Renal Stones: Radiologic Diagnosis
Guest: Dr. Nancy Curry – Radiology, MUSC
Host: Dr. Linda Austin – Psychiatry, MUSC
Dr. Linda Austin: I’m Dr. Linda Austin. I’m interviewing Dr. Nancy Curry, who is Professor of Radiology and a uroradiologist here at MUSC. Dr. Curry, let’s talk about the radiologic diagnosis of renal stones. If a patient has kidney stones, that’s, obviously, very painful. Can you tell us what the workup for that involves?
Dr. Nancy Curry: In the days before CT, we used to evaluate a patient for a suspected kidney stone by obtaining a standard x-ray of the abdomen. In the new era of CT, we’re now able to, much more efficiently, diagnose stone disease. CT can uncover much smaller stones than a standard radiograph, and it involves only a slightly greater degree of radiation. It involves about nine seconds of the patient’s time, and no bowel preparation. And CT has the unique ability to identify all stones, whereas a standard x-ray of the abdomen can identify, probably, up to 90 percent, but they have to fairly large in order to do so. So, we have a very sophisticated and very simple way to identify stone disease in our patients.
Dr. Linda Austin: I remember, back in medical school, taking radiology, and the brilliant radiologist would show us radiographs. There would be very vague clouds and we’d say, oh yeah, I see it too. But with these CT scans of the abdomen, would the stones be pretty obvious?
Dr. Nancy Curry: Yes. They show up as bright white objects, even if they don’t appear at all on a standard x-ray. Some types of stones, uric acid stones, for instance, are somewhat rare. They’re only about ten percent of kidney stones. They’re not radio-opaque. They’re not dense enough to be seen on a standard x-ray. On a CT, they’re blazing white; very easy to see.
The other thing that’s really nice about the CT is that there’s no magnification or artifact introduced. An x-ray is like shining a flashlight in front of your hand against the wall. If your hand is away from the wall to some extent, there will be a very magnified picture of your hand on the wall. CT is different. We have an x-ray apparatus which rotates around the patient, and computers help us convert multiple imaging points into one cross sectional image of the abdomen. Obviously, when we’re looking for kidney stones, we’re looking at the kidneys, the ureters, and the bladder.
The nice thing about CT is that size is not distorted. We get an accurate representation of stone size. We can also see their relationship to the interior of the kidney. We know if they’re in the upper part of the kidney, the lower part of the kidney, whether they’re going to be accessible for treatment by certain kinds of external treatment; like lithotripsy, or whether they can be managed without an operation, through an interventional procedure performed by interventional radiologists.
Dr. Linda Austin: So then, the uroradiologist can really guide the treatment of these kidney stones in a very precise way, I would think?
Dr. Nancy Curry: Absolutely; not only pretreatment, but post-treatment. If there are any small stones remaining or if the patient is predisposed to develop more stones, this is the most accurate way to evaluate whether they’re still there, or they’re recurrent, and tells the referring clinician what to do about it.
Dr. Linda Austin: So, no longer is the physician between a rock and a hard place in deciding what to do? I’m sorry. I just couldn’t resist that. Dr. Curry, thanks so much for joining us today.
Dr. Nancy Curry: Thank you for having me.
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