Isolated megalourethra: A rare case report and review of literature.

Megalourethra is a rare congenital disorder of anterior urethra and erectile tissue of penis. It mainly appears in two types-a milder scaphoid type and severe fusiform type. Fusiform type is commonly associated with congenital anomalies of various systems of the body. Isolated megalourethra without other congenital anomalies is extremely rare. We report one such case which was detected postnatally and successfully treated by reduction urethroplasty.

INTRODUCTION

Megalourethra is a rare congenital mesenchymal anomaly of the male anterior urethra characterized by a nonobstructive dilatation of the penile urethra.[12] Nesbitt in 1955 defined it as “a congenital dilatation of penile urethra without distal obstruction”. He performed first reduction urethroplasty for this condition.[3] Less than 100 cases have been reported in literature till now.[245] Dorairajan classified congenital megalourethra into two types based on findings of urethrography.[6] The more common scaphoid type with a deficiency of the corpus spongiosum is seen as bulging of ventral urethra. The fusifrom type with deficiency of both corpus spongiosum and cavernosum is seen as circumferential expansion of urethra.

CASE REPORT

A 6-month-old male child presented with dribbling of urine with a noticeable swelling of undersurface of penis which increased during the act of micturition. On examination a scaphoid swelling of size 4 × 3 cm was seen on the ventral aspect of shaft of penis which ballooned out during micturition. The child voided from normally placed meatus [Figure 1a]. Both testes were palpable in scrotum.

Figure 1a

Clinical photograph of scaphoid megalourethra

On investigation, renal function tests were normal. Ultrasound of abdomen and pelvis showed normal kidneys and bladder with no post void residue. Retrograde urethrogram showed scaphoid dilatation of ventral aspect of distal and mid penile urethra confirming the diagnosis of congenital megalourethra [Figure 1b]. Cystourethroscopy showed wide saccular dilatation of penile urethra about 1 cm from external urethral meatus. Proximal urethra and bladder were normal.

Figure 1b

Retrograde urethrogram showing ventral saccular dilatation of urethra

A reduction urethroplasty was done through circumcoronal penile incision. After degloving the penis scaphoid dilatation of ventral aspect of penile urethra was noted [Figure 2]. The dilated urethra was incised in ventral midline and the redundant urethra with deficient corpus spongiosum was excised and the urethra was reconstructed over 6 Fr infant feeding tube using 5-0 PDS suture. Postoperative recovery was uneventful. On removal of the catheter after 2 weeks child voided normally without any penile swelling. Regular follow-up at 1 year showed no recurrence of penile swelling with normal voiding pattern and sonologically normal bladder and upper tracts.

Figure 2

Intraoperative photograph of megalourethra after degloving of penis

DISCUSSION

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.[2] Another assumption is that delayed or deficient canalization of the glandular urethra may be associated with maldevelopment of the corpus spongiosum and corpora cavernosae.[7] Due to the poor development of erectile tissue which normally provides support there will be stasis of urine causing functional obstruction.[78]

Two types of megalourethra are described depending upon the extent of associated embryonic maldevelopment of erectile tissue. Age of detection of megalourethra was between 16 weeks gestation and 24-years-old.[19]

Megalourethra is associated with other congenital anomalies of which genitourinary are most common. Jones et al., in a review identified associated anomalies in 66 of 78 reported cases of megalourethra.[2] In this review, associated congenital anomalies are seen in 80% of scaphoid type and 100% of fusiform type.

The commonly described genitourinary anomalies include renal dysplasia-hypoplasia, hydronephrosis, hydroureter, vesicoureteric reflux, prune-belly syndrome, urethral duplication, megacystis, hypospadias, posterior urethral valves, and undescended testes. Other system anomalies including VATER (vertebral, anal atresia, trachea-esophageal fistula, and renal anomalies) and VACTERYL (vertebral, anal atresia, cardiac, trachea-esophageal fistula, renal, and limb deformities) are described.[10]

In view of associated anomalies, the workup of megalourethra should include renal function tests and imaging of upper and lower urinary tracts. The status of upper urinary tract will determine the ultimate outcome.[1]

Urethral anomalies mimicking megalourethra like urethral atresia, a web, duplication, and a diverticulum are considered in the differential diagnosis.[10]

Prenatally diagnosed megalourethra has to be thoroughly evaluated for associated congenital anomalies and followed up serially by ultrasound for amniotic fluid index, urinary bladder volume, and upper tract dilatation. Termination of pregnancy may be advised in cases with other severe congenital anomalies and renal impairment. In some milder forms of megalourethra spontaneous resolution has been observed in fetuses at 19-34 weeks gestation.[10]

The treatment of megalourethra may be one stage or two stage urethroplasty depending on the age of presentation and general condition of the patient. For scaphoid type, Nesbitt described a longitudinal reduction urethroplasty.[3] Heaton and colleagues described a technique of urethral plication for some cases of scaphoid megalourethra.[11] The management of fusiform type is complicated ranging from sex reassignment to major phallic reconstruction.[2] Long-term follow-up is required in these patients to see for the erectile function and fertility potential.[1012] Patients of fusiform type may require placement of penile prosthesis in the adult period.[13]

CONCLUSION

Congenital megalourethra though rare can be detected antenatally by ultrasound. Management has to be individualized depending on type and the presence of associated congenital anomalies. In isolated scaphoid type of megalourethra reduction urethroplasty gives excellent results as seen in our case.