To sum up: it may be said that icterus is probably never due to simple inactivity of the liver: it may, however, be caused by excessive secretion of bile which is re-absorbed from obstructed bile ducts or bowels:—it may result from imperfect transformation, in the blood, of the bile which is normally re-absorbed from the intestine: or it may possibly be caused by the formation of pigments in the blood from the abnormal transformation of bile acids, or by solution of the hæmoglobin of the blood corpuscles.
The gravity of jaundice varies as much as its causes. It is well known that the system may be saturated with bile, and the tissues and urine deeply stained without much constitutional disorder. The pigment alone is not an active poison. But there may be much attendant suffering from obstructed biliary ducts or bowels, from diseases of the lungs, or from disintegration of the blood globules and imperfect nutrition, or there may be profound nervous prostration and disorder from uræmia, or from the presence in the blood of an excess of effete and partially oxidized albuminoids (See Azotæmia). According to our present knowledge, constitutional disorder, prostration and suffering in cases of jaundice, are mainly due to the presence in the circulation of these albuminoids, and of taurocholic acid which latter has a most destructive effect on the blood corpuscles.
The symptoms, therefore, are not characteristic apart from the yellow coloration of the tissues and urine and the chemical reactions of the bile acids and bile pigments furnished by the latter.
The coloration of the tissues may be a simple tinge of yellow especially noticeable in the eye (conjunctiva), or it may amount to the darkest shades of orange and brown. It may or may not be complicated by the presence of spots or patches of blood-staining (ecchymosis) on the visible mucous membranes but especially in cases complicated by poisoning with taurocholic acid or effete nitrogenous products.
The urine may be similarly colored in all shades of yellow or orange brown, and may leave a correspondingly deep stain on white paper.
The test for bile pigments (Gmelin’s) is simple and beautiful. Pour a little nitric acid into a test tube held obliquely and then add a few drops of sulphuric acid, and finally a little urine, so slowly, that it will remain on the surface. Soon at the point of junction appear in succession the various colors of the rainbow: yellow, green, blue, violet, red and lastly a dirty yellow. It is open to this objection that the characteristic play of colors may be produced by alcohol in the absence of bile pigments. Indican also will produce the green and yellow with blue between but never the violet nor red, nor all in their regular order.
A second mode of applying this test is by spreading a few drops of the urine on a white plate and letting fall a drop of nitric acid in the centre. The play of colors is very characteristic.
The test for bile acids (Pettenkofer’s) is to place a portion of the urine in a test tube, and after adding a drop of syrup, to add cautiously, drop by drop, two-thirds of the amount of sulphuric acid. Shake the mixture and set aside for some minutes. If sufficient heat is not produced by the mixing of the acid and urine warm slightly. The mixture becomes of a dark violet color which is destroyed by a temperature a little above 140° Fah.
A convenient application of this test (Stranburg) is to add a little cane sugar to the urine, dip a piece of filtering paper in the mixture, dry it thoroughly, pour a drop of sulphuric acid on the paper and allow it to run partially off. In a quarter of a minute a beautiful violet color is produced, best seen by holding up the paper to the light and looking through it (Brunton).
In cases due to obstruction of the bile ducts the dung is destitute of bile, whitish, often clayey and fœtid, while in cases due to reabsorption without obstruction the fæces have their natural color and odor.