In a case where the obstruction is known to be irremediable, and where the hydro-nephrosis, if existing only on one side, is likely to increase, it is not desirable to make the puncture too early or to repeat it too frequently, since by allowing the pressure to increase the atrophy of the kidney will be more rapidly accomplished, and the need of frequently emptying the sac will not arise so often in the future. On the other hand, if there is a prospect of a restoration, if both kidneys are affected, or if the kidney not involved in the hydro-nephrosis is known to be seriously impaired in function, and it is desirable to preserve the secreting structure as long as possible, the punctures should be so arranged as to keep the pressure at its minimum. This must, however, be regarded as a temporary expedient. The puncture may be made either from the back or front, though in most cases the latter position, if the puncture be made with a small clean needle, would be the more convenient, and equally safe notwithstanding its traversing the peritoneum. A hydro-nephrosis may be treated either by removal or by drainage. Both of these methods have been resorted to, and are to be employed according to the circumstances of the individual case. A pyo-nephrosis naturally demands interference more peremptorily and more promptly than a simple hydro-nephrosis, because it exposes the patient to the dangers not only of its pressure and of its tendency to destruction of the renal substance, but to those more urgent ones of purulent infection or of perforation and perinephritic abscess. Removal is to be undertaken by the ordinary rules of laparotomy. Drainage has been arranged in cases where removal was impossible or unadvisable by stitching the edges of an opened sac to the external wound. It is possible that the choice between the two operations can be made only after the primary incisions and explorations have advanced sufficiently to enable the extent of adhesions and the amount of healthy renal substance to be approximately determined. Staples of Dubuque states, on the basis of 71 cases collected by him, that "63 per cent. of patients operated on are cured by lumbar nephrectomy, 68 per cent. by open methods in general, and up to date 100 per cent. by either lumbar incision and drainage or the creation of a fistula." Malignant Growths. As pathological rarities only, and having but little clinical interest, may be mentioned, as occurring in the kidneys, fibroma, lipoma, {61} myxoma, anginoma, and adenoma. Malignant growths originating in or involving the kidneys, sarcoma or carcinoma, are, however, more frequent and more important.