ORIGINAL

Primary vesicoureteral reflux and extravesical ureteral reimplantation in children

García-Mérida M*, Gosalbez Jr. R**, Rius-Díaz F***, Labbie A**, Castellán M**

*Section of Pediatric Urology. Maternal-Children’s University Hospital of Málaga. **Division of Pediatric Urology. Miami Children’s Hospital and Jackson Memorial Hospital, University of Miami, Florida, USA. ***Department of Biostatistics. Department of Preventive Medicine and Public Health. University of Málaga, Spain

Actas Urol Esp 2006; 30 (6): 602-609

ABSTRACT

PRIMARY VESICOURETERAL REFLUX AND EXTRAVESICAL URETERAL REIMPLANTATION IN CHILDREN

Purpose: To assess the results of the Lich-Gregoire procedure in the treatment of primary vesicoureteral reflux (VUR).

Materials and methods: Over a 2.5-year period, 141 children with primary VUR underwent vesicoureteral reimplantation using the Lich-Gregoire procedure in 101 patients (158 ureters) and the Cohen procedure in 48 patients (68 ureters). Patients were evaluated retrospectively in a non-randomized fashion, and data were recorded on patient age, indications for surgery, days with the bladder catheter, length of stay, and short- and long-term complications.

Results: The average control time was 1.71 years (range 8 months to 3.5 years).

A) Early complications. No obstruction was seen in this series. Five children (8.6% of those simultaneously operated upon bilaterally) showed urinary retention, but only three needed replacement of the bladder catheter, and only one of them required temporary clean intermittent catheterization. Nausea, vomiting, pain and hematuria were sporadic and limited in time.

B) Late complications. The long-term results were good (95%). Seven ureters (4.4%) showed persistent VUR, and 3 children (6.7% of the unilateral cases) had contralateral VUR. Only 3 ureters needed new surgical treatment (2%) for persistent ipsilateral VUR.

Short and long-term complications, days with bladder catheter, and length of stay in hospital were significantly lower in the group of patients operated with the Lich-Gregoire procedure than in the patients operated with the Cohen technique.

Conclusions: The Lich-Gregoire procedure is associated with shorter postoperative hospitalization and less discomfort, pain and hematuria than the intravesical technique. Both techniques were effective in correcting VUR. Extravesical reimplantation can cause transient bladder dysfunction in a small percentage of the bilateral cases.

Keywords: Vesicoureteral reflux. Ureteral reimplantation. Voiding dysfunction. Urinary retention. Ureter.

A number of open surgical techniques are available for correcting vesicoureteral reflux (VUR), though the procedures most widely used in children are the Cohen intravesical, Lich-Gregoire extravesical and mixed Politano-Ledbetter techniques^1,2. The extravesical implantation procedure described by Lich-Gregoire^3,4, or its variants⁵, offers advantages over the intravesical techniques, and is therefore gaining popularity. In effect, the extravesical technique does not involve bladder aperture, and there is a lesser risk of wound infection. In addition, the surgical time is shorter, the postoperative course is better tolerated (less hematuria, fewer detrusor muscle spasms, and less discomfort), less postoperative analgesia is required, and fewer catheterization and in-hospital days prove necessary³. Nevertheless, the technique also has a number of inconveniences, such as transient postoperative urinary retention in cases of simultaneous bilateral reimplantation, and the fact that the bladder cannot be visualized to assess associated disorders such as diverticuli, anomalous contralateral meatuses, etc.^6,7. It is therefore necessary in some cases to perform prior cystoureteroscopy in the same surgical act.

OBJECTIVES

A non-randomized retrospective study was made of the patients subjected to ureteral reimplantation, with the purpose of establishing the short- and long-term results, bladder catheterization time and days of hospital stay.

MATERIALS AND METHODS

Over a 2.5-year period (June 1998 to January 2001) a total of 171 children with VUR of different origins were operated upon in the Division of Pediatric Urology of Miami Children’s Hospital (Florida, USA). Of these patients, 141 presented primary VUR and were subjected to ureteral reimplantation as follows: 101 using the Lich-Gregoire technique and 40 with the Cohen procedure. A thorough analysis was made of the 101 patients subjected to the extravesical procedure, establishing comparisons with the results of the intravesical technique. An evaluation was made of patient age, degree of VUR, associated procedures, days of bladder catheterization, hospital stay, and the short- and long-term results obtained. The statistical analysis was carried out using the Pearson chi-square test for qualitative variables and the Student t-test in application to quantitative variables. The multiple response variables in turn were processed by two-proportions contrasting for each of the possible response items.

