Effect of augmentation cystoplasty on bone metabolism in chronic uremic rats

We examined the impact of urinary diversion using several types of intestinal segments on the bone metabolism of growing rats with renal insufficiency.

A total of 110, 8-week-old Sprague-Dawley rats underwent 2-stage subtotal nephrectomy by removal of 5/6 of the renal mass or sham operation. Except for a uremic control group all uremic rats underwent enterocystoplasty using stomach, ileum or colon. An additional group with colic augmentation received the bisphosphonate ibandronate. Bone mineral density of the tibia and lumbar spine, serum analysis and urinary excretion of the bone resorption marker deoxypyridinoline were determined monthly for 12 weeks. At study termination bone ash weight, bone mineral analysis and serum osteotropic hormone levels were determined.

All groups undergoing subtotal nephrectomy had a decreased endogenous creatinine clearance of approximately 30%. The lowest gains in tibial and lumbar spine bone mineral density were observed in animals undergoing ileocystoplasty. Femoral calcium content was significantly decreased in uremic ileocystoplasty rats compared with uremic controls. These changes were not induced by alterations in serum pH, nor were they associated with accelerated bone resorption as assessed by deoxypyridinoline. Ibandronate prevented changes related to bone resorption and increased bone mass.

Our results suggest that cystoplasty using ileum segments can aggravate renal bone disease in growing rats with mild uremia. Since the acid-base state was unchanged, other properties of the interposed ileum segment must be responsible for the negative effect on bone metabolism.