Diagnostic peritoneal lavage: is 100,000 RBCs a valid figure for penetrating abdominal trauma?

Controversy exists regarding the interpretation of diagnostic peritoneal lavage results. This is especially true in the evaluation of patients sustaining penetrating trauma, specifically stab wounds to the lower chest and abdomen. Ideally one wants to avoid missed injuries and minimize unnecessary operations.

This is a retrospective review of 195 patients sustaining stab wounds to the anterior lower chest and abdomen at Parkland Memorial Hospital between 1993 and 2005, looking at missed injuries and false positive rates using red cell counts of 100,000, 10,000, and the standard criteria for blunt trauma including >500 white blood cells (WBCs), amylase, and/or bile.

The first analysis used >100,000 red blood cells (RBCs)/mm3 as a positive value. The false positive rate was 12.2%. The second analysis used >10,000 RBCs/mm3 as a positive value with a false positive rate of 44%. When considering the entire study population (195 patients), the false positive rate increased when using the lower number (>10,000) from 2.5% to 15.8% (p < 0.001). There were no missed injuries when using >100,000 red cells and/or >500 white cells, the presence of bile or amylase.

Decreasing the red blood cell count from >100,000 to >10,000 as the criteria for operating on patients with stab wounds to the anterior lower chest and/or abdomen will significantly increase the number of nontherapeutic procedures. Based on this study, >100,000 RBCs/mm3 appears to be a valid and safe number to use when evaluating these patients, particularly when used with other positive criteria such as increased white cells, bile, and amylase.