CONGENITAL ANOMALIES OF THE FEMALE URETHRA
DISTAL URETHRAL STENOSIS IN INFANCY AND CHILDHOOD (SPASM OF THE EXTERNAL URINARY SPHINCTER) AND DYSFUNCTIONAL VOIDING
Congenital anomalies of the urethra are rare. These include urethral valves (posterior and anterior), urethral atresia, congenital urethral stenosis, cloacal malformations, female epispadias, bladder–sphincter dysfunction without neurologic abnormality, and congenital urethrovaginal fistula. The purely anatomically based obstructive urethral abnormalities are found chiefly in males (posterior urethral valves). The largest population-based prevalence study of lower urinary tract obstruction showed 3.3 urethral abnormalities in 10,000 births. Most of these were due to posterior urethral valves, with 1.9 in 10,000 births (Malin et al, 2012). There are only six reported cases of congenital urethrovaginal fistulas; the most recently reported ones are due to a low transverse vaginal septum (Amer et al, 2016).
Congenital urethral stenosis is rare. The more common lower urinary tract obstruction in girls is dysfunctional voiding. Clinical presentation is similar in both. This includes hesitancy in initiating micturition, a slow and interrupted urinary stream, recurrent cystitis, and pyelonephritis. On further evaluation, the patient may exhibit vesicoureteral reflux. Enuresis and involuntary loss of urine during the day are common complaints. Abdominal straining may be required in order to void. Small amounts of residual urine are found, which impair the vesical defense mechanism. A voiding cystourethrogram may reveal an open bladder neck and ballooning of the proximal urethra (Figure 42–1).
Distal urethral stenosis with reflux spasm of voluntary urethral sphincter. Left: Voiding cystourethrogram showing bilateral vesicoureteral reflux, a wide-open vesical neck, and severe spasm of the striated urethral sphincter in the middle portion of the urethra (arrow) secondary to distal urethral stenosis. Right: Postvoiding film. The bladder is empty and the vesical neck open, but the dilated urethra contains radiopaque fluid proximal to the stenotic zone. Bacteria in the urethra thus can flow back into the bladder. (Used with permission from AD Amar.)
In girls with congenital distal urethral stenosis, the obstruction is due to secondary spasm of the striated external sphincter rather than bladder neck obstruction. Lyon and Tanagho (1965) found that the distal urethral ring calibrates at 14Fr at age 2 years and at 16Fr between the ages of 4 and 10 years. From the hydrodynamic perspective, even though such a stenotic area should not be obstructive, almost all observers agree that dilatation of the ring does relieve symptoms in these children and that it results in cure or amelioration of persistent infection or vesical dysfunction in 80% of cases (Kondo et al, 1994). Tanagho et al (1971) measured pressures in the bladder and in the proximal and midurethra simultaneously in symptomatic girls and found high resting pressures, some as high as 200 cm of water (normal, 100 cm of water) in the midurethral segment. Attempts at voiding caused intravesical pressures ...