while we're on the subject of edema, can someone clarify the difference betn pitting and non-pitting edema. i've never really read anything so far in med school that differentiates betn the 2.
So, in a very basic sense, pitting edema will indent when pressure is applied to the edematous area, usually over the tibia when talking about the lower extremity. Nonpitting edema will not indent.
That being said, classic causes of pitting edema, ie lymphedema, is soft and will pit early in the course. It is not until the chronic stages in which the area gets that woody feel from the tissues becoming fibrotic that the edema becomes nonpitting.
The other main cause of nonpitting edema is myxedema. This does not pit because it's not fluid being displaced into the interstitial space, rather it's an accumulation of increased amounts of mucopolysaccharides in the dermis, and thus will not pit.
So, I hope that answers your question. I think the most important thing here is that although pitting vs nonpitting certainly may speak as to etiology, the early stages of nonpitting etiologies will indeed pit. (Except for myxedema, but it's relatively rare, and the other stigmata of thyroid dz should be apparent at this stage.) So, instead of making a differential based on pitting vs nonpitting, I think it's a good idea to base a differential on bilateral vs. unilateral distribution, in conjunction with , as always, a good history. (Obviously a history of CHF, renal dz, or thyroid pathology will influence your differential.)
Hope that helps.
http://en.wikipedia.org/wiki/Dermis
