Validity of visual inspection of diagnostic peritoneal lavage fluid

Objective: To determine the positive and negative predictive values of visual inspection of peritoneal lavage fluid and the threshold concentration of erythrocytes for diagnosing significant hemoperitoneum by this method. Design: Nineteen residents in surgery and 21 staff surgeons were asked to inspect mock peritoneal lavage fluid and state whether they would proceed with urgent laparotomy. Main Results: The overall positive and negative predictive values for visual inspection were 52.0% and 98.9%, respectively. The threshold for diagnosing significant hemoperitoneum by visual inspection was between 10000 and 20000 erythrocytes/mL for most subjects. There were no significant differences between residents and staff surgeons. Conclusions: Visual inspection of peritoneal lavage fluid has good negative but poor positive predictive value, and the threshold for diagnosing significant hemoperitoneum by visual inspection is less than 100000 erythrocytes/mL. Therefore, patients whose condition is stable and for whom visual inspection of lavage fluid indicates apparently significant hemoperitoneum should not undergo laparotomy without confirmation by laboratory testing.