Validity of visual inspection of diagnostic peritoneal lavage fluid

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.

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.

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 10,000 and 20,000 erythrocytes/mL for most subjects. There were no significant differences between residents and staff surgeons.

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 100,000 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.