Medical Post Diabetes and Kidney Disease - 1
By Dr. Shafiq Qaadri, MD
What are some of the lessons learned from Canada’s Aboriginal populations?
Dr. George Pylypchuk, a nephrologist in Saskatoon, has been working with this group for years.
He found a very high percentage of diabetes in this population, approaching 23% of adults--predominantly type II diabetes—and a very high prevalence of kidney disease in these diabetics.
What does diabetes actually do to the kidney?
Diabetes causes the kidneys to wear out faster than they would otherwise. In diabetes, the kidneys become sclerosed. The afferent arterioles, the arterioles leading into the glomeruli, become fixed and open—this allows systemic blood pressure into the glomerulus, and this causes premature wearing out…In fact, diabetes is the number one cause of kidney failure in Canada.
Why do patients who have both hypertension and diabetes have such added risk?
High blood pressure is a cause of kidney disease in and of itself. Diabetes is a cause of kidney disease in and of itself. When an individual has both conditions, it’s double trouble for the kidneys…this greatly increases the rapidity of the decline of kidney function.
All patients with kidney disease develop hypertension, and when someone with diabetes develops hypertension, it’s often an early manifestation of kidney disease.
Why is it that people with kidney disease develop such difficult-to-treat, refractory blood pressure?
Kidney disease is the most common form of secondary hypertension. All patients with kidney disease have a sodium-mediated component to their hypertension; they may also have a renin-dependent component—all these patients require multiple medications to control their blood pressure.
In the ALLHAT Trial, it was demonstrated, almost universally, that diabetic patients required two or more medications to control their blood pressure.
Our experience reflects this…90% of our patients with both diabetes and hypertension required two or more medications.
What sort of referrals do nephrologists get from family physicians, and is there a difference between the types of cases that a community or university nephrologist might see?
I believe that both community and academic nephrologists see largely the same type of referrals from their referring docs.
Most referrals consist of patients who have impaired kidney function, and tend to have high blood pressure also… Nephrologists would like to see patients with chronic renal failure earlier... As the GFR (glomerular filtration rate) dips below 60 ml/min, those patients can be plugged into the pre-dialysis clinics. Data has shown that we can extend the length of time—perhaps even delay altogether—dialysis.
Nephrologists do not want to take patients away from family doctors—the idea here is to co-manage patients with community caregivers.
What have been the trends in kidney disease over the past few years?
The number of patients with kidney disease has, unfortunately, rising significantly every year. The point prevalence of patients requiring dialysis has risen approximately 10% annually for almost the last decade.
This has created a crisis in health care resources, and underlines and accentuates the need for aggressive prevention programs.
Why is hypertension so poorly controlled, with only about 15% of hypertensive patients reaching target?
Unfortunately, blood pressure control is poor in the Canadian population. There are many reasons for this—it’s a multifactorial issue.
Our medications are good, but are often required in combination therapy, and some patients as well as physicians may be uncomfortable using them in combination.
Patients may also have difficulty accepting the need for lifelong medications, and may not be entirely convinced of the necessity.
Another issue is that physicians may be reluctant to aggressively manage blood pressure, because it takes time and requires a lot of counselling.
What is the time frame for developing kidney disease in a patient with a BP of 150/100 and moderately controlled diabetes?
A person with uncontrolled diabetes and blood pressure already likely has renal damage. If we did a renal biopsy in this patient, I’m sure we would see arteriolar changes and some early glomerular sclerosis.
The progression of kidney disease for this patient will actually be quite rapid from that point on. If left untreated, our best data suggest that that individual would lose their GFR 10 to 12 ml/min per year. In five to seven years, they’d likely end up on dialysis.
The significant issue is that high blood pressure is completely treatable, a completely reversible risk factor.
Is there a relationship between ethnicity and renal disease?
Ethnicity definitely plays a role in the kidney disease matrix. Black patients, African-American patients, are definitely at a higher risk of kidney disease related to hypertension.
Our aboriginal population is at higher risk of kidney disease related to diabetes. There’s work going on at McMaster looking at the South Asian population’s cardiovascular and renal risk factors.
We know also, for example, that ethnic Chinese from Hong Kong have a much higher incidence of cough with ACE Inhibitors than the Caucasian population.
Is there such a thing as childhood proteinuria?
