Subtotal nephrectomy in the rabbit: a model of chronic hypercalcemia, nephrolithiasis, and obstructive nephropathy

The association of a critical reduction in renal mass with the subsequent destruction of remaining nephrons has been observed in several species. We studied this process in experimental rabbits after 1 2/3 nephrectomy to define the course and its pathogenesis in this species. Control rabbits underwent sham operative procedures. After renal ablation, rabbits became increasingly cachectic and developed polyuria and hypertension. Despite food intake similar to that of controls (grams per kilogram per day), experimental rabbits developed severe hypercalcemia by 5 to 8 weeks after renal ablation, a change that persisted until death. During the study 17 experimental animals died of uremia 9 to 27 weeks after surgery, and the remaining seven experimental and 25 sham-operated rabbits were sacrificed at 5 to 7 months. At death, 19/24 experimental rabbits had severe obstruction of their collecting systems by concretions of gravel (n = 3) or large calcium carbonate stones (n = 16). Renal biopsy at 4 weeks revealed focal interstitial round cell infiltration progressing by 12 weeks to diffuse tubulointerstitial inflammation and fibrosis. Histologic evidence of obstruction was also evident at this time and became extensive on all subsequent examinations. By contrast, the glomeruli remained well preserved without evidence of sclerosis. We speculate that chronic hypercalcemia and, perhaps more significantly, urinary obstruction may have altered intrarenal hemodynamics and prevented the development of progressive sclerosis observed in the rat remnant kidney model. The present study describes an experimental model of chronic hypercalcemia and spontaneous calcium carbonate nephrolithiasis.