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What is Acute abdomen and explain in detail?
An acute abdomen refers to a sudden, severe abdominal pain. It is in many cases a medical emergency, requiring urgent and specific diagnosis. Several causes need immediate surgical treatment.

Differential diagnosis
The differential diagnosis of acute abdomen includes:
Acute appendicitis
Acute peptic ulcer and its complications
Acute cholecystitis
Acute pancreatitis
Acute intestinal ischemia (see section below)
Acute diverticulitis
Ectopic pregnancy with tubal rupture
Ovarian torsion
Acute peritonitis (including hollow viscus perforation)
Acute ureteric colic
Bowel volvulus
Bowel obstruction
Acute pyelonephritis
Adrenal crisis
Biliary colic
Abdominal aortic aneurysm
Familial Mediterranean fever
Hemoperitoneum
Ruptured spleen
Kidney stone
Sickle cell anaemia
Carcinoid

Peritonitis
Acute abdomen is occasionally used synonymously with peritonitis. While this is not entirely incorrect, peritonitis is the more specific term, referring to inflammation of the peritoneum. It manifests on physical examination as rebound tenderness, or pain upon removal of pressure more than on application of pressure to the abdomen. Peritonitis may result from several of the above diseases, notably appendicitis and pancreatitis. While rebound tenderness is commonly associated with peritonitis, the most specific finding is rigidity.

Ischemic acute abdomen
Vascular disorders are more likely to affect the small bowel than the large bowel