Glucosuria (glucose in the urine)
Glucosuria is the detection of glucose in the urine. In the urine of a healthy person, glucose is contained in a very low concentration (0.06-0.083 mmol / l). Therefore, as well as due to the low sensitivity of the methods, it is not detected in the study of urine in clinical diagnostic laboratories.
Detection of glucose in urine indicates pathology. Glucosuria depends on three factors:
- blood glucose concentration
- the amount of filtrate of the glomeruli of the kidney in 1 minute
- the amount of glucose reabsorbed in the tubules in 1 ml
Glucosuria is often preceded by hyperglycemia. Glucose filtered in the renal glomeruli is reabsorbed in the proximal renal tubules.
With normally functioning kidneys, glucosuria appears only when the blood glucose level exceeds 8.8-9.9 mmol / L, the so-called "renal threshold" or glomerular glucose clearance. This concept is relative, since the "renal threshold" is determined by the enzyme system of the renal epithelium and, therefore, is largely individual. The child has a "renal threshold" higher (10.45-12.65 mmol / l).
Glomerular filtration volume also affects glucosuria levels. Its decrease even with high blood glucose levels may not cause glucosuria. Therefore, in some chronic kidney disease, the glucose threshold rises. In the case of nephropathy accompanied by impaired glucose resorption (renal diabetes), glucosuria is also possible with normal or low blood glucose levels.
Causes of glucosuria
The causes of glucosuria can be:
- insulin deficiency
- decreased kidney and/or liver function
- violation of hormonal regulation of carbohydrate metabolism, eating a large number of carbohydrates
Pathogenesis of glucosuria
Glucosuria are of the following types:
- pancreatic (insular) - due to insufficiency of the insular apparatus
- extrapancreatic (extrainsular), resulting from a violation of one of the links in the regulation of carbohydrate metabolism
Types of glucosuria
The following types of glucosuria are distinguished:
- Diabetic glucosuria
- Glucosuria observed in acute pancreatitis
- Glucosuria with prolonged fasting
- Alimentary glucosuria, appearing 30-60 minutes after a meal rich in carbohydrates
- Glucosuria of nervous origin in traumatic brain injury, brain tumors, meningitis, toxicosis, encephalitis, seizures, intracranial hemorrhage, anesthesia
- Emotional glucosuria - with crying, fear, hysteria
- Glucosuria in case of poisoning (toxic)
- Endocrine glucosuria resulting from the impaired secretion of adrenaline, thyroxine, glucocorticoid hormones, with acromegaly, Itsenko-Cushing's syndrome, pheochromocytoma, hypernephroma, an overdose of ACTH, cortisol preparations, or their prolonged use
- Renal (renal) glucosuria develops as a consequence of the pathology of glucose resorption in the tubules
Distinguish between primary and secondary renal glucosuria:
- Primary glucosuria, so-called renal diabetes, is an abnormality in the mechanism of glucose resorption in the proximal renal tubules. The renal glucose threshold is reduced to 6.32-0.82 mmol / l without disturbing the intermediate metabolism of carbohydrates.
- Secondary renal glucosuria can occur with various organic kidney lesions (chronic nephritis, nephrosis, acute renal failure, glycogen disease).
Hyperglycemia and glucosuria options:
- impaired resorption of glucose in the tubules is characterized by glucosuria with normal blood glucose
- hyperglycemia, not accompanied by glucosuria, is observed in cases where the concentration of glucose in the urine does not exceed the threshold for glucose reabsorption in the tubules; when the renal threshold is exceeded, hyperglycemia is accompanied by glucosuria
- an increase in blood glucose and its absence in urine indicates impaired renal filtration
- in old age, due to a decrease in the activity of enzymes of the renal epithelium, slight glucosuria may be observed, which is easily compensated by diet