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A. Membranes in the posterior urethra cause a narrowing of the passage way between the base of the bladder and the tip of the penis.
It is seen with a frequency of one in 4000/8000 male infants.
It may be diagnosed before birth may not become obvious until later in childhood.
It can an have an effect on the development and function of the urinary tract. As a result of poor bladder drainage before birth/during pregnancy, the kidney system develops under high pressure. This can result in dilatation (swelling) of the kidneys and the tubes that drain them. If this is severe then it usually shows up on the 20-week ultrasound scan.
A. The presence of membranes in the urethra is due to remnants of tissue remaining from an early stage of fetal development, which would usually become incorporated into the internal structure of the urinary tract.
This takes place at an early stage in a baby’s development sometime between seven and 11 weeks of the pregnancy.
There are no recognised risk factors, although the condition is seen occasionally in twins or brothers, which suggests possible familial influence.
A. Before birth:
At Birth: usually there are no external signs of a problem, however there may be:
Early Childhood:
A. A number of tests will be required to confirm the diagnosis and undertake any surgery required.
Ultrasound scan (USG) of your baby’s kidneys, bladder and ureters (tubes which run from kidney to bladder one from the left kidney and one from the right) is usually undertaken a few days after birth.
Micturating Cystourethrogram (MCUG) uses a contrast fluid which is put into the bladder with a thin tube or catheter to show whether there is reflux and an x-ray is taken. Reflux means the urine is pushed up the ureters towards the kidneys causing poor drainage. This x-ray will also show an enlarged posterior urethra where the urine is pooling above the blockage.
Cystoscopy is an investigation which is carried out under a general anaesthetic, allowing a tiny camera in a narrow tube to look inside the bladder and see the membranous valves in the urethra.
Blood tests will show how well the kidneys are working and whether there has been any damage to them. The kidneys act as a filter to maintain the fluid and electrolyte balance (salts and water ratios) of the body and ensure that your baby remains healthy.
Any ill effect caused by the blockage will show in these tests. The level of creatinine in the blood stream is particularly important in helping to show how efficiently the kidneys are working. This test is only used 24 hours or more after birth.
A. This depends on the symptoms and how ill your baby is when diagnosed. Emergency treatment will be carried out before there has been a diagnosis if necessary for those babies with breathing problems, infection or electrolyte abnormalities.
A very fine tube or catheter will drain the distended bladder and aim to prevent further damage to the kidneys.
Urinary tract infection and electrolyte imbalance will be treated with intravenous fluids and antibiotics. Once your baby’s condition is stable, a surgical procedure will be carried out to remove the extra membranes which have been causing the blockage and backflow.
The procedure is known as ‘ablation of the posterior urethral valve’ and is carried out in the operating theatre with your baby fully anaesthetised. There is usually no need to cut the skin, as the operation is done with a cystoscope which is a tiny camera in a tube with an integral instrument to remove or resect the extra membranes.
A. This is a very delicate procedure done with great care as there is a small risk in the order of less than 1% of causing incontinence if the external sphincter is damaged. The external sphincter is a muscle which controls the outflow of urine from the bladder and is situated just behind the area where the membranes are found, so it could be damaged in the resection process. It is therefore preferable to resect too little than too much, which means that occasionally a second resection may be required at a later date.
In severe cases where a baby has an extremely low birth weight, a temporary urinary diversion may need to be considered in order to drain urine from the bladder above the level of the valves, or from higher up the urinary tract, for example, the ureter or the kidney. This would take the form of a surgically placed short tube to allow the urine to drain from higher up the normal drainage pathway reducing the pressure within the system.
A. Your baby will be closely monitored by the urology team to check for any long-term problems the severity of which will depend on how serious the blockage was before treatment.
The potential problems include:
Regular monitoring by the consultant and team at our outpatient clinic will ensure early recognition of problems, and involvement of a wider team of professionals can ensure the best outcome for your child.