severe stress, heart failure, or strenuous exercise before the test can also increase levels of protein in your urine.) Should the results show increased microalbumin in your urine, the test needs to be repeated. If the second test is also positive, treatment to return this number to normal should begin.
Tighten your control. To keep your kidneys healthy or prevent problems from becoming worse, you need to keep blood glucose tightly controlled. Kidney problems result from an increased glucose load, causing a buildup of AGEs. The closer to normal you keep your glucose levels, the better for your kidneys. With the guidance of your team, strive for an HbA1c of less than 7 percent, or less than 6 percent if that's possible without risking hypoglycemia (low blood glucose).
Keep your blood pressure in check. It is important to maintain a normal blood pressure and to check it often. When blood pressure is high (above 130/80 mm Hg), it slowly damages the kidneys. Have your pressure checked often, and learn how to monitor it at home. If it is consistently high, early treatment is important. Nicotine, salt, caffeine, and alcohol all may raise blood pressure. By contrast, adding extra physical activity to your life can help lower your blood pressure.
Watch your meds. Make sure you avoid medications that can damage your kidneys. When your doctor chooses a drug for you, such as an antibiotic for infection, confirm that it does not have kidney damage as a possible side effect. Be aware that some over-the-counter drugs can cause problems, too. Excessive use of non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin and ibuprofen, can cause damage to the kidneys. It is safe for you to use these once in a while as recommended on the bottle. Large daily doses have been associated with kidney problems, however, so if you need to treat ongoing pain or inflammation, talk to your doctor before using large doses of NSAIDs.
Say no to nicotine. To maintain the health of your kidneys, you must avoid all forms of nicotine. Nicotine is as harmful to the kidneys as untreated high blood pressure is. Because nicotine is so addictive, the best policy is to never start. If you already smoke or chew tobacco, ask your doctor about resources to help you quit.
Take an ACE or ARB. To help slow or reverse kidney disease, it is recommended that prescription medications called angiotensin converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) be used when needed. Studies have shown that these classes of blood pressure medicines can slow kidney disease and protect the kidneys from further damage. In addition, they prevent damage to other blood vessels in the body. Started slowly, and taken until there is a change in your kidney status, they will not abnormally lower your blood pressure. If you are already taking a medication for high blood pressure, speak with your doctor and make sure you are on an ACE inhibitor or an ARB.
Go easy on protein. Finally, lower the amount of protein in your diet, since it can aggravate kidney problems. When your kidney function begins to decrease, eating less protein generally helps to slow the process. The protein is an extra load for the kidneys to handle, because the nitrogen from the breakdown of proteins tends to poison the kidneys. For an exact diet prescription to maintain your kidney health, consult your doctor, diabetes educator, and dietitian.
The feet -- the focus of our final section -- also are vulnerable in people who have diabetes. In fact, amputation can occur in a worst-case scenario.
