Finding the right tests…
Emergency services available 24 x 7
Emergency services available 24 x 7
Finding the right tests…
CT Scan
If your doctor suspects a kidney stone, this is very likely the scan they'll order. CT KUB stands for kidneys, ureters, and bladder, and the plain version uses x-rays alone, no iodine dye, to look for a stone anywhere along that path. Stones are dense enough to show up clearly without contrast, and research on standardized CT KUB protocols reports sensitivity around 95 to 96 percent and specificity around 98 percent for detecting stones this way. It's also why medical guidelines list non-contrast CT as the standard first-line imaging for suspected kidney stones ahead of a contrast scan, since dye isn't needed to see a stone and can occasionally make small ones harder to spot.
The radiologist checks the kidneys, ureters, and bladder for a stone, its size and location, and any sign of blockage or swelling upstream. Bowel and nearby structures are also glanced at, since they sit in the same images. A written report goes to your doctor to guide treatment.
Kidney stones are made of calcium and other dense material that shows up clearly on a CT scan without any contrast dye. Because of this, non-contrast CT KUB has become the standard first-line imaging test when a stone is suspected, ahead of both ultrasound and contrast-enhanced CT, according to research on nephrolithiasis imaging.
Adding contrast doesn't make a stone easier to see and can sometimes make small stones harder to distinguish from the dye itself. Skipping contrast also means no risk of an iodine reaction and no wait for the dye to circulate, which matters for patients often in significant pain.
- The size, number, and exact location of any stone - Whether a stone is blocking the flow of urine - Swelling in the kidney caused by that blockage
Radiation is a genuine consideration with this scan, particularly since stones can recur and some people need repeat imaging over the years, so ask your doctor how this fits into your overall care.
Kidney stones are dense enough to show up clearly on a CT scan without any contrast, so dye isn't needed to find them. Skipping it also avoids any risk of an iodine reaction and means no wait for contrast to circulate.
Research on standardized CT KUB protocols reports sensitivity around 95 to 96 percent and specificity around 98 percent for detecting kidney stones. That makes it one of the most reliable tests available for this purpose.
CT KUB generally offers higher accuracy for detecting stones than ultrasound, particularly for smaller stones or ones in the ureter. Your doctor weighs this against radiation exposure, especially if you're young or likely to need repeat imaging in the future.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
CT KUB does involve x-ray radiation, and research notes that urinary stone imaging accounts for a meaningful share of overall medical radiation exposure, partly because stones often recur and lead to repeat scans. Ask your doctor how often repeat imaging might be needed in your case.
Since no contrast is involved, extensive fasting usually isn't required, but exact instructions can vary. Confirm directly with your doctor or the diagnostic centre what's expected before your appointment.
Tell your doctor and the technologist about any chance of pregnancy before the scan, since it uses x-ray radiation even without contrast. Doctors generally look for alternatives, like ultrasound, first during pregnancy when a stone is suspected.
A plain CT KUB can sometimes show an unrelated finding, like a mass, that needs a closer look with contrast. If that happens, your doctor will discuss whether the contrast version of CT KUB or another test is the right next step.