While performing a voiding cystourethrogram on a 45-year-old male, the urologist was too forceful when he inserted the catheter and accidentally damaged the wall of the membranous portion of the urethra in the deep perineal compartment (urogenital diaphragm). Which of the following structures would most likely be traumatized at this location?

If the membranous portion of the urethra is injured, urine and blood can leak upward into the retropubic space (of Retzius) limited inferiorly by the urogenital diaphragm and the muscle within (compressor urethra), which would be injured. The bulbospongiosus muscle and other perineal muscles, the corpus cavernosa penis, and the openings of the bulbourethral ducts are inferior and anterior to the region of injury.