Retrograde Urethrogram (RUG) & Voiding Cystourethrogram (VCUG)

The retrograde urethrogram and voiding cystourethrogram remain the cornerstone imaging studies for reconstructive urological evaluation. Together they provide luminal roadmaps of the anterior and posterior urethra that no other single modality can replicate. This page covers technique, interpretation, pitfalls, and clinical applications in sufficient depth for operative planning.

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1. Overview

What RUG Shows — and What It Does Not

The retrograde urethrogram fills the urethral lumen with iodinated contrast under retrograde pressure, producing a fluoroscopic silhouette of the patent lumen from the meatus to the bladder neck. It is critical to understand what this image represents:

• RUG shows the lumen — the contrast column traces the fluid-filled channel, not the surrounding corpus spongiosum or periurethral fibrosis.
• Spongiofibrosis — the dense fibrotic reaction within the spongy erectile tissue that surrounds a stricture — is not visible on RUG. The contrast column ends at the mucosal surface of the strictured segment.
• As a result, RUG systematically underestimates stricture length by approximately 1 cm at each shoulder, because the transitional mucosa where normal epithelium blends into fibrotic epithelium is not distinguishable from the lumen edge.

:::warning Underestimation of Stricture Length RUG underestimates stricture length by ~1 cm (at the shoulder margins). This is clinically significant: graft lengths and mobilization estimates based purely on RUG will be too short. Add a buffer and correlate with sonourethrogram (SUG) for complex or recurrent strictures. McAninch et al. (1988) demonstrated that RUG underestimated length in 78% of cases compared to intraoperative measurement. :::

Why RUG Remains Irreplaceable

Despite the availability of ultrasound urethrography, MRI urethrography, and flexible cystoscopy, RUG retains a unique role:

• It is fast (5–10 minutes), widely available, and can be performed in an outpatient radiology suite, clinic, or operating room with a C-arm.
• It provides the best global overview of the entire anterior urethra in a single image, including multiplicity, contour, and fistulous tracts.
• It is the reference standard for post-urethroplasty surveillance.
• It remains the only way to image the entire urethral lumen simultaneously from both ends (combined RUG+VCUG), which is the gold standard for posterior urethral distraction defects (PFUI).

Indications: RUG vs. VCUG vs. Combined

Indication	Study of Choice	Rationale
Anterior urethral stricture (suspected)	RUG	Best retrograde luminal detail
Stricture length/location for OR planning	RUG ± SUG	RUG for overview; SUG for spongiofibrosis depth
Posterior urethral stricture (membranous/prostatic)	VCUG or combined	Posterior urethra not accessible retrogradely
Pelvic fracture urethral injury (PFUI)	Combined RUG + VCUG	Gap length, bladder neck assessment
Bladder neck contracture post-prostatectomy	VCUG	Antegrade phase shows bladder neck directly
Vesicoureteral reflux	VCUG	Antegrade filling reveals ureteral reflux
Female urethral stricture	VCUG (wine-glass sign)	RUG rarely diagnostic alone in females
Urethral diverticulum (female)	Double-balloon urethrogram or MRI	RUG misses most diverticula
Neurogenic bladder evaluation	VCUG	Detrusor-sphincter relationships
Post-urethroplasty surveillance	RUG	Standard 3-month surveillance study

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2. RUG — Equipment

Item	Specification	Notes
Foley catheter	16–18 Fr silicone or latex	Insert 2–3 cm; do not advance into bladder
Balloon inflation	1.5–2 mL in fossa navicularis	Creates meatal seal; more causes trauma
Contrast agent	Omnipaque 240 (iohexol 240 mg I/mL)	Iso-osmolar; well tolerated; water-soluble
Dilution	50:50 with normal saline	Reduces attenuation artifact; improves mucosal detail
Volume	20–60 mL	Sufficient to fill urethra to bladder neck
Syringe	60 mL piston (Toomey) syringe	Allows controlled slow injection
Fluoroscopy	C-arm (preferred) or dedicated fluoro table	C-arm allows RPO positioning
Radiation dose	0.1–2 mSv per study	Lower end with pulsed fluoroscopy
Brodney clamp	Penile clamp alternative to Foley	No balloon; reduces meatal trauma; useful in meatal stricture
Knutsson clamp	Dual-component external clamp	Older alternative; less commonly used

:::info Contrast Dilution Rationale The 50:50 dilution of Omnipaque 240 is deliberate. Full-strength contrast (240 mg I/mL) creates high radiodensity that can obscure fine mucosal detail and make estimation of stricture margins difficult. Dilution to ~120 mg I/mL produces a gray column that clearly delineates the luminal wall and makes subtle narrowing more apparent. Avoid diluting beyond 50% (i.e., do not use <120 mg I/mL) as contrast becomes too faint for reliable stricture detection. :::

