A model of sterile vesicoureteric reflux in the sheep

Abstract

Eighteen Coopworth ewe lambs were divided into three groups based on the initial cystourethrogram and cystometry findings at 5-7 weeks of age: group 1, 6 lambs with spontaneous low-pressure bilateral vesicoureteric reflux (VUR) on bladder filling were used to study the natural history of reflux; group 2, 5 lambs with no VUR detected were used to establish an experimental model of bilateral VUR using an unroofing surgical procedure; group 3, 7 lambs with spontaneous VUR detected during micturition had the same surgical procedure to increase the degree of VUR. All three animal groups were followed for 4-10 months. Spontaneous VUR was demonstrated in 13 of 18 lambs (25/36 ureters). The presence and severity of spontaneously occurring reflux in group 1 lambs diminished with increasing age. VUR was created successfully in group 2 and increased in degree in group 3 animals. The only significant histological finding in all three animal groups with grades II and III VUR was distal renal tubular dilatation. The sheep is a useful and readily available animal for studying VUR. During 4-10 months of follow-up, sterile reflux without bladder outflow obstruction resulted in distal renal tubular dilatation, but no renal parenchymal damage.

Clinicopathological study of vesicoureteral reflux (VUR)‐associated pyelonephritis in renal transplantation

“…As some of these morphological features could be non‐specific, they might be found in chronic allograft nephropathy. However, distal tubular dilatation has been found to be a specific histological feature during VUR, as demonstrated in experimental sheep kidneys (14). In our study, both proximal and distal tubules were found to be dilated in the biopsy tissues obtained from transplant patients with VUR.…”

Invited Commentary

“…The small bladders in these infants have urodynamic abnormalities with high voiding pressures. Sterile vesicoureteral reflux in the absence of elevated voiding pressures or bladder dysfunction does not produce renal damage (including scars) (17). Renal growth rates are unaffected by the initial severity or the persistence of vesicoureteral reflux, and no new renal scars develop after puberty (18).…”