(1)
Pediatric Surgery, Al Azher University, Cairo, Egypt
Abstract
Megalourethra is a rare but surgically correctible malformation of the urogenital mesenchymal of the male anterior urethra and erectile tissue of penis, characterized by severe dilatation of the penile urethra due to congenital absence of the corpus spongiosum and corpus cavernosum. It presents as two types, a milder scaphoid type and severe fusiform type. The prognosis is related to the degree of associated renal impairment and the severity of other accompanying congenital anomalies.
Keywords
Scaphoid megalourethraFusiform megalourethraCorpus spongiosumCorpus cavernosumDefinition
It is a rare but surgically correctible malformation of the urogenital mesenchymal of the male anterior urethra and erectile tissue of penis, characterized by severe dilatation of the penile urethra due to congenital absence of the corpus spongiosum and corpus cavernosum. It presents as two types, a milder scaphoid type and severe fusiform type. The prognosis is related to the degree of associated renal impairment and the severity of other accompanying congenital anomalies.
26.2 Historical Background
The first case of congenital megalourethra was reported for the first time by Obrinsky in1949 [2], who also described its association with prune-belly syndrome, but Benacerraf et al., in 1989 [3] were the first to report this condition prenatally, and so far only a handful of cases have been reported. Techniques of surgical repair of the scaphoid megalourethra were first published by Nesbit and Baum more than 50 years ago [4].
26.3 Etiology
The exact embryological cause of congenital megalourethra is not clearly understood. The most commonly held theories propose a defect in the migration, differentiation, or development of the mesenchymal tissues of the phallus. Another hypothesis is that delayed or deficient canalisation of the glandular urethra may be associated with maldevelopment of the corpus spongiosum and corpora cavernosa, secondary to the distal urethral obstruction. Mild delays with earlier and more complete canalisation may be associated with scaphoid while longer delays with later and less complete canalisation and fusiform megalourethra. Owing to the poor development of supporting erectile tissue there is stasis of urine causing functional obstruction.
More severe form as corpus spongiosum and corpora cavernosa both are involved resulting in fusiform (spindle) dilatation of the phallus during voiding.
26.4 Classification
Dorairajan classified congenital megalourethra into two types based on findings of urethrography. The more common scaphoid type with a deficiency of the corpus spongiosum presents as bulging of ventral urethra. (Fig. 26.1), and the less common fusiform type, with deficiency of both corpus spongiosum and cavernosum which is seen as circumferential expansion of urethra (Fig. 26.2) [5].
Fig. 26.1
Scaphoid Megalourethra
Fig. 26.2
Fusiform Megalourethra
Recently, Amsalem et al. [6] classified the condition into: −
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- (a)
Primary or (ex-vacuo), caused by absence or hypoplasia of the corpora spongiosa and cavernosa, associated with normal amniotic fluid volume, with usually preserved renal function and better outcome.
- (b)
Obstructive (secondary), which results in oligohydramnios with a higher incidence of renal failure, pulmonary hypoplasia and thus a high mortality (Figs. 26.3 and
