Impaired bone growth after ileal augmentation cystoplasty.

PURPOSE

We evaluated how ileal augmentation cystoplasty predisposes growing animals to hyperchloremic acidosis and abnormal skeletal development.

MATERIALS AND METHODS

Weanling female Wistar rats weighing 35 to 50 gm. underwent ileal augmentation cystoplasty or sham operation consisting of a similar ileal resection and closure (ileoileostomy). Both groups were stressed with 1% ammonium chloride loading. Serial bone densitometry measurements, weight and blood gas studies were performed in an 8-week growth period. Femur bone ashing and mineral analysis, arterial blood gas studies and serum bone mineral determinations (calcium, magnesium and phosphorus) were obtained at study conclusion.

RESULTS

Augmented and control animals had similar serum calcium, phosphorus and magnesium concentrations. In augmented animals metabolic acidosis developed with respiratory compensation and decreased mean serum bicarbonate plus or minus standard deviation compared to controls (18.34 +/- 3.23 versus 21.76 +/- 2.46 mEq./l., p <0.003). Growth curves of both groups were similar, although augmented animals had shorter femur lengths than controls (p <0.04). Bone density results were mixed. Whole body bone density was decreased (p <0.05), while bone ash and mineral content (except phosphorus) were not. When rats with augmentation cystoplasty given 1% ammonium chloride were fed an equal molar diet of sodium bicarbonate, metabolic acidosis and bone mineral density normalized to control values.

CONCLUSIONS

Acid challenged weanling rats that underwent ileal augmentation cystoplasty demonstrated decreased bone mineral density and growth compared to controls. These changes were prevented by bicarbonate replacement.