The patients were subjected to preoperative ultrasound, cystography and isotopic gammagraphy with dimethylmercaptosuccinic acid (DMSA).

Extravesical antireflux treatment was provided with the Lich-Gregoire inverted-Y technique without ureteral deinsertion. Although the technique was the classical procedure described by the authors^3,4, it comprised the following steps: intraoperative Foley catheter placement to control bladder distension. Through a Pfannenstiel incision, the bladder is accessed, with dissection of the anterior and corresponding lateral surface. The bladder is voided. The external iliac vessels are located, reflecting the peritoneum cranially to locate the ureter, and the Dennis-Brown separator is positioned. The obliterated umbilical artery is located and ligated and sectioned if necessary. The ureter is easily located beneath the umbilical artery, between the bladder and peritoneum. Traction is applied to the ureter with a vessel loop, dissecting ventrally to the point of insertion, and over a length of 3-4 cm, avoiding excessive use of the electrical scalpel. In bilateral cases bipolar forceps cauterization is used. Close to the ureterovesical junction (UVJ) are located a series of vessels, originating from the inferior vesical artery, which must be ligated or cauterized to avoid undesirable hematomas. Since the bladder is retracted towards the side contralateral to the side where reimplantation is to take place, the orientation of the tunnel must be designed to avoid ureteral angulations and obstructions after returning the bladder to its normal position. The superficial layer of the detrusor muscle is opened with a fine-needle electrical scalpel, with continuation of muscle separation to the mucosa with scissors and a right angle. With the bladder half full, the mucosa protrudes outwards, and dissection proves easier. Thorough dissection is required of the ventral surface, together with a little of the lateral aspects of the ureteral insertion in the form of an inverted “Y”. No detrusor fiber is to be left in the UVJ, so that the ureter inserts well in the bladder, and to ensure that its fibers do not obstruct the ureter on sealing the neotunnel. In the event modeling proves necessary, the ureter is deinserted from the bladder. The length of the tunnel should observe a proportion of 4-5/1 with the diameter of the ureter. If the bladder mucosa is opened, it should not be sutured, since the orifice would enlarge; a mosquito is positioned, and sealing is carried out with 5-0 reabsorbable material ligation. The detrusor is closed with 4-6 loose vicryl or monocryl 4-0 stitches, using a right angle to ensure that there is no proximal ureteral obstruction. The bladder is returned to the normal position, and it is checked that the ureter does not insert angled into the bladder. Careful hemostasia is applied, with layered suturing; no drainage is placed. A Foley bladder catheter is left in place for 24-48 hours in the unilateral cases, and for 48-72 hours in the bilateral cases.

In almost all patients subjected to extravesical ureteral reimplantation, prior cystoureteroscopy was carried out to determine the position and appearance of the ureteral meatuses, the length of the submucosal tunnel, and to identify other possible associated malformations (diverticuli, lithiasis, duplications, etc.).

Intravesical antireflux treatment was always based on the Cohen procedure; the Foley-type bladder catheter was left in place for three days in the unilateral cases, and for four days in the bilateral cases. In selective cases (modeling), external ureteral tutors (Nelaton catheters) were placed.

In the immediate postoperative period all patients received oxybutinin chloride treatment while carrying the bladder catheter or ureteral tutor, together with antibiotic coverage and analgesia (paracetamol with codeine). In no case was caudal block or wound infiltration with topical anesthesia applied. Plasma creatinine was determined in the bilateral and single-kidney cases. Posteriorly, antibiotic treatment at prophylactic doses was prescribed until healing of VUR was confirmed by the postoperative cystogram. All patients were subjected to ultrasound control after three months, with isotopic cystography after 6 months.

RESULTS

Of the 101 patients subjected to extravesical reimplantation, 62 (61.4%) were females and 39 (38.6%) males. The right side was operated upon in 17 cases (16.8%), the left in 27 (26.7%), and bilateral surgery was carried out in 57 (56.5%) – representing a total of 158 refluxing kidney units. There were three cases of single kidney. The degree of VUR is reported in Table 1.

