Endoscopic treatment of vesicoureteral reflux using calcium hydroxyl apatite in dogs

BACKGROUND: Injection of biomaterial to suburetral region, using minimally invasive procedure, has become an interesting topic for urologists to treat vesicoureteral reflux. The objective of this study was to evaluate the feasibility of injecting newly introduced calcium hydroxyl apatite to suburetral region, for treating an experimentally induced vesicoureteral reflux in dogs. FINDINGS: Bilateral vesicoureteral refluxed (VUR) mixed breed dogs (n = 12; 10-15 kg live weight, 3-6 months of age) were selected for this study. The presence and grade of the reflux were determined using cystography. Accordingly, 6 dogs displayed grade 1 & 2 and the other 6 showed grade 3 & 4 bilateral VUR. Every single dog, with bilateral VUR, underwent endoscopic treatment and received an injection of calcium hydroxyl apatite (an Iranian made product) into the left (treated side) and an injection of the similar volume of normal saline in to the right (control side) subureteric space. One week, 3 and 6 months after treatment, cystography was performed. On each occasion, 4 dogs were euthanized by gas inhalation and biopsy samples were collected for histopathological study from ureter, bladder, kidney, lung and spleen in order to investigate the biomaterial migration into different organs. Data were analyzed using Chi-squared test. In control sides, radiographs confirmed the same grade of VUR, found at the initiation of the study. VUR was resolved in 100% (6/6) of Grade 1 & 2 and 83.33% (5/6) of Grade 3 & 4 in treated side. Therefore, the total success rate of this study was 91.67% (11/12). Macroscopic examination of the vesicouretral region of the treated side revealed a firm and consistent biomaterial mass at the site of injection. Histological findings confirmed inflammation at treated side. In contrast, there was no tissue reaction on control side. There was no evidence for biomaterial migration in macroscopic and microscopic observations in this study. CONCLUSION: In the present study, a new biocompatible material produced a firm, consist and sustainable biomaterial mass in the suburetral region for treating vesicouretral reflux without any evidence of biomaterial migration.