A male patient with a saddle-type perineal injury has priapism and inability to void. Urethral disruption is suspected. The bulbous urethra has ruptured and extravasation of urine occurs. Which fascial layer limits the spread of extravasating urine to the scrotum, perineum, and lower anterior abdominal wall?

• A Dartos fascia
• B Colles' fascia (membranous layer of superficial perineal fascia) ✓
• C Scarpa's fascia (membranous layer of superficial fascia of abdomen)
• D Perineal membrane (inferior fascia of urogenital diaphragm)

Explanation

Colles' fascia is the membranous layer of the superficial fascia of the perineum. It is continuous with Scarpa's fascia of the anterior abdominal wall and dartos fascia of the scrotum. In rupture of the bulbous urethra (within the perineal pouch), urine extravasates into the superficial perineal pouch and spreads along Colles' fascia into the scrotum, penis, and up the anterior abdominal wall deep to Scarpa's fascia — but NOT into the thighs (because Colles' fascia attaches to the ischiopubic rami and the posterior edge of the perineal membrane, blocking posterior spread).

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.