The etiology of megalourethra is still not clearly understood [4, 5]. It is believed that a dysgenesis of the mesoderm occurs during the 7th week of embryonic development, which leads to the absence of the corpus spongiosum in the anterior region of the penis and, in some cases, partial or total absence of the corpora cavernosa. The penile glands and the navicular fossa are not affected [4, 11]. Due to the lack of these structures, a balloon-shaped dilated anterior urethra is formed, leaving the body of the penis dilated and deviated in its ventral portion [11].

Two types of congenital megalourethra have been described in the medical literature: scaphoid, which is the most common and consists of deficiency or exclusive absence of the corpus spongiosum, and fusiform, which is less prevalent and associated with a combined malformation of the corpora cavernosa and corpus spongiosum [3, 12]. The severity of the disease varies according to the association with other urinary tract malformations or deformities, and the fusiform megalourethra is considered the most severe form, as it is more frequently associated with other congenital malformations [5, 13].

Cases of congenital megalourethra linked to renal dysplasia and hypoplasia, posterior urethral valve, ureteral duplicity, vesicoureteral reflux, hydronephrosis, hypospadias, Prune-Belly syndrome, VACTERL syndrome, cryptorchidism, and anorectal malformations have been described [6, 14, 15]. The associated malformations are present in 80% of scaphoid cases and 100% of fusiform cases [6].

The diagnosis of congenital megalourethra can be made either prenatally or postnatally [6]. Benacerraf first identified the malformation in the prenatal period, through morphological obstetric USG [6]. The earliest prenatal diagnosis ever recorded was made at 13 weeks of gestational age in a fetus with multiple malformations, but most cases are detected only in the second trimester [16]. Additionally, fusiform megalourethra is more easily diagnosed in the prenatal period, by obstetric USG, than scaphoid [6].

In the postnatal period, the diagnosis can be made by clinical examination and retrograde urethrocystography, which helps differentiate the scaphoid and fusiform types. Urinary tract USG complements the diagnosis and aids detection of potential concomitant renal malformations [4, 6, 9].

The patient presented in this case report had already shown signs suggestive of megalourethra at obstetric USG before birth, demonstrating the relevance of this test for early diagnosis. Additionally, postnatal USG made it possible to identify renal alterations such as hydronephrosis. The patient does not realized retrograde urethrocystography, which would help to see a possible anterior urethral valve associated in some cases.

The definitive treatment to correct congenital megalourethra is surgical, namely, urethroplasty in cases of scaphoid megalourethra [9, 17]. In cases of fusiform megalourethra, besides urethroplasty, the placement of a penile prosthesis in adulthood can be considered [4]. The technique for surgical correction of scaphoid megalourethra was published by Nesbit and Baum more than 50 years ago, and this procedure continues to be used today, with modifications [6, 9].

The etiology of congenital urethrocutaneous fistula is not completely elucidated too. Champbell states that the fistula represents an embryonic urethral defect caused by a distal congenital obstruction. The diagnosis can be clinical, based on urine output through the orifice of the ventral region of the penis, or retrograde urethrocystography [10]. Treatment of both megalourethra and urethrocutaneous fistula is exclusively surgical, by urethroplasty, which follow the same basis as the hypospadias technique [1, 7, 10, 18].

In the case presented here, the patient did not undergo retrograde urethrocystography. However, it was possible to confirm the diagnosis of scaphoid megalourethra intraoperatively, since the corpus spongiosum was absent while the corpora cavernosa were present. Regarding the diagnosis of urethrocutaneous fistula, it was confirmed by physical examination. It is worth mentioning that the penile reconstruction was technically difficult, due to the large dilatation of the urethra and the reduced size of the glans, which can be observed in the figures presented above.