Table 1

Reflux grade	n (percentage)
I	6 (3.8%)
II	53 (33.5%)
III	57 (36.1%)
IV	29 (18.4%)
V	13 (8.2%)

Ultrasound revealed kidney pathology in 45 children, with a total of 49 affected kidneys (31%). Isotopic gammagraphy with DMSA was carried out in 92 children, and the mean differential renal function was 55.5% (range 12-85%) for the right side and 48.5% (range 15-88%) for the left side. Nephropathy was present in 57 children, with a total of 69 affected kidneys (44%). Nephropathy was more common in high-grade VUR and in the smaller children.

There were various surgical indications for each patient (Table 2). No patient had a prior history of micturition dysfunction. All grade I VURs subjected to surgery had higher-grade contralateral VUR.

Table 2

Indications for surgery	n (percentage)
Nephropathy	49 (49%)
VUR grade	42 (42%)
Recurrent urinary tract infection	39 (39%)
Age at presentation and duration of VUR	25 (25%)
Parents refuse to continue medical treatment	11 (11%)
No response to antibiotic treatment	11 (11%)
Others: Puberty Single kidney Arterial hypertension Prior pyeloureteral plasty	10 (10%) 5 3 1 1

The mean patient age at surgery was 5.4 years (range 4 months – 24 years). Seventy-five children were subjected to prior cystoureteroscopy, which revealed no important anomalies, while 5 underwent ureteral modeling. An external-thread double-J catheter was left in place for one week in the modeled ureters, in the single kidneys and in one high-grade bilateral VUR. The catheter was removed after 7 days in the polyclinic.

Seventy-nine children experienced no incidents in the immediate postoperative period, while 22 patients (22%) suffered 28 immediate complications (Table 3).

Table 3

Early complications following extravesical reimplantation

	n (percentage)
No	79 (78.2%)
Yes	22 (21.8%) children / 28 complications
Nausea/vomiting	11 (11%)
Pain (bladder spasm)	10 (10%)
Urinary retention	5 (5%)
Hematuria	1 (1%)
Transient obstruction	1 (1%)

One patient, subjected to bilateral reimplantation, developed transient oligo-anuria for 22 hours, with spontaneous resolution. Five bilateral reimplantations presented urinary retention after removing the Foley catheter 72 hours after the operation (Table 4). Of these patients, one started to urinate after 24 hours, another after 48 hours, and the remaining three required bladder catheter reinsertion due to elevations in plasma creatinine. Two healed by the seventh day, and the other on day nine – though intermittent bladder catheterization proved necessary for four weeks until healing, followed by normal micturition.

Table 4

Cases that developed urinary retention

Age (years)	Sex	VUR grade	Reimplant side	Time (days)	Serum creatinine	Treat.	Result
7	Female	III Bil	Bilateral	1	0.5 mg/dl	No	Healed
4	Male	III Bil	Bilateral	2	0.6 mg/dl	No	Healed
7	Female	III/IV	Bilateral	3	2.1 mg/dl	Foley	Healed
1	Male	III/V	Bilateral	3	3 mg/dl	Foley	Healed
5	Female	IV/III	Bilateral	5	6.7 mg/dl	Foley	Healed

The Foley catheter was left in place for an average of 2.6 days (range 2-9 days), while the mean duration of hospital stay was 2.86 days (range 2-9 days). The results of the ultrasound exploration three months after surgery are reported in Table 5.

Table 5

Postoperative ultrasound findings (after three months)

	n (percentage)
Normal	71 (70%)
same as before surgery	24 (24%)
Increased nephropathy	4 (4%)
Reduction in dilatation	2 (2%)

One patient was lost to follow-up, and 10 ureters (6.9%) presented late complications: 7 (4.4%) showed persistent VUR and 3 (6.8% of unilateral cases) contralateral VUR; all were of grade I to III. Procedures attributable to the complications only proved necessary in three children with persistent ipsilateral VUR, and in all of them endoscopic antireflux measures were applied with hyaluronic acid dextranomer using the conventional technique. The contralateral VURs healed without surgery. VUR subsided in all the reoperated cases. The mean duration of follow-up has been 1.71 years (range 8 months – 3.5 years).

