Using MRIs to predict kidney failure

The top two images compare mild and severe scarring using conventional MRI technique. The bottom two images contrast mild and severe kidney scarring with the new MRI technique being tested in transplanted kidneys at St. Michael’s. (Images courtesy of Dr. Kirpalani and Dr. Leung, St. Michael's MRI Research Centre).

One in every two patients diagnosed with will not be alive in three years.

“The major reason that kidneys fail is scarring,” says Dr. Darren Yuen, a nephrologist with St. Michael’s Hospital. “If we could figure out who has a lot of scarring, we could better predict which patients are most likely to develop kidney failure and treat these patients more aggressively.”

Scarring is irreversible and can cause ongoing kidney injury that can eventually leads to kidney failure. Regardless of whether a patient has diabetes, high blood pressure or another condition affecting the kidney, all these diseases can cause scarring, which ultimately can lead to organ failure.

Needle biopsy is the current “gold standard” diagnostic test for assessing . A long needle is injected into the kidney and a sample—about the size of a mechanical pencil’s tip—is removed from the organ.

“The problem with biopsy is that such a small sample means even after patients undergo this painful test, we still don’t know what most of the kidney looks like,” says Dr. Yuen, who is also a scientist in the hospital’s Keenan Research Centre for Biomedical Science. “The sample may show no scarring, but the rest of the organ may be severely scarred. We have no way of knowing and so clinicians are hesitant to subject patients to a test that provides limited information and has risks such as internal bleeding.”

Dr. Yuen teamed up with Medical Imaging specialists Dr. Anish Kirpalani and Dr. General Leung to apply and study a specific magnetic resonance imaging test—called an elastogram—and its ability to detect scarring in transplanted kidneys.

If their new technique is able to quickly and clearly tell the difference between mild and severe kidney scarring, it may prove particularly helpful for kidney transplant patients.

“In the first year after surgery, patients with transplanted kidneys generally do very well,” says Dr. Yuen. “Their long-term prognosis, however, is unfortunately not as good.” Ten years after transplantation, up to 60 per cent of patient’s kidneys have some degree of scarring that can cause kidney failure.

“We’ve begun using MRI to measure a transplant kidney’s stiffness,” says Dr. Kirpalani, a radiologist and director of St. Michael’s MRI Research Centre. “Stiffness is an early sign of scarring, and this has been shown with MRI in organs other than the kidney. Healthy tissue is more flexible whereas scar tissue is more rigid.”

The team has begun studies to evaluate whether MRI can measure kidney scarring in patients more safely and accurately than biopsy. Unlike biopsy, the MRI test does not require needles or injections and MRI can analyze the whole organ for scarring, rather than just the small biopsy sample.

“We’ve already tested this technique in more kidney transplant patients than anywhere else in the world,” says Dr. Kirpalani. “If we’re able to detect scarring more safely and accurately than a needle biopsy, we may be able to better guide how kidney transplant patients are treated early on and improve their long-term outcomes.”