Interesting Conversations About Toluidine Blue Dye Use

With the interesting conversation about toluidine blue dye use going on over at the IAFN community site, a quick reminder, we have a clinical guide on that topic here at FHO. There seems to be some disagreements about where it can be used, however, so click through for excerpts from the peer-reviewed literature that may help provide guidance:

From Significance of toluidine blue positive findings after speculum examination for sexual assault (Jones, et al., 2004): “Before the insertion of a speculum or examining fingers, a 1% aqueous solution of toluidine blue was applied to the posterior fourchette, fossa navicularis, and the posterior aspect of the labia using cotton-tipped applicators…” (p 201); “…external genital injuries from sexual assault were documented in 67% (18 of 27) of the patients using toludine staining. A total of 37 external genital injuries were documented (mean number of genital injuries, 1.37). These injuries occurred at the following sites: posterior fourchette (12), fossa navicularis (10), labia minora (nine), perineum (three), and labia majora (three). Tears appeared most often on the posterior fourchette and fossa; abrasions appeared on the labia minora.” (p 202).

From Chapter 6, Atlas of Sexual Violence (Rossman, et al., 2013): “If used to assist with visualization during the anogenital examination, toluidine blue dye should be applied to the posterior fourchette, fossa navicularis, labia minora, perineum, or anus prior to the insertion of the examiner’s finger, speculum, or anoscope.” (p 100) [ed: I assume anus in this context actually refers to perianal, since I don’t believe anyone is putting TB dye inside the anal canal.] A photo of dye uptake to fossa navicularis lacerations is on the same page.

From Chapter 28, Adult Sexual Assaults: Practical Management (Girardin, Faugno & Howitt, 2003): “After the examination of the posterior fourchette and the fossa navicularis, and the collection of swabs and photographs, apply 1% toluidine blue dye to the posterior fourchette and fossa navicularis from 4 to 8 o’clock…Toluidine blue dye stains nucleated squamous cells in the deeper layers of the epidermis.” (p 422).

There are several issues with the current listserv discussion regarding TB dye: 1.) much of the literature vaguely references its application to the posterior fourchette area (in which the fossa navicularis resides) or to the external genitalia (again, fossa navicularis included); and 2.) the assertion that the fossa is mucosa is somewhat fuzzy due to the fact that we know TB dye doesn’t adhere to mucosa, and yet we have plenty of people who have the experience of using TB dye on injuries to the fossa. I have been trying to identify a source that clearly states the fossa is in fact mucosa and haven’t had a whole lot of luck. There is an 1883 reference to the fossa navicularis as skin from the Medical and Surgical Reporter (Vol 48–h/t Kim Day). It corrects a previous assertion that the fossa was believed to have been mucosa, so there’s that, but it’s somewhat outside my 10 year window for references. [Add: anyone who has an actual reference that clearly states that the fossa navicularis is mucous membrane, please provide it–contrary to some snarky suggestions on a different site, my nurse midwife colleague and I searching through numerous dermatology, OB/GYN, nurse midwifery and basic anatomy texts turned up nothing. I have no issue with being wrong on this. I just want the citation(s), vice it being suggested I’m a moron who doesn’t know how to do a lit search.] 

What isn’t being discussed is that TB dye is problematic when it’s applied poorly. Perhaps that should be the bigger concern. I review cases regularly where it’s inartfully applied and injury is overcalled because all of the pooling of dye is not recognized as such. TB dye should be used like a highlighter, not like a searchlight. As an expert consultant and witness, that is a bigger and more pressing issue in the use of TB dye.

This is an interesting debate taking place, and I look forward to seeing what else surfaces on the issue. In the meantime I will continue to update the clinical guide as I receive new, credible information.

And as a continued reminder, FHO is a no shaming space, so please continue to send questions, post comments and share resources. I am thoroughly enjoying the discussion, and hope people will continue to freely share and dialogue.

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