Table 6 presents the global results of the entire series of ureteral reimplantations (extra- and intravesical) – good results being recorded in 95% of cases. Table 7 in turn specifies the results of isolated extravesical reimplantation, showing similar results. The percentage of persistent postoperative ipsilateral VUR was also almost similar in the two patient groups, with values of between 4.4% and 4.8%. The percentage contralateral VUR was higher in the extravesical group (6.8%) than in the overall series (5.4%), though the difference was not statistically significant. The children with persistent VUR were subjected to observation, and surgery only proved necessary in five patients (2%) – two corresponding to intravesical cases, with ipsilateral reflux. In all of them endoscopic antireflux measures were applied using hyaluronic acid dextranomer, with a good outcome.

Table 6

Primary vesicoureteral reflux. Global results of ureteral reimplantation (extra- and intravesical)

Grade	Ureters	Efficacy		VUR	PO	VUR	PO	Observation		Reoperation
		No.	%	Ipsilateral		Contralateral		No.	%	Nº	%
I	6	6	100
II	70	66	94.3	4	5.7%	2	2.8%	3	4.3	1	1.4
III	78	73	93.6	5	6.4%	1	1.3%	3	3.8	2	2.6
IV	48	47	97.9	1	2.0%			1	2.0
V	24	23	95.8	1	4.1%			1	4.2
Total	226	215	95.1%	11	4.8%	3	5.4%	6	2.6%	5	2.2
Abbreviations: No.: number of cases; %: percentage; VUR: vesicoureteral reflux; PO: postoperative period; Contralat: contralateral

Table 7

Primary vesicoureteral reflux. Results of extravesical ureteral reimplantation

Grade	Ureters	Efficacy		VUR	PO	VUR	PO	Observation		Reoperation
		No.	%	Ipsilateral		Contralateral		No.	%	Nº	%
I	6	6	100
II	53	51	96.2	2	5.7	2	3.8%	2	4.3
III	57	53	92.9	4	6.4%	1	1.7%	2	3.8	2	3.8
IV	29	28	96.6	1	2.0%
V	13	13	100	0
Total	158	151	95.6%	7	4.4%	3	6.8%	4	2.5%	3	1.9%
Abbreviations: No.: number of cases; %: percentage; VUR: vesicoureteral reflux; PO: postoperative period; Contralat: contralateral

Comparisons were made of the results of the extravesical reimplantations (101 children with 158 refluxing ureters) versus the intravesical reimplantations (40 children with 68 refluxing ureters), operated upon in the same center:

1. Immediate complications (Table 8). Early complications were recorded in 22 children (21.78%) of the extravesical reimplantation group, and in 23 children (57.5%) belonging to the intravesical group – the difference being statistically significant (p: <0.0001). Pain and hematuria were both significantly more frequent in the intravesical group than in the extravesical series. No significant intergroup differences were recorded for nausea and vomiting, urinary retention or obstruction.

Table 8

Immediate complications of reimplantations. Comparison between extra- and intravesical surgery

	Extravesical 101 children / 158 ureters	Intravesical 40 children / 68 ureters	Statistical significance
No. of children	22 (21.8%) 28 complications	23 (57.5%) 27 complications	p < 0.0001
Nausea and vomiting	11 (11%)	3 (7.5%)	NS
Pain	10 (10%)	11 (27.5%)	p <0.04
Hematuria	1 (1%)	11 (27.5%)	p < 0.0001
Urinary retention	5 (5%)	1 (2.5%)	NS
Obstruction	1 (1%)	1 (2.5%)	NS
Abbreviations: NS: nonsignificant

2. Comparison of days of indwelling Foley catheter. The mean duration was 2.6 days (range 2-9) in the extravesical group, and 3.4 days (range 2-7) in the intravesical group – the difference being statistically significant (p: <0.0001).

3. Comparison of hospital stay. The mean duration was 2.86 days (range 2-9) in the extravesical group, and 3.65 days (range 2-7) in the intravesical group – the difference being statistically significant (p: <0.0001).

4. No statistically significant intergroup differences were observed in late complications, persistent ipsi- or contralateral VUR.

DISCUSSION

The current goals of medical care are to limit hospital stay and costs without adversely affecting patient quality of life. On considering the different open ureteral reimplantation techniques, the extravesical approach is seen to involve less morbidity than the intravesical approach, due to the reasons commented above^3,7.

The fundamental principles of antireflux surgery are the creation of a submucosal tunnel of sufficient length; the existence of firm muscle support of the ureter; and the absence of ureteral tension^8-10. The tunnel length should be in a proportion of 4-5/1 with respect to the ureteral diameter¹¹. In the present series we used the classical original technique of Lich-Gregoire^3,4, without ureteral deinsertion, and with the particularities indicated under Materials and Methods.

