A posterior urethral valve is where there is tissue at the proximal end of the urethra (closest to the bladder) that causes obstruction of urine output. It occurs in newborn boys. The obstruction to the outflow of urine creates a back pressure into the bladder, ureters and up to the kidneys, causing hydronephrosis. A restriction in the outflow of urine prevents the bladder from fully emptying, leading to a reservoir of urine that increases the risk of urinary tract infections.
It can vary in severity. Mild cases may be asymptomatic or present with:
- Difficulty urinating
- Weak urinary stream
- Chronic urinary retention
- Palpable bladder
- Recurrent urinary tract infections
- Impaired kidney function
Severe cases can cause obstruction to urine outflow in the developing fetus resulting in bilateral hydronephrosis and oligohydramnios (low amniotic fluid volume). The oligohydramnios leads to underdeveloped fetal lungs (pulmonary hypoplasia) with respiratory failure shortly after birth.
Severe cases may be picked up on antenatal scans as oligohydramnios and hydronephrosis.
To investigate cases presenting after birth, for example young boys presenting with urinary tract infections:
- Abdominal ultrasound may show an enlarged, thickened bladder and bilateral hydronephrosis
- Micturating cystourethrogram (MCUG) shows the location of the extra urethral tissue and reflux of urine back into the bladder
- Cystoscopy involves a camera inserted into the urethra to get a detailed view of the extra tissue. Cystoscopy can be used to ablate or remove the extra tissue.
Mild cases may simply be observed and monitored. If required a temporary urinary catheter can be inserted to bypass the valve whilst awaiting definitive management. Definitive management is by ablation or removal of the extra urethral tissue, usually during cystoscopy.
Last updated August 2019