Correct Answer: C. Retrograde cystourethrogram with penile urethral stricture
The image shows a retrograde cystourethrogram (RCU), identified by contrast injection into the urethra in a retrograde direction (from distal to proximal), which is the gold standard for detecting urethral strictures. The stricture is located in the penile (anterior) urethra, characterized by a narrowed segment with a "string-like" appearance on imaging. This is the most common site for traumatic urethral strictures in India, typically following straddle injuries, instrumentation, or iatrogenic trauma during catheterization. RCU is the investigation of choice for anterior urethral pathology because it allows direct visualization of the stricture site, length, and degree of narrowing without bladder filling artifacts. The penile urethra extends from the external urethral meatus to the bulbar urethra, and strictures here present with dysuria, weak stream, and post-void dribbling. RCU combined with voiding cystourethrography (VCUG) provides complete assessment of the entire urethra and bladder.
Why the other options are wrong
A. Micturating cystourethrography with prostatic urethra stricture — Micturating cystourethrography (VCUG) is used to assess the urethra during voiding and is better for posterior urethral pathology and bladder dynamics. Prostatic urethral strictures are rare and typically result from TURP complications or prostatitis, not the common traumatic mechanism shown here. The image clearly shows retrograde contrast injection, not voiding-phase imaging. B. Retrograde cystourethrogram with membranous urethra stricture — While RCU is correct, the membranous urethra is part of the posterior urethra (between prostatic and bulbar segments) and strictures here are uncommon and usually follow pelvic trauma or pelvic fracture-associated urethral injuries. The image shows an anterior urethral stricture, not a posterior one. Membranous strictures present differently clinically and require different management. D. Micturating cystourethrography with bulbar stricture — VCUG is inappropriate for anterior urethral assessment; RCU is the standard. While bulbar strictures are common in India (second most common site after penile), the image demonstrates a penile urethral stricture based on the anatomical location of the narrowing. Bulbar strictures typically follow perineal trauma or instrumentation and have a different radiological appearance.
High-Yield Facts
- Retrograde cystourethrogram (RCU) is the gold standard investigation for anterior urethral strictures; contrast is injected retrograde into the urethra.
- Penile urethra strictures are the most common site for traumatic strictures in India, typically from straddle injuries or catheterization trauma.
- RCU + VCUG combination provides complete urethral assessment: RCU for anterior urethra anatomy, VCUG for posterior urethra and voiding dynamics.
- String-like narrowing on RCU is pathognomonic for urethral stricture; length and degree of narrowing determine management (dilation vs. urethroplasty).
- Micturating cystourethrography (VCUG) is used for posterior urethral pathology, bladder outlet obstruction assessment, and vesicoureteral reflux evaluation.
Mnemonics
RCU vs VCUG: Anterior vs Posterior RCU = Retrograde = Anterior urethra (penile, bulbar). VCUG = Voiding = Posterior urethra (membranous, prostatic). Use RCU for strictures you suspect are in front; use VCUG when you need to see the bladder and posterior urethra during micturition. Common Stricture Sites in India (Frequency) PB = Penile (most common) → Bulbar (second most common). Penile strictures follow straddle/instrumentation; bulbar strictures follow perineal trauma or instrumentation. Remember: anterior urethra = RCU; posterior = VCUG.
NBE Trap
NBE pairs "micturating cystourethrography" with stricture location to trap students who confuse the investigation modality with the anatomical site. The key discriminator is recognizing that RCU (retrograde injection) is for anterior urethra, while VCUG (voiding phase) is for posterior urethra and bladder dynamics.
Clinical Pearl
In Indian practice, straddle injuries (fall on bicycle bar, motorcycle accident) are the leading cause of penile urethral strictures in young males. RCU is performed as an outpatient procedure and guides decision-making: short strictures (<1 cm) may respond to dilation, while longer strictures require urethroplasty—a common reconstructive procedure in Indian urology centers.
_Reference: Bailey & Love Ch. 62 (Urethra); Harrison Ch. 279 (Urinary Tract Obstruction)_