Urinalysis - Glucose
Introduction
Glucose is normally found in the urine. The upper level of physiologic glucosuria in the first morning urine is about 0.8 mmol/L glucose. This concentration is too small to be detectable by test strip. Glucose excretion by urine (glucosuria) depends on glucose concentration in the blood and renal function, i.e. on the renal threshold a for glucose (serum glucose concentration 8-10 mmol/L).
Glucosuria per se is not an evidence of diabetes mellitus, as it may also ensue from other causes. There are three types of glucosuria:
1. Alimentary glucosuria
Diets rich in carbohydrates or intake of great amounts of glucose (e.g. glucose load tests) may cause glucosuria also in healthy individuals, because the serum concentration of glucose in exceeds renal threshold over a certain period of time.
2. Glucosuria in diabetic patients
Glucosuria occurs in a majority of diabetic patients. The amounts of excreted glucose depend on the blood glucose concentration and renal threshold, which is higher in diabetic patients than in healthy individuals. Demonstration of glucosuria is of utmost importance for early recognition, control, and self-control of diabetes mellitus.
3. Renal glucosuria
In individuals with impairment of tubular glucose reabsorption, glucosuria occurs at a normal blood glucose concentration.
Glucosuria frequently occurs in pregnancy, due to the reduced kidney function.
Beside glucose, other sugars can also be found in the urine, e.g. fructose or some pentoses following an abundant fruit meal, or in pregnant women excreting lactose. The finding of these sugars in the urine has no diagnostic relevance, however, a finding of galactose in the urine is indicative of a serious illness in children.
Low and false-negative results are usually due to high amounts of ascorbic acid in the urine, excreted after vitamin C intake. In suspected cases, the test should be repeated at least 10 hours after the last vitamin C intake.
|
Print ::