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Background:
In recent years, indications for endoscopic injection of dextranomer/hyaluronic acid copolymer (DxHA) in the treatment of vesicoureteral reflux (VUR) have expanded. The Food and Drug Administration did not approve DxHA injection in duplicated collecting systems until 2007. Although recent studies have shown promising results of DxHA injection in duplicated systems, outcomes data in this population is still limited. We sought to compare our success rates of DxHA injection in duplicated versus single systems.
Methods:
A retrospective case control analysis was performed in patients undergoing DxHA injection for primary VUR between 2001 and 2014 at our institution. Patients with duplicated systems were matched by VUR grade, surgeon, and age at intervention to single system control patients on a case by case basis. Duplex systems with VUR into both upper and lower pole ureters were matched according to the higher grade of VUR present. Treatment success was defined as complete resolution of VUR on postoperative voiding cystourethrogram. Fisher’s Exact test was used for categorical comparisons, and t-test or Mann-Whitney U test was used for continuous variables.
Results:
Between 2001 and 2014, 364 patients underwent DxHA injection for primary VUR. Of these patients, 22 cases with duplex systems were identified and matched to 22 control patients with single systems. All but two patients were matched by the exact grade of VUR. One patient with grade II VUR in a duplex system was matched with a single system control with grade III VUR, and one duplex system with grade IV VUR was matched with a grade III control. (Table 1)
Success rates were 59.1% in duplicated systems and 81.8% in single systems. This difference was not statistically significant. (p=0.267) (Table 2)
Information on injection techniques was available in 19 cases and 19 controls. Techniques included subureteral transurethral injection (STING) (9 controls, 11 cases), hydrodistention-implantation technique (HIT) (3 controls, 2 cases), double HIT (1 control, 3 cases), and HIT/STING. (6 controls, 3 cases)
Due to our limited cohort size, we were unable to match cases based on injection technique. However, a subgroup analysis was performed on ten cases treated with the same injection technique as their matched controls. VUR resolution rates were not significantly different between these two groups. (80% in cases, 70% in controls, p=1.0)
Conclusions:
Although the difference in the success rate of DxHA injection between duplex versus single systems was not statistically significant (59.1% versus 81.8%), this difference is noteworthy. A multicenter study with increased sample sizes and comparison by injection technique could validate these findings and result in a more accurate estimate of success rates.
We continue to enroll patients in a prospective database in hopes of strengthening the existing literature.
Table 1: Patient characteristics

Characteristic	Duplex systems (case)	Single systems (control)	p-value
Patients	22	22
VUR Grade, n (%)			0.927
I	1 (5%)	1 (5%)
II	9 (41%)	8 (36%)
III	6 (27%)	8 (36%)
IV	6 (27%)	5 (23%)
Age at Surgery, years, mean (±SD)	7.2 (± 3.5)	7.2 (± 2.9)	0.911
Gender, n (%)			0.698
Female	19 (86%)	17 (77%)
Male	3 (14%)	5 (23%)
Age at Diagnosis, years, mean (±SD)	6.2 (± 4.0)	5.9 (± 3.0)	0.771
Follow-up, months, median (range)	19 (3-92)	21 (3-104)	0.981

Table 2: Treatment outcomes

VUR Outcome, n (%)	Duplex systems (case)	Single systems (control)	p-value
Resolved	13 (59.1%)	18 (81.8%)	0.267
Improved	4 (18.2%)	1 (4.5%)
Stable	4 (18.2%)	3 (13.6%)
Worsened	1 (4.5%)	0