Levulosuria

LEVULOSURIA, the appearance in urine of the monosaccharide levulose, or fructose (see). Since levulose, introduced into the intestine and absorbed into the blood, is assimilated only by the liver [at least according to experiments with liver removal in frogs (Sachs) and in dogs (Mann, Magath)], a dietary load of levulose can serve as a diagnostic test for determining the functional capacity of the liver in the sphere of carbohydrate metabolism (Strauss). After introduction per os of 50 to 100 g of levulose, part of it may appear in the urine [determined qualitatively by Selivanov's reaction, but it is better to determine quantitatively by ordinary methods (levulose rotates the plane of polarization to the left and gives reduction reactions) in each portion of urine for 1/5-1 day after the load]. In normal conditions, in the vast majority of cases, levulose does not appear in urine after administration per os or passes into it in negligible amounts [0.1-0.3 g, at most 0.6 g (Worner, Reiss)], whereas in liver diseases several grams of levulose pass into the urine. Most often (approximately in 80% of cases) such a positive result of the test is obtained in acute lesions of the hepatic parenchyma (various infectious or toxic hepatitis, including here 'catarrhal' and syphilitic jaundices, Icterus gravis, etc.). The test is also often positive in chronic hepatitis (cirrhoses), mainly in cases of more widespread and far-advanced processes, much less frequently in focal diseases of the liver and in cardiac congestion (17-40% of cases); in hemolytic jaundice the test is negative, as well as in cholecystitis and cholangitis. Unlike the test with galactose, this test is often positive also in jaundice due to obstruction of the bile ducts by a stone (Hohlweg). Consequently, the test does not make it possible to determine what form of jaundice (mechanical or functional) we are dealing with in a given patient. Apparently, the acute retention of bile itself can disrupt the utilization of fruit sugar by liver cells. Levulosuria can be obtained in acute infectious patients (Sabadovsky), as well as in pregnant women. In pregnant women, levulosuria may depend not on hidden liver insufficiency, but on greater permeability of the kidneys for sugar (Hetenyi, Liebmann)]. In general, for the diagnosis of liver diseases, alimentary levulosuria must be used with great caution, since many extraliver factors (the autonomic nervous system, endocrine glands, etc.) also influence the process of assimilation of this type of sugar.