EXAMINATION OF THE RENAL SECRETION.
The urine affords us important information in all cases of jaundice. In fact, an examination of it alone would in many cases enable us to discover the presence or absence of this affection.
Diagnostic Value of the Colour of the Urine.
The urine of jaundice has invariably a peculiar tint, ranging from a saffron-yellow to a dark olive-green, or almost black hue. It must not be forgotten that the colour of normal urine varies with the degree of concentration. Where little is passed, being of a high, where much is passed, of a pale colour; the depth of colour depending on the degree of dilution of the urohæmatine. Again, it must also be remembered that there are many diseases, which change the colour of urine very materially, some only deepening, others actually changing the tint. Foods, and medicines also, alter the colour of the renal secretion. Rhubarb, and santonine give to it a saffron hue, arsenious acid gas a black colour. Bearing in mind these facts, one would hesitate before giving a decided opinion as to the presence or absence of icterus from a mere inspection of the urine. For this reason, it is generally recommended in cases of jaundice to pour a little of the urine on a white plate, and watch the play of colours produced by strong nitric acid. This method, however, is not always satisfactory, for the play of colours depends on the different stages of oxidation through which the pigment passes, and other animal pigments, besides biliverdine, unfortunately act in a somewhat similar manner.
A very simple, and more convenient way of testing the pigment without changing its physical characters, is to separate it in combination with uric acid. This is readily done by simply acidulating the urine with a few drops of hydrochloric acid, and setting it aside for twenty-four hours to crystallize. The white uric acid in crystallizing takes up the colouring matter, and assumes the hue of the pigment present in the urine. I have thus obtained crystals of all the different hues from a bright golden yellow tint through the intervening shades of red, brown, blue, olive, to a dark, almost black colour. This experiment has another advantage, for if we take a measured quantity of urine, and collect, dry, and weigh the uric acid obtained from it, we can readily calculate the total quantity passed in the twenty-four hours, and thereby assist in diagnosing the presence or absence of malignant disease of the liver, as I shall afterwards have occasion to point out.
The urine of jaundice is generally described as being of a saffron colour; but if I may be allowed to form an opinion from my own observations, which are tolerably numerous, I should say that it, in colour, much more frequently resembles old ale than anything else with which I am acquainted. On standing, the colour changes very considerably, in consequence of the pigment becoming slowly oxidized by its exposure to the air. When there is a very great excess of bile pigment present in the blood, the kidneys have some difficulty in eliminating it. Occasionally even, it chokes up the renal capillaries, and thereby complicates the jaundice by inducing secondary disease in the kidney. In such cases the external surface of the kidney, after the removal of the capsule, looks as if it had been sprinkled over with ink. The black specks vary in size from the minutest visible point to that of a pin-head. The accompanying chromo-lithograph (Plate II.) represents a kidney in this condition. It will also be observed that it is studded over with a number of small abscesses; but whether these resulted from the blocking-up of the capillaries just alluded to or not, it is impossible to say. In the case in question no albumen was detected in the urine during life, and it was only on careful analysis, after the post-mortem had revealed the above state of matters, that a small quantity was discovered; and even then, had not the experiment been carefully performed, the presence of albumen might have been overlooked.
| Plate II. |
| Kidney from a Case of Permanent Jaundice. |
Diagnostic Value of the presence of the Bile-Acids in the Urine.
All acquainted with the recent literature of jaundice know how hard a battle is being fought between two sets of observers in Germany, regarding the presence of bile-acids in urine. One class, with Frerichs and Städler at their head, believe that the biliary acids are decomposed in the blood, and are consequently never to be detected in the urine. The other class, headed by Kühne, state as positively that they have detected these substances in the urine. Indeed, Kühne states that by adopting Hoppe's method,18 he never fails to detect the presence of the biliary acids in the urine of patients labouring under icterus, as well as in the urine of dogs with the bile-duct ligatured. When first studying this question, I was very much perplexed by these contradictory statements, for neither the judgment, nor the power of observation of either of the authorities could for a moment be called in question; and on experimenting for myself, so unsatisfactory were the results obtained, that I almost threw the question aside in despair. On one occasion, however, I at length met with such unmistakeable evidence of the presence of bile-acids in the urine, that I could no longer doubt the fact of their existence, and was forced to search for an explanation of the previous contradictory results. Fortunately, it was not very long before a solution to the difficulty was obtained, and, what was of still greater importance, led to the observation that the contradictory results arose from a circumstance which might be turned to account, as a means of differential diagnosis. The discovery was, that in certain cases of jaundice not a trace of the biliary acids is to be detected in the urine, although the bile pigment is present in abundance; while in certain other cases both biliary acids, and bile pigment occur in notable quantity. What, then, is the cause of this difference? Simply this. In jaundice from suppression the liver does not secrete bile; consequently no bile-acids being formed, none can enter the circulation, and they are therefore not to be detected in the urine. In jaundice from obstruction, on the other hand, bile is secreted, and absorbed into the blood; and the bile-acids not being all transformed in the circulation, as Frerichs supposed, are eliminated by the kidneys, and appear in the urine, where they can be detected by Hoppe's method, or even, with proper precautions, by simply adding sulphuric acid and sugar. Here, however, some skill and experience are requisite, in order not to confound the colour produced by the action of the reagents on other substances with the fine purple produced by the biliary acids. As the majority of cases of jaundice result from suppression of the hepatic function, and as many of the cases of obstruction ultimately merge into the former, it is easily understood how the existence of the biliary acids in the urine has been so frequently denied. I have myself seen, in a case of obstruction of the common duct, the biliary acids slowly and gradually diminished in the urine, until they at length almost entirely disappeared as the case approached a fatal termination. Here the disappearance of the biliary acids went on step for step with the impairment of the secreting powers of the liver, in consequence of the pressure exercised on its parenchyma by the retained bile.