Keynote Message

By definition, ageing represents a persistent decline in the specific fitness components of an organism, mainly due to degeneration processes. In kidney, the biologic consequences of aging include progressive structural and functional changes, and these are among the most dramatic of any organ system. The histologic and ultrastructural features of renal ageing have been insufficiently investigated in veterinary medicine, but, as far as we are aware, they tend to mimic those in humans. The anatomical, structural modifications include a decreased number of functional glomeruli from an increased prevalence of nephrosclerosis (glomerulosclerosis and tubular atrophy with interstitial fibrosis). To some extent, there is a compensatory hypertrophy mechanism of the remaining nephrons that initially preserves the renal function but progressively leads to a vicious circle of self-destruction, accelerating the probability of their destruction. The aforementioned structural changes have an impact on the glomerular filtration rate, altered tubular handling of creatinine, reduction in sodium reabsorption and potassium secretion. These changes can alter the normal renal function, causing a higher susceptibility to infectious diseases, toxic and pharmaceutical treatment, impair the ability of the kidney to withstand and recover from injury, contributing to increased propensity to develop progressive CKD. It's also true that the structural changes of aging kidneys are nonspecific and can be seen in many pathological conditions (i.e., FSGS) and it should be emphasized that comorbid conditions that are frequently found in old animals can amplify these morphological alterations.

In the near future, improved understanding of the mechanisms of renal aging in veterinary medicine will definitely help to optimize management of senior dogs and cats.

Key References

1.  Cianciolo RE, Benali SL, Aresu L. Aging in the canine kidney. Veterinary Pathology.2016;53:299–308. DOI: 10.1177/0300985815612153.

2.  Glassock RJ, Rule AD. The implications of anatomical and functional changes of the aging kidney: with an emphasis on the glomeruli. Kidney International.2012;82:270–277.

3.  Horster M, Kemler BJ, Valtin H. Intracortical distribution of number and volume of glomeruli during postnatal maturation in the dog. Journal of Clinical Investigation. 1971;50:796–800.

4.  Martin JE, Sheaff MT. Renal ageing. Journal of Pathology. 2007;211:198–205.