Transudate

TRANSUDATE (from Latin trans-through and sudo-sweat), oedematous fluid accumulating in tissue clefts and body cavities, resembling lymph in its composition. Usually, a transudate is colourless or pale yellowish and transparent. Less often it turns out to be slightly turbid due to, for example, an admixture of desquamated epithelium of the cavities, lymphocytes, fat droplets, and the like. Sometimes a transudate contains loose gelatinous masses of fibrin (hydrops fibrinosus). The specific gravity of a transudate ranges within 1.006-1.012 (inflammatory exudate 1.018-1.020). The protein content in a transudate usually does not exceed 3%, but nevertheless fluctuates within wide limits (0.5-3%). Transudates with a protein content of over 3% are undoubtedly observed, approaching exudates in this respect, for example, in nephritic oedemas, in certain cases of ascites, and the like. Other things being equal, the more protein there is in a transudate, the longer the time elapsed since the development of the transudate. The proteins of a transudate are serum albumin and globulin, and less often, as indicated, fibrin. The composition of salts more or less corresponds to blood serum, although significant fluctuations may also be observed here. The colloid-osmotic pressure in a transudate is low; therefore, the difference between the colloid-osmotic pressure of blood and transudate is very large. In practice, it is mostly not difficult to distinguish a transudate from an exudate, however, in some cases the boundaries between these two types of pathological fluids become blurred: the transudate turns out to be turbid, the amount of protein in it rises to 4-5%, etc. The solution to the problem in such cases is best sought in the study of the entire complex of clinical, anatomical, and bacteriological phenomena (pain, temperature reaction, inflammatory hyperaemia, haemorrhages, presence of microorganisms in the fluid, etc.). On the other hand, it should be kept in mind that there are no absolute boundaries between a transudate and an exudate in general, since those factors which have pathogenetic significance in oedemas in the form of disturbances of osmotic, oncotic pressure, toxic and stagnant phenomena in tissues, are observed to varying degrees in inflammatory exudation as well. It is also necessary to remember that a transudate easily becomes infected, giving rise to mixed pictures of transudate-exudate, e.g., hydrothorax-pleuritis, ascites-peritonitis, etc. To distinguish transudate from exudate, certain reactions (tests) have been proposed. The Moritz-Rivalta test is based on the fact that a weak solution of acetic acid with a transudate does not produce turbidity. The test has a very relative significance. Literature see literature to the article Oedema.