The open surgical techniques for VUR offer a 95% success rate for grades I to IV, versus 80% in the case of grade V presentations that require modeling¹². In the case of the extravesical procedures the percentage ranges from 90-99%^7-9,13,14. In the present series, the percentage success rates for all reimplantations and for the extravesical reimplantations considered isolatedly were quite similar: 95% for all grades of VUR, and between 93% for grade III and 100% in grades I and V (Tables 6 and 7).

The risk of ureteral obstruction is practically inexistent with the extravesical procedures, and only transient ureterohydronephrosis has been documented in 3% of cases¹³. In contrast, such problems are found in 1-9% of cases in which intravesical surgery is performed¹⁵. Paradoxically, the extravesical techniques are the most appropriate for easy placement of the double-J catheter in cases of ureterovesical obstruction, since the longitudinal trajectory of the ureter is not altered.

Contralateral VUR presents in 5.3-32% of all antireflux procedures^6,15-17 – the underlying etiology being uncertain. The condition may result from surgical distortion of the trigone during reimplantation; the existence of prior unknown contralateral VUR; the appearance of bladder dysfunction; or because on eliminating high-grade VUR bladder pressure increases, and the pop-off mechanism destabilizes the contralateral ureter^12,16-18. The incidence varies according to the surgical technique used for unilateral reimplantation: 0-19% with the Cohen procedure; 9-27% with the Politano-Ledbetter technique; 17% with the Glen-Anderson procedure; 20% with the Paquin approach; and 7% with endoscopy^15-18. Minevich et al.¹⁶, in a review of the literature, recorded a 5.3% incidence of contralateral VUR in 206 extravesical reimplants. The results of this series show an incidence of 6.8% of the unilateral reimplants (47 children), and the operated side presented VUR grade II in two cases and grade III in the rest – thus excluding the pop-off mechanism. Logically, in the literature contralateral VUR is less frequent in the procedures that induce less trigone destructurization, such as the extravesical and endoscopic approaches^12,16,17; however, in our series there were no cases in the unilateral reimplants performed with the Cohen technique – though the difference failed to reach statistical significance. To avoid this complication, in the presence of prior contralateral VUR, regardless of its grade, bilateral reimplantation is advised. Patient age, the contralateral VUR grade and the appearance of the ureteral meatus appear to play no role in the origin of the problem^15-18. Contralateral VUR resolves spontaneously in two-thirds of cases, while surgery is required in the remaining third^12,15,16. In our series, all contralateral VURs healed under observation and with the provision of antibiotic prophylaxis.

Urinary retention is the most feared immediate complication of extravesical antireflux procedures, though the problem is infrequent and transient – lasting a maximum of one month. Intermittent catheterization is required in 26% of such cases^5,13,14,19. It is the most serious complication, since it can cause bilateral ureterohydronephrosis and acute renal failure if catheterization is not performed (as in three of our patients). This problem has not been recorded in the unilateral extravesical procedures or with the uni- or bilateral Cohen technique^8,14,18-21. It is only seen in bilateral extravesical reimplants performed simultaneously^5,10,14,19, with a prevalence of 1.3-26%^{5-10,13,14,22}. Our incidence was 8.6% of the extravesical bilateral reimplants, though only three children (5.2%) required repositioning of the Foley catheter, and one (1.7%) posteriorly needed intermittent clean catheterization for one month. All patients recovered their normal micturition pattern. Bladder dysfunction has also been described in 2.1% of patients subjected to the Politano procedure, probably because it is a combined intra- and extravesical technique^19,20.

Studies have been made with the different variants of the Lich-Gregoire technique, and it has been seen that urinary retention is somewhat more frequent with the ureteral deinsertion and advancement variant of Zaont, since in this case dissection of the UVJ is greater – though the differences are not statistically significant^6,13,19.

It has been shown to be more common in high grade VUR, in children under three years of age, and in males¹³, though these observations do not coincide with our own findings – since there was only one child under three years of age; 60% were high grade on one side only; and 60% of the patients were girls (Table 4). Postoperative urinary retention does not influence the resolution of VUR⁸.

