Renal Glycosuria

Renal glycosuria, in which there is glucose in the urine in subjects demonstrated to have normal blood glucose levels, who are not starved and who have no other urinary abnormality, is uncommon.

Such patients have either a defect in the tubular threshold for reabsorption of glucose in the proximal tubule (a 'splayed' reabsorption curve) or a defect in the maximal tubular reabsorption of glucose.

Both autosomal dominant and recessive inheritance have been postulated. It has no clinical significance except in the differential diagnosis of patients with diabetes mellitus or other tubular disorders such as the Fanconi syndrome.

If glycosuria occurs because a normal renal threshold has been exceeded this is usually indicative of impaired glucose tolerance or frank diabetes. It can occur in the non-diabetic if a substantial amount of food high in sugar is consumed and transiently overwhelms the insulin response causing glycosuria.

In most affected individuals, the condition causes no apparent symptoms (asymptomatic) or serious effects. When renal glycosuria occurs as an isolated finding with otherwise normal kidney function, the condition is thought to be inherited as an autosomal recessive trait.