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3. RUG — Step-by-Step Technique

Step 1 — Patient Positioning

• Patient lies supine on the fluoroscopy table.
• Rotate the patient into right posterior oblique (RPO) 45° — this is the most important technical step.
• The right leg is straight and extended; the left knee is flexed (left foot flat on the table) to stabilize the oblique position.
• The penis is stretched over the right thigh at 45° to the body axis (i.e., angled caudally and to the right, not straight up or horizontally).
• This positioning opens the bulbar curve and separates the penile urethra from the bulbar urethra in the fluoroscopic image, preventing overlap that would obscure bulbar pathology.
• The C-arm detector is positioned overhead.

:::tip Positioning Is the Most Common Source of Error Inadequate obliquity (less than 40°) causes the penile and bulbar urethra to overlap, making bulbar strictures invisible or artificially shortened. Always confirm RPO 45° before injecting. If anatomy is unclear on initial images, increase obliquity to 60° and re-image. :::

Step 2 — Foley Catheter Placement

• Gently insert the tip of a 16–18 Fr Foley catheter 2–3 cm into the urethral meatus — do not advance past the fossa navicularis.
• Inflate the catheter balloon with 1.5–2 mL of sterile water or saline to seat the balloon within the fossa navicularis and create a seal against retrograde contrast leakage.
• Do not use more than 2 mL in the fossa — overdistension is painful and can cause meatal or fossa navicularis trauma, particularly in patients with existing strictures at or near the meatus.
• If the patient has a meatal or fossa navicularis stricture preventing Foley insertion, use a Brodney clamp (external penile clamp) applied around the distal glans, or insert the smallest Foley catheter that passes and use minimal balloon inflation.
• Attach the 60 mL syringe of diluted contrast to the catheter port.

Step 3 — Contrast Preparation

• Prepare diluted Omnipaque 240 in a 50:50 mixture with normal saline in a 60 mL syringe.
• Confirm the syringe is free of air bubbles — air produces filling defects indistinguishable from filling defects caused by polyps or tumors.
• Keep a second 60 mL syringe of diluted contrast available if additional volume is needed to reach the bladder neck.

Step 4 — Slow Contrast Injection Under Fluoroscopy

• Begin fluoroscopy before injecting — capturing the start of urethral filling is essential for meatal and fossa navicularis evaluation.
• Inject contrast slowly and steadily, at a rate that produces a visible leading edge advancing from the meatus toward the bladder neck.
• Do not forcibly inject — high-pressure injection causes external sphincter spasm, producing an artifactual narrowing at the membranous urethra that mimics membranous stricture.
• The total injection volume to fill from meatus to bladder neck is typically 20–40 mL.
• Pause injection momentarily when the leading contrast column reaches the bulbomembranous junction to obtain a dedicated bulbar/membranous image.

Step 5 — Image Acquisition Timing

Obtain fluoroscopic spot images (or save cine loop frames) at three stages:

Stage	Timing	Structures Captured
Early fill	Contrast in meatus/fossa/penile urethra	Meatus, fossa navicularis, distal strictures
Mid-fill	Contrast reaching penoscrotal junction/proximal penile urethra	Penile urethra, penoscrotal junction
Full fill	Contrast in bulbar urethra, approaching/entering membranous	Bulbar stricture, bulbomembranous junction, posterior extent

• For the final full-fill image, continue injecting until the bladder neck becomes faintly opacified — this confirms contrast has reached the posterior urethra.
• If bladder neck is not visualized, a combined VCUG is required to assess the posterior segment.

Step 6 — Combined RUG + VCUG for Posterior Urethra

When posterior urethral assessment is required (see Section 13 for PFUI protocol):

• After completing retrograde injection, leave the Foley catheter in place.
• Fill the bladder via suprapubic catheter (or via a separate urethral catheter if one passes) with 150–200 mL of diluted contrast.
• Remove the urethral catheter from the meatus.
• Ask the patient to void while imaging in the RPO 45° position.
• The voiding urethra fills the posterior urethra antegradely while the residual contrast column in the anterior urethra shows the retrograde extent.
• In a PFUI gap study, both columns fill simultaneously and the gap between them is measured.

