Megalourethra as a rare cause for erectile dysfunction.

MRI findings of megalourethra have not previously been reported. We present a case of an adult presenting with lifelong erectile dysfunction secondary to poor development of the corpus spongiosum and corpora cavernosa. The pathogenesis, typical presentation, and treatment of megalourethra, as well as the use of modern imaging techniques to aid in the diagnosis and treatment of this disease are discussed.

Case report

A 28-year-old came to the urology department complaining of lifelong erectile dysfunction. Past medical history included an admission, as a neonate, for urinary retention, fever, and renal impairment. The infant's penis was noted on clinical examination to be abnormally large. An antegrade cystogram via a vesicostomy demonstrated a megalourethra with gross posterior urethral dilation. Normal voiding and renal function was achieved following an urethroplasty.

Clinical examination demonstrated normal external genitalia. The serum hormone profile was normal. An MRI of the penis revealed a dilated urethra and poor development of the corpus spongiosum and corpora cavernosa anteriorly (Fig 1, Fig 2). A diagnosis of fusiform-type megalourethra was suggested, and later confirmed by retrograde urethrogram.

Fig 1

Axial, T2-weighted image shows a dilated urethra (arrowheads) and poor development of corpora cavernosa (long arrows).

Fig 2

Sagittal, T2-weighted image shows a dilated urethra (arrowheads) and poor development of the corpus spongiosum (long arrows).

Discussion

Megalourethra is a rare congenital condition with fewer than 100 reported cases in the literature. There is no quoted incidence of this disease.

Megalourethra results from the failure of development of the corporal bodies from the phallic mesoderm (1). Megalourethra has classically been divided into two types: scaphoid and fusiform. In the scaphoid type, the corpus spongiosum is absent, leading to a boat-shaped dilation of the penile urethra. Fusiform megalourethra involves abnormal development of the corpora cavernosa in addition to the corpus spongiosum, giving a spindle-shaped dilation of the urethra. Reported pathological abnormalities of the corpora cavernosa have been highly variable, ranging from complete absence to segmental atresia of one or both corpora cavernosa.

The initial presentation is frequently in the first few days or weeks of life, though there are reports of antenatal diagnosis (2). Megalourethra is usually apparent on clinical examination, with obvious enlargement of the phallus. In other cases, it becomes apparent during micturition, when the dilated segment of urethra may balloon. Co-existent developmental abnormalities are frequently present; they include renal tract abnormalities, prune-belly syndrome, and the VATER association.

Management of this condition depends on the patients’ clinical status and the presence of any associated abnormalities. Definitive repair of the urethra in the early years of life is advocated, as failure to do so may result in frequent urinary tract infections. Surgical reconstructive options have been well documented and are reportedly highly successful at producing a normal external appearance and normal voiding function. However, the possibility of erectile dysfunction may, as in this case, not be addressed until the patient presents in adult life with this complaint. The associated prevalence of erectile dysfunction in this cohort of patients remains unknown.

This is the first case report to describe MRI findings for this pathology. The previously reported descriptions of this condition arise from surgical and pathological case series. A retrograde urethrogram has traditionally been the investigation of choice to confirm the abnormality of the penile urethra; however, the MRI can clearly demonstrate corporal anatomy and pathology. In our institution, imaging is performed with the penis taped to the abdomen, using T2-weighted, high-resolution images with a small field of view in the sagital, axial, and coronal planes. This can differentiate between the fusiform and scaphoid subtypes of megalourethra and give an accurate determination of the degree of abnormality of the corpora cavernosa, thus aiding in the planning of reconstructive surgery.