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Dilatation vs. Dilation – We Have a Winner Here [May be?]

I have always had this confusion. Should I be saying “No bile duct dilatation.” or “No bile duct dilation.”? Is there a difference?

I thought it was only me but I soon realized that I am not alone. In fact, there are actual PubMed indexed journal papers on this topic! I could at least find four :).

Dilatation vs dilation Pubmed Research Articles

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And even the #radtwitter had its own reservations:

Dilatation vs dilation debate Twitter

And the debate is not limited to radiologists as even obstetricians, cardiologists and ophthalmologists frequently encounter this term.

So is there any difference between dilatation and dilation ? What is the correct usage?

Lets dig into the history a bit. According to Google Ngram (a search engine that charts word frequencies from a large corpus of books that were printed between 1500 and 2019), word dilatation has been used more frequently in literature than dilation as depicted in this graphic but recently the latter has taken over. Although using Google Ngram is not an ideal method to track usage (a post on the WIRED describes it as seductively simple), it does gives us a basic idea.

Dilatation vs dilation Google Ngram Viewer

Even in the scientific literature, the word dilatation has been more common than dilation as per an article published by Mahroof et al. in the British Journal of Opthalmology.

Bloom et.al concluded that these words convey the same meaning and conclude by saying: “Attempted distinction between the two, namely that of an action versus a condition, seems arbitrary and without historical evidence or support. ” A few authors have suggested that the ORIGINAL word dilatation has been shortened by Americans to dilation to save space, which according to me is hard to believe.

So can you and should you use these terms interchangeably? The answer is no. At least that what I think. Here is my understanding :

Dilation (verb) is the act of dilating and dilatation (noun) is the region of abnormal enlargement or dilation. Read more 👇

There is pancreatic duct dilatation (noun) secondary to an ampullary adenocarcinoma.


Outcomes of ampulla dilation with different sized balloons to remove common bile duct (CBD) stones were studied.


Ampullary dilation techniques can be used to achieve dilatation of the CBD.


  1. Ophthalmologist dilate the pupils.
  2. Obstetricians dilate the cervix.

Another differentiation is that dilation usually refers to physiological processes such as dilation of pupils, vessels and cervix vis-a-vis dilatation which refers to surgical procedures such as dilatation and curettage, balloon dilation valvuloplasty.

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Here is a list of all articles using these terms on PubMed: (dilation) OR (dilatation) on Pubmed. How many of these do you think have used the term incorrectly? I could spot at least a few in the top 100 results.

Pubmed Articles with the terms dilation or dilatation

Hopefully I have made it easier for you. Or have I confused you more? Let me know your thoughts in the comments!

Dilatation vs dilation meme

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About the Author

Dr. Amar Udare, MD, DNB

Dr Amar UdareDr. Amar Udare is a board-certified radiologist. He is currently working as a fellow radiologist at McMaster University, Canada. He has a passion for teaching (#FOAMrad and #FOAMed) and has been a semi-finalist for the 2018 and 2020 Aunt-Minnie Most effective Radiology Educator Awards. He has authored multiple peer-reviewed publications which can be accessed on PubMed and Google Scholar.

1 thought on “Dilatation vs. Dilation – We Have a Winner Here [May be?]”

  1. Cody James

    Good stuff!
    I always used to have this confusion. Thanks for sharing :).

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