Step 7 — Documentation Requirements

The formal RUG report must include:

• Date, indication, contrast agent and dose
• Patient positioning (confirm RPO)
• Stricture location (by anatomical segment — see Section 5)
• Stricture length in centimeters (measured from fluoroscopic landmarks)
• Estimated caliber at narrowest point (in French or millimeters)
• Number of strictures (single, multiple, panurethral)
• Contour description (smooth, irregular, moth-eaten, spicular)
• Presence or absence of fistulous tracts
• Proximal urethral anatomy (dilated, normal)
• Bladder neck appearance (if visualized)
• Any extravasation

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4. Fluoroscopy Settings

Appropriate fluoroscopy technique minimizes radiation exposure to both patient and operating team while maintaining image quality sufficient for diagnosis.

Parameter	Recommended Value	Rationale
kVp	70–80 kV	Optimal soft tissue contrast for iodinated contrast in the pelvis
mA	2–4 mA	Low mA sufficient given high iodine concentration in urethra
Mode	Pulsed fluoroscopy at 7.5 fps	50–70% dose reduction vs. continuous fluoroscopy; no diagnostic penalty
Collimation	Tight to pelvis/perineum	Reduce scatter; protect gonads and adjacent tissue
DAP	50–200 mGy·cm²	Typical dose-area product for a standard RUG
Total exam time	<2 minutes fluoroscopy	Achievable with pulsed mode and experienced technique

:::warning Avoid Continuous Fluoroscopy Continuous fluoroscopy at standard frame rates (30 fps) delivers 50–70% more radiation than pulsed mode at 7.5 fps without meaningful gain in diagnostic information for a urethral study. Use pulsed mode as the default. If the system does not offer pulsed fluoroscopy, minimize live screening time by acquiring only when injecting and obtaining spot images at key phases. :::

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5. Normal RUG Anatomy by Segment

Segment	Normal Caliber	Normal Appearance	Key Points
Urethral meatus	≥18 Fr	Rounded or vertically slit opening	Narrowest normal point; meatal stenosis if <18 Fr
Fossa navicularis	20–24 Fr	Slightly wider than meatus, smooth walls	Within glans penis; site of LS involvement
Penile (pendulous) urethra	22–28 Fr	Parallel walls, uniform caliber	Extends from fossa to penoscrotal junction
Penoscrotal junction	22–26 Fr	Slight angulation, smooth	Transition to bulbar; a common stricture site
Bulbar urethra	24–30 Fr	Widest anterior segment; smooth, slightly irregular wall normal	Longest anterior segment; most common stricture site
Bulbomembranous junction	Apparent narrowing	Slight funnel narrowing on RUG	Site of external sphincter; apparent narrowing is normal
Membranous urethra	18–22 Fr	Short, narrowed on RUG	External sphincter causes apparent narrowing — normal finding
Verumontanum	Filling defect	Posterior midline defect visible on VCUG antegrade	Landmark for posterior urethra on VCUG
Prostatic urethra	22–28 Fr	Widens proximally; verumontanum filling defect	Best seen on VCUG; inaccessible on retrograde RUG
Bladder neck	Closed at rest	Opens smoothly into a funnel on voiding	Failure to funnel on VCUG suggests bladder neck stenosis

:::info The Membranous Narrowing — Normal vs. Pathological The membranous urethra always appears narrowed on RUG due to involuntary external sphincter tone during retrograde injection. This is a normal finding and should not be reported as a stricture unless the narrowing persists during the voiding phase of VCUG, measures <16 Fr, or is associated with post-void residual. Membranous strictures from radiation or post-prostatectomy are best characterized on VCUG, not RUG. :::

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6. Stricture Interpretation

A systematic approach to RUG interpretation prevents missed lesions and incomplete surgical planning. Report the following parameters:

Location

Use standard anatomical segment terminology:

Segment	Boundaries	Notes
Meatus / fossa navicularis	External meatus → fossa navicularis	Often LS-related; missed on casual RUG
Penile (pendulous) urethra	Fossa navicularis → penoscrotal junction	Traumatic, instrumentation, LS
Penoscrotal junction	Junction of penile and bulbar urethra	Common post-hypospadias site
Bulbar urethra	Penoscrotal junction → bulbomembranous junction	Most common overall; straddle injury, idiopathic
Bulbomembranous junction	Transition zone, proximal bulbar	Post-TURP, radiation
Membranous urethra	External sphincter to apex of prostate	Post-prostatectomy, pelvic fracture
Prostatic urethra	Apex of prostate → bladder neck	Post-TURP, radiation; VCUG required

Length

• Estimate stricture length in centimeters from the fluoroscopic image using bony landmarks (pubic symphysis, ischial tuberosities) as reference scales.
• For multiple strictures, measure each individually and record the intervening normal segment length.
• Remember: RUG underestimates by ~1 cm; report the measured value but note this limitation.

