To determine whether intravenous indigo carmine provides a visualization advantage compared to saline in the evaluation of ureteral patency in a randomized, controlled clinical trial.

Patients undergoing urological or gynecological surgical procedures in which the patency of the ureter was to be assessed received a saline injection and were randomized to receive 2.5 mL or 5.0 mL of indigo carmine. Blinded video assessments were conducted by independent reviewers using a conspicuity scale ranked 1 (poorest) to 5 (best), and subjects with scores ≥3 and at least a + 1-point difference from saline were considered responders. Time to visualization was recorded for indigo carmine. A responder analysis evaluated whether indigo carmine showed improved visualization.

There were 96 ureters evaluated with the 5.0 mL dose of indigo carmine, 92 with the 2.5 mL dose, and 180 with saline. Most ureters were scored a 4 or higher on the conspicuity scale following indigo carmine; both doses were significantly better than saline (P < .0001). Overall, 92.3% of patients were rated as a responder for either ureter. The median time to visualization of blue color was not significantly different (6.0 minutes in the 5.0 mL group and 5.9 minutes in the 2.5 mL group). There were no adverse events related to indigo carmine use.

Both dose levels of indigo carmine were significantly better than saline as a visualization aid for ureter patency.