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THE common causes of glucosuria are diabetes mellitus, stress-related hyperglycaemia (in cats), inherited or acquired defects in renal tubular transport proteins, or damage to tubular epithelial cells in acute renal failure. Glucosuria is rarely observed in non-specific chronic kidney disease in dogs, cats or human beings.
Glucosuria may be a consequence of hyperglycaemia exceeding the renal tubular maximum (Tm G) for glucose reabsorption, whether the Tm G is normal or abnormal. Stress-induced transient glucosuria is very common in cats ( Wamsley and Alleman 2007 ), in which Tm G is often exceeded with plasma glucose concentrations above 12 to 16 mmol/l. In dogs, Tm G for glucose reabsorption is exceeded with plasma glucose concentrations above 11 to 12 mmol/l (DiBartola 2005).
A form of chronic kidney disease was described in Norwegian elkhounds in the 1970s; three of the six original cases had glucosuria of ++ (scale 0 to ++++). Breeding trials indicated that the condition was heritable, as 21 of 56 offspring of affected dogs also had kidney disease. Of these 21 offspring, three had persistent glucosuria ( Finco 1976 ). Two of 12 dogs tested had more pronounced α-aminoaciduria than healthy dogs. Affected dogs developed clinical signs at different ages, between three months and six years of age. Serial biopsies revealed periglomerular fibrosis to be one of the earliest histopathological changes in the renal tissue of affected animals ( Finco and others 1977 ).
During the 1990s, familial kidney disease was detected in Norwegian elkhounds in the Netherlands ( Wiersma and others 2007b ). Mild to severe histopathological changes were observed, again often with periglomerular fibrosis as a prominent feature. In 19 of 55 dogs tested (47 related and eight unrelated), kidney disease was established by the observation of histopathological changes in biopsy material, a reduced glomerular filtration rate, or both. Five of the affected dogs had mild proteinuria (urinary protein:creatinine ratio 0.29 to 1.33) and three had glucosuria; only one dog had concomitant glucosuria and proteinuria ( Wiersma and others 2007b ).
Pedigree analyses of related dogs revealed an inheritance pattern consistent with autosomal dominant inheritance, although testing for COL4A3 /COL4A4 suggests that these genes are not likely candidates for the disease in the family from the...