Lactosuria

Lactosuria, the appearance of lactose, milk sugar, in the urine; observed: 1) in the last days of pregnancy and the first time after childbirth (in connection with the active work of the mammary glands at this time); 2) in newborns (especially premature) children in the first days after birth (Nothmann); 3) in infants with severe nutritional disorders as a symptom of increased permeability of the intestinal wall; 4) sometimes to a slight degree with enhanced milk food. This symptom has diagnostic value only with reference to point 3. Lactose is discovered in the urine by the same Trommer test as glucose, and also rotates the plane of polarization to the right. To distinguish it from glucose, the inability of lactose in boiled urine to ferment under the influence of pure yeast cultures is used, as well as the Belka-Malfatti reaction (Wohlk, Malfatti): to 5 cm³ of urine add 2-5 cm³ of concentrated ammonia solution and 5 drops of 10% caustic alkali, place on a hot (but not boiling) water bath; after 5 min. or later a red coloration appears. A more precise method is that based on the isolation of lactose from urine, given by Hofmeister.