A Clinical Lecture on the Differential Diagnosis in Cases of Albuminuria

H. French
1911 BMJ (Clinical Research Edition)  
ALBUMINURIA is the term used to denote the passave in the urine of preteid that is coagulable on boiling. More than one substance is included in the word " 1 albumen " in this sense, and there are varying proportions of serum albumen and serum globulin in different cases. So variable may be the relative amounts of these, not only in different diseases, but also in different cases of the same disease and in the same patient at different times, that there is little useful clinical information to
more » ... e o'btained by dealing with the albumen and the globulin separately, at any rate so far as present knowledge goes. Nacleo-proteid or nucleo albumen comes in quite a different category. Although a large number of different tests for albumen have been devised and advocated, for clinical purposes there is little need to trouble about more than the two common ones-namely, the acetic apid and boiling, and the cold nitric acid tests. It is true that each of these has fallacies; but the latter are not common to both, and therefore, if there is any doubt in the interpretation of one of the two tests, it can readily be confirmed or otherwise by the other. It is alleged that more delicate tests exist; but there is such a thing as too great delicacy in a clinical method. One does not want to find albumen in minute traces where it does not matter, and it seldom matters until its amount is sufficient to give both the common tests. THE ACETIC ACID AND BOILING TBST. A test-tube three parts full of urine-cleared if need be by filtration-is held by its lower end, whilst its upper -part is carefully heated to boiling point. It is, best not to add any acetic acid before boiling unless the specimen is distinctly alkaline, in which case it may be just acidulated with a drop of acetic acid. After boiling, the tube should be held in a good surface light against a dark background, each as the sleeve of one's coat; any opalescence will be obvious at once, and there may be a dense white cloud. Except in very rare cases of Bence-Jones's albumosuria this cloud will be due to one or more of three thingsnamely, calcium and magnesium phosphate, calcium carbonate, or coagulated albumen. One, two or more drops of acetic acid solution (B.P.) are now added; if the cloud disappears entirely, quietly, and at once, it was due to earthy phosphates, and no albumen is present; if it-disappears entirely but with brisk effervescence, the latter is due to calcium carbonates amongst the phosphates, and no albumen is present; if, on the other hand, the cloud clears up but partially, or remains unaltered, or actually increases and becomes more flocculent, albumen is almost certainly present. There is only one serious fallacy remaining, and that is in regard to nucleo-proteid; this is precipitated by acetic acid, and it is possible for a cloud of phosphates to be cleared up by the latter and yet for a faint cloud of nucleo-proteid to come down in the place of the phosphates in such a way as to suggest that the original cloud was not wholly solable in the acid, and therefore that albumen -is present when it is not. There are three ways of obviating this source of fallacy: the first is to add a single drop of dilute non-faming nitric acid to the suspicious cloud that remains after the addition of acetic acid; if it is due to albumen, it will persist or even increase, whilat if it is due to nucleo-proteid the nitric acid will disperse it; the second is to perform the cold nitric acid test for albumen as described below-nueleo-proteid will not give a definite localized white ring with it; and thirdly, a control test may be done, acetic acid being added to another specimen of the urine without boiling, and the. cloud .ue to.-any nucleo-proteid present compared with the cloud in the acidulated and boiled specimen. 3 HELLER'S COLD NITRIC ACID TEST. About 1 in. of urine is poured into a test-tube, the latter is held much inclined, and colourless nitric acid is allowed to flow gently down the side, until about one-third as much as the urine has beenadded. The nitric acid is heavier than urine and goes to the bottom; if albumen is present, a white ring forms at the junction of the two guids. Some prefer to pour the nitric acid into the test-tube first and then to add the urine carefully with a pipette. It is important not to shake the tube or the nitric acid and the urine will mix, and there will be no definite line of junction between them; Fuming nitric acid must be avoided, because the nitrous oxide fumes caune decomposition of the urea, and the resultant bubbles mix the flaids; sometimes there is bubbling even when the nitric acid is colourless, in which case this is due to C02 set free from carbonates. The test is very delicate: if any large quantity of albumen is present, the ring appears at once; if there is only a trace, the white ring may not appear for a littb, and the tube should be set aside and looked at again in a few minutes. Broadly speaking, it takes three minutes for it to develop when the amount of albumen is 1 part in 30,000. This, test is open to more fallaoies, however, than the acetic acid and boiling test, so that the nitric acid test should not be trusted to alone, unless it is negative. In concentrated urines it is common to get a dark brown, reddish-brown, or violet-brown ring of colour at the janction. This is nothing to do with albumen; it is generally most marked in cases of indicanuria. White rings, more or less like that due to albumen, may also be due to any of the following: 1. Re8in.-If the patient is taking copaiba resin, or other similar drug, enough of the resin may be excreted in the urine to form a diffuse white cloud above the nitric acid. This source of fallacy is best avoided by bearing it in mind and checking the nitric acid test by the heat test; this latter safeguard applies to all cases of suspected albuminuria. 2. AlbumoMes.-These generally occur in association with albumen; should they occur alone, the ring will disappear with warming, to reappear on cooling, and there will be no cloud with the heat test. 3. Bence-Jones'8 Albumo8e.-This occurs without albumen, gives a ring -with nitric acid that disappears on warming, to reappear on cooling; with the heat test a dense cloud appears about 600 C., to disappear on further heating to boiling point. 4. Nucleo-albumen.-The ring with this is not in contact with the nitric acid, but higher up and diffuse; it may be a real difficulty in diagnosis from -albumen, for it is also precipitated by acetic aoid, and may therefore give a cloudiness with the boiling test. The methods of avoiding this fallacy are mentioned above. 5. Urateo.-These may form a cloud near the nitric acid if the urine is very concentrated; the cloud will disappear on gentle warming, to reappear on cooling, so that it may also be mistaken for albumose; this fallacy may be avoided by diluting the urine with plain water before the nitric acid test is employed. 6 Urea Nitrate.-If the urine contains a large percentage of urea, a crystalline deposit of urea nitrate may form at the junction. As a rule, -the crystalline nature of the ring is obvious on inspection, but in case of doubt the urine should be diluted and the test repeated. It does not matter which test is most relied upon when the result is negative, but before the positive deduction that a urine contains albumen is drawn, both the acetic acid and boiling, and the cold nitric acid tests should be positive.
doi:10.1136/bmj.1.2617.417 fatcat:xwhq72ric5eyhglz4djzol4tca