This study focuses on children experiencing thrombotic episodes, which are instances where blood clots form, within superficial venous malformations. A venous malformation is an abnormal buildup of blood vessels located close to the surface of the skin. The purpose of the study is to evaluate the effectiveness of acetylsalicylic acid compared to a placebo in managing the pain associated with these events. Participants in the study also use diclofenac, a type of non-steroidal anti-inflammatory drug, which is applied topically as a gel to the affected area.

The research follows a cross-over design, meaning that participants will receive different treatments at different times during the study. During the trial, some will receive the active medication, while others receive the placebo, in addition to the local gel. This process is conducted as a double-blind trial, which means neither the participants nor the researchers know which specific treatment is being administered at any given time. The treatment periods will last between 3 and 14 days.