Severity (Caliber at Narrowest Point)

Grade	Estimated Caliber	Clinical Significance
Mild	>15 Fr	Likely symptomatic; may trial dilation or DVIU (first episode, <1.5 cm, bulbar)
Moderate	10–15 Fr	Significant obstruction; urethroplasty likely required
Severe	<10 Fr	Near-complete obstruction; urethroplasty required
Complete obliteration	0 Fr (no contrast passage)	No luminal continuity visible; PFUI or obliterative BXO

:::tip Severity Classification Caliber estimates from RUG are approximate. The contrast column width at the narrowest point correlates roughly with luminal diameter. Cystoscopy at the time of urethroplasty will give the true caliber. RUG severity influences patient counseling and consent discussions but should not prevent operative planning. :::

Multiplicity

• Single stricture: most common; straightforward planning.
• Multiple discrete strictures: each must be characterized separately; affects technique selection.
• Panurethral stricture: continuous narrowing over most of the anterior urethra; typically LS or prior failed hypospadias repair; requires two-stage substitution or staged reconstruction.

Contour

Contour Pattern	Description	Clinical Implication
Smooth, tapered	Regular walls, gradual transition to normal	Low spongiofibrosis; good candidate for DVIU (first episode, short)
Smooth, abrupt	Sharp demarcation without irregularity	Moderate fibrosis; EPA or onlay
Irregular	Wall irregularity, indistinct margins	Dense spongiofibrosis; substitution likely needed
Moth-eaten / spicular	Contrast enters crevices; ragged margins	Lichen sclerosus (BXO) pattern; multistage reconstruction
Fistulous tract	Contrast exits urethra into perineum or skin	Fistula; modify surgical approach

Additional Findings to Report

• Fistulous tracts: extravasation of contrast through the periurethral tissue toward skin or rectum.
• Proximal anatomy: Is the proximal urethra and posterior urethra normal? Dilated proximal urethra suggests chronic high-grade obstruction.
• Dilated proximal urethra: Pre-stricture dilation indicates prolonged obstruction; may complicate anastomotic tension if present at the bulbomembranous junction.
• Bladder neck appearance: If contrast reaches the bladder neck, comment on opening, trabeculation visible, or suggestion of bladder neck stenosis.
• Vesicoureteral reflux: Only visible on VCUG voiding phase.

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7. Common Pitfalls

Pitfall	Mechanism	Appearance	Solution
Membranous apparent narrowing	External sphincter spasm during retrograde injection	Short, smooth narrowing at membranous — indistinguishable from stricture	Inject slowly; confirm during VCUG voiding phase; narrowing resolves on voiding if normal
Short-appearing stricture	Incomplete urethral filling distal to dense obstruction	Stricture appears shorter than true length	Increase injection volume and pressure slightly; combine with antegrade SUG
Extravasation artifact	Foley balloon not seated in fossa; prior meatal trauma; high injection pressure	Contrast outside urethra, creating irregular periurethral staining	Re-seat catheter; reduce injection pressure; reduce balloon inflation
Poor oblique positioning	RPO <40° causing penile/bulbar overlap	Bulbar urethra obscured by overlapping penile urethra	Confirm 45° RPO; increase obliquity to 60° if needed; stretch penis further caudally
Dilution artifact	Contrast too dilute (<120 mg I/mL)	Pale contrast column with poor wall definition	Use 50:50 dilution (Omnipaque 240 : saline); do not dilute beyond 50%
Air bubble artifact	Air in syringe or tubing	Round filling defect within contrast column mimicking polyp or tumor	Purge air from syringe before injection; tilt syringe upright during preparation
Failure to image early fill	Starting image capture mid-injection	Meatal and fossa navicularis strictures missed	Begin fluoroscopy before injecting; acquire early-fill image
Foley advanced too far	Catheter inserted into bulbar urethra	Proximal displacement of contrast; distal urethra not filled	Withdraw catheter to fossa navicularis; re-image

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8. Female RUG

Why RUG Is Rarely Diagnostic Alone in Females

The female urethra is short (3–4 cm), mobile, and does not develop the same retrograde pressure gradient as the male urethra during RUG. Standard single-catheter retrograde injection produces inconsistent filling, frequent early voiding, and poor visualization of the entire lumen. The wine-glass sign of female urethral stricture is better appreciated on VCUG during voiding.

