Indications

Suspected urethral stricture (dysuria, weak stream, recurrent UTI)
Urethral trauma (pelvic fracture, straddle injury, instrumentation injury)
Urethral fistula or diverticulum
Periurethral abscess
Pre-operative planning for urethral reconstruction
Post-urethroplasty evaluation

Normal Urethral Anatomy

Segment	Location	Normal Caliber	Key Landmark
Meatus (fossa navicularis)	External opening	Narrowest normal segment	Contrast enters here
Penile (anterior) urethra	Penile shaft	Uniform 7–10 mm	No filling defects
Bulbar urethra	Perineum; most dependent segment	Widest anterior segment; 10–15 mm	Most common site of stricture
Membranous urethra	Urogenital diaphragm	Narrowest normal internal segment	External sphincter — normal narrowing on filling
Prostatic urethra	Through prostate	Widens toward bladder neck	Verumontanum = midline filling defect (normal)
Bladder neck	Proximal end	Should open with VCUG

Posterior vs. anterior urethra: The membranous urethra is the dividing point. Anterior urethra = bulbar + penile (below external sphincter); posterior urethra = membranous + prostatic (above external sphincter). Bulbar urethra straddle injuries → anterior; pelvic fracture urethral injuries → posterior.

Key Findings

Urethral Stricture

Feature	Description
Location	Bulbar urethra most common (straddle injury, instrumentation, infection); penile urethra (gonorrhea, hypospadias repair); membranous urethra (pelvic fracture)
Morphology	Focal narrowing with smooth or irregular margins; abrupt or tapered transition; length measured in cm
Associated findings	Proximal dilation of urethra; false passages (from prior traumatic catheterization); periurethral extravasation if severe

Urethral Trauma — Goldman Classification

Grade	Description
I	Stretching or elongation without mucosal tear — urethra intact; contrast fills normally
II	Tear at prostatomembranous junction; contrast extravasates above urogenital diaphragm
III	Combined partial or complete tear of anterior and posterior urethra below and through the urogenital diaphragm

Pelvic fracture urethral injury (PFUI): Any male with a pelvic fracture and inability to void, blood at the meatus, or perineal hematoma should have a RUG before urethral catheterization. Blind catheterization of a disrupted urethra can convert a partial tear to complete disruption.

Other Findings

Finding	Description
Urethral diverticulum	Outpouching from posterior urethra or bulbar segment; fills with retrograde contrast; communication with urethra confirmed
Periurethral fistula	Contrast tracks into perineal tissues or rectum; associated with Fournier's, trauma, Crohn's
False passage	Irregular channel paralleling the urethra from traumatic catheterization; may communicate with perineal tissues
Anterior urethral valve	Rare; filling defect/valve at bulbar urethra in males; causes proximal dilation

Reporting Checklist

Study quality: adequate distension / incomplete fill / contrast extravagated before complete study
Stricture: absent / present — location (fossa navicularis / penile / bulbar / membranous), length (cm), caliber at narrowest point (mm), smooth vs. irregular
Extravasation: absent / present — location (above / below urogenital diaphragm), extent
False passages: absent / present
Diverticulum or fistula: absent / present — location
Posterior urethra (if VCUG performed in conjunction): caliber, PUV excluded
Recommendation for VCUG if posterior urethra not assessed

Common Pitfalls

Pitfall	How to Avoid
Membranous urethra narrowing misread as stricture	The membranous urethra is normally the narrowest internal segment due to the external sphincter — this is physiologic; true strictures are abrupt, irregular, or persist on multiple views
Inadequate distension of posterior urethra	RUG alone cannot evaluate prostatic urethra — VCUG or cystoscopy required for complete posterior urethral assessment
Kinking artifact at bulbar/penile junction	The urethra curves sharply at this junction — oblique positioning (45° RPO) unfurls the bulbar urethra; strictures here require oblique views to characterize
Missing proximal extension of stricture	If contrast extravasates before posterior urethral filling, length cannot be assessed — correlate with cystoscopy; report as "proximal extent indeterminate"
Verumontanum mistaken for filling defect	Verumontanum = normal midline posterior filling defect in the prostatic urethra on voiding cystourethrogram; smooth, symmetric, fixed position

Step-by-step fluoroscopy technique and systematic search patterns available in RadCall Pro.

Retrograde Urethrogram — Interpretation and Findings