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The value of repeating diagnostic peritoneal lavage (DPL) when initial results are indeterminate or negative has not been defined. From January 1974 to June 1980, 1884 patients underwent DPL. Ninety-six had repeat DPL. Eighty-eight (4.7%) patients with indeterminate initial DPL results had repeat DPL. Results were true positive in 20, false positive in non, false negative in three, and true negative in 64 patients. If results for all 88 patients had initially been considered positive and all had undergone operation, the additional yield would have been low, three patients (3.4%); 64 patients would have undergone unnecessary laparotomy. If all 88 results had been considered negative, 20 patients (23%) with intra-abdominal injuries would have been diagnosed late or not at all. Eight patients with initial negative DPL but with persistent abdominal pain underwent repeat DPL. Results were true positive in three, false negative in one, and true negative in four. Repeat lavage has an accuracy of 95.8%, sensitivity of 85.2%, and specificity of 100%; with repeat lavage, DPL overall has high accuracy (98.4%), sensitivity (94.2%), and specificity (99.7%). Repeat lavage can be helpful in evaluating patients with initial negative lavage but with persistent abdominal pain. Repeat lavage is also indicated when initial results are indeterminate.

From January 1974 through July 1979, 1,588 patients underwent diagnostic peritoneal lavage. The test had an accuracy of 98.6%, sensitivity of 94.3%, and specificity of 99.8%. It was true positive in 21.9%, false positive in 0.1%, false negative in 1.3%, and true negative in 76.6%. Fifty-nine patients from the true-positive group had grossly equivocal tests, but had positive lavage results based on quantitative cell count. Thus without cell count the test would have a sensitivity of 78.3%, accuracy of 94.8%, and specificity of 99.8. Eight patients had positive lavage based on WBC count but negative RBC count; all of these patients had bowel injuries. Measurement of lavage fluid amylase resulted in minimal or no improvement in the accuracy (0.06%), sensitivity (0.3%), or specificity (0.0%). Five of six patients with positive amylase levels but grossly negative tests had concomitant positive WBC count. The added cost of the amylase measurement is estimated to be $154,472. Peritoneal lavage has high accuracy, sensitivity, and specificity. Cell counts significantly improve sensitivity. Patients with a grossly equivocal test but with a positive cell count should undergo laparotomy. The lavage-fluid amylase measurement is costly and is of insignificantly yield.

The criteria for declaring the results of a diagnostic peritoneal lavage (DPL) positive have been controversial. Lowered cell count criteria result in increased sensitivity, decreased specificity, and altered accuracy. Consecutive lavages on 105 patients with penetrating trauma (PT) to the lower chest and abdomen (48 gunshot wounds and 57 stab wounds) and 1812 patients with blunt abdominal trauma (BT) were studied. Varied cell count criteria were analyzed. The best criteria for BT were as follows: positive, lavage fluid red blood cells (LRBCs) greater than 100,000/mm3 or lavage fluid white blood cells (LWBCs) greater than 500/mm3; indeterminate, LRBCs 50,000/mm3 to 100,000/mm3 or LWBCs 100 to 500/mm3; and negative, LRBCs less than 50,000/mm3 and LWBCs less than 100/mm3. Based on these criteria the accuracy of the test was 99.1%. The highest accuracy would be achieved for PT if the criteria were as follows: positive, LRBCs greater than 50,000/mm3 or LWBCs greater than 500/mm3; indeterminate, LRBCs 25,000 to 50,000/mm3 or LWBCs 100 to 500/mm3; negative, LRBCs less than 25,000/mm3 and LWBCs less than 100/mm3. Based on these criteria the accuracy of the test for PT would range from 96.2% (101 of 105) to 98.1% (103 of 105), depending on the results of repeat lavage for two patients with indeterminate initial lavages. The standard lavage criteria were the best for BT and achieved the highest accuracy. However, the LRBC criteria should be lowered for PT.