Unreliability of standard quantitative criteria in diagnostic peritoneal lavage performed for suspected penetrating abdominal stab wounds

Thirty-five patients with abdominal stab wounds in whom clinical examination was equivocal on 2 separate occasions underwent diagnostic peritoneal lavage (DPL) prior to laparotomy. The red and white blood cell counts (cells/mm3) of the lavage effluent were compared with the operative findings. There were 26 positive and 9 unnecessary laparotomies, the latter consisting of 4 negative and 5 non-therapeutic operations. Use of the standard quantitative criteria for red cells in DPL failed to identify significant injury in eight patients (31%), while the standard white cell count missed six injuries (23%). Their combined use resulted in three missed injuries (12%). Two false-positive results occurred using the red cell count alone and four using the white cell count alone, producing a combined false-positive result in four patients (11%). Reducing the cell threshold level to exclude missed injuries would increase dramatically the rate of unnecessary laparotomies. Although the standard quantitative criteria for DPL are superior to clinical assessment in patients with equivocal findings, their use in penetrating trauma does not achieve the same diagnostic accuracy as in blunt abdominal trauma.