Surgery for Posterior Urethral Valves



Surgery for Posterior Urethral Valves


ROSALIA MISSERI

KENNETH I. GLASSBERG



A posterior urethral valve (PUV) is the most common cause of congenital bladder outlet obstruction in boys. It is associated with a dilated posterior urethra, poor urinary stream, and incomplete bladder emptying. Bilateral hydroureteronephrosis of varying degrees is almost always present and frequently accompanied by vesicoureteral reflux and/or bladder diverticula.




INDICATIONS FOR SURGERY

Although some controversy still exists as to what to do once the bladder has been drained with a catheter, almost all valves are currently treated with transurethral ablation (Fig. 97.2). For severe hydronephrosis, some report better long-term outcomes when these infants are temporarily diverted, while most feel that primary valve ablation is the treatment of choice (5). For those who believe temporary diversion is best, many methods of vesical and supravesical diversion of the obstructed bladder exist.






FIGURE 97.2 Proposed management of PUVs. Cr, creatinine; TURV, transurethral valve ablation.






FIGURE 97.1 VCUG of newborn with PUVs. Note the dilated posterior urethra and bladder diverticulum.


ALTERNATIVE THERAPY

There is no effective alternative to surgical therapy. Antenatal attempts at valve ablation, transurethral stenting, and percutaneous vesicoamniotic shunting are offered at few select centers and remain quite controversial.


SURGICAL TECHNIQUE


Transurethral Valve Ablation

Valve ablation is most commonly accomplished transurethrally. The size of the infant’s fossa navicularis usually limits the size of cystoscope that may be used. Typically, a 7.5Fr or 8.5Fr scope is used in infants, while a larger scope may be used
in older children. The cystoscope should be well lubricated and advanced under direct vision. Gentle dilation of the distal urethra may be required to advance the cystourethroscope. With the bladder full and applying gentle suprapubic pressure, the valve leaflets are more easily seen coming off the verumontanum and extending distally to fuse anteriorly (Fig. 97.3). The goal of valve ablation is to disrupt the leaflet, hence destroying the obstruction.






FIGURE 97.3 Cystoscopic appearance of type 1 PUV.

A PUV may be ablated or incised in several ways. The decision to proceed with one technique over another is often based on surgeon preference, availability of equipment, and the size of the child’s urethra. The valve may be ablated using a 3Fr Bugbee electrode through a cystoscope. Alternatively, the wire insert of a 3Fr ureteral catheter with the distal end connected to electrocautery may be used. All but the tip of the wire is insulted by the catheter to avoid thermal injury. Once in position, the Bugbee or wire is advanced and pushed into the valve at the 5 and 7 o’clock positions while employing a cutting current of 20 to 25 W. (Note that power settings may vary from machine to machine.) When using cautery, care must be taken to ensure that thermal energy is targeted at the valves alone. The holmium:YAG laser may also be used to incise the valves (6). These techniques may be particularly useful if the infant resectoscope is too large for the child’s urethra.

When using a small pediatric resectoscope, the valves are incised with a right-angle hook, loop electrode, or hook-shaped cold knife. When using a loop electrode, a narrow, more oblong loop is preferable to a wider, more circular loop. Some debate exists as to the best location for valve incision. Williams et al. (4) preferred incising at the 12 o’clock position, while Gonzales (7) advocated cutting at the 4, 8, and 12 o’clock positions. However, many prefer incising at the 4 to 5 o’clock and 7 to 8 o’clock positions using a hook-shaped cold knife or with the cutting current set at 20 to 25 W pure cut.

Additional methods of PUV ablation have also been described for use in patients with small-caliber urethras that do not allow passage of even the smallest cystoscope. With the advent of smaller scopes, perineal urethrostomy is now rarely necessary for valve ablation. Zaontz and Firlit (8) have described percutaneous antegrade ablation of PUV as well as antegrade incision of PUV in infants with small-caliber urethras. At our institutions, small or premature infants who are critically ill and cannot be successfully catheterized have had percutaneous suprapubic catheters placed at the bedside.

