Long-term metabolic effects of urinary diversion on skeletal bone: histomorphometric and mineralogic analysis

OBJECTIVES. To evaluate the long-term influence of different types of intestinal urinary diversion on skeletal bone and its mineral content. METHODS. Densitometry was used to estimate bone mineral content, and bone biopsies were analyzed with histomorphometric technique. The study comprised 20 patients with conduit urinary diversion and 19 with cecal continent reservoir, all followed up for more than 5 years, with normal or near-normal renal function. RESULTS. Bone mineral content did not differ significantly between the patients with cecal continent urinary reservoir and those with conduit diversion or between these groups and a reference group. At the cellular level, the histomorphometric analysis revealed no defective bone mineralization or increased bone resorption in either group of patients. The trabecular bone volume was greater than normal in the reservoir group, but not in the conduit group. The appositional rate was significantly below normal in both groups of patients, but did not differ between conduit and reservoir patients. CONCLUSIONS. Subtle changes in electrolytes and acid-base homeostasis identified in adults with intestinal segments incorporated in the urinary tract and with largely normal renal function do not seem to influence bone mineralization in the long term. At the cellular level, a lower than normal appositional rate was found in the patients with conduit or continent urinary diversion. In the latter group, this finding, together with increased trabecular bone volume, may indicate a decrease of bone turnover.