Urethral strictures - Etiology

Etiology of male urethral strictures
The male urethra is a tubular structure about 18 cm in length, and it may present an occlusion or reduction of his caliber that is called urethral stricture. Male urethral stricture may be due to congenital abnormality or acquired diseases.
Hypospadias is a condition manifested by three separate anatomical problems: abnormal location of the urethral meatus, penile curvature and abnormal foreskin development or dorsal-hooded foreskin. It is the most common congenital anomaly of the penis, occurring in 1 out of 300 live births, with a multifactorial etiology: genetic susceptibility plus endocrine disruptors. Recent studies have shown that the incidence of hypospadias has been increasing in Western countries, and even higher figures are expected for developing countries and in the third world. There are four type of hypospadias: glandular, balanic, penile and scrotal. Hypospadias may be associated with external urinary meatus strictures or penile/bulbar urethral strictures.
The urethral valve is an anomaly of the urethral mucosa, than can cause partial or complete obstruction of the urethra. The urethral valves are located in the posterior urethra and are often associated with complex malformations of the kidney, ureter and bladder. The urethral valve is rarely located in the penile or bulbar urethra. They can be located using ultrasonography during  pregnancy.
Diverticulum or urethral duplication
Congenital urethral diverticulum or duplication are normally located in the bulbar urethra. Dilation of the bulbar cause postvoiding dribbling during micturition.
Etiology of non-congenital male urethral strictures
Any type of traumatic urethral lesion or disruption can cause a urethral stricture.

Pelvic trauma associated with posterior urethral disruption

Blunt perineal trauma associated with bulbar urethral lesion

Penile trauma during sexual intercourse associated with penile urethral lesion
The most frequent cause of urethral stricture is the blennorrhagia
Disease of the penile skin
The most frequent cause of urethral stricture is Lichen sclerosus
Surgery for hypospadias repair
Many patients who had undergone hypospadias repair during childhood developed a urethral stricture as an adult. These patients are classified as “Failed hypospadias repair”.
Urethral instrumentation
Endoscopic procedures: any type of endoscopic urethral instrumentation (TURP,TUIP,HOLEP) may cause a urethral stricture.

Urethral catheter: any type of urethral catheter may cause urethral strictures. The incidence of a urethral stricture following catheter is high in patients who underwent cardiovascular surgery or who were cared for in the resuscitation recovery room.
Any type of primary urethral tumor may cause urethral strictures. Primary penile cancer may cause urethral involvement and stricture.
It is sometimes not possible to establish the stricture etiology in some patients. These “strictures of unknown etiology” have been related to unrecognized minor trauma occurring in childhood.