Impaired bone metabolism following augmentation cystoplasties in growing rats

The aim of this study was to evaluate the possible risk of impaired bone metabolism following augmentation cystoplasties with different gastrointestinal segments.

60 young rats underwent augmentation cystoplasties using gastric, ileal or sigma segments, or sham operations. An additional group undergoing sigma-cystoplasty received the bisphosphonate ibandronate to inhibit osteoclast-mediated bone resorption. Bone mass in the lumbar spine and tibia was analyzed monthly by in vivo densitometry. Bone turnover was assessed monthly using current bone metabolism markers for a period of 16 weeks. Bone ashing and serum analyses of the osteotropic hormones parathyroid hormone (PTH), and 25-OH vitamin D3 were performed at study conclusion.

Following ileocystoplasty, reduced bone mineral density (BMD) was seen throughout the observation period; this was pronounced in the trabecular bone. The decline in BMD was associated with decreased serum 25-OH vitamin D3 levels. Following sigmacystoplasty, bone calcium content was significantly decreased; this could be prevented by ibandronate. No skeletal changes occurred in the gastrocystoplasty group. Serum pH was not altered in any group, and markers of bone resorption indicated normal bone resorption rates.

There is a significant correlation between impaired bone metabolism and the type of segment used for bladder augmentation. While the use of the ileum (and probably the colon too) causes osteopenia, gastrocystoplasties seem to have little influence on bone turnover.