The mechanism underlying bladder dysfunction is not known, though alterations in bladder innervation are believed to be involved^9,10,19-21. A number of anatomical and experimental studies have been carried out to determine the neuroanatomy and neurophysiology of this zone, and to define a physiopathological explanation for bladder dysfunction^19-21. The studies of Leissner et al.¹⁹, in human cadavers, showed that the pelvic plexus – responsible for bladder voiding – is located on the dorsal and medial aspect of the UVJ, and that branches of the plexus for a network around the dorsal ureter, trigone and rectum. Yucel and Baskin²⁰, in human fetuses aged 21-40 weeks, and using immunohistochemical techniques, observed a very similar innervation. The experimental work of Martínez-Portillo²¹ showed that bilateral stimulation of the pelvic plexus nerves induces bladder contractions with pressures of 50 cm of water, and that unilateral stimulation only induces ipsilateral bladder contraction with vesical pressures of 18 cm of water. It is not known whether bladder dysfunction is caused by sectioning of the innervation, nerve distension during traction upon the bladder, or thermal injury – though the duration of the condition points to one of the latter two possibilities, rather than to transection. In any case, aggressive dissection of the UVJ, excessive coagulation or the ureteral anchoring sutures when the Zaont variant is used can induce alterations in the innervation^6,19,21. In our series, ureteral dissection was minimal and limited to the ventral surface of the ureter and to the UVJ, to avoid damage to the perivesical nerves and voiding dysfunction. In order to avoid bladder dysfunction, Leissner et al.¹⁹ recommend performing bilateral ureteral reimplantations in two different surgical sessions spaced three months apart. Other authors^14,21 recommend avoiding the procedure in children with a prior history of bladder dysfunction. On the basis of our results, we have introduced some technical modifications in bilateral extravesicular reimplantation, in order to minimize damage to the nerves of the pelvic plexus that may result in transient retentive bladder dysfunction. In these cases, detrusor dissection is carried out only with Metzenbaum scissors; cauterization, where needed, is carried out with bipolar forceps. We avoid Y-dissection of the UVJ, limiting dissection of the distal ureter to the crossing of the lower bladder tributary vessels.

The administration of anticholinergic agents in the immediate postoperative period does not appear to play any role in urinary retention. These drugs are systematically used in all surgical procedures requiring postoperative bladder catheterization, and when the catheter and medication are withdrawn, all patients present a normal micturition pattern.

Nausea and vomiting, which until recently lacked importance, have received relevance because they prolong hospital stay and expenditure. On comparing the complications, days of bladder catheterization and duration of hospital stay between the extra- and intravesical procedures, statistically significant differences were observed in the number of immediate complications such as pain and hematuria, days of bladder catheterization and hospital stay, which were greater with Cohen-type reimplantations (Table 8).

The factors that influence hospital stay are: the age of the patient, associated morbidity, surgical procedure, surgical time, and postoperative management⁷. For all these reasons, the Lich-Gregoire antireflux procedure meets the requirements needed for application in the context of short hospital stay.

At present, endoscopic treatment with hyaluronic acid dextranomer is an attractive alternative for the surgical management of VUR. The procedure is performed on an outpatient basis and requires only minimal postoperative analgesia. However, efficacy and morbidity over the long term have not yet been established. The short-term resolution of VUR ranges from 70-89% for reflux grades I to IV^23,24, in contraposition to open vesicoureteral reimplantation, which offers a higher healing rate over the long term (94-99%)^7-9,13,14.

CONCLUSIONS

1. The Lich-Gregoire technique is effective for correcting uni- and bilateral VUR.

2. Children operated upon with the extravesical procedures have a better immediate postoperative course than those subjected to intravesical surgery: less discomfort, pain and hematuria.

3. The Lich-Gregoire technique can cause transient bladder dysfunction in bilateral cases (8.6% in our series).

4. It is a short hospital stay procedure.

This study was carried out during the stay of the first signing author in the Miami Children’s Hospital (Florida, USA), with a grant from the Foundation for Research in Urology, destined for stays in foreign hospitals.

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24. Kirsch AJ, Perez-Brayfield M, Smith EA, Scherz, HC: The modified sting procedure to correct vesicoureteral reflux: improved results with submucosal implantation within the intramural ureter. J Urol. 2004;171(6):2413-2416.[PubMed]

Dr. M. García-Mérida

E-mail: mgmerida@terra.es

(Manuscript received on February 14, 2006)