The most effective way to make a patient contract his abdominal muscles is to put your hand beneath both heels and lift them up 30 cm, and then ask him to hold his straight legs up from the bed on his own.
This makes the rectus abdominal muscles contract and any mass deep to them is completely impalpable.
Annotations allow you to add information to this page that would be handy to have on hand during a consultation. E.g. a website or number. This information will always show when you visit this page.