Changes in bone structure after augmentation cystoplasty in chronic uraemic rats

OBJECTIVE: To investigate the effect of urinary diversion using several types of intestinal segments on cortical and cancellous bone structure of growing rats with renal insufficiency. MATERIAL AND METHODS: In all, 110 female Sprague-Dawley rats (8 weeks old) had either a two-stage subtotal nephrectomy by removing five-sixths of the renal mass, or a sham operation. Except for a uraemic control group, all uraemic rats then had an enterocystoplasty using stomach, ileum or colon (20 animals per group). An additional group with colic augmentation received the bisphosphonate ibandronate. After 12 weeks, the left tibia was assessed using peripheral quantitative computed tomography and bone histomorphometry. RESULTS: After subtotal nephrectomy all groups had approximately 30% less endogenous creatinine clearance. Renal failure alone or in association with gastric or colic augmentation induced only negligible changes in the mass and structure of cortical and cancellous tibial bone. In contrast, rats after ileal augmentation and renal failure had a significant reduction in cancellous bone mineral density (P < 0.05) whereas the reduction in trabecular bone area and volume was not statistically significant. Furthermore, ileocystoplasty caused a decrease in trabecular number and perimeter, increased trabecular separation and enlarged bone marrow space, whereas ileocystoplasty had no effect on cortical bone. The changes were not associated with alterations in serum pH. Ibandronate treatment in the colonic cystoplasty group increased trabecular bone mass and structural variables over the untreated colonic cystoplasty group. CONCLUSIONS: These results suggest that cystoplasty using an ileal segment causes a decrease in bone mass and architecture in growing rats with mild uraemia. It remains open to question whether the results obtained from experimental animals can be directly extrapolated to the clinical situation.