Blumberg's sign is a sign that is elicited during physical examination in medicine

Medicine

Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

. It is indicative of peritonitis

Peritonitis

Peritonitis is an inflammation of the peritoneum, the serous membrane that lines part of the abdominal cavity and viscera. Peritonitis may be localised or generalised, and may result from infection or from a non-infectious process.-Abdominal pain and tenderness:The main manifestations of...

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The abdominal wall is compressed slowly and then rapidly released. Presence of pain

Pain

Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...

 makes the sign positive. It is very similar to rebound tenderness

Rebound tenderness

Rebound tenderness is a clinical sign that a doctor or other health care provider may detect in physical examination of a patient's abdomen. It refers to pain upon removal of pressure rather than application of pressure to the abdomen...

 and might be regarded by some authors as the same thing, or at least a particular application of it.

The name comes from German surgeon Jacob Moritz Blumberg

Jacob Moritz Blumberg

Jacob Moritz Blumberg was a German Jewish surgeon and gynaecologist and inventor and namesake of the Blumberg sign.-Biography:...

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Positive Blumberg sign or rebound tenderness is indicative of peritonitis. This method is specially useful in diagnosing appendicitis requiring urgent management.