What is a urethrogram, its indications, and how is it performed?

Urethrogram: Definition, Indications, and Technique

A urethrogram is a radiographic imaging study that visualizes the urethra using contrast material, with retrograde urethrography (RUG) combined with voiding cystourethrography (VCUG) serving as the gold standard for diagnosing and characterizing urethral strictures, determining their exact location, length, and severity. 1

What is a Urethrogram?

A urethrogram is a specialized X-ray examination of the urethra performed by injecting radiopaque contrast material to outline the urethral anatomy. The study comes in two main forms:

• Retrograde Urethrography (RUG): Contrast is injected in a retrograde fashion through the urethral meatus to visualize the anterior urethra
• Voiding Cystourethrography (VCUG): The patient voids after bladder filling with contrast, allowing visualization of the entire urethra including the posterior (prostatic and membranous) segments

RUG combined with VCUG remains the study of choice for complete urethral evaluation, as it delineates stricture length, location, and severity more comprehensively than either study alone 1. Dynamic retrograde urethrography is particularly important as it can detect soft scarring that may be missed on voiding studies alone 2.

Primary Indications

Diagnostic Indications

Urethral stricture disease is the most common indication for urethrography 3. The study should be performed when:

• Men present with decreased urinary stream, incomplete emptying, dysuria, recurrent UTIs, or rising post-void residual 1
• Initial evaluation shows peak flow rate <12 mL/second on uroflowmetry combined with voiding symptoms 1
• Preoperative planning is needed to determine stricture length and location before definitive treatment 1

Trauma Indications

In trauma settings, retrograde urethrography should be performed in:

• All penetrating lower abdominal/perineal trauma when urethral injury is suspected 4
• Male patients with pelvic fractures associated with: gross hematuria, bloody urethral discharge, inability to void, perineal/penile swelling or ecchymosis, or high-riding/boggy prostate 4
• Pelvic fracture urethral injury (PFUI) for preoperative planning before delayed urethroplasty 5

Preoperative Planning

For surgical planning, combined RUG and VCUG provides critical information:

• Determines stricture length, location, and severity to guide treatment selection 1
• Assesses bladder neck competency and proximal urethral anatomy in PFUI 5
• Evaluates the gap length in complete urethral disruptions 6
• Provides dynamic voiding patterns that influence choice between endoscopic versus open repair 6

How the Study is Performed

Retrograde Urethrography Technique

1. Patient positioning: Typically oblique position (30-45 degrees) to separate urethral segments
2. Contrast injection: Water-soluble contrast is gently injected through a catheter-tipped syringe or specialized clamp device placed at the urethral meatus
3. Dynamic fluoroscopy: Images are obtained during active injection under fluoroscopic guidance 2, 7
4. Gentle pressure: Contrast should be injected with gentle, controlled pressure to avoid extravasation or intravasation into venous structures 8

Voiding Cystourethrography Technique

1. Bladder filling: The bladder is filled with contrast material (retrograde via catheter or antegrade via suprapubic tube)
2. Voiding phase: Patient voids while images are obtained to visualize the entire urethra, including posterior segments
3. Combined views: VCUG allows visualization of the urethra proximal to strictures that may not fill on RUG alone 6

Critical Technical Points

Important caveats to avoid complications:

• Obtain sterile urine before the study to minimize risk of bacteremia and sepsis 8
• Elicit history of contrast allergies and asthma 8
• Avoid excessive injection pressure, which can cause contrast extravasation, intravasation into venous structures, bacteremia, and worsening of stricture 8
• Perform under dynamic fluoroscopy rather than static imaging to detect subtle abnormalities 2
• Never perform voiding urethrography alone without retrograde study, as soft scarring may be missed 2

Alternative Imaging

Ultrasound urethrography may serve as an alternative diagnostic modality with high sensitivity and specificity in the anterior urethra, though it requires a skilled ultrasonographer and shares the drawback of patient discomfort 1.

Urethro-cystoscopy can identify and localize strictures and evaluate distal caliber, but cannot assess stricture length or the urethra proximal to the stricture in most cases 1.