The access and invasiveness-based classification of medical procedures to clarify non-invasive from different forms of minimally invasive and open surgery.

Background: The rapid development of less invasive and traumatic medical procedures has resulted in a mixture of terms used to describe them, without any agreed definition for each. This is confusing to both medical professionals and patients and can lead to unrealistic patient expectations. The aim of this article is to show the current confused nomenclature and to suggest a new, simple classification based on access and invasiveness (AI) that can be applied to any medical procedure.

Methods: We performed an online search for definitions for 'non-invasive', 'non-surgical', 'minimally invasive', 'minimal access', 'pinhole' and 'keyhole'. We then searched peer-reviewed medical papers (PRMPs) and patient facing websites (PFWs) for the following index procedures, to see which of the original 6 terms were used to describe them: transvaginal ultrasound, sclerotherapy for leg veins, botulinum toxin injections, dermal fillers, endovenous thermal ablation and laparoscopic gall bladder removal.

Results: We found a wide variety of definitions for each of the initial terms. In both PRMPs and PFWs, there were a variety of terms used for each index procedure (i.e.: transvaginal ultrasound, injections of sclerotherapy, botulinum toxin or dermal fillers being both 'non-invasive' and 'minimally invasive') showing confusion in the classification of procedures. We suggested the 'AI classification' based on access (A - none, B - natural orifice or C - penetrating an epithelial surface) and invasiveness (1 - none, 2 - surface damage, 3 - needle = <21G, 4 - cannula >21G but not a surgical trocar, 5 - surgical trocars or small incisions and 6 - incisions).

Conclusion: The current confusion of terms used for procedures that are less invasive than the open surgical alternatives leads to confusion and possible false patient expectations. We have proposed an AI classification that can be applied easily to any procedure, giving a uniform classification for medical professionals and patients to understand.