In patients with type 2 diabetes,
silent cerebral infarction (SCI)—small areas of brain damage caused by injury
to small blood vessels—signals an increased risk of progressive kidney disease
and kidney failure, according to a study appearing in an upcoming issue of the
Journal of the American Society Nephrology (JASN).
If SCI is present in the brain,
it could be an indicator that small-vessel damage is present in the kidneys as
well, suggests the new study by Takashi Uzu, MD (Shiga University School of
Medicine, Otsu, Japan). Uzu comments, "Silent
cerebral infarction may be a new marker to identify patients who are risk for
declining kidney function."
The study included 608 patients
with type 2 diabetes, all initially free of symptomatic stroke, heart disease,
or kidney disease (overt proteinuria or renal dysfunction). On magnetic
resonance imaging (MRI) scans of the brain, 177 of the patients (29 percent)
had SCI—subtle areas of brain damage caused by disease of the brain blood
vessels, but not severe enough to cause overt symptoms of stroke.
At long-term follow-up, diabetic
patients with SCI had higher risks of progressive kidney disease. Compared to
those with normal brain MRI scans, patients with SCI were about 2.5 times more
likely to die or develop end-stage kidney disease. Their risk of declining
kidney function or dialysis was nearly five times higher.
New approaches are needed to
assess the risk of diabetes-related kidney disease. "Microalbuminuria—small
amounts of the protein albumin in urine—is the most important marker to predict
the progression of kidney disease in diabetic patients," explains Uzu.
"However, decreased kidney function without microalbuminuria is common in
patients with type 2 diabetes."
The new study shows that diabetic
patients with subtle brain damage detected on MRI scans are more likely to
develop serious kidney disease, independent of microalbuminuria.
"Evaluating both SCI and microalbuminuria may be useful for determining
the risk of progression of kidney disease in diabetic patients," says Uzu.
The study had some risk of bias related to patient
selection. Also, although most of the patients with SCI had multiple small
areas of brain damage, the study did not exclude patients with relatively large
areas of brain damage. "Therefore, not only small vessel disease but also
relatively large vessel disease might have affected the progression of kidney
disease in our patients," adds Uzu.