Urinary protein loss in the dog: nephrological study of 29 dogs without signs of renal disease.

In 29 dogs without any sign of renal disease, the total daily urinary protein loss was measured and related to renal morphology. The daily urinary protein loss was less than 10 mg/kg bodyweight in most dogs (24 out of 29). The median value of the protein loss in dogs with and without lesions differed significantly, as well as the median values of the ages of dogs with and without lesions. Polyacrylamide gel electrophoresis of urinary protein revealed the presence of albumin, high molecular weight and low molecular weight proteins. With immunofluorescence, especially, the presence of IgA (21 out of 28) and IgM (17 out of 28) was shown. In 12 out of 14 dogs with glomerular lesions IgA deposits were demonstrated (graded as +/- in two dogs and as + in 10 dogs), whereas in nine out of 14 dogs without glomerular lesions IgA deposits were demonstrated (graded as +/- in four dogs and as + in five dogs). The presence of IgA was significantly related to the presence of glomerular lesions (P less than 0.05). Fibrinogen degradation products were not detectable in urine from 15 of 23 dogs.