What causes hypospadias in newborns?

In real life, hypospadias is a relatively common congenital malformation of the reproductive organs, and hypospadias in newborns is also a relatively normal phenomenon. It is one of the congenital malformations of newborns. Hypospadias will affect the health of the child. Generally, there are many reasons for hypospadias in newborns. This is caused by genetic reasons or embryonic development problems.

Causes of hypospadias in newborns

1. Genetic inheritance

There is a certain familial tendency for hypospadias, but the specific genes or chromosomes involved are still unclear. 20% to 25% of adjacent cases have genetic factors, and the chance of brothers of hypospadias patients also suffering from hypospadias is 10 times that of normal people. It has been reported that 10% of the fathers of the children and 15% of the brothers of the children have hypospadias.

2. Endocrine factors

Hormones produced from the fetal testicles influence the formation of the male external genitalia. Testosterone is produced by interstitial cells stimulated by human chorionic gonadotropin in the 8th week of pregnancy and then converted into dihydrotestosterone. The development of the external genitalia is regulated by dihydrotestosterone. Insufficient or delayed testosterone production, or abnormal conversion of testosterone to dihydrotestosterone can lead to genital malformations. Hypospadias is often associated with cryptorchidism and hermaphroditism, which is related to this. The mother's use of hormones before and during pregnancy also has a certain impact on the development of the fetal reproductive system. Environmental factors also affect the development of the urethra mainly through the endocrine systems of the mother and fetus.

3. Embryological factors

Hypospadias is caused by abnormal development of the external genitalia during the embryonic period. Hypospadias occurs when the urethral groove is not completely fused due to endocrine abnormalities or other reasons during the embryonic period. Since the formation of the distal urethra is in the final stage, hypospadias with the urethral opening located at the distal end of the penis accounts for the largest proportion.

Clinical manifestations

1. Ectopic urethra

The ectopic opening may be anywhere from the proximal end of the normal urethral opening to the perineum. Some urethral openings are mildly stenotic because their surface is incompletely covered by a very thin layer of mucosal-like tissue. Sometimes a section of the urethra is missing and its walls are thin. The urine stream generally flows backwards, so children often squat to urinate. It is more obvious when the urethral opening is located proximal to the penis.

2. Curvature of the penis

The ventral curvature of the penis is mainly caused by the hyperplasia of fibrous tissue of the urethral plate distal to the urethral opening, the lack of tissue in various layers of the ventral penis and urethral wall, and the asymmetry of the dorsal and ventral sides of the corpus cavernosum of the penis.

3. Abnormal distribution of foreskin

The foreskin on the ventral side of the glans penis fails to fuse in the midline, so it is missing in V lines, the frenulum of the foreskin is missing, and the foreskin is piled up in a cap-like shape on the dorsal side of the glans penis.

Hypospadias is divided into 4 types according to the location of the urethral opening: glans type, body type, penoscrotal type, and perineal type.

This classification is often difficult to determine preoperatively. In some cases, the curvature of the penis is very severe, and the urethral opening can still be located at the distal end of the penis. The child can even urinate while standing. However, once the fibrous cord tissue is loosened during the operation, the urethral opening will fade to the proximal end of the penis. In order to estimate the effect of surgery, the type should be classified according to the position of the urethral opening after the penile curvature is fully corrected.

The most common associated malformations of hypospadias are inguinal oblique hernia and incomplete testicular descent, each accounting for about 10%. The more severe the hypospadias, the higher the incidence of associated deformities.

Prostatic cysts are often associated with severe hypospadias. It is generally believed that the incidence of prostatic cysts in perineal and penile scrotal hypospadias can be as high as 10% to 15%. Some even report that it can reach 57%. The prostatic capsule may be the incomplete degeneration of the paramesonephric duct or the relic of incomplete masculinization of the urogenital sinus, opening behind the prostatic urethra.

The incidence of upper urinary tract malformations in children with hypospadias ranges from 1% to 3%, such as ureteropelvic junction obstruction and duplication malformations. A small number of patients also have combined anorectal malformations, cardiovascular malformations, and chest wall deformities. Severe cases of hypospadias are often accompanied by penoscrotal transposition, penile torsion, micropenis, and duplicated urethra.