(1)
Pediatric Surgery, AlSadik Hospital, Qatif, Saudi Arabia
21.1 Introduction
The term hypospadias is derived from the Greek words hypo (below, too little) and Spadone (crack, gutter).
Hypospadias is defined as the combination of three anatomical abnormalities of the penis (Figs. 21.1, 21.2, 21.3, and 21.4):
Figs. 21.1 and 21.2
Clinical photographs showing two patients with hypospadias. The ectopic urethra is located on the ventral side of the shaft penis. Note the ectopic urethral meatus and also the dorsal winged prepuce
Figs. 21.3 and 21.4
Clinical photographs showing two patients with hypospadias. Note the lack of prepuce ventrally. Note also the ventral curvature of the penis
Ectopic proximally placed meatus which may be located on the ventral side of the penis at any position between the tip of the glans and the perineum.
A dorsal winged prepuce and lack of ventral prepuce.
A ventral penile shaft deviation.
The second and third characteristics may not necessarily be present.
The megalomeatus is an exception as it is characterized by a complete prepuce and a coronal lying meatus adjacent to a non-closed-glans with an open navicular fossa. This is also called (MIP) Megameatus with Intact Prepuce (MIP) variant of hypospadias.
Hypospadias is caused by the arrest of normal development of the urethra, at various stages of embryonic development (9–13 weeks of pregnancy).
Hypospadias is among the most common birth defects in males.
The exact incidence of hypospadias is not known but it has been estimated that hypospadias affects approximately 1 of every 200–250 male live newborns.
The incidence of hypospadias is higher in whites than in blacks.
Hypospadias is more common in Jewish and Italian people.
Hypospadias is also more common in the Caucasian population followed by African-Americans and then the Hispanic Americans.
The incidence of hypospadias is reported to be increasing in both Europe and North America from an incidence of 20.2 per 10,000 in 1970 to a current incidence of 39.7 per 10,000 children born in the U.S.A.
The reason for this increase is not exactly known
There is a definite familial occurrence of hypospadias. This is estimated to be about 7 %.
In approximately 80–90 % of cases, hypospadias is of the distal part while the remaining 10–20 % have proximal hypospadias.
There is an increased probability for the occurrence of hypospadias in the following situations:
Father with hypospadias
Low birth weight
Twin or triplet births
Maternal iron supplements
Smoking mothers
Fathers with pesticide contact
Chordee is fibrous remnant of the corpus spongiosum distal to the meatus. It extends in a V shape on both sides, and acts by the lack of elasticity producing a ventral deformity (Figs. 21.5 and 21.6).
Figs. 21.5 and 21.6
Clinical photographs of two patients with hypospadias. Note the shape of chordee and the ventral curvature of the penis
Chordee (downward bending of the penis) is another feature of hypospadias seen more commonly in those with proximal hypospadias. This is found in 10 % of distal hypospadias and 50 % of proximal hypospadias.
Scrotal transposition is seen usually in patients with more proximal hypospadias and it is associated with bifid scrotum (Penoscrotal transposition and bifid scrotum) (Figs. 21.7 and 21.8).
Figs. 21.7 and 21.8
Clinical photographs showing scrotal transposition in two patients with hypospadias. Note the severe hypospadias in the second photograph
Characteristically, in the majority of patients with hypospadias the foreskin is underdeveloped and does not wrap completely around the penis, leaving the underside of the glans penis uncovered by foreskin (Hooded foreskin). The only exception to this is the megameatus.
It must be emphasized that not all newborns with partial foreskin development have hypospadias, as some have a normal urinary opening with a hooded foreskin (This is called “chordee without hypospadias”).
Megameatus with intact prepuce (MIP) variant of hypospadias occurs when the foreskin is normal and there is a concealed hypospadias. The condition is discovered during newborn circumcision or later in childhood when the foreskin begins to retract (Figs. 21.9 and 21.10).
Figs. 21.9 and 21.10
Clinical pictures of one patient with megameatus. Note the complete normal looking foreskin. Note the size of the meatus after retracting the foreskin
The most common associated defect with hypospadias is an undescended testicle, which has been reported in approximately 3 % of infants with distal hypospadias and 10 % of those having proximal hypospadias (Figs. 21.11 and 21.12).
Figs. 21.11 and 21.12
Clinical photographs of two patients with hypospadias and undescended testes. In the first one, there are bilateral undescended testes while in the second one there is unilateral undescended testis
In patients with proximal hypospadias, a karyotype and endocrine evaluation should be performed to detect disorders of sexual development or hormone deficiencies.
Using modern surgical techniques, a normal appearing penis can usually be expected from hypospadias repair.
Hypospadias repair should be performed only by experienced surgeons and at centers with extensive experience.
To emphasize this, Duckett in 1995 coined the concept of hypospadiologists (surgeons who subspecialize in hypospadias repair).
Currently, hypospadias is repaired not only for functional reasons but also for cosmetic reasons.
The postoperative penis should:
Be suitable for normal voiding
Be suitable for future sexual intercourse
Have an acceptable cosmetic appearance
More than 300 different types of repairs have been described in the medical literature.
The most common operation to repair hypospadias is the tubularized incised plate or “TIP” repair. This procedure can be used for all distal hypospadias repairs.
There are several techniques to repair proximal hypospadias as a single stage or two stage operations.
There are several factors that contributed recently to increased success of hypospadias repair. These include:
Better understanding of the anatomy of the penis
Improved anesthetic techniques
Fine instrumentations and sutures
Improved dressing materials, and antibiotics
21.2 Effects of Hypospadias
Abnormal urinary stream. The more proximally ectopic the position of the urethral meatus, the more likely the urinary stream is to be deflected downward. Any element of chordee can exacerbate this abnormality.
