Dr. Qaadri

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Medical Post Diabetes and Kidney Disease - 2

By Dr. Shafiq Qaadri, MD

Why is the incidence of kidney disease skyrocketing?
It’s a combination of factors: An aging population, which has more type II diabetes and essential hypertension. These individuals are also living long enough to develop the complications of kidney failure.

What are the most important day-to-day functions of the kidney?
The kidneys perform a large number of functions. The most important one is the regulation of fluid and electrolyte balance, and the elimination of body wastes.

There are also endocrine functions, helping to maintain hemoglobin, and to regulate blood pressure.

Why are patients who have both hypertension and diabetes especially prone to kidney disease?
Both conditions individually can be associated with kidney failure, and we’ve known this for some time. When you have both conditions coexisting, they combine in such a way that makes the kidney disease more common and more severe.

Patients with untreated hypertension, for example, will develop a more accelerated rate of decline of kidney function.

Do patients actually follow lifestyle-modification advice?
The short answer is that patients do not follow lifestyle-modification advice to the extent that physicians wish they would.

Perhaps our society looks for quick-fixes, and lifestyle-modification of course requires that people make fundamental changes. For many, that can be very challenging to sustain over an extended period of time…We all eat too much—too much salt, too much fat, and don’t get nearly enough exercise. These all aggravate diabetes and hypertension, and the likelihood of developing complications like kidney failure.

Why has the blood pressure target for the diabetic hypertensive been lowered to 130/80 mm Hg?
This is based on the results of ongoing clinical trials…As we learn more about the impact of controlling blood pressure, and the prevention of cardiovascular disease, we’ve learned that lower blood pressures are associated with a lower risk of complications.

It’s not just for diabetics that we’re reducing targets; it’s also the case for essential hypertension. As the research progresses, I’m sure we’ll be revising targets again.

Will these new lowered BP targets generally require multiple medications to achieve?
The one thing that’s clear from all of the trials that have been done, is that for the vast majority of patients, we’re going to require more than one medication in order to achieve these new targets.

I think that’s one of the most difficult things for patients to understand: that their blood pressure treatment is going to require not just a combination of lifestyle changes, but more than one medication, in order to maximize their protection against end-organ damage.

What is the importance of measuring proteinuria, both as a marker and for the prevention of kidney disease?
Proteinuria is an early indicator of kidney damage, particularly in diabetes, for which we have quite good information.

The development of small amounts of proteinuria, known as microalbuminuria, is often the first sign that the kidneys are stressed…It’s an early warning that the patient is at risk of developing more serious levels of kidney damage, and ultimately, kidney failure…Having protein traffic through the glomeruli, the filters in the kidney, leads to damage.

I should also emphasize that not everyone who has high blood pressure will have protein in the urine, but it is a useful and easy thing to look for.

Is proteinuria microalbuminuria?
Microalbuminuria is a term that’s applied to a specific range of albumin excretion in the urine. We all have a little bit of protein in our urine every day—most of that is protein derived from the tubules of the kidney, about 150 mg of protein per day.

Albumin is not normally present in any large amounts in our urine. Typically we would have less than 30 mg per day. Microalbuminuria refers to a range of excretion that is higher than that 30 mg per day, but less than what we could pick up with a dipstick test…the dipstick test picks up albumin of more than 300 mg per day.

Microalbuminuria refers to that intermediate stage, more than 30 mg, but less than 300 mg per day.

Why are nephrologists always ordering 24-hour urine tests?
I don’t think it’s true that nephrologists always order 24-hour urine tests, although the types of patients that nephrologists see are often the more complex cases who have other problems in addition to diabetes and hypertension.

For example, they may have a form of glomerulonephritis, inflammation of the filters of the kidney, the glomeruli. In those situations, the 24-hour urine protein is often a more useful marker to follow. Also, in research studies, most of the information that we have relates to targets of 24-hour urine proteins.

But as a screening test in general practice, a spot microalbumin measurement, especially if it’s linked to a measurement of urinary creatinine, will be a very effective tool.

Should other physicians also treat proteinuria, targeting the kidney? For example, cardiologists seem to have been slow to get this message.
I think any physician who regularly treats patients with hypertension and/or diabetes should be aware of the importance and risks of proteinuria.

Such physicians should regard both blood pressure as well as urinary protein as important to treat.
While nephrologists will use dihydropyridine Calcium Channel blockers for controlling blood pressure, when we’re trying to reduce urinary protein, we use ACE Inhibitors, Angiotensin-Recepotor blockers, and the non-dihydropyridine Calcium Channel blockers.

What is dialysis, and why does it cost $100,000 per year per patient?
Hemodialysis costs $100,000 per year, but peritoneal dialysis is somewhat cheaper.

Hemodialysis is a technique whereby the patient’s blood is circulated outside the body through a special machine which purifies the toxins that would normally be removed by the kidney. These sessions last three to four hours, three times a week.

Certainly it is an expensive undertaking, but it is life-saving…Without this therapy, these patients would be dead.

Does lowering cholesterol benefit the kidney?
That’s an excellent question. It’s controversial…there is data in experimental forms of kidney disease that suggest that cholesterol-lowering might benefit the kidney. But in the real world situation, it’s very hard to identify if there’s a specific role for cholesterol-lowering therapy…We don’t have the studies in which we lowered the cholesterol and left everything else the same.

The impact of cholesterol-lowering on the kidney is probably small, compared with the impact, for example, of lowering BP…but there is a general cardiovascular benefit.

What should our daily water intake be, and is this modified for patients with renal disease?
In general, most people should try and drink between six to eight glasses of water per day, about 1.5 to two litres.

In most patients with chronic kidney disease, it’s not necessary to modify fluid intake greatly. Even patients with advanced kidney failure are able to manage their water intake well.

Patients on dialysis, on the other hand, often have to have quite significant fluid restrictions, because they produce little or no urine…and they can rapidly accumulate fluid.

What is the connection between anemia and the kidney?
One of the endocrine functions of the kidney is that it produces a hormone called Erythropoietin. This stimulates red blood cell production in bone marrow.

When the kidneys fail, the production of Erythropoietin fails…That’s why the vast majority of patients with advanced kidney disease have anemia.

What is your final message to physicians who wish to treat kidney disease appropriately?
Be aware of the conditions in which patients are at risk for chronic progressive kidney disease, specifically diabetes, hypertension, or any form of glomerular disease.

You should identify the patients at risk by screening them on a regular basis for the presence of proteinuria. Patients who have proteinuria need more aggressive control of their BP, and you need to consider medications that target proteinuria as part of the regimen—those would include ACE Inhibitors, Angiotensin-Recepotor blockers, and the non-dihydropyridine Calcium Channel blockers.

If we all worked towards this, we would see the burden of illness of diabetic and hypertensive renal damage diminish.

Dr. Shafiq Qaadri is a Toronto family physician and Continuing Medical Education lecturer. www.doctorQ.ca

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