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Medical research unit in a District General Hospital.

undertaken before the patient's clinical state has had time to deteriorate, while a negative finding means that the presence of a serious internal injury is unlikely. The technique of introducing a pliable catheter into the pouch of Douglas appears free of major hazard unless there are extensive abdominal adhesions. It has the added advantage that if peritoneal dialysis is needed, as in the dialysis treatment of acute haemorrhagic pancreatitis, the catheter can be left in position. Finally, if there is still doubt after a negative finding in the pouch of Douglas the catheter can be manipulated gently towards the spleen or liver and a small dialysis wash-out performed in these regions. The success rate of this series with respect to obtaining a positive result when disease was present and a negative one in the absence of disease, as well as a comparative lack of falsepositive and false-negative results, was very rewarding and much higher than that reported in earlier series when a simple needle aspiration technique was used.7 The incidence of false-negative results was significantly lower than the 10% previously reported.2 8 The improvement in the result is presumably due to the technique and materials used-that is, using a catheter long enough to reach into the pouch of Douglas and which is firm enough to be directed there. Washing out the area with a dialysate solution in order to recover even small quantities of exudate is also an advancement in the technique. With these improvements a negative finding has achieved greater significance and in our hands has led to an appreciable reduction in the need for exploratory laparotomy. Fears have been expressed about the danger of damaging a ViSCUS.9 While this may have been a real hazard when spinal needles or glass tubes were used, with modern synthetic materials, which are both flexible and pliable, it was apparent that this risk has been much reduced. This accords with our own experience of repeated peritoneal catheterization for peritoneal dialysis, in which patients have had repeated catheterizations, sometimes extending over a period of several years, for treatment of renal failure without any complication of this kind. The findings of abdominal paracentesis, however, cannot be considered on their own but must be taken into consideration along with the patient's history and clinical condition. A negative finding in patients with pains arising de novo does not necessarily exclude abdominal disease; it merely means that the visceral peritoneum is not inflamed and so not generating any exudate. Such patients should be watched carefully and if necessary the abdominal catheterization repeated if the clinical condition continues to warrant this. From the results presented, however, it is clear that abdominal paracentesis is a useful diagnostic aid and not infrequently prevents patients having an unnecessary laparotomy. Equally important is that where an early diagnosis can be made the appropriate surgical treatment can be started immediately, before the patient's clinical condition has had time to deteriorate.