Galactosuria

GALACTOSURIA, GALACTOSEMIA, the appearance in the urine and blood of one of the monosaccharides—galactose. Galactose, absorbed from the intestine, is assimilated, apparently, only in the liver (which converts galactose into glycogen), and moreover, much more difficultly than grape sugar. In some liver ailments, its ability to assimilate galactose decreases, and galactose enters the blood and urine. A test with a dietary load of galactose can therefore serve as one of the methods for determining the functional capacity of the liver. According to the suggestion of Bauer, patients are given 20–40 g of galactose on an empty stomach, and then the amount of sugar excreted in the urine on that day is determined. In healthy individuals, it equals 1–2 g. In persons with a diseased liver, more galactose is excreted in the urine—up to 30% of the administered amount. The test is positive in diffuse diseases of the liver parenchyma: in acute atrophy of the liver, in so-called "catarrhal" and "infectious" jaundice, and in syphilitic jaundice (hepatitis). In cirrhosis, the test gives a positive result depending on the stage and form of the disease (in cases of more extensive destruction of liver tissue). A congested liver rarely causes galactosuria. Mechanical jaundice (obstruction of the common bile duct by a stone or tumor) and hemolytic jaundice do not cause increased galactosuria, just as diseases of the bile ducts and gallbladder do not. Limited diseases of the liver (gumma, tumor metastases, echinococcus, abscess) also do not cause it, unless they involve a large part of the organ. The test can sometimes be positive with a healthy liver (Basedow's disease and other diseases of the endocrine system, severe neuroses, as well as in healthy individuals of asthenic constitution, and in infants). Nevertheless, the test is of great importance, allowing one to differentiate the hepatic (parenchymal) type of jaundice from the mechanical type and serving as one of the methods for investigating the function of the liver as an organ of carbohydrate metabolism. In urine, galactose is determined in the same way as glucose, with a conversion to galactose (e.g., with a polarimeter, multiplying each division by 0.7). Another method is the repeated determination of blood sugar after the administration of galactose (in the form of "hyperglycemic curves"): in healthy individuals, an average rise of 0.03% is observed (after an hour), while in patients with diffuse liver disease, it is 0.05–0.12%; a pathological rise is observed in the same cases as pathological galactosuria (and has the same significance); it is considered that this method is more sensitive. When converting figures for grape sugar to galactose, one must keep in mind that the reducing capacity of the former relates to the reducing capacity of the latter as 1 : 0.848.