URINARY SEDIMENTS is a general term which includes all those substances which Occur in a non-dissolved state in the urine. Most of these sediments are not formed un til after the urine has been discharged and has cooled; some, however, are formed in the urinary organs, and under favoring conditions may give rise to urinary concretions. Hence it is a point of importance to ascertain whether a sediment occurring in a speci men of fresh urine has been formed before or after its discharge.
The chemical and microscopical character of these sediments has a double bearing on the detection of disease: (1.) "From the investigation of these sediments," says pro fessor Vogel, "we can draw sure conclusions regarding special changes that are going on in the general nutrition of the body. They show us that an excessive quantity of certain substances (as for example, uric, hippuric, or oxalic acid) is being discharged with the urine, and has therefore been produced in the body; and we thus often obtain at a glance information of great importance, which could otherwise only be procured by a tedious process; and (2) they point out to us certain local diseases of the urinary system. Thus, from a sediment containing pus. we infer that suppuration in going on in some part of that system; and the presence of cylindrical casts or tubes in the sediment informs us of certain morbid changes in the structure of the kidneys; and if the ordinary symptoms reveal the presence of stone in the bladder, we can ascertain its probable nature from the character of the sediment or gravel." The mode of formation of morbid sediments is well illustrated by a sketch of the changes which healthy urine undergoes after prolonged exposure to the air. In the course of two or three days, the acidity ef the urine is found to hare increased, and this condition of acid fermentation will frequently continue for S01118 weeks, giving rise to the disposition of (1) free uric acid; (2) acid Orates (chiefly orate of soda); and (3) oxalate of lime. In a few weeks, or often much sooner, the urea becomes alkaline, or alkaline fermentation is established, in consequence of the urea being converted into carbonate of ammonia. The urine now becomes paler, while the red or yellow crystals of uric acid are replaced by white amorphous granules and colorless refracting prismatic crys tals. In other words, the former precipitate is replaced by (1) phosphate of ammonia
and magnesia (commonly known as triple phosphate); (2) phosphate of lime; and (3) unite of ammonia, In certain forms of disease, these changes take place much more rapidly, and the second change—the alkaline fermentation—may occur without a pre existing acid fermentation, and even within the bladder. In addition to the above named substances, which arise from the decomposition of healthy urine, others occur in various morbid conditions of the system; and we may divide the urinary sediments gen erally into the two great groups of (1) the unorganized and (2) the organized deposits. The unorganized sediments include uric acid, the orates (chiefly mate of soda), hippurie acid, oxalate of lime, earthy phosphate (viz., phosphate of lime, and triple phosphate), crystine, xanthine,pypoxanthine (formerly known as guanine), and tyosine; while the or ganized sediments include mums and epithelial scales, blood corpuscles, pus corpuscles, cancerous and tubercular matter, fibrinous casts of the tubes of the kidney, spermatozoa, lungs, infusoria, etc. Of the unorganized sediments uric acid, the orates (excepting unite of ammonia), hippurie acid, and crystine occur only in acid urine, and mate of ammonia, triple phosphate and phosphate of lime, in alkaline or neutral urine. Oxalate of lime and the onranized sediments occur both in acid and alkaline urine; but alka line urine is the more natural habitat for fungi and mfusoria. It is comparatively seldom that a sediment consists of a simple ingredient. Most of our knowledge on this important subject is due to the labors of English physicians. amongwhom the names of Prom and Golding Bird are especially deserving of notice. For details regarding the mode of treat ment suitable in the most important of the sediments, we may refer to the articles LITItIC ACID DIATHESIS, OXALURIA, and PHOSPHATIC DIATHESIS, in this work, and 10 Dr. G. Bird's UrinarY Deposits and their Treatment; while for details regarding their chemical and microscopical characters, Neubauer and Vogel, On the Urine, translated under the auspices of the New Sydenham society, may be consulted.