Background

Congenital megalourethra is a rare form of lower urinary tract obstruction caused by dysgenesis of the corpora cavernosa and spongiosa which results in extensive dilatation of the penile urethra.¹ It can be diagnosed antenatally but can also present later in life with erectile dysfunction.^1-3 The first case of congenital megalourethra was described by Obrinsky,⁴ who also reported its association with prune belly syndrome (PBS). There are 2 variants of megalourethra: scaphoid and fusiform, which is the most severe.⁵ The survival of these patients depends on the prenatal renal damage and severity of pulmonary hypoplasia caused by oligohydramnios.³ We present the case of a newborn with a fusiform megalourethra and PBS.

Case Report

The patient was a term baby, born at 37 weeks by cesarean section, with an antenatal history of oligohydramnios, an unspecified malformation of the genitalia, and pulmonary hypoplasia. Due to the suspected severity of the pulmonary hypoplasia, termination of the pregnancy was offered, but the parents refused. At birth, physical examination revealed deficient abdominal wall muscles and an elongated penis, 5-6 cm long, without any palpable corpora (Figure 1). There was passage of urine with lower abdominal compression, bilateral nonpalpable testes, low-set ears, retrognathia, and bilateral clubfoot (Figure 1). Further investigations demonstrated a normal brain and lumbosacral spine on ultrasound and spinal MRI. Several renal function tests showed a rising creatinine despite a normal diuresis. Due to his progressive renal failure, he was transferred for further management. A renal, bladder, and perineal ultrasound and a micturating cystourethrogram were performed, demonstrating bilateral hyperechogenic kidneys with multicystic dysplasia on the right, a dilated penile urethra and empty scrotum (Figure 2, A), and left grade IV vesicoureteral reflux with a fusiform megalourethra (Figure 2, B). His renal insufficiency progressed, and the decision was made to perform a Blocksom vesicostomy to ensure bladder drainage and to insert a Tenckhoff catheter in view of the possible need for dialysis. At the time of insertion, a diagnostic laparoscopy (Figure 3, A), examination under anesthesia, and cystourethroscopy were performed to determine the location of the testes and to the assess the urinary tract (Figure 3, B). The testes were approximately 1 cm from the internal inguinal rings. The penis was long, with a small glans and absent corpora. There was dilatation of the penile and proximal urethra with a normal verumontanum, but the bladder neck was high and open. The bladder was distended and elongated with trabeculations. The patient is now 2 months old and has remained stable, but his renal function has further deteriorated despite a good diuresis and he has commenced peritoneal dialysis.

Discussion

Congenital megalourethra is an extremely rare malformation of the urethra that arises as a developmental anomaly of the corpora cavernosa around the 7th week of gestation.^1-3 The term “megalourethra” was introduced by Nesbit in 1955,⁶ who described the absence of the corpus spongiosum in the distal urethra and in some cases partial or complete absence of the corpora cavernosa.^6,7 Because of the missing structures, the distal urethra is unnaturally widened despite the lack of mechanical obstruction. It can be diagnosed antenatally on ultrasound with a distended bladder, dilated ureters, and hydronephrosis and, in some cases, oligohydramnios.^1,3,8-10 It can be suspected when there is a cystic structure in the perineum, which represents the dilated fetal penis. The condition can present later in childhood or adult life with erectile dysfunction.^2,7

According to Dorairajan⁵ and Stephens and Fortune,⁷ this condition has 2 variants. The scaphoid type is the most common one (80%) and presents with partial or complete absence of the corpus spongiosum with intact corpus cavernosum, making the penis curved dorsally. The fusiform type has complete aplasia of both the corpus spongiosum and cavernosum, and the penile urethra is covered by a thin layer of skin and connective tissue, making the penis a cystic rod-shaped structure. This type has a worse prognosis with a high prevalence of associated anomalies.

PBS (Eagle-Barrett or triad syndrome) is a rare congenital disorder characterized by deficient abdominal musculature, undescended testes, and urinary tract abnormalities.^4,10 The malformation occurs early in pregnancy with a disruption of the normal development of the corpus spongiosum on the ventral side and cavernosum on the dorsal side of the penis, leading to aplasia of erectile tissues and progressive dilatation of the penile urethra, causing retrograde bladder outlet obstruction.¹⁰ It has a broad spectrum of presentations, and the survival and prognosis depend on the severity of renal dysplasia and secondary pulmonary hypoplasia, due to oligohydramnios, with a perinatal mortality between 10% and 25%.^10-13 Beyond the neonatal period, urinary tract complications predominate, and about one-third of patients may progress to renal failure.¹³

Management of megalourethra depends on the variant and the presence and severity of the associated congenital anomalies. The goal of antenatal diagnosis is to inform parents of the condition and prognosis. Termination of pregnancy may be offered in cases with other severe congenital anomalies, renal dysplasia, pulmonary hypoplasia, and severe oligohydramnios.³

After birth, the urethral anomaly can be corrected surgically; however, in some cases a temporary urinary diversion is required to preserve renal function. The available literature regarding the surgical management is scarce and does not provide a unique technique.¹⁴ The operative technique for fusiform megalourethra with complex genital malformation is highly individualized, depending on intraoperative and endoscopic findings.¹⁵ In most cases, the treatment will be a 1- or 2-stage urethroplasty depending on the age and general condition of the patient.^3,14,15 However, a successful repair may be impossible when there is a lack of supportive corporal tissue. Previously described options range from sex reassignment to major phallic reconstruction,¹⁶ and severe cases may require a penile prosthesis in adult life.¹⁷ Long-term follow-up is mandatory to assess renal function, continence, erectile function, and fertility potential.

Conclusions

Congenital megalourethra is a rare malformation of the anterior urethra. It can be detected antenatally by ultrasound and should be suspected in all fetuses with lower urinary tract obstruction and oligohydramnios. Due to its rarity, it can be often misdiagnosed and treated incorrectly. Management has to be individualized depending on the type and severity of the associated anomalies.