Which Scan for Kidney Stones? Ultrasound, CT KUB or X-Ray

At a Glance

How do ultrasound, CT KUB and X-ray compare?

KUB means kidneys, ureters and bladder. Prescriptions may say USG KUB or sonography, NCCT KUB or plain CT KUB, X-ray KUB, or CECT urography. Kidney stone in Hindi: गुर्दे की पथरी; in Marathi: मुतखडा.

• Ultrasound KUB: no radiation. It shows stones in the kidneys, in the bladder and where the ureter enters the bladder, and clearly shows a kidney swollen by blocked urine (hydronephrosis). Very small stones, and stones in the middle of the ureter hidden by bowel gas, can be missed, and stone size on ultrasound is less exact than on CT.
• Plain low-dose CT KUB: no injection. It finds almost all stones from kidney to bladder, including uric acid stones that X-ray misses, with each stone's size in millimetres, position, density and any blockage, and it can show another cause for the pain.
• X-ray KUB: one quick, low-dose picture. Most calcium-containing stones show on it, so it suits follow-up of a stone known to be visible on X-ray and checking the position of a DJ stent. Uric acid stones, small stones and stones lying over bone or bowel may not show, and it does not show blockage.
• CT urography (CECT urography) or X-ray IVU (also called IVP): a contrast injection outlines the whole urinary tract. These are not needed just to find a stone; they are used mainly for blood in the urine, unusual anatomy or planning complex surgery. CT urography has largely replaced the X-ray IVU.

Which test in which situation?

These are the usual patterns; your doctor may choose differently because of your earlier scans or kidney function.

• Adult with sudden colicky pain in the side or back spreading to the groin: either an ultrasound first, followed by a plain CT KUB if a stone needs confirming or the ultrasound is unclear, or a plain CT KUB straight away. Both approaches are standard.
• Pregnancy: ultrasound first. Mild swelling of the kidneys is normal in pregnancy, so the result is read with this in mind. If ultrasound does not answer the question, your doctor decides on any further test; CT is used only if your doctor decides the benefit clearly outweighs the risk.
• Children: ultrasound first. CT only if ultrasound does not answer the question, with the dose adjusted to the child's size.
• Before lithotripsy (ESWL), ureteroscopy or PCNL: plain CT KUB, for each stone's size, position and density. Before PCNL or complex surgery, your urologist may sometimes also ask for CT urography to see the drainage system of the kidney.
• Follow-up, repeated stones or a DJ stent: ultrasound, X-ray KUB or both, to limit radiation; CT only when the result will change the plan, such as checking for fragments after treatment. If you have a DJ stent, have it removed or changed by your urologist on the date advised, because a stent left in too long can become coated with stone and blocked.
• Blood in the urine without a clear cause: usually CT urography; for some people ultrasound is enough, depending on age and risk. A scan does not replace a check of the bladder lining (cystoscopy), which your urologist may also advise. Blood in the urine, even once and even without pain, should always be shown to your doctor.

When should I go to an emergency department first?

Once the pain is controlled and your doctor has advised a scan, message us on WhatsApp and mention the pain.

What does the report tell my doctor?

A stone report gives the number of stones, the size of each in millimetres, where each lies (kidney, ureter or bladder) and whether the kidney is blocked; a CT KUB adds stone density, which helps a urologist choose a treatment. Small stones in the ureter, around 5 mm or less, often pass on their own, especially lower down near the bladder, and larger ones are less likely to, but your doctor makes that decision together with your symptoms.

None of these scans measures how well each kidney works. A blood creatinine test shows overall kidney function; if your urologist needs to know each kidney's share of the work, a different test, a nuclear renogram (such as a DTPA scan), is used, and it is done in a nuclear medicine department.

How do I prepare?

This is general guidance. Our team confirms the exact preparation when you book on WhatsApp.

• Ultrasound KUB: drink 3-4 glasses of water about an hour before and do not pass urine until after the scan. KUB alone usually needs no fasting; if the whole abdomen is to be scanned, have nothing to eat for about 4-6 hours (water is allowed). Usually about 15-30 minutes.
• Plain CT KUB: usually no fasting; you may be asked to drink water so your bladder is comfortably full. Usually about 10-15 minutes in the scan room.
• X-ray KUB: usually about 5-15 minutes; any instructions are given when you book. Mention any barium test in the last few days, because barium can hide stones.
• CT urography: nothing to eat for about 4 hours before, water allowed; allow about an hour at the centre. X-ray IVU preparation is given when you book.
• Contrast tests: a recent serum creatinine report may be requested; if you do not have one, the test can be done here before the scan. Tell us about any earlier contrast reaction, asthma or serious allergy, kidney disease, an overactive thyroid, and diabetes, especially if you take metformin: we check your kidney function (eGFR) and advise you. Do not stop any medicine on your own. Tell us if you are breastfeeding.
• Tell us before any CT or X-ray if you are, or might be, pregnant, and bring earlier reports and CDs so the radiologist can compare stone size and position.

Radiation and contrast: what to know

Ultrasound uses no radiation and X-ray KUB uses a low dose. A plain CT KUB here uses a dedicated low-dose stone protocol, adjusted to your body size, with a lower dose than a routine abdominal CT; CT urography takes images in more than one phase, so its dose is higher than a plain CT KUB. When your doctor considers a CT necessary, the expected benefit is generally greater than the small risk, but doses add up over repeated scans, so CT should not be repeated without reason.

The iodine-based contrast used for CT urography and IVU is well tolerated by most people. Mild itching, a rash or nausea can occur, and serious reactions are rare. Tell the staff straight away if you feel unwell during or after the injection. Unless your doctor has limited your fluids, drink plenty of water for the rest of the day.

Kidney stone scans at AV Scan, Dadar West

Ultrasound KUB, X-ray KUB, X-ray IVU, plain CT KUB and CT urography are all done at our centre, so if your doctor moves from one test to another you do not need to go elsewhere.

• Reported by our radiologists, Dr. Avinash Bansal and Dr. Vaishnavi Bansal, both MD (Radiology), who compare your scan with the earlier reports and images you bring
• Ultrasound on the GE Voluson E10 and Philips Affiniti 70G; CT on the Fujifilm Supria CT, with contrast only when the clinical question needs it
• WhatsApp a photo of your prescription to +91 98200 51511 and our team confirms the test, the preparation and the exact price before your visit
• Samples for serum creatinine, uric acid, calcium or urine routine, if your doctor has asked for them, can also be given at the centre
• Cashless with most major insurers and TPAs; empanelled for CGHS, ECHS and MJPJAY; most reports the same day, sent to your WhatsApp
• Open Monday to Saturday 8am-10pm and Sunday 8am-5pm; ground floor and step-free, which matters when you are in pain; near Shivaji Park and Siddhivinayak Temple