RGU (retrograde urethrogram) is a contrast X-ray study of the urethra, most often used to define a urethral stricture or assess urethral injury. Contrast is gently introduced through the opening of the penis while X-ray images are taken. The report usually describes where the narrowing is, approximately how long it is, how tight it appears and whether contrast passes beyond it. RGU is especially useful for planning urethral reconstruction, but technique matters and the reported length can underestimate the true scar if the urethra is not adequately stretched or the stricture is nearly obliterated.

Why is an RGU done?

• Weak stream or suspected urethral stricture.
• Recurrent stricture after dilatation, DVIU or urethroplasty.
• Planning before urethral reconstruction.
• Suspected urethral injury after pelvic/perineal trauma.
• Assessment of fistula, false passage or complex urethral anatomy in selected cases.

How the test is performed

The patient is positioned obliquely so the urethra can be seen without overlapping the thighs. A small catheter or adaptor is placed at the urethral opening and water-soluble contrast is injected gently. Fluoroscopy or timed X-rays capture the contrast column. The test is brief, but pressure and instrumentation can cause temporary discomfort.

How to read the report

Site

Common sites include meatus/fossa navicularis, penile urethra and bulbar urethra. Posterior urethral anatomy is often better assessed with a voiding study, especially in pelvic fracture urethral injury.

Length

Length is measured radiographically and is crucial for surgical planning, but it is an estimate. Foreshortening, inadequate penile stretch and a very tight stricture can make it appear shorter than it truly is.

Calibre or severity

Terms such as “narrowing,” “tight stricture,” “pin-hole” or “near-obliterative” describe how much lumen remains. Complete failure of contrast to pass may indicate an obliterative segment, but combined studies may be needed to define the gap.

Extravasation

Contrast leaking outside the urethra can be seen with acute injury, false passage or recent instrumentation. Its significance depends on the clinical setting.

RGU and MCU together

In complex or posterior urethral disease, RGU may be combined with MCU/VCUG. The RGU outlines the urethra from below, while the voiding study shows the bladder neck and posterior urethra from above. Together they can define a distraction defect or complex stenosis more accurately.

What RGU cannot tell

RGU does not directly show the depth of spongiofibrosis (scar in the surrounding urethral tissue), bladder function or whether weak stream is caused by poor bladder contraction. Urethroscopy, ultrasound urethrography or urodynamics may be added in selected patients.

After the test

Mild burning on urination or a small spot of blood can occur briefly. Persistent bleeding, fever, inability to pass urine or worsening pain is not expected and should prompt medical review.

Before treatment, confirm that the anatomy matches the symptoms

A urethral stricture seen on RGU is relevant when it explains weak stream, recurrent retention, infection or difficult catheterisation. Very short mild narrowings can occasionally be overcalled if the urethra is not well distended. Conversely, a near-obliterative scar may hide the true proximal extent. The reconstructive urologist therefore combines RGU with flow, endoscopy and prior operative history before selecting a technique.

Why the actual RGU image matters for surgery

For urethral reconstruction, the typed phrase “short bulbar stricture” is not enough. The surgeon may look at the urethral calibre before and after the narrowing, the distance from the sphincter, whether the segment is nearly obliterated, associated false passages and the quality of the proximal urethral outline. These details influence whether a short excision/anastomotic repair, a graft augmentation or a more complex reconstruction is appropriate.

If the study was painful or contrast was injected against high resistance, tell the surgeon. A technically poor RGU may need to be repeated rather than planning major reconstruction from an uncertain image.

Why the image matters more than the one-line RGU conclusion

For urethral reconstruction, the surgeon usually wants to see the urethrogram images, not only the sentence ‘short bulbar stricture’. Apparent length depends on penile stretch, patient position, contrast distension and whether the proximal urethra is adequately outlined. Dense spongiofibrosis can extend beyond the narrowest radiographic segment.

The practical questions are: where does normal-calibre urethra end, how tight is the narrowing, how long is the diseased segment, and is the proximal urethra/bladder neck visible? These details help decide whether endoscopic treatment, anastomotic repair or substitution urethroplasty is realistic.

What to bring for a urethral-stricture consultation

• RGU images, not only the typed report.
• Previous MCU/VCUG or urethroscopy findings.
• Uroflowmetry and post-void residual if done.
• Details of previous catheterisation, DVIU, dilatation or urethroplasty.
• Discharge summaries and operative notes from prior urethral surgery.

FAQs

Related reading

• MCU Test Explained
• Uroflowmetry Report Explained
• Post-Void Residual Urine Explained
• Urologist in Latur

References

• European Association of Urology. EAU Guidelines on the Management of Non-neurogenic Male LUTS: Diagnostic Evaluation. 2026 https://uroweb.org/guidelines/management-of-non-neurogenic-male-luts/chapter/diagnostic-evaluation
• Rosier PFWM, Schaefer W, Lose G, et al. International Continence Society Good Urodynamic Practices and Terms 2016: Urodynamics, uroflowmetry, cystometry, and pressure-flow study. Neurourol Urodyn. 2017;36(5):1243-1260. doi:10.1002/nau.23124.