In trauma cases involving navel stabs, doctors often look for (blood) in the peritoneal cavity. If the patient is stable, they might use a CT scan to check for internal damage. If they are unstable or the "bleed" is significant, an emergency laparotomy (exploratory surgery) is usually the next step. If you have more details, I can help clarify:
Hand-to-stomach clutching animation is triggered to stem the flow.
The phrase appears to be a shorthand notation for a combat event in a gaming or tabletop RPG context: