How chronic kidney disease affects bone strength in dogs

Abstract

BACKGROUND: Chronic kidney disease (CKD) is common in companion animals. Secondary hyperparathyroidism is an inevitable consequence of the disease and may have deleterious effect on the bone; however, the information regarding CKD-associated bone abnormalities in companion animals is scarce. HYPOTHESIS/OBJECTIVES: Dogs with CKD have decreased bone quality compared to dogs without CKD. ANIMALS: Nine dogs diagnosed with naturally occurring CKD for at least 6 months and 9 age-matched controls. METHODS: Dogs with CKD were enrolled and compared to 9 age-, weight-, and sex-matched control dogs with no evidence of CKD. Samples were assessed using light microscopy, mechanical testing, and microcomputed tomography. Variables evaluated included microstructural features such as number, size, and density of Haversian canals, resorption cavities and osteocytic lacunae, bone mineral density, porosity and Young's modulus. RESULTS: Median lacunae size was significantly smaller in the CKD group compared to the control group (P = 0.001). Resorption cavity density was higher in the CKD compared to the control group (10 [8-14] vs. 7 [4-9]/mm, respectively, P = 0.001). Overall porosity was significantly (2.3-fold) higher in the CKD compared to the control group. There was no difference in Young's moduli between groups. CONCLUSIONS AND CLINICAL IMPORTANCE: Naturally occurring CKD affects bone quality in dogs, but these changes are relatively mild and likely not to be manifested clinically. The duration of the disease in dogs evaluated here is short compared to cats and human patients, likely accounting for the more subtle changes in dogs compared to other species.