Vesicovaginal reflux

Vesicovaginal reflux is a well-known entity rarely encountered by radiologists. It is a behavioral disorder, a type of dysfunctional elimination syndrome commonly encountered in pre-pubertal girls. It is defined as reflux of urine into the vaginal vault either in supine or upright position during voiding. The clinical presentation varies form asymptomatic bacteriuria, dysuria, recurrent urinary tract infections, vulvovaginits and post-voiding incontinence. Although usually diagnosed clinically, radiological diagnosis is usually made by complete resolution of hydrocolpos on a post-voiding scan. It is important for the radiologist to be aware of this entity so as to differentiate this functional disorder presenting as hydrocolpos from other obstructive causes of hydrocolpos which require surgical management.

Epidemiology

Vesicovaginal reflux is commonly encountered in pre-pubertal girls, many of them being obese. Behavioral factors like infrequent voiding or abnormal toileting position are contributory.

Clinical presentation

It is a functional disorder with varied clinical presentation. The spectrum varies from asymptomatic bacteriuria to recurrent urinary and genital infections, frequency, urgency, daytime incontinence, and post-voiding dribbling. Some patients also experience filling of a second bladder allowing them to refrain from voiding for longer periods.

Pathology

During overdistension, straining or voiding (even in the absence of obstructive pathology) urine passes into the vagina through the introitus, i.e. there is vesicovaginal reflux. Upon standing, urine collected in the vagina unintentionally dribbles out leading to incontinence. The etiology is unclear, with following predisposing factors being implicated:

• obesity with tightly apposed, large labia majora which prevent passage of urine
• abnormal toileting position with voiding with legs apposed tightly
• adhesions of labia minora
• ureteral duplication or ectopic ureter with insertion into vagina
• female hypospadias
• spastic pelvic floor muscles due to functional disorder or cerebral palsy
  

Radiographic features

Voiding cystourethrogram (VCUG)

A voiding cystourethrogram (VCUG) demonstrates direct filling of the vagina during micturition. The vagina and urethra are both contrast-opacified with visualization of a normal intervening septum. It provides with rapid and effective detection of reflux, making it a reference examination. An associated abnormally wide bladder neck or spinning top urethra (constricted proximal urethra) may also be demonstrated. Risk of radiation exposure in a female with child-bearing potential in VCUG warrants the use of other non-ionizing investigations.  

Ultrasonography

In a patient with clinical suspicion of vesicovaginal reflux, ultrasound in the prevoiding state is usually the first investigation. If it reveals an anechoic cystic lesion outlining the cervical os posterior to the urinary bladder, a diagnosis of hydrocolpos is made which requires further evaluation in post-voiding state to differentiate non-obstructive from obstructive causes. Complete resolution of hydrocolpos on a post-voiding scan suggests the diagnosis of vesicovaginal reflux.

CT

Cross-sectional imaging is the next investigation to rule out an organic or congenital cause. CT has the disadvantage of radiation exposure but may be indicated in patients having absolute contraindications for MRI. It can reveal a grossly distended vagina with fluid on a pre-voiding scan with complete resolution on a post-voiding scan. Moreover, reflux of contrast opacified urine into the vagina helps in confirming the diagnosis of urocolpos. CT has a better spatial resolution and is less susceptible to motion artefacts of respiration and urethral/ureteral peristalsis.

MRI

Unless contraindicated, MRI is the investigation of choice to rule out anatomic and structural abnormalities. Typical findings include resolution of hydrocolpos on a post-voiding scan.

Treatment and prognosis

Treatment includes behavioral therapy with voiding retraining. Proper toileting position (i.e. voiding with legs wide apart) and maintenance of a voiding diary are other management strategies. Prognosis is usually good.

Differential diagnosis

Imaging differential

• obstructive hydrocolpos: imperforate hymen, vaginal agenesis or atresia, transverse vaginal septum etc. are the common obstructive causes of hydrocolpos/hematocolpos in young females; in these cases the hydrocolpos does not show any change between pre- and post-voiding state; treatment of these is surgical
• vesicovaginal fistula (VVF): the finding of complete resolution of hydrocolpos on a post-voiding scan may also be noted in cases of a vesicovaginal fistula with small fistulas not being apparent on cross-sectional imaging; however, a detailed clinical and radiological assessment differentiates these two entities; VVF presents with continuous dribbling of urine per vaginal, however in the case of reflux, there is intermittent dribbling of urine pooled in the vagina; also VVF is unlikely in young adolescents as it occurs as a result of postoperative and obstetric complications, pelvic malignancy or irradiation and trauma; on imaging VVF is unlikely to present with over-distended bladder and large hydrocolpos as there is continuous dribbling of urine; also usually inflammatory changes are noted adjacent to the fistula tract