Observations bearing upon the operation of prostatectomy

THE majority of surgeons will admit the difficulty of ascertaining the state of the renal function from a purely clinical inquiry, and they will agree that some additional test in the form of a laboratory examination is necessary. Owing to the variety of tests at present in use i t is very difficult for any single observer to possess an intimate knowledge of all, with the result that each worker adheres to some test of which he has special experience. It will perhaps be as well to review very briefly these various tests, and to epitomize the current opinion upon them. It is not proposed here to enter into a detailed classification of the various tests, but merely to refer to them singly. To commence with, practically all authorities are agreed that the mere examination of the urine for albumin, casts, pus, organisms, and other abnormal constituents, although important, is not reliable as a guide to operative prognosis, since i t is quite possible to have very advanced renal changes coexisting with slight urinary alterations. Moreover, the results of backpressure from prostatic enlargement or other causes rarely produce any marked changes in the urine. A series of very important tests depends upon the administration of some natural or foreign substance and noting the excretion of the body in question. These are of two main varieties: first, those in which dyes are given, and, secondly, those employing substances such as urea, benzoic acid, phloridzin, etc. The dye tests in general use are the indigo-carmine and the phenolsulphonephthalein reactions. The former is usually performed clinically, and the excretion of each kidney can be investigated, either by means of the ureteric catheter or the cystoscope. That the performance of some such test as this is an absolute necessity when dealing with unilateral lesions no one will doubt. In fact, this type of method constitutes the only one by which the individual functions of the kidney can be judged. The phenolsulphonephthaleiii test has proved reliable, but suffers from certain serious drawbacks. Thus the presence of blood in the urine renders the colorimetric estimation of the dye content exceedingly difficult, if not impossible. Another test, used extensively in England, is the urea-concentration test of H. MacLean.' This test is of proved value in medical cases, but its value, when taken alone, in cases with obstruction, is not quite so certain. In Table I can be seen a comparison between the urea-concentration test and