Fertility may be affected as hypospadias may preclude effective insemination.
Painful erection
Psychological stress
21.3 Embryology
Hypospadias is a congenital defect that is thought to occur during urethral development.
This occurs between 8 and 20 weeks’ gestation.
Embyologically, the external genitalia are identical in males and females until about 8 weeks’ gestation.
In males, the external genitalia develop a masculine phenotype under the influence of testosterone.
Testesterone is converted to dihydrotestesterone under the influence of 5-alpha reductase.
Dihydrotestesterone acts locally to change the external genitalia into a masculine phenotype.
As the phallus grows, the open urethral groove extends from its base to the level of the corona.
The urethral folds coalesce in the midline from base to tip, forming a tubularized penile urethra and median scrotal raphe.
This accounts for the posterior and middle parts of the urethra.
The anterior or glanular urethra is thought to develop in a proximal direction, with an ectodermal core forming at the tip of the glans penis, which canalizes to join with the more proximal urethra at the level of the corona.
The higher incidence of subcoronal hypospadias supports the vulnerable final step in this embryological theory of development.
In 2000, Baskin proposed a modification of this theory in which the urethral folds fuse to form a seam of epithelium, which is then transformed into mesenchyme and subsequently canalizes by apoptosis or programmed cell resorption. Similarly, this seam theoretically also develops at the glanular level, and the endoderm differentiates to ectoderm with subsequent canalization by apoptosis.
The prepuce normally forms as a ridge of skin from the corona that grows circumferentially, fusing with the glans. Failure of fusion of the urethral folds in hypospadias impedes this process, and a dorsal hooded prepuce results.
On rare occasions, a glanular cleft with intact prepuce may occur. This is termed the megameatus intact prepuce (MIP) variant.
Chordee (ventral curvature of the penis) is often associated with hypospadias, especially the more proximal forms of hypospadias.
This is thought to result from a growth disparity between the normal dorsal tissue of the corporal bodies and the attenuated ventral urethra and associated tissues.
Rarely, the abortive spongiosal tissue and fascia distal to the urethral meatus forms a tethering fibrous band that contributes to the chordee.
21.4 Etiology of Hypospadias
The etiology of hypospadias is multifactorial but in the majority (65–75 %) the cause remains unknown.
There has been several etiological factors for hypospadias.
Several etiologies for hypospadias have been suggested, including genetic, endocrine, and environmental factors.
Defects in the androgen synthesis or its action during embryogenesis (A defect in testosterone biosynthesis).
Mutations in the 5-alpha reductase enzyme, which converts testosterone to the more potent dihydrotestosterone (DHT).
There is a fivefold increased risk of hypospadias in males born through IVF. This may be related to maternal exposure to progesterone, which is commonly administered in IVF protocols. Progesterone is a substrate for 5-alpha reductase and acts as a competitive inhibitor during the process of conversion of testosterone to DHT.
Hypospadias is also found in the most common disorder of sex development, the familial male pseudohermaphroditism.
Ingestion of substances with estrogenic activity, such as insecticides, natural estrogens, organic products from the manufacture of plastics and pesticides, which are included in food.
A higher incidence of hypospadias in winter conceptions has also been proposed.
Increased estradiol concentration in placental basal syncytiotrophoblasts of boys with undescended testes.
A genetic predisposition to hypospadias.
There is a genetic predisposition to hypospadias.
The inheritance is likely polygenic.
There is an eight times increased in incidence of hypospadias among monozygotic twins.
Hypospadias was also shown to be familial.
The probability to have a second child with hypospadias is 14 % if the first child has hypospadias.
If the father has hypospadias, the probability that one of his sons suffers from the same pathology is 8 %.
Hypospadias is present in many syndromes, such as Smith-Lemli-Opitz syndrome or Robinow syndrome.
Hypospadias is associated with increasing parity, increasing maternal age, and low birth weight.
21.5 Associated Anomalies
A patent processus vaginalis (9 %)
Undescended testes and inguinal hernias are the most common anomalies associated with hypospadias.
The incidence of undescended testes and inguinal hernias with hypospadias is about 9 % for each.
Undescended testis is seen in about 5 % of mild forms of hypospadias (Figs. 21.13 and 21.14).
Figs. 21.13 and 21.14
Clinical photographs showing severe hypospadias and bilateral undescended testes
The incidence of undescended testes is more than 30 % in those with more proximal hypospadias.
The incidence of inguinal hernias is about 20 % in those with more proximal hypospadias.
The combination of hypospadias and undescended testis should raise the possibility of an underlying disorder of sexual development (DSD) (Fig. 21.15).
Fig. 21.15
A clinical photograph showing a newborn with disorder of sexual development resembling hypospadias clinically
DSD were identified in approximately 30 % of patients with unilateral or bilateral undescended testes and hypospadias. The incidence approaches 50 % in those with nonpalpable testes but if the testes are palpable, the incidence is only 15 %.
The more proximal hypospadias have a higher association with DSD.
A prostatic utricle is another association with hypospadias. This is more likely so in those with more proximal hypospadias.
Sometimes hypospadias is associated with a low-grade vesicoureteral reflux (Fig. 21.16).
Fig. 21.16
A micturating cystourethrogram showing mild vesicoureteral reflux in a patient with hypospadias
Upper urinary tract anomalies are rarely associated with hypospadias and do not justify routine imaging in these patients.Related posts:
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