CHAPTER 16 Urethral Strictures
What portions of the urethra make up the anterior versus the posterior urethra?
The designation of the anterior and posterior urethra refers to a developmental division between the distal and proximal urethra. The anterior urethra is composed of the meatus, fossa navicularis, the pendulous (penile urethra), and the bulbar urethra. The pendulous urethra is bounded distally by the meatus and proximally by the penile scrotal junction. The bulbar urethra begins at the junction of the pendulous urethra and is proximally defined by the urogenital diaphragm. The posterior urethra is composed of the short membranous urethra, starting at the urogenital diaphragm and ending at the prostate, and the prostatic urethra, which travels through the prostate to the bladder neck.
What is the arterial blood supply to the anterior urethra?
There are 2 arteries that supply blood to the anterior urethra. The bulbar artery arises from the internal pudendal artery and enters the urethra at the proximal bulb. The second artery is the dorsal penile artery, which also arises from the internal pudendal artery. This artery courses along the dorsal aspect of the corporal bodies giving off penetrating arteries to the urethra along its course.
How is the distal urethra perfused when the urethra is transected during trauma or an anastomotic urethroplasty?
If the bulbar artery is transected, the blood supply to the distal urethra is maintained by penetrating arteries from the dorsal penile artery as well as retrograde flow via the connection or arborization between the distal bulbar artery and the dorsal penile artery located in the glans of the penis.
What is the blood supply for a pedicled penile skin flap?
The dorsolateral and ventrolateral artery arise from the external pudendal artery, which in turn arises from the femoral artery.
What is the blood supply to the scrotal skin?
Superiorly, it is also supplied by branches of the external pudendal artery arising from the femoral artery. Inferiorly, a posterior scrotal artery arises from the perineal artery, which in turn arises from the internal pudendal artery, and ultimately the hypogastric artery.
Increased urinary pressure behind a tight urethral stricture can have what effect on the urethra?
Spongiofibrosis, which is the scarring process in the corpus spongiosum underlying the visually evident stricture, may develop for a considerable distance both proximally and distally due to cracking of the epithelium and underlying scar tissue as high-pressure urine is forced by the strictured area.
Where is a dorsal onlay graft or flap placed versus a ventral onlay graft or flap?
Dorsal refers to the dorsum of the urethra, similar to the dorsum of the penis. So a dorsal onlay graft or flap would rest against the ventral aspect of the corpora cavernosa; these corporal bodies serving as its roof and vascular bed of the graft. A ventral onlay graft or flap lies on the ventral aspect of the urethra. If a free graft is used, the corpora spongiosum is often closed below it to provide a vascular bed to nourish the graft.
What process occurs after a graft placement which allows for survival of the graft?
There is a 2-step process, lasting approximately 96 hours, called imbibition and inosculation. In the first step, imbibition, which lasts about 48 hours, the graft absorbs its nutrients passively from the graft bed or “imbibes” these nutrients. The second step is called inosculation and is the process of connection of vessels from the graft bed to the graft and ingrowth of capillaries.
True/False: Congenital urethral strictures are common etiologies of stricture disease.
False. Congenital urethral strictures are rare and are probably overestimated. Histopathologically they differ from acquired strictures in that their walls consist of smooth muscle rather than scar tissue. They form as a result of inadequate fusion of the anterior and posterior urethra.
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