B. ABNORMAL CONSTITUENTS
Those substances which appear in the urine only in pathologic conditions are of much more interest to the clinician than are those which have just been discussed. Among them are: proteids, sugars, the acetone bodies, bile, hemoglobin, and the diazo substances. The "pancreatic reaction" and detection of drugs in the urine will also be discussed under this head.
1. Proteids.—Of the proteids which may appear in the urine, serum-albumin and serum-globulin are the most important. Mucin, albumose, and a few others are found occasionally, but are of less interest.
(1) Serum-albumin and Serum-globulin.—These two proteids constitute the so-called "urinary albumin." They usually occur together, have practically the same significance, and both respond to all the ordinary tests for "albumin."
Their presence, or albuminuria, is probably the most important pathologic condition of the urine. It is either accidental or renal. The physician can make no greater mistake than to regard all cases of albuminuria as indicating kidney disease.
Accidental or false albuminuria is due to admixture with the urine of albuminous fluids, such as pus, blood, and vaginal discharge. The microscope will usually reveal its nature.
Renal albuminuria refers to albumin which has passed from the blood into the urine through the walls of the kidney tubules or the glomeruli. It probably never occurs as a physiologic condition, the so-called "functional albuminuria" being due to obscure or slight pathologic changes.
Renal albuminuria may be referred to one or more of the following causes. In practically all cases it is accompanied by tube-casts.
(a) Changes in the blood which render its albumin more diffusible, as in severe anemias, purpura, and scurvy. Here the albumin is small in amount.
(b) Changes in circulation in the kidney, either anemia or congestion, as in excessive exercise, chronic heart disease, and pressure upon the renal veins. The quantity of albumin is usually, but not always, small. Its presence is constant or temporary, according to the cause. Most of the causes, if continued, will produce organic changes in the kidney.