Once the valves are endoscopically ablated, the bladder should be cystoscoped to evaluate for diverticula, trabeculations, and the appearance of the ureteral orifices. A full stream should be noted at the end of the procedure while applying gentle pressure to the suprapubic area. A small urethral catheter is left in place for 1 to 2 days following the procedure or until an elevated creatinine nadirs. Repeat serum electrolytes and creatinine should be obtained 24 hours after catheter removal while the boy is still hospitalized. A renal ultrasound is useful in the postoperative period to evaluate for improvements in hydronephrosis. Its timing should be dictated by the surgeon’s level of concern. A VCUG may be performed after the catheter is removed to assess the success of the procedure. Timing of the VCUG is determined by the surgeon based on his or her confidence in the adequacy of ablation. The urethra, degree of reflux, and bladder appearance should be evaluated on VCUG. A VCUG and urodynamics or preferably videourodynamics should be delayed no longer than 6 to 8 weeks after ablation. If there is suspicion of inadequate ablation or continued obstruction, “second-look” cystoscopy with ablation of residual leaflets should be considered. Some have recommended routine cystoscopy a few weeks after valve ablation because of the high incidence of residual obstruction (9).

Follow-up renal ultrasound and serum creatinine and electrolytes should be performed at the time of the VCUG and urodynamics but may be obtained sooner based on the child’s renal function and clinical presentation.

If the child is found to have diminished compliance or detrusor hyperactivity, anticholinergic therapy should be considered. Anticholinergic therapy may also be instituted immediately after valve ablation or prior to closure or reversal of vesical or supravesical diversion. Alpha-blocker therapy may be considered even in the first months of life in the face of high detrusor voiding pressures and in the absence of residual valve obstruction or postvalve ablation stricture (10,11).


Vesicostomy

While most patients with PUV are treated with primary valve ablation, a vesicostomy may be useful in neonates whose urethra will not accommodate a cystoscope or in those whose creatinine rises despite adequate valve resection.

With the patient in the supine position, the lower abdominal skin is prepared and draped in the typical fashion. The procedure is more easily performed with a full bladder. A 2-cm transverse incision is then made midway between the pubic symphysis and umbilicus. The rectus fascia is exposed and a 2 cm × 2 cm cruciate incision is made. Alternately, a triangle or circle of rectus fascia measuring 2 cm may be excised. One must remember that the size of the fascial opening ultimately determines the caliber of the stoma. The rectus muscles are then retracted laterally, exposing the bladder. A 3-0 suture is placed near the dome of the bladder and used for traction. Using the traction suture, the bladder is mobilized superiorly. The peritoneum is gently swept off the superior aspect of the bladder. Additional cephalad sutures may be placed in a
stepwise fashion to help bring the dome into the surgical field. Care is taken to avoid the peritoneal contents. With gentle traction, one should be able to visualize the urachus or obliterated hypogastric artery.

The vesicostomy may be created in one of two ways. In the first method, a stay suture is placed proximal to the urachus. The urachus is then transected and excised. In the second method, the portion of the bladder cephalad to the urachal remnant is used as the site for the vesicostomy. The bladder is incised and the fascial edges are sewn to the outer bladder wall using 3-0 or 4-0 polyglactin sutures approximately 0.5 to 1 cm from the opening created in the bladder. The vesicostomy should be calibrated to 24Fr or large enough to allow passage of the surgeon’s fifth digit. If the fascial defect is too large, interrupted 3-0 polyglactin sutures may be used to narrow the opening. The edges of the detrusor are then sewn to the skin using 4-0 polyglactin sutures in an interrupted fashion. If the skin incision is wider than the stoma created, the skin is approximated with a suture of choice (Fig. 97.4).






FIGURE 97.4 Blocksom vesicostomy. A: A 2-cm transverse incision is made midway between the pubic symphysis and umbilicus. B: A 2 cm × 2 cm cruciate fascial incision is made. C: Using the traction suture the bladder is mobilized superiorly. The peritoneum is gently swept off the superior aspect of the bladder. D: The urachus is incised and the bladder is further mobilized. E: The urachus is excised. F and G: The outer bladder wall is sewn to the edges of the incised rectus fascia. H: The edges of the detrusor are sewn to the skin. (Modified with permission from Belman AB, King LR. Vesicostomy: useful means of reversible urinary diversion in selected infant. Urology 1973;1:208-213. Copyright © 1973. Published by Elsevier Inc.)

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Apr 24, 2020 | Posted by in UROLOGY | Comments Off on Surgery for Posterior Urethral Valves
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