Medically reviewed by Prof. Dr. Aamer Nadeem Chaudhary, M.B.B.S., D.M.R.D., F.C.P.S. (Diagnostic Radiology), Consultant, Al-Nasar Lab & Diagnostic Centre. Updated October 2026.
Quick answer: An ultrasound KUB examines the Kidneys, Ureters and Bladder using sound waves, with no radiation and no injection. It is the usual first test for flank pain, blood in urine and urinary infections, and it measures the prostate in men. It takes about 15 minutes and needs a comfortably full bladder. For small stones lodged in the ureter, CT KUB is more accurate.
Book a kidney ultrasound: call 0300 0341944. Performed at our main Johar Town campus.
What an ultrasound KUB shows
| Finding | What it means |
|---|---|
| Kidney stones | Stones inside the kidney are usually seen well |
| Hydronephrosis | Swelling of the kidney from a blockage further down. Often the most important finding |
| Kidney size and texture | Small, bright kidneys suggest long standing kidney disease |
| Cysts | Simple cysts are very common and usually harmless |
| Masses | Solid lumps that need further assessment, usually with CT or MRI |
| Bladder wall and stones | Thickening, stones or growths in the bladder |
| Post void residual | How much urine stays behind after you empty, important in prostate problems |
| Prostate size | Enlargement in men with urinary symptoms |
Ultrasound or CT KUB, which do you need?
Both are good tests. They suit different situations.
| Ultrasound KUB | CT KUB | |
|---|---|---|
| Radiation | None | Yes, low dose stone protocol |
| Stones in the kidney | Good | Excellent |
| Stones in the ureter | Often hidden by bowel gas | Excellent, the most accurate test |
| Blockage and swelling | Good | Excellent |
| Pregnancy and children | First choice | Avoided where possible |
| Repeated follow up | Ideal, no cumulative dose | Kept for when the answer changes treatment |
A sensible pattern is ultrasound first, then CT KUB when pain is severe, the ultrasound is unclear, or surgery or lithotripsy is being planned.
Why ultrasound can miss a stone
Worth knowing so that a normal scan is not over trusted.
The ureter is a narrow tube running behind the bowel. Gas in the bowel blocks sound waves, so a small stone stuck partway down the ureter is often not visible. That is exactly where stones cause the worst colicky pain.
What ultrasound usually can see is the consequence of that stone: the kidney above it swells. So a swollen kidney with no visible stone still points to an obstruction, and that finding guides what happens next.
If your pain is severe and the ultrasound looks normal, a CT KUB is the right next step rather than reassurance.
When is a kidney ultrasound needed?
- Flank or side pain, especially if it comes in waves and travels to the groin
- Blood in the urine, visible or found on a urine test
- Recurrent urinary infections
- A raised creatinine or reduced eGFR on a kidney function test
- Men with a weak stream, frequency or getting up at night, to measure the prostate and residual urine
- Follow up of known stones or cysts
- Long standing diabetes or high blood pressure, to look at kidney size
- A family history of polycystic kidney disease
How to prepare
- Drink four to five glasses of water, finishing about an hour before your appointment
- Do not empty your bladder before the scan. A full bladder is needed to see its wall and, in men, the prostate
- You may be asked to empty your bladder partway through, so the remaining urine can be measured
- No fasting is needed for a KUB on its own. If a whole abdomen ultrasound is being done at the same time, fast for 6 hours
- Bring previous scan reports and your latest kidney function and urine results
Stones: what to do after the scan
If a stone is found, its size and position decide the plan. Small stones often pass with fluids and pain relief. Larger ones, or those causing blockage or infection, need a urologist.
Prevention matters as much as treatment. Drinking enough water to keep urine pale is the single most effective measure, and it matters more in Lahore summers. Repeat stone formers benefit from blood and urine testing, including uric acid and calcium, to find the cause.
Kidney ultrasound at Al-Nasar Lab
Al-Nasar Lab & Diagnostic Centre has served Lahore since 1996 and holds ISO 15189:2022 accreditation from the Pakistan National Accreditation Council. Ultrasound, CT KUB, kidney function testing and urine examination are all available at our Johar Town campus, so stone investigation can usually be completed in one visit.
See our accreditations, find your nearest location, or contact us to book.
Frequently Asked Questions
Do I need a full bladder for a kidney ultrasound?
Yes. Drink four to five glasses of water an hour before and do not empty your bladder until after the scan.
Can ultrasound detect kidney stones?
Stones inside the kidney are usually seen well. Small stones in the ureter can be hidden by bowel gas, where CT KUB is more accurate.
Is a kidney ultrasound safe in pregnancy?
Yes. It uses no radiation and is the first choice for kidney problems in pregnancy.
Does a KUB ultrasound check the prostate?
Yes. In men it measures prostate size and how much urine remains after emptying.
How long does it take?
About 15 minutes, a little longer if a residual urine measurement is needed.
This article is for general information and is not a substitute for medical advice. Please discuss your results with a qualified doctor.