Indications for dedicated female urethral imaging:

• Suspected female urethral stricture (post-instrumentation, post-radiation, lichen sclerosus, prior pelvic surgery)
• Urethral diverticulum (palpable periurethral mass, post-void dribbling, dyspareunia)
• Urethrovaginal fistula

Double-Balloon Urethrogram for Diverticulum

The double-balloon catheter technique (also called the Davis catheter or Trattner catheter technique) is the dedicated fluoroscopic method for urethral diverticulum:

1. A specialized double-balloon catheter is placed in the urethra; one balloon is inflated at the bladder neck and one at the urethral meatus, creating a closed urethral chamber.
2. Contrast is injected into the isolated urethral lumen under pressure.
3. The diverticulum fills with contrast and is visualized as a saccular outpouching from the posterior urethral wall, most commonly at the 3 and 9 o'clock positions in the midurethra.
4. Images are obtained in AP and oblique projections.

:::info MRI Is Now Preferred for Diverticulum MRI pelvis with dedicated urethral protocol (small field-of-view, T2-weighted axial and sagittal) has replaced double-balloon urethrogram at most centers for urethral diverticulum evaluation. MRI defines the diverticulum extent, its relationship to the sphincter, and identifies multilocular or horseshoe configuration that changes the surgical approach. Double-balloon urethrogram is reserved for cases where MRI is unavailable or contraindicated. :::

Wine-Glass Sign on VCUG

In female urethral stricture, the VCUG voiding phase demonstrates the wine-glass sign (also called the champagne-flute sign):

• The proximal urethra dilates upstream of the obstruction, forming the wide "bowl" of the wine glass.
• The stricture itself forms the narrow "stem."
• The distal urethra may appear normal in caliber below the stricture.

This pattern is pathognomonic for intrinsic female urethral stricture and distinguishes it from bladder neck dyssynergia or external sphincter hypertonia, both of which cause narrowing at a different anatomical level.

:::tip Diagnostic Threshold for Female Urethral Stricture A urethral caliber of <14 Fr on calibration or VCUG is the widely accepted diagnostic threshold for female urethral stricture. Normal female caliber is 18–24 Fr. Clinical symptoms alone (dysuria, weak stream, incomplete emptying) are insufficient — objective caliber measurement is required to confirm diagnosis and plan reconstruction. :::

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9. VCUG — Overview and Indications

The voiding cystourethrogram images the urethra and bladder during antegrade flow (voiding), providing information about segments not accessible by retrograde RUG. VCUG is complementary to — not a replacement for — RUG.

Indications

Indication	Specific Finding Sought
Posterior urethral stricture	Membranous and prostatic urethral caliber during voiding
Bladder neck contracture post-radical prostatectomy	Absence or distortion of bladder neck funneling
Pelvic fracture urethral injury (PFUI)	Combined with RUG for gap length; bladder neck assessment
Vesicoureteral reflux evaluation	VUR grade; ureteral and calyceal dilation
Female urethral stricture	Wine-glass sign during voiding
Urethral diverticulum (female)	Contrast filling of diverticulum during or after voiding
Neurogenic bladder assessment	Detrusor-sphincter coordination, trabeculation, diverticula
Post-augmentation cystoplasty surveillance	Anastomotic leak or outlet obstruction
Post-urethroplasty posterior reconstruction	Adequacy of voiding channel after bulbomembranous reconstruction

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10. VCUG — Technique

Bladder Filling Phase

1. With the patient supine, insert a 14–16 Fr catheter transurethrally (if there is no contraindication from a stricture) or via suprapubic catheter if one is in situ.
2. Fill the bladder with 150–200 mL of diluted iohexol (Omnipaque 240 diluted 50:50, or Omnipaque 300 diluted 70:30 for better visualization of reflux).
3. Obtain AP and oblique filling phase images to assess bladder outline, trabeculation, and diverticula.
4. Do not overfill — urgency and detrusor instability may cause involuntary voiding before optimal positioning.

Voiding Phase

1. Remove the urethral catheter (leave suprapubic catheter in situ if present).
2. Position the patient in RPO 45° oblique — same as for RUG — for optimal urethral visualization.
3. Ask the patient to void. In male patients, the entire anterior and posterior urethra will opacify antegradely.
4. Obtain fluoroscopic spot images during active voiding (not at the beginning or end when flow is intermittent).
5. Capture at least one image with the entire urethra in view (meatus to bladder neck).

Post-Void Phase

1. After voiding is complete, obtain a final AP post-void image to:
   • Assess post-void residual (PVR).
   • Identify delayed filling of a urethral diverticulum with contrast that remains after voiding.
   • Confirm resolution of VUR (contrast should clear from the ureters).

Modifications for SPC In Situ (PFUI Patients)

When a suprapubic catheter (SPC) is in place and the patient cannot void voluntarily (pelvic fracture, inability to void against obstruction):

• Fill the bladder to capacity (250–350 mL) via the SPC.
• Keep the SPC clamp closed.
• Simultaneously inject contrast retrogradely via a meatal catheter.
• Two columns of contrast (antegrade from bladder; retrograde from meatus) fill toward the obliteration site from both ends.
• Fluoroscopic images are acquired at the moment of maximal simultaneous filling.
• The gap between the two contrast columns is measured and recorded as the estimated defect length.

