The causes of non pitting edema can be retained with the help of the mnemonic "e- ELASTIC". In contrast to pitting edema, oncotic and hydrostatic pressure alterations are not the underlying etiologies in non-pitting edema. Instead, there is either inflammation, lymphatic pathology or abnormal extracellular matrix deposition. Source: http://www.rxpgonline.com/medicalmnemonic91454.html