a. In all cases an abundance or pale limpid urine, of low specific gravity, which yields a distinct precipitate of albumen, affords certain evidence of serious disease of the kidney.
b. A very abundant precipitate of albumen, whatever be the condition of the urine, can only be caused by disease of the kid ney, whether in the form of congestion or simple inflammation, or of scarlatinal nephritis, or of degeneration at a particular stage, or of a special form.
c. If the amount of albumen be small, the evidence of its pre sence doubtful, and the secretion scanty, the inference is less cer tain when disease of the heart exists, because passive congestion of various organs is one of its usual concomitants. When, there fore, there is evidence of valvular lesion traceable to rheumatic attacks, urine, which is scanty and loaded, may continue for a time to contain a trace of albumen, while no disease of the kidney exists : when, on the other hand, the heart-disease is of the form of hypertrophy, or dilatation, the continuance of a trace of albu men is a more suspicious sign, because it is not improbable that the changes in its muscular structure, as they are not c,aused by valvular lesion, may be the effects of renal disease. In either case the diagnosis can only be considered certain when, with an in crease of the secretion, the albumen persists, and the specific gravity falls. Somewhat similar relations have been observed when in cases of dropsy dependent on other causes, any special circumstance gives rise to congestion of the kidney : such, for example, as anasama accompanying ascites or ovarian dropsy, when pressure opposes the return of the blood through the renal veins: an exactly analogous relation is said to exist very frequently in the dropsy of pregnancy.
d. When dropsy is not present there are no doubt many eir cumstances which may give rise to the casual occurrence of a trace of albumen ; and when this change is not constant, and the specific gravity is normal, great hope may be entertained that the condition of disease is only transient, and not altogether beyond the reach of art. In investigating these cases the microscope may be of much service in showing either the presence of a few blood-globules, or of pus, or what are called exudation-corpuscles, or mucus-globules in such numbers as to resemble pus rather than mucus, all of which are found in simple congestion of the kidney; or it may discover fibrinous casts of the tubuli, which can only be present in very active congestion, or in permanent disorganization. These casts present either a homogeneous appear
ance, smooth and transparent, or they are filled up with granular matter, and sometimes they contain blood-globules or particles of oil. The smooth or waxy casts, as they are called, serve to indi cate the most advanced condition of disease, and those containing blood-globules generally result from congestion ; but their appear ance must not be made too absolutely a guide to diagnosis.
e. When the urine is tinged with blood, the indications are somewhat similar to those derived from the presence of albumen, and what is true of the one is in great part true of the other, with this difference, that blood may come from any part whatever of the urinary organs and passages. The first question when blood is present is, whether more albumen can be precipitated than is accounted for by the admixture of blood if it had been added after the urine was voided. This is a point which experience only can determine, and for which no rules can be laid down. When we conceive the amount of albumen to be greater than would be contained in urine colored by blood to the same extent, it must be regarded just as if the blood was not present, for we know that the excess of albumen must be secreted by the kidney; when the amount of albumen is small, the next question is as to the source of the hemorrhage; and probably the only reliable evidence of its coming from the kidney is when the microscope discovers tubular casts. The existence of small clots, visible to the naked eye, proves that the hemorrhage has occurred in some part of the canal from the pelvis of the kidney to the end of the urethra, and not in the kidney itself: and then there are generally local symp toms to guide us in determining at what point it took place. Sometimes it is distinctly passed before the urine begins to flow, and it probably issues from the urethra ; sometimes it only escapes with the last drops of urine, when its source is generally the blad der. In females, blood flowing from the uterus may be mixed with the urine as it is voided : hiematuria is also one of the forms of hemorrhage which occurs without any special lesion, depend ing simply on a deficiency of plastic material in the blood itself. It is only when the blood retains somewhat of its natural color, and the urine is red or pinkish, that doubts regarding the source of the hemorrhage can be entertained : when dark-colored or smoky, the blood almost certainly comes from the kidney.