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11. VCUG — Interpretation

Normal Prostatic Urethra

• The prostatic urethra widens proximally from the apex of the prostate toward the bladder neck.
• The verumontanum appears as a smooth posterior filling defect (posterior midline oval) at the mid-prostatic level — a critical normal landmark.
• The membranous urethra appears as a slight narrowing just below the apex; this resolves once full voiding flow is established.

Bladder Neck Funneling

• Normally, the bladder neck opens into a smooth funnel during voiding, transitioning from the wide bladder trigone into the caliber of the prostatic urethra.
• Absence of bladder neck funneling, or a shelf-like deformity at the bladder neck, suggests bladder neck contracture after benign outlet surgery or radiation.
• The posterior commissure of the bladder neck is a critical surgical landmark for PFUI repair — failure of the bladder neck to funnel normally, or deviation of the bladder off-midline, suggests a complex posterior injury involving the bladder neck.

BNC / VUAS — Champagne Glass Absence

• In native bladder neck contracture, the normal funnel is replaced by a narrowed, sometimes eccentric opening at the bladder neck.
• After radical prostatectomy, the analogous narrowing is vesicourethral anastomotic stenosis at the bladder-to-urethra anastomosis.
• Severe BNC or VUAS appears as complete absence of the funnel, with a pinhole or eccentric opening visible only at peak voiding pressure.
• Distinguish from posterior urethral stricture: VUAS affects the anastomotic site specifically, while membranous urethral stricture is typically distal to this.

Trabeculation and Diverticula

• Bladder wall trabeculation (thickened irregular wall with ridges) on filling phase indicates chronic bladder outlet obstruction or neurogenic dysfunction.
• Bladder diverticula appear as saccular outpouchings that fill and may fail to empty on post-void images.

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12. VUR Grading (International Reflux Study Committee — IRSC)

Vesicoureteral reflux graded on VCUG during filling or voiding phase:

Grade	Description	Surgical Implications
I	Reflux into ureter only; ureter not dilated	Conservative management; no upper tract risk
II	Reflux to renal pelvis and calyces; no dilatation	Conservative; antibiotic prophylaxis
III	Mild-to-moderate dilatation of ureter and pelvis; mild or absent calyceal blunting	Close surveillance; consider injection or repair
IV	Moderate ureteral and pelvicalyceal dilatation; complete obliteration of sharp calyceal angles; moderate tortuosity of ureter	Surgical correction usually required
V	Gross dilatation and tortuosity of ureter; gross dilatation of renal pelvis and calyces; intrarenal reflux	Urgent surgical correction; nephrology co-management; risk of renal scarring

:::warning VUR and Urethral Reconstruction Grades IV–V VUR discovered on pre-operative VCUG in a patient undergoing urethral reconstruction warrant nephrology co-management, pre-operative renal function baseline (creatinine, GFR), and post-operative upper tract imaging. High-grade reflux combined with post-void residual after reconstruction accelerates renal deterioration. Discuss timing of VUR correction relative to urethral repair. :::

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13. Combined RUG + VCUG for PFUI

When to Use

Combined simultaneous RUG+VCUG is the imaging gold standard for pelvic fracture urethral injury (PFUI). It is indicated:

• At initial presentation when urethral disruption is suspected (blood at meatus, inability to void, perineal hematoma, high-riding prostate).
• At 3–6 months post-injury for pre-reconstruction planning (after pelvic fracture stabilization and resolution of pelvic hematoma).
• When prior imaging is incomplete or inconclusive.

Simultaneous Technique

1. Ensure the patient has a suprapubic catheter (SPC) in place — this is standard care for PFUI.
2. Position the patient in RPO 45° oblique.
3. Fill the bladder via the SPC with 200–300 mL of diluted contrast.
4. Keep the SPC open (filling clamp open) during the study to maintain bladder pressure.
5. Simultaneously, insert a 16 Fr Foley catheter 2 cm into the urethral meatus, inflate balloon 1.5 mL, and connect to a filled 60 mL syringe of diluted contrast.
6. Under fluoroscopy, inject retrograde contrast from the meatus while maintaining antegrade pressure from the SPC.
7. Two contrast columns fill simultaneously from both ends toward the obliteration zone.
8. Acquire fluoroscopic spot images when both columns are maximally filled and the gap is clearly defined.
9. Measure the gap length between the most distal point of the antegrade column and the most proximal point of the retrograde column.

