By increasing urine color, 400 mg of oral riboflavin the night before gynecologic surgery makes it easier to see and confirm urine flow during intraoperative cystoscopy, according to results of a randomized, blinded, placebo-controlled trial.
The traditional go-to for that purpose, intravenous indigo carmine, has been in short supply, if possible to get at all, so surgeons have been looking for other options. Alternatives include intravenous methylene blue, intravenous fluorescein, and oral phenazopyridine, but each have their own problems, including cost, contraindications, and anaphylaxis.
So the study team turned to riboflavin – vitamin B2 – which, in excess, turns the urine bright, sometimes almost neon yellow. It’s “safe, readily available without prescription, and inexpensive ... and should be considered for routine use,” wrote investigators led by Michael L. Stitely, MD, an ob.gyn. at the University of Otago in Dunedin, New Zealand.
The team randomized 33 women to four 100-mg capsules of riboflavin the night before surgery and 33 to four 1,000-IU capsules of vitamin D3, which served as the placebo. Participants, clinicians, researchers, and study staff all were blinded to group allocation, the investigators noted in Obstetrics & Gynecology.
Surgeons rated urine color a median of 2 (slight yellow) in the riboflavin group, compared with 1 (clear) in the placebo arm, on a 3-point scale (P less than .001). About 13 women on riboflavin got a rating of 3 – strong yellow – versus 1 woman in the placebo arm.
The operating surgeons also said it was easier to visualize urine flow in the riboflavin group, giving a median of 5, compared with 4 in the placebo group, on a 5-point scale (P less than .013). They gave a score of 5 to 19 women in the riboflavin group but only to 8 placebo women, meaning that they “strongly agreed” that it was easy to see urine flow; a score of 4 meant that they simply agreed with the statement.
Overall, surgeons confirmed bilateral urine flow in 30 women (91%) in the riboflavin group, compared with 28 women (85%) in the placebo group (P = .71). When a blinded investigator checked the videos, their assessments of the same parameters correlated with those of the surgeons.
No significant differences were found between the groups in age, height, weight, body mass index, or ethnicity. The most common procedure was a midurethral sling (10 in the riboflavin group; 4 in the placebo arm), followed by cystoscopy with botox (4 in the riboflavin group; 7 in the placebo group). None of the women required intervention for urinary tract injury.
Among the limitations cited was the use of subjective and nonvalidated measures of urine color.
The work was funded by the Healthcare Otago Charitable Trust and the Australasian Gynaecological Endoscopy and Surgery Society. The authors reported no conflicts of interest.
SOURCE: Stitely ML et al. Obstet Gynecol. 2019 Jan 8. doi: 10.1097/AOG.0000000000003063.