Anatomy and Patho-Physiology

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The male urethra is divided in to anterior part of meatus, penile and bulbar portions and posterior part of membranous and prostatic urethra.

The anterior urethra is surrounded by corpora spongiosa and the narrowing of the urethral lumen due to spongiofibrosis is called a stricture. The posterior urethra is devoid of corpora spongiosa and the urethral narrowing is termed as stenosis.

In the penile portion the urethra lies in the center of spongiosa and in the bulbar portion the urethra lies dorsally in the spongiosa. So dorsal urethrotomy causes less bleeding and is more popular compared to ventral urethrotomy during urethroplasty.

Normal urethra is pink as the blood filled spongy tissue surrounds the urothelium. Spongiofibrosis does not allow the blood flow and urethra is white at the site of the stricture.

Stricture due to trauma in the bulbar urethra can be treated by excision and end to end anastomosis as we have normal urethra on both sides of the trauma.

In a non traumatic bulbar stricture, we have  white strictured urethra and gray urethra between the white and pink normal urethra due to subepithelial spongiofibrosis. Anastomosis of the two gray urethras may lead to restricture formation later.

The bulbar urethra has blood supply from proximal to distal end with the bulbar arteries. It also gets blood supply in a retrograde fashion through the cavernosa in to glans and penile urethra. It also gets blood supply laterally from cavernosa through circumflex vessels.

When we mobilize the bulbar urethra from cavernosa the lateral blood supply is lost. If we transect the bulbar urethra the distal portion loses its proximal blood supply.

And the distal spongiofibrotic urethra already has compromised blood flow. So transection of bulbar urethra should be avoided whenever possible. Unless it is already transected by trauma.

Bulbar urethra can be opened dorsally or ventrally with longitudinal urethrotomy. Ventral urethrotomy does not need mobilization of the bulbar urethra, so Asopa’s technique of ventral urethrotomy and dorsal onlay graft works well.