MCU Test for Urethral Stricture
MCU (micturating cystourethrogram), also called VCUG (voiding cystourethrogram), is an X-ray study that shows the bladder and urethra while a patient passes urine. In urethral stricture disease it is especially useful when the proximal urethra cannot be seen well on RGU, such as a nearly obliterated stricture or pelvic fracture urethral injury. MCU is commonly interpreted together with RGU rather than as a replacement for it. The test also shows the bladder neck opening and can help assess urinary leakage or other lower-tract anatomy.
What is an MCU / VCUG?
The bladder is filled with contrast, usually through a catheter. X-ray images are then taken while the bladder is full and while you urinate. As contrast passes from the bladder through the urethra, the proximal urethra and bladder neck become visible.
Why is MCU useful in urethral stricture?
- To show the urethra above a very tight or nearly obliterated stricture.
- To combine with RGU for pelvic fracture urethral injury and estimate the distraction defect.
- To assess bladder-neck opening and proximal urethral anatomy.
- To help distinguish posterior stenosis or obstruction patterns.
- To assess leakage after selected urethral reconstructions when used as a voiding urethrogram.
RGU versus MCU: what is the difference?
| RGU | MCU / VCUG |
|---|---|
| Contrast enters from the urethral opening. | Contrast starts inside the bladder. |
| Best for mapping the anterior urethra. | Best for showing bladder neck and proximal urethra during voiding. |
| Can stop at a nearly obliterated stricture. | Can show the proximal side of that narrowing. |
| Often done without filling the bladder. | Requires the bladder to contain contrast and the patient to void. |
How should you prepare?
Preparation varies by centre. You may be asked to provide a urine test if infection is suspected. Tell the team if you have fever, severe urinary symptoms, known contrast reactions or difficulty tolerating catheters. Routine fasting is usually not required unless another procedure is planned.
How is the test performed?
A catheter is used to fill the bladder with diluted contrast. Once the bladder is adequately filled, the catheter may be removed or imaging may be adapted to the clinical question. You are then asked to urinate while fluoroscopic images are taken. Some patients find voiding in the X-ray room awkward; the staff will guide positioning and privacy as far as practical.
What can the report show?
- Bladder contour and capacity.
- Bladder-neck opening during voiding.
- Proximal urethral calibre.
- Location of a posterior narrowing.
- The proximal end of a pelvic-fracture urethral gap.
- Residual contrast or incomplete emptying.
Why can a patient be unable to urinate during MCU?
The setting is unfamiliar, there may be anxiety, and patients with obstruction may already have difficulty initiating flow. In post-urethroplasty leak testing, if a patient cannot void after catheter removal, a retrograde/pericatheter urethrogram can be used instead.
Does MCU diagnose every urethral stricture?
No. It is most useful for the proximal urethra and voiding phase. RGU remains the main radiographic mapping test for male anterior strictures. Cystoscopy, uroflowmetry and examination provide complementary information.
Risks and discomfort
- Temporary burning from catheterisation.
- Small amount of blood in urine or at the meatus.
- Urinary infection.
- Radiation exposure.
- Rare contrast reaction.
What happens after the test?
Your urologist reviews the actual images along with the RGU. In pelvic fracture injury, the apparent gap, position of the proximal urethra and bladder-neck appearance help plan reconstruction. In other strictures, the combined imaging helps determine whether an endoscopic procedure is reasonable or urethroplasty is more appropriate.
What to bring for consultation
- MCU/VCUG images and written report.
- RGU images if done.
- Uroflowmetry and post-void residual.
- Previous pelvic-trauma or urethral-surgery records.
- Details of a suprapubic catheter if present.
What MCU adds to an RGU
MCU/VCUG images the bladder and outlet while contrast is being passed during voiding. In urethral-stricture work it is especially useful when the proximal urethra needs to be seen from above – for example, after pelvic fracture urethral injury or when an anterior study cannot cross a completely obliterated segment.
If a suprapubic catheter is already present, the bladder can often be filled through that catheter for the study. The resulting images can show bladder-neck opening, the posterior urethra and the proximal end of a distraction defect. This complements RGU, which outlines the urethra from the distal end.
MCU is not required for every short anterior stricture and it does not replace direct cystoscopic assessment when there is concern about bladder pathology. Its value is highest when the reconstructive question specifically involves the bladder neck, posterior urethra or an obliterated segment. The surgeon should review the actual dynamic images whenever possible.
FAQs
Is MCU the same as an ultrasound?
No. MCU is a fluoroscopic X-ray study using contrast. Ultrasound does not show the urethral lumen in the same way during voiding.
Why do I need MCU if I already had RGU?
RGU may not show the urethra above a very tight narrowing. MCU can outline the proximal urethra from the bladder side.
Is MCU needed for every simple bulbar stricture?
Not always. It is most valuable when proximal anatomy is unclear, the stricture is near-obliterative/posterior, or pelvic fracture injury is being assessed.
Can MCU show reflux to the kidneys?
A formal VCUG can show vesicoureteral reflux if present, although in adult urethral-stricture work-up the main question is often the bladder neck and urethra.
What if I cannot pass urine during the test?
Tell the team. Alternative imaging, including retrograde urethrography, may still provide the information needed.
Related reading
- RGU Test for Urethral Stricture
- Pelvic Fracture Urethral Injury
- Posterior Urethral Injury Explained
- Cystoscopy in Urethral Stricture
- Urethroplasty Surgery Explained
- Urologist in Latur
References
- European Association of Urology. EAU Guidelines on Urethral Strictures: Diagnostic Evaluation, 2026 https://uroweb.org/guidelines/urethral-strictures/chapter/diagnostic-evaluation
- European Association of Urology. EAU Guidelines on Urological Trauma, 2026 https://uroweb.org/guidelines/urological-trauma
- European Association of Urology. EAU Guidelines on Urethral Strictures: Perioperative Care of Urethral Surgery, 2026 https://uroweb.org/guidelines/urethral-strictures/chapter/perioperative-care-of-urethral-surgery
- European Association of Urology. EAU Guidelines on Urethral Strictures, 2026 https://uroweb.org/guidelines/urethral-strictures
- American Urological Association. Urethral Stricture Guideline (2023 amendment) https://www.auanet.org/guidelines-and-quality/guidelines/urethral-stricture-guideline