Gap Length Measurement and Surgical Approach Thresholds

Gap Length	Expected Anatomy	Surgical Approach
<1 cm	Short obliteration; bulbomembranous	Perineal approach alone; end-to-end anastomosis
1–3 cm	Moderate gap; may involve membranous/proximal bulbar	Perineal ± adjunctive maneuvers (inferior pubectomy, corporal body separation, crural splitting, transpubic)
>3 cm	Long gap; complex posterior injury; may involve prostatic urethra	Complex reconstruction; transpubic approach; staged procedures; consider abdominal-perineal combined approach

:::warning Gap Length Overestimation The fluoroscopic gap between contrast columns overestimates the true surgical defect because the proximal urethral stump may not fill completely under low antegrade pressure, and the distal retrograde column may not penetrate dense periurethral fibrosis. Perform MRI pelvis (T2-weighted sagittal) as a complementary study — MRI provides the relationship of the urethral remnants to the pubis, the degree of upward displacement of the bladder, and the spatial relationship to the pelvic floor. :::

Bladder Neck Assessment — Critical for PFUI Planning

VCUG during the combined study must specifically assess the bladder neck:

• A normal, smooth bladder neck funnel indicates the injury is distal to the bladder neck — the surgeon will perform anastomosis distal to the verumontanum.
• A distorted, deviated, or non-funneling bladder neck indicates possible bladder neck involvement, which dramatically complicates reconstruction and increases risk of post-operative incontinence.
• Bladder neck incompetence after PFUI repair is one of the most devastating complications — preoperative identification of bladder neck injury allows for patient counseling and surgical planning.
• Deviation of the bladder from midline (visible on AP image) may indicate hematoma or fibrosis tethering the bladder — relevant for surgical access planning.

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14. Post-Urethroplasty Surveillance

Standard 3-Month RUG

The standard post-urethroplasty surveillance RUG is performed at 3 months after surgery. Rationale:

• Urethral anastomoses mature over 6–12 weeks; the 3-month study captures the initial healed state.
• Early detection of recurrence (symptomatic or asymptomatic) allows for timely intervention.
• A normal 3-month RUG does not guarantee long-term patency — re-stricturing can occur years after surgery, particularly after substitution urethroplasty.

What to Look for on Post-Urethroplasty RUG

Finding	Significance
Normal caliber at anastomosis site	Successful repair; continue uroflowmetry surveillance
Smooth narrowing at anastomosis <15 Fr	Early recurrence or anastomotic scar; consider dilation or re-RUG at 6 months
Irregular narrowing at anastomosis	Recurrent stricture; consider cystoscopy and early intervention
Extravasation at anastomosis	Anastomotic leak; if early (<3 weeks post-op), may require catheter replacement
Fistulous tract	Post-operative fistula; assess size, location, and drainage
Panurethral irregularity	LS progression; evaluate for disease activity at other sites

Combining RUG with Uroflowmetry and Post-Void Residual

RUG in isolation is insufficient for complete post-urethroplasty surveillance. The standard surveillance protocol combines:

1. Uroflowmetry: Qmax ≥15 mL/s and voided volume ≥150 mL considered normal; Qmax <10 mL/s suggests recurrent obstruction.
2. Post-void residual (PVR): Measured by bladder scan; PVR <50 mL normal; PVR >100 mL indicates incomplete emptying.
3. RUG: Anatomical confirmation of patency; required when uroflowmetry is abnormal or symptoms recur.
4. Symptom score: IPSS or PROM-BUS (Patient-Reported Outcome Measure for BUrethral Stricture) at each visit.

:::tip Symptom-Flow-Anatomy Triad Post-urethroplasty surveillance is most effective when symptoms, uroflowmetry, and anatomy are assessed together. A patient with normal flow and low PVR does not routinely need a RUG beyond the initial 3-month study unless symptoms develop. A rising IPSS with declining Qmax warrants RUG even in the absence of a prior normal study. :::

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15. Clinical Pearls

1. RUG underestimates length — plan accordingly. The ~1 cm underestimation at each shoulder means a stricture measuring 1.5 cm on RUG may require 2.5–3 cm of graft or excision. Always add a buffer to graft length estimates derived from RUG alone. For complex or recurrent strictures, order SUG.

2. Use pulsed fluoroscopy at 7.5 fps. Switching from continuous to pulsed mode reduces radiation dose by 50–70% with no loss of diagnostic quality for urethral imaging. This should be the institutional default for all fluoroscopic urethrography.

3. The combined RUG+VCUG is the gold standard for PFUI. Never plan posterior urethral reconstruction based on RUG alone. Simultaneous antegrade (via SPC) and retrograde filling gives the true gap length and — critically — shows bladder neck integrity, which determines incontinence risk after repair.