There is proteinuria in childhood, and that is the realm of the pediatric nephrologist. Usually, childhood proteinuria is related to glomerular nephritis from minimal change disease.
However, diabetes is also playing a role in childhood now. Children as young as 11 and 12 with type II diabetes, who have already developed signs of kidney disease, with abnormal amounts of albumin in the urine.
Why are our treatment targets for everything—BP, cholesterol, sugar—always being lowered?
Treatment targets are being lowered in response to evidence that the lower levels are associated with better outcomes.
The achieved blood pressure is the best indicator of how well our patients are going to do—not so much where they start, but where they end up.
For example, a patient who is not able to bring their blood pressure down at the start, is telling us that his vasculature is more ill…
Studies like the UKPDS (the United Kingdom Prospective Diabetes Study), demonstrate that bringing sugars towards normal are also associated with better outcomes.
With the Heart Protection Study, it was shown that lower levels of LDL cholesterol were also associated with better outcomes.
So the general trend to lower targets has been fueled by the evidence from recently completed clinical trials.
Should family physicians routinely measure proteinuria, even as a screen?
Measuring proteinuria is the right thing to do in people with diabetes, and the best way to measure it is with a urine albumin/creatinine ratio. This can be done on a spot urine, anytime of the day.
There’s a question of whether we should be measuring albuminuria in hypertensive but non-diabetic patients. Right now, we do not have that recommendation in Canada, but the European Society of Hypertension has recommended urine albumin testing in hypertensives without diabetes. It’s a controversial area…
Is proteinuria that strong a marker?
Finding abnormal amounts of albumin in the urine is a potent marker in patients with diabetes and in hypertensives without diabetes as well.
Whether that is enough to lead to a change in recommendations is uncertain.
What do nephrologists learn with the 24-hour urine tests compared to the spot urine?
Nephrologists hold the 24-hour urine near and dear to their heart.
For people with nephrotic proteinuria, for people with glomerulonephritis, the 24-hour urine provides an excellent way to monitor and follow that patient.
Unfortunately, patients don’t like to do this test. And if they miss some samples, as is often the case, then the information gleaned from that test is really diminished.
How do Canadian Diabetes Association affect the practice of nephrologists?
The CDA guidelines, which were published on Dec 15, 2003 will not change the practice of nephrologists all that much, as we’ve been managing according to these principles all along.
I hope that the screening guidelines for nephropathy are easier to use. We are recommending that physicians screen patients with diabetes annually, that a standardized urine dipstick is used; and that if a patient has abnormal urine protein on dipstick, they have nephropathy. This would demand appropriate treatment.
The CDA guidelines focused on one class of calcium channel blockers as also being helpful in reducing urine proteinuria—can you comment?
There’s been a controversy over using calcium channel blockers in people with diabetes and hypertension and nephropathy. The evidence is overwhelming that such patients should be on a blocker of the Renin-Angiotensin-Aldosterone System (RAAS): ACE Inhibitors or Angiotensin Receptor blockers.
It’s imperative that their blood pressure be brought under control. Patients will require combination therapies, which should consist of diuretics, RAAS blockers, and other agents necessary to bring BP under control.
We have good evidence, that once the patient is on a RAAS blocker, it doesn’t matter which long-acting calcium channel blocker the patient takes.
We’ve included that in our clinical practice guidelines for nephropathy, but the emphasis is on controlling blood pressure.
We have insights on how ACE Inhibitors benefit the kidney. Do we know how the non-dihydropyridine calcium channel blockers help the kidney?
Animal studies suggest that the non-DHP calcium channel blockers further reduce intraglomerular pressure.
What’s the highest blood pressure you’ve ever seen?
The highest BP I ever saw in my office was 250/150, and we had to admit that patient right from the office to the coronary care unit.
What are the research trends in nephrology?
There are many diverse and exciting trends. For example, there’s a lot of research in diabetes at the basic science level, trying to prevent the development of diabetic nephropathy…
What’s your final message from the field of nephrology for family doctors?
Prevent kidney disease, screen your patients for blood pressure, make sure their BP is brought to target. That will do the most for protecting the kidneys and preventing progression to dialysis.
Dr. Shafiq Qaadri is a Toronto family physician and Continuing Medical Education lecturer. www.doctorQ.ca
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