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Kidney Alert
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Are you aware of the risks of high blood pressure and kidney disease?
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By Kalia Doner
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Diabetes Focus Summer 2009
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 Uncontrolled high blood pressure is the second leading cause of kidney failure in the United States—and two out of three people with diabetes have high blood pressure. That may be why diabetes accounts for nearly 44 percent of new cases of kidney failure. Here, Leslie Spry, M.D., talks about the interplay of diabetes, kidney disease and other related issues.
You have identified a classic what-came-first-the-chicken-or-the-egg problem that has always complicated thinking about diabetes, kidney disease and hypertension. To figure out what’s cause and what’s effect, you have to look at a lot of things.
For example, a family history of hypertension predisposes a person to developing kidney disease, as does diabetes. Kidney disease from either cause then elevates blood pressure, which accelerates the kidney disease.
Many people with type 2 also have cardiovascular disease at the time they are diagnosed, and they often develop high blood pressure as a result. High blood pressure in turn damages the small vessels in their kidneys. In fact, 30 to 40 percent of people with type 2 will have kidney disease at the time they are diagnosed. That’s why, for people with type 2, from the day they are diagnosed, we suggest they have their blood pressure carefully monitored, as well as have a test for microalbuminuria [protein in the urine that is a marker of kidney damage]—and of course take steps to control cholesterol and other lipid levels.
In contrast, among those with type 1 diabetes, almost 99 percent do not have high blood pressure until they have diabetic kidney disease, which takes five or so years after they are diagnosed with diabetes to develop. When they do, we suggest regular checkups for protein levels in the urine.
Eventually 15 to 20 percent of people with type 1 end up with kidney disease.
Think of the interior structure of the kidney as a group of grape clusters. The stalks of the grapes are the mesangium. The glucose levels cause these stalks to expand and develop scars. That puts pressure on associated grapes—and ultimately blocks up the filtering system in the kidney. That is kidney disease.
One interesting fact: These days we see fewer and fewer patients with type 1 who have kidney disease. That’s because of improved glucose control overall.
The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) says to shoot for 130/80 or less except if you have a significant amount of protein in the urine. Then we lower the target to 125/75.
For type 1 patients, an ACE [angiotensin-converting enzyme] inhibitor and dietary intervention can be used together very effectively.
In those who have type 2, we generally use dietary intervention and a different drug, called an ARB [angiotensin II receptor blocker]. However, on average it takes three or four different drugs, including a diuretic, for anyone with high blood pressure to achieve 130/80 or 125/75, whether or not the person has diabetes. As for dietary changes that help control blood pressure, I am a fan of the DASH diet—but only if a person has no problem handling potassium. So before starting a DASH diet, you should have a blood test to measure your potassium levels. Women who follow the DASH diet can expect to see around a 16-point drop in their blood pressure; men can expect around an 8-point drop.
Regular exercise is important: People with diabetes have less progression of kidney diseases if they walk at least 20 minutes a day. Also, if someone is a candidate for a kidney transplant, studies show a tendency to do better post-transplant if he or she exercises regularly before the operation. True, blood pressure goes up during exercise. But when you stop, it goes down and eventually will remain lower, so that is a good thing.
There is a new medicine. Aliskiren is the generic name. It works earlier on the cascade of changes than an ARB does. The major drawback is that this drug reduces the excretion of potassium, so the risk of heart problems increases, especially for people with diabetes. A variation is a drug whose generic name is spironolactone. It too decreases potassium excretion, but on the plus side it seems to cut down on scarring of the heart and possibly the kidney. You have to be cautious.
At my practice we have 40 patients on home dialysis now, and it is very effective. They can give it to themselves for 2½ hours six times a week, instead of going in somewhere and having to do it for 4 hours three times a week. Infection is not a problem. In fact, our patients have lower infection rates and spend fewer days in the hospital than do those who go into the dialysis center, and psychological tests show they are happier. My personal choice, if I were to go on dialysis, would be peritoneal dialysis. New technology gives more control, and it doesn’t disrupt life so much.
For people with diabetes, we are recommending a live donor when possible. Also, individuals with diabetes who go directly to a transplant and never see dialysis do much better than those who go on dialysis first and then receive a transplant. Another option is a cadaver kidney/pancreas transplant. That can be very effective in restoring both kidney function and the beta cells that produce insulin.
| Leslie Spry, M.D., is medical director of the Dialysis Center of Lincoln in Lincoln, NE, and an active member of the public policy committee at the National Kidney Foundation.
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