December 19, 2000
Question from a physician in India:
I am practising as a diabetic specialist from India, and recently got a query for the treatment of renal glycosuria in a nondiabetic patient. Usually we don’t give any treatment but I am eager to know other causes of renal glycosuria and their treatment modalities.
Renal glycosuria is defined as the excretion of excessive amounts of glucose in the urine in the presence of normal filtered loads of glucose. Implicit in the definition is the concept of an abnormality in tubular glucose transport. Such an abnormality may occur in association with generalized proximal tubular dysfunction such as in the Fanconi’s syndrome. FamiliaI renal glycosuria is an isolated defect in renal glucose transport in which intestinal glucose transport is normal. The renal tubular defect in glucose transport can occur secondary to a decrease in maximal tubular reabsorption of glucose (Type A) or an increase in splay of titration curve of glucose reabsorption giving a reduced threshold for glucosuria (Type B). The diagnosis of familial renal glycosuria includes (1) exclusion of other causes of mellituria (pentosuria, fructosuria, sucrosuria, maltosuria, galactosuria, lactosuria); (2) glycosuria in the presence of a normal filtered load of glucose and a normal glucose tolerance test; (3) exclusion of other tubular defects such as excessive uricaciduria, phosphaturia, and aminoaciduria; (4) family history of glycosuria and (5) absence of progression to diabetes mellitus. Glycosuria without hyperglycemia also may be observed in either pregnant women or patients with renal disease and glomerular filtration rates less than 15 ml per minute.
Familial glycosuria is a benign disease that has an excellent prognosis and requires no treatment. Prolonged starvation must be avoided as it can lead to hypoglycemic episodes especially in Type A cases.