The cases in which diagnosis is most difficult are (a), when a unilocular cyst in a female has come to occupy the whole of the abdomen ; (b) , when fluid contained in the peritoneum is limited by adhesions.
a. The history shows, perhaps, that the disease began on one side, and the patient's health is not seriously affected, except so far as inconvenience and derangement are caused by pressure. For further particulars on this subject, the reader is referred to the chapter on diseases of the ovaries. The physical examination has reference to two great considerations ; first, that in the ne cessary displacement of the viscera, they are pushed to one side by a cyst which has grown up among them, either in the iliac region or in the hypogas trium, while they are forced directly upwards by fluid, which has been always free, and has, therefore, necessarily accumulated in the most depending part of the peritoneum. The second consideration is, that fluid having always this tendency to gravitate among the intestines, will naturally, in change of pos ture, flow to that part of the cavity which is made to assume the lowest level, except it be restrained by the cyst membrane which surrounds it; and, con nected with this, that the intestines being fastened to the body by long loose folds of peritoneum, float at the surface of a fluid which immediately cur rounds them, but cannot so float if the fluid be separated from them by being contained in a distinct bag ; although it be true that the fluid is heavier than they, and, if the cyst have room to change its place, it will tend to occupy the lowest position.
If these principles are steadily kept in view, the details of their application will readily occur to the mind. Thus we map out by percussion the relative positions of the fluid and the more resonant contents, and observe whether the line of dulness passes horizontally or in a curve, when the patient is in an erect or semi-erect position. We make her change her posture, and again observe the course of the resonance, whether it dips down below the fluid at any part. We place her horizontally on her back, and mark whether reso nance about the umbilicus appears, and move her from side to side, in order to observe whether there be any indication of the intestine floating in the fluid. Such experiments, conducted with a right understanding of what we
want to prove, will generally leave no doubt as to the nature of the case.
b. It now and then happens that, when ascites exists, old adhesions of the intestines are found binding them down in certain positions ; nay, more, almost the whole of the bowels may be fixed in their places, and the fluid poured out into one portion only of the cavity, where it is retained even more firmly than when contained in a cyst. In considering such cases, information sufficient to put us on our guard against mistake may be derived from the early history of the case and the condition of the patient, with reference to the date of formation and the actual size of the supposed cyst. The pain of peritonitis, such as must have existed to cause the adhesions, and the whole character of the seizure can never be simulated by the pain occasionally attending the first appearance of ovarian dropsy. Neither does the same disturbance of the general health manifest itself when an ovarian cyst has become filled to the same extent for the first time, as must of necessity accompany ascites with adhesions so extensive. A mistake is most liable to be made when the patient asserts that swelling existed before the occurrence of pain, and other causes have led to derangement of health.
Hydatid cysts are much less liable to be mistaken for ascites. They are discriminated by the history and mode of growth, their firm feeling and less distinct fluctuation, and often by their irregularity of outline ; but they are even more readily distinguished than ovarian dropsy by the position of the fluid with reference to the intestine, as ascertained by percussion, not obeying the laws of gravitation.
Ilydrometra is only liable to be confounded with the earlier stages of ova rian dropsy. A distended bladder cannot lead to any mistake, except by neglect of one of the essential inquiries—the condition of the urine, and ex treme carelessness in investigating the case.