POSTERIOR URETHRAL VALVES (PUV) IN BOYS
EARLY DIAGNOSIS AND ENDOCSOPIC LASER-TREATMENTS
Semir A. S. Al Samarrai
PUV are one of the few life-threatening congenital anomalies found during the neonatal period and the most frequent cause of lower urinary tract obstructions in boys. Despite optimal treatment, PUV in children may result in renal insufficiency in nearly one-third of cases (1-3).
This congenital obstruction of the urethra is one of the most devastating anomalies that occur in the urinary tract and is one of the few that are life-threatening in the neonatal period.
These lesions usually result in life-long disabilities with incontinence and decreased renal function despite optimal medical management. The condition of posterior urethral valves is still relatively common and makes up the vast majority of congenital urethral obstructions.
The term valves is unfortunate because it implies function. This obstructive membrane has no active function and is not a developmental stage in the embryology of the urethra. It is simply a passive barrier to urine flow.
Posterior urethral valves occur in 1 in 8,000 to 25,000 live births and make up 10% of urinary obstructions diagnosed in utero (Casal 1990). The diagnosis has been made an average in 1 in 1,250 fetal ultrasound screening (4).
They are three types of posterior urethral valves:
Type I (90-95%) is the most common type there is a ridge lying on the floor of the urethra, continuous with the verumontanum. These processes are continued as thin membranous sheets, directed upward and forward. The thickness of the valves varies from rigid, thick tissue, to thin almost transparent membranes (5).
Type II valve was described as arising valve from the verumontanum and extending along the posterior urethral wall toward the bladder neck (5).
Type II valve was described as a membrane lying transversely across the urethra with a small perforation near its center and is distal to the verumontanum, this type make up only 5% of the total (5).
However, today, only type I and type III are found to be obstructive. As type II seems to be more like a fold and not obstructive (5).
The diagnosis of this PUV through the ultrasound either transabdominal or transurethral can be done without any problem. An obstruction above the level of the urethra affects the whole urinary tract in varying degrees.
- The prostatic urethra is distended and the ejaculatory ducts may be dilated due to urinary reflux. The bladder neck is hypertrophied and rigid.
- The hypertrophied bladder occasionally has multiple diverticula.
- Nearly all valve patients have dilatation of both upper urinary tracts. This may be due to the valve itself and the high pressure in the bladder, or due to obstruction of the ureterovesical junction by the hypertrophied bladder.
- If there is secondary reflux, the affected kidney functions poorly in most cases.
Voiding-Cystourethrography confirms a PUV diagnosis. This study is essential whenever there is a question of an intravesical obstruction, as the urethral anatomy is well outlined during voiding.
A secondary reflux is observed in at least 50% of patients with PUV (6).
Reflux is consistently associated with renal dysplasia in patients with PUV. It is generally accepted that reflux in the renal units act as a “pressure pop-off valve”, which would protect the other kidney, leading to a better prognosis (7).
Other types of pop-off mechanism include bladder diverticula and urinary extravasation, with or without ascites (8).
Nuclear renography with split renal function is important to assess kidney function. Creatinine, blood-urea nitrogen and electrolytes should be monitored closely during the first few days. A nadir creatinine of 80 µmol/L is correlated with both prognosis (3).
- Bladder drainage. If a boy is born with suspected PUV, drainage of the bladder and, if possible, an immediate voiding-cystourethrography (VCUG) is necessary. A neonate can be catheterized with a 3.5-5 F catheter. Balloon catheters are not available in this size. A VCUG is performed to see if the diagnosis is correct and whether the catheter is within the bladder and not in the posterior urethra. An alternative option is to place a suprapubic catheter, perform a VCUG and leave the tube until the neonate is stable enough to perform an endoscopic incision or resection of the valve.
- Valve ablation. When the medical situation of the neonate has stabilized and the creatinine level decreased, the next step is to remove the intravesical obstruction. Small paediatric cystoscopes and resectoscopes are now available either to incise or to resect the valve at the 4-5, 7-8 or 12 o’clock position, or at all three positions, laser vaporization with 80-W KTP Laser or PlasmaButton vaporization is alternative procedure to avoid postoperative urethral stricture due to extensive electrocoagulation by the standard electroresection of the valve.
- Suprapubic-Drainage. If the child is too small or too ill to undergo endoscopic surgery, a vesicostomy is used to drain the bladder temporarily. If initially a suprapubic tube has been inserted, this can be left in place for 6-12 weeks.
- High Diversion. If bladder drainage is insufficient to drain the upper urinary tract, high urinary diversion should be considered. Diversion may be suitable if there are recurrent infections of the upper tract, no improvement in renal function and/or an increase in upper tract dilatation, despite adequate bladder drainage, the choice of urinary diversion depends on the surgeon’s preference for high loop ureterostomy, ring ureterostomy, end ureterostomy or pyelostomy, with each technique having advantages and disadvantages (9-11). Reconstructive surgery should be delayed until the upper urinary tract has improved as much as can be expected.
Lifelong monitoring of these patients is mandatory, as bladder dysfunction is not uncommon and the delay in day- and night-time continence is a major problem (6, 3). Between 10% and 47% of patients may develop end-stage renal failure (1-3).
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14. Singh-Grewal D, Macdessi J, Craig J. Circumcision for the prevention of urinary tract infection in boys: a systemic review of randomized trials and observational studies. Arch Dis Child 2005 Aug;90(8):853-8. http://www.ncbi.nlm.nih.gov/pubmed/15890696
Correspondence:Prof. Dr. SEMIR AHMED SALIM AL SAMARRAI
Professor Doctor of Medicine-Urosurgery, Andrology, and Male Infertility
Dubai Healthcare City, Dubai, United Arab Emirates.
Mailing Address: Dubai Healthcare City, Bldg. No. 64, Al Razi building, Block D,
2nd floor, Dubai, United Arab Emirates, PO box 13576