This article discusses various urethral anomalies observed in male infants and children and the distinct entity of urethral prolapse in prepubescent females. Urethral prolapse is a protrusion of urethral mucosa beyond the urethral meatus and generally occurs in prepubertal black girls or in postmenopausal white females. This article discusses the pediatric entity of urethral prolapse.
Similarities in the modes of presentation of these conditions are striking, underscoring the importance of a thorough history, physical examination, and radiologic imaging with careful and complete cystourethrography, ultrasonography, or endoscopy.
Lacuna magna, also known as sinus of Guérin, is a dorsal diverticulum in the roof of the fossa navicularis presenting either as a pit or a 4-mm to 6-mm sinus, dorsal and parallel to the urethra. This lesion is thought to arise embryologically from an incomplete fusion between the ingrowing ectoderm at the tip of the penis and the glandular urethra.
Urethral duplications are rare anomalies characterized as epispadiac, hypospadiac, and Y-type. They may be either complete, if venting externally, or incomplete, in which case the connection with the urinary tract varies. In complete duplications, the patient may void with a double stream. Epispadiac duplications are usually associated with significant dorsal curvature of the penis. The most common type of urethral duplication is the Y-type; individuals with Y-type urethral duplication have an orthotopic meatus and a perineal meatus, through which most of the urine passes. The etiology of these conditions is unknown.
Anterior urethral valves
Anterior urethral valves are rare anomalies, occurring 7-8 times less frequently than posterior urethral valves (PUV), but with consequences just as devastating. These lesions can occur anywhere in the anterior urethra, and the valve mechanism is usually formed by an associated diverticulum; isolated valves formed by cusps or irislike diaphragms have also been reported. The diverticulum has been postulated to arise from incomplete formation of the ventral corpus spongiosum, an incomplete urethral duplication, or a congenital cystic dilation of a periurethral gland. However, these lesions are embryologically distinct from the much more common PUV and occur distal to the urinary sphincter.
Megalourethra can be described as a urethral diverticulum that affects the entire penile urethra. Two types, scaphoid and fusiform, have classic descriptions. Scaphoid megalourethras have an absence of corpus spongiosum, whereas fusiform megalourethras lack both spongiosum and corpora cavernosa. Often associated with lethal congenital anomalies, fusiform megalourethras are present in some stillborns; therefore, this finding has more academic than clinical pertinence. Temporary obstruction during early development may be an etiologic factor in fusiform megalourethra. In the scaphoid type, in which failure of development of erectile tissue is present, a mesenchymal defect is suggested akin to what is observed in prune belly syndrome.
Anterior urethral diverticula
Anterior urethral diverticula occur in males and may involve the proximal part of the penile urethra and the distal part of the bulbous urethra. An underlying defect in the spongiosum is suggested, as observed in scaphoid megalourethra, or, possibly, these lesions may result from the rupture of a periurethral cyst or a partial duplication of the urethra.
Urethral polyps are rare anomalies, characterized as benign urothelial-lined masses attached to a fibrovascular stalk arising from the verumontanum, presenting almost exclusively in boys. Urethral polyps' association to the verumontanum suggests the embryologic persistence of Müllerian structures. Some of these polyps, diagnosed later in life, may represent acquired lesions.
Cowper duct cysts
Cowper duct cysts involve the Cowper glands, 2 paired periurethral structures located in the urogenital diaphragm, which are drained by ducts measuring 2-3 cm long that empty into the bulbous urethra through 2 small, flush openings. These glands, homologous of the Bartholin gland in the female, secrete a clear fluid that functions as a lubricant and a coagulation factor for semen during ejaculation. Abnormalities of these glands and their ducts may result from obstruction and, less frequently, trauma and infection.
Urethral prolapse is the complete protrusion of the urethral mucosa beyond the meatus in females. This is an uncommon condition observed particularly in prepubertal black and Latin American girls. Increased incidence has been reported in children from the lower socioeconomic strata. This condition is thought to result from poor attachments between the longitudinal and circular, oblique, smooth muscle layers and the mucosa of the urethra in association with recurrent episodes of increased intraabdominal pressure. Other contributing factors such as trauma, malnutrition, urinary and vaginal infections, and urethral mucosa redundancy have been postulated in the etiology of this condition. 
Most conditions discussed in this article are infrequent or rare.
Although the dorsal urethral diverticulum in the roof of the fossa navicularis (ie, lacuna magna) may be present in approximately 30% of examined boys, this condition is rarely symptomatic. Urethral duplications are rare; only 150 cases had been reported in the literature prior to 1986. A ratio of the incidence of anterior urethral valves relative to that of PUV is 1:8; PUV occurs in 1 in 8000 to 1 in 25,000 live male births. Fewer than 50 cases of megalourethra had been reported in the literature by 1993; the scaphoid type is more common. Megalourethras have often been associated with other severe anomalies, such as prune belly syndrome, cloacal malformations, and the vertebral, anal, cardiac, tracheal, esophageal, renal, and limb (VACTERL) association of congenital anomalies.
Diverticula of the anterior urethra are uncommon but are the second most common form of congenital urethral obstruction, after PUV, in infants and children. Both Cowper duct cysts and congenital urethral polyps are quite rare. Urethral prolapse has an estimated incidence of 1 in 3000 and is most common in young black or Latin American girls.
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Morbidity of the sinus of Guérin (ie, lacuna magna) is limited to those few symptomatic patients who present with dysuria, hematuria, or hematospermia.
Although most patients with incomplete urethral duplications are asymptomatic, patients with complete duplications can present with urinary obstruction, incontinence, infection, or double stream.
Epispadiac duplications are associated with a significant dorsal curvature of the penis. In general, associated upper urinary tract anomalies are infrequent but should be investigated.
In at least 50% of patients with anterior urethral valves, associated hydronephrosis or vesicoureteral reflux (VUR) is present.
Although most attention has been focused on PUV, anterior valves can be just as obstructing and devastating, in some cases leading to chronic renal failure or end-stage renal failure.
Prognosis of patients with megalourethra depends on the number and severity of the associated anomalies. Often, patients with fusiform megalourethras have associated lethal congenital malformations.
Urethral diverticula, polyps, and Cowper duct cysts are benign conditions that may cause urinary retention, hematuria, irritative voiding symptoms, dribbling, or urinary tract infections (UTIs). Because these lesions may be obstructive, evaluation of the upper urinary tracts is essential.
Urethral prolapse may result in dysuria, hematuria, blood spotting on the underwear, or bleeding and, if unattended, can lead to necrosis of the prolapsed portion of the urethra.
Prepubertal black and Latin American girls have the highest incidence of urethral prolapse.
Urethral prolapse is the only condition discussed in this article that affects females.
Urethral prolapse in the pediatric population occurs most commonly in prepubertal black girls.
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