Prognosis

Animals with CRF often survive for many months to years with a good quality of life. The diagnosis is more difficult in dogs because the symptoms occur later. Compensatory mechanisms maintain a state of biochemical homeostasis despite significant renal dysfunction. As renal failure progresses, the animals are forced to live in a narrowed state of physiologic activity. A uraemic crisis may be suddenly precipitated by decreased intake of nutrients or water, development of concomitant diseases or inappropriate administration of certain drugs.

Progression of CRF: role of the compensatory mechanisms

Chronic renal failure is an inherently progressive disease. Its progression either results from continuing renal damage induced by the nephropathy or from mechanisms independent of the initiating lesion and responsible for the spontaneous self perpetuation of the disease.

Mechanisms of compensatory adaptation

Hyperfiltration model : compensatory hyperfiltration and intraglomerular hypertension occur initially as an adaptive response to a reduction in the number of nephrons but eventually leads to progressive proteinuria, glomerular sclerosis and loss of functional nephrons.

Nephrocalcinosis causes tubular-interstitial injury characterised by tubular atrophy and dilation, interstitial fibrosis and interstitial inflammation. Excess PTH, caused by hyperphosphatemia, promotes too great a flux of calcium into these cells, thus activating enzymes that destroy phospholipids, proteins, and nucleic acids. These effects result in cell dysfunction and death.