4. Diluted contrast (50:50) is not optional. Full-strength iohexol 240 creates excessive radiodensity that obscures mucosal wall detail and makes accurate stricture margin identification difficult. The 50:50 dilution is the standard protocol; do not skip it because it "looks less impressive."

5. The membranous narrowing on RUG is almost always normal. External sphincter spasm in response to retrograde injection creates an apparent narrowing at the membranous urethra in virtually every male patient. This is a normal physiological response. Only call it a stricture if it persists as a fixed narrowing on VCUG voiding phase with a caliber <16 Fr.

6. Ensure RPO 45° positioning before injecting. Inadequate obliquity is the single most common technical error. The penile and bulbar segments must not overlap. Check positioning fluoroscopically before injection and repeat if positioning is suboptimal.

7. For female urethral stricture, use VCUG — not RUG. The wine-glass sign on voiding VCUG is the diagnostic criterion. Standard RUG in women produces unreliable results due to the short, mobile urethra. MRI is the next step for diverticulum or complex pelvic floor pathology.

8. Post-urethroplasty surveillance is not time-limited. Recurrent stricture can occur years after technically successful urethroplasty, particularly after substitution grafting in lichen sclerosus. Counsel patients on lifelong annual surveillance with uroflowmetry and PVR, and RUG for any new or worsening symptoms.

9. VUR discovered on pre-operative VCUG changes the operative plan. Grade IV–V VUR in a patient with a long-standing obstructing stricture mandates upper tract evaluation, renal function assessment, and nephrology co-management. Do not defer this evaluation to the post-operative period.

10. Extravasation during RUG requires technique adjustment, not abortion of the study. Small amounts of contrast extravasation from the periurethral glands or a minor fossa tear do not represent bladder perforation and are not dangerous with water-soluble contrast. Withdraw the catheter slightly, reduce injection pressure, and continue the study. Document the extravasation but complete the urethral evaluation.

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16. References

1. Wessells H, Angermeier KW, Elliott S, et al. Male Urethral Stricture: American Urological Association Guideline. J Urol. 2017;197(1):182–190. https://doi.org/10.1016/j.juro.2016.07.087

2. Lumen N, Barratt R, Cornford P, et al. EAU Guidelines on Urethral Strictures. European Association of Urology. 2021. PMID: 33610545

3. Gallentine ML, Morey AF. Imaging of the male urethra for stricture disease. Urol Clin North Am. 2002;29(2):361–372. https://doi.org/10.1016/S0094-0143(02)00046-6

4. Chapple C, Andrich D, Atala A, et al. SIU/ICUD Consultation on Urethral Strictures: The management of anterior urethral stricture disease using substitution urethroplasty. Urology. 2014;83(3 Suppl):S31–S47. https://doi.org/10.1016/j.urology.2013.09.012

5. Koraitim MM. Pelvic fracture urethral injuries: the unresolved controversy. J Urol. 1999;161(5):1433–1441. https://doi.org/10.1016/S0022-5347(05)68926-4

6. McAninch JW, Laing FC, Jeffrey RB Jr. Sonourethrography in the evaluation of urethral strictures: a preliminary report. J Urol. 1988;139(2):294–297. https://doi.org/10.1016/s0022-5347(17)42400-x

7. Trojan L, Lenz P, Thomas T, et al. Sonographic diagnosis of urethral strictures using a standardized ultrasound protocol. Urology. 2001;58(6):1007–1010. https://doi.org/10.1016/S0090-4295(01)01418-1

8. Majumdar A, Bhattacharya S, Mukherjee P, et al. Radiation dose in retrograde urethrogram: assessment and optimization strategies. Radiat Prot Dosimetry. 2018;178(3):292–297. https://doi.org/10.1093/rpd/ncx163

9. Pavlica P, Barozzi L, Menchi I. Imaging of male urethra. Eur Radiol. 2003;13(7):1583–1596. https://doi.org/10.1007/s00330-002-1787-5

10. Alwaal A, Blaschko SD, McAninch JW, Breyer BN. Epidemiology of urethral strictures. Transl Androl Urol. 2014;3(2):209–213. https://doi.org/10.3978/j.issn.2223-4683.2014.04.07

11. Chapple CR, Png D. Contemporary management of urethral trauma and the post-traumatic stricture. Curr Opin Urol. 1999;9(3):253–260. PMID: 10452091

12. Nikolavsky D, Blakely S, Hadley D, et al. Open reconstruction of female urethral stricture disease. Urol Clin North Am. 2019;46(1):65–74. https://doi.org/10.1016/j.ucna.2018.08.009