An MR Urography (Magnetic Resonance Urography) is a specialized MRI scan that focuses on the urinary tract — the kidneys, the ureters that carry urine from the kidneys to the bladder, and the bladder itself.
Doctors request this scan when investigating blood in the urine, recurrent urinary infections, suspected obstruction in the ureters, or anatomical abnormalities of the kidneys and urinary system.
Unlike CT urography, which uses X-ray radiation and an iodine-based dye, an MR Urography uses no radiation at all. This makes it the preferred test for children, pregnant women, young adults who will need repeated scans, and patients with an iodine contrast allergy.
Why would my doctor ask for an MR Urography?
Your doctor may recommend an MR Urography to look closely at your urinary system, especially if you have:
- Blood in your urine (visible or detected on a urine test).
- Recurrent or unexplained urinary tract infections.
- Persistent flank pain that may suggest a blockage.
- A known or suspected kidney stone causing obstruction, when CT is not suitable.
- A suspected tumor or mass involving the kidney, ureter, or bladder.
- Congenital anomalies of the urinary system (especially in children).
- Previous surgery on the kidney or ureter requiring follow-up imaging.
- An allergy to iodine-based CT contrast that prevents a standard CT urogram.
What can an MR Urography detect?
An MR Urography helps doctors visualize:
- Both kidneys, their internal structure, and surrounding tissues.
- The full length of both ureters from the kidney to the bladder.
- The bladder wall and the inside of the bladder.
- The blood vessels supplying the kidneys.
It is particularly useful for identifying:
- Obstruction (blockage) in the ureter and the level at which it occurs.
- Stones in the kidney or ureter, especially in patients who should avoid radiation.
- Tumors of the kidney, ureter, or bladder.
- Congenital abnormalities such as a duplex (split) ureter, horseshoe kidney, or pelvic kidney.
- Scarring or damage from previous infections or surgery.
- The function of each kidney separately.
Do I need any special preparation for an MR Urography?
Yes, preparation is important for a successful MR Urography:
- Hydration: You may be asked to drink a moderate amount of water before the scan so that the urinary system is well-filled and clearly visible.
- Empty bladder: You may be asked to empty your bladder shortly before the scan starts so that you are comfortable and able to stay still.
- Fasting: Some centers ask you to fast for 4 hours before the scan. Confirm with your imaging center.
- Remove all jewelry, body piercings, and metal objects, and change into a hospital gown.
- A medication called a diuretic (such as furosemide) may be given to help the kidneys produce urine during the scan, making the ureters easier to see.
Will I be injected with dye for this scan?
Yes, in most cases. A contrast agent called gadolinium is usually injected through an IV in your arm. The dye is filtered by the kidneys and travels down the ureters into the bladder, lighting up the entire urinary tract on the scan.
Some MR Urography studies — especially in pregnancy or in patients with reduced kidney function — can be performed without contrast, using a technique that relies on the natural urine already present in the system. Your radiologist will choose the approach that gives the safest, clearest answer.
What does an MR Urography feel like?
The scan is painless. You will lie flat on a padded table that slides slowly into the MRI scanner. A receiving device (a coil) will be placed lightly over your abdomen to capture clearer images.
You will hear loud knocking and humming sounds while the machine works, and earplugs or headphones will be provided. The radiographer will be able to see and speak with you throughout the scan.
Because the urinary system is in the abdomen and moves with breathing, you will be asked to hold your breath for short periods (10–20 seconds) at a time while the images are taken.
If you receive a diuretic to encourage urine production, you may feel a strong urge to pass urine toward the end of the scan. This is normal and expected — the team will let you use the bathroom as soon as the scan is complete.
Is it safe for pregnant women or children?
Yes. MR Urography is one of the main reasons MRI is so valuable for these groups. It is the preferred scan for pregnant women with suspected kidney stones or obstruction, because it avoids the radiation of CT. Gadolinium contrast is usually avoided in pregnancy unless absolutely necessary, and a non-contrast technique is used instead. For children, MR Urography is the preferred scan when they need detailed imaging of the urinary system, especially when repeated scans are likely.
How long does an MR Urography take?
The scan usually takes 45 to 60 minutes, longer than a routine MRI. This is because the team needs to capture images both before and after the dye reaches the urinary system, and may take multiple sets of images as the dye moves through.
When will I get my results?
After the scan, a Radiologist reviews the images and prepares a detailed report for your urologist or referring doctor. Results are typically ready within a few days. Your doctor will discuss the findings and recommend next steps, which may include medication, stone removal, surgery, or further follow-up imaging.
How is this different from a CT urogram or an ultrasound of the kidneys?
A kidney ultrasound is quick, cheap, and uses no radiation — it is often the first scan when there is a suspicion of a urinary problem, but it cannot show the full ureter clearly. A CT urogram gives excellent detail of the entire urinary system but uses X-ray radiation and iodine-based contrast. An MR Urography gives detail similar to a CT urogram, but without any radiation and using a different type of dye. Your doctor will choose based on what they need to see, your age, your kidney function, and any allergies.
Why might I be given a diuretic during the scan?
A diuretic — usually a small dose of furosemide given through your IV — encourages your kidneys to produce more urine during the scan. This stretches and fills the ureters and bladder, making them much easier to see and measure. Without the diuretic, the ureters can appear collapsed and a partial blockage can be missed. The medicine works quickly and you will feel a strong urge to pass urine toward the end of the scan, which is completely normal and a sign that the medication is doing its job.
What if I can't hold my breath as long as the radiographer asks?
Tell the radiographer at the start. Most sequences only need a 10–20 second hold, but if you have asthma, heart problems, or simply find it difficult, the team can shorten the breath-hold or use techniques that work with normal breathing. Try not to push through and gasp halfway — a calm partial breath-hold gives much better images than a forced full one followed by sudden movement. Holding the breath out (after exhaling) is usually easier than holding it in.
What if I'm nervous about being inside the scanner?
It is common to feel anxious, especially with a longer scan. You will be in contact with the radiographer through an intercom and can hold a squeeze ball to alert them if you need a break. If you are very claustrophobic, ask your doctor about a mild sedative or check whether your center has a wider-bore or open MRI machine.
Conclusion
An MR Urography is a safe, detailed, and radiation-free way to evaluate the kidneys, ureters, and bladder. It is especially valuable for pregnant women, children, and patients who cannot have CT contrast — giving your doctor a clear picture of what is happening inside the urinary system and guiding the right treatment plan.