Which of the following is a sign of internal abdominal bleeding?

A rigid abdomen is a significant indicator of internal abdominal bleeding. This symptom suggests that the abdominal muscles are tensing in response to internal irritation, which can occur due to bleeding and associated inflammation or peritonitis. When blood accumulates in the abdominal cavity, it can lead to increased pressure and subsequent involuntary muscle contraction (guarding), resulting in rigidity when palpated.

In comparison, though poor appetite, increased thirst, and rapid heart rate can be related to various conditions, they are not specific indicators of internal abdominal bleeding. In particular, a rigid abdomen stands out as a physical sign that may require immediate medical attention, as it could indicate a serious underlying issue such as organ damage or significant blood loss within the abdominal cavity. Detecting this sign can be crucial for timely diagnosis and treatment in emergency situations.