To a certain extent, information may be aequired from the history of the case, regarding the causes and progress of mites ; because we either learn that it has been preceded by pain in some part of the abdomen, or that, to the patient's own consciousness, there has been nothing but a gradually increasing fulness and tension. The history also enables us to exclude local enlarge ments which have been first observed in some particular region of the abdomen; and affords primd facie evidence of the case being one of asoites depending on disease of the liver, when the patient has been a person of intemperate habits, or has had an at tack of jaundice.
The presence of fluid' is learned from the existence of fluctua tion; by which is meant the impression received by the hand, of a wave-like movement through the fluid, across the abdomen, when a blow is struck at a distant point. The accurate determi nation of this fluid-motion requires much care and frequent prac tice: the extreme mobility of the contents of the abdomen, or an aocumulation of fat which, at the temperature of the body, is in a semi-fluid state, are each liable, in certain circumstances, to give rise to a sense of re,silience, extremely like the feeling of fluctua tion. On the other hand, the intervention of a portion of bowel distended with gas may annul the wave of fluctuation when fluid is really present. The first step in the examination of a distended abdomen ought to be to place the patient flat on the back, and observe the general contour of the abdomen, and then to proceed to determine by percussion the position of bowel resonance; next, to seek for evtdence of fluid where that resonance ceases or is greatly diminished, observing how far the fluctuation extends in various directions from the part struck ; and, lastly, by change of posture to satisfy ourselves as. to the relations of the fluid to the other abdominal contents, whether it be freely movable or comparatively fixed in one locality. And, having made out to our ovrn satisfaction that fluid is present within the cavity of the peritoneum, we may then, from a consideration of the whole his tory of the case, the various symptoms which have-attended the origin and progress of the disease, and the present condition of the patient, form some idea of its cause. And, if we would avoid false deductions and injudicious treatment, the actual state of all the organs of the abdomen must be analyzed with great e.are.
The history of the case affords more assistance in determining the particular cause of the effusion than in assuring us of its locality, except when it speaks positively of local enlargement. Students must guard against either con founding for themselves, or leading the patient to confound, pain for enlarge ment; a mistake which, in my own experience, has led careless observers astray. Patients are very generally first conscious of abdominal tension by a
feeling of fulness at the waist; and both sexes will alike assert that their in crease of size began there, when we are perfectly certain 'that the fluid was at the time collecting in the lower part of the abdomen.
The patient's statement of local enlargement may be often verified by the peculiar shape which the abdomen presents in the horizontal posture: in ascites it is usually uniform. Percussion resonance determines the relative position of the intestine, in which gas is almost always present, and of the foreign substance, whatever it may be. It may indicate a distinct level line all round to which fluid rises, or it may show that one coil of intestine dips down below it, or that a very large portion of intestine on one side is alto gether below the level of the dull part on the other ; on the other hand, it may prove that the whole surface is resonant, or that dulness is very limited and local.
The evidence of fluctuation is much more liable to be indistinct when the fluid is contained within some cyst, than when it is free in the peritoneum. Fallacy is best avoided by producing the effect in various ways ; tapping gently, giving a short sharp stroke, or rubbing the finger rapidly along ; fluc tuation will result in each case if fluid be present. In addition to the evidence it gives of the actual presence of fluid, we learn from fluctuation its amount and distribution, by comparing the effect at different distances, and observing their relation to what we have already ascertained of the position of the bowel by percussion. In very many instances, the remarkable distinctness of flue tuation when the hands of the observer are placed near to each other, and its entire absence at a greater distance, afford conclusive evidence of the limita tion of the space in which it is contained ; or, on the other hand, its indistinct ness when the hand is placed over the surface of tympanitic bowels, and its precision when the hand is passed beyond them to the lumbar region, prove with equal clearness that it is free in the abdomen. But the examination is not complete till we have observed the effect of change of posture. Imme• diately on any change, fluid which is unlimited by membrane gravitates to that which is now the lower part of the cavity, and all the relations of per cussion and fluctuation are more or less altered. This cannot occur to the same extent when the fluid is encysted ; but it is to be remembered that it is specifically heavier than intestine, and, though more slowly, it will still obey the laws of gravitation, as far as its mobility will permit.