Acute abdomen

The acute abdomen is a surgical emergency characterized by sudden onset of severe abdominal pain and tenderness and muscular rigidity. Because of the severe pain and potentially life-threatening conditions associated with it (e.g., abdominal aneurysm rupture), rapid diagnosis and management are crucial. Differential diagnoses should be ruled out with a thorough physical examination, followed by laboratory tests and imaging, such as ultrasound, x-ray, or CT. Management depends on the specific diagnosis and ranges from medical treatment to emergency surgical intervention.

Pain location	Causes	Typical findings	Laboratory tests	Next diagnostic step
RUQ	Liver abscess	Recent biliary or systemic infection Fever, malaise, weight loss Tender hepatomegaly	↑ Bilirubin ↑ AP ↑ Transaminases	Ultrasound
	Acute cholecystitis	Fever Right shoulder referred pain Nausea, vomiting Murphy sign	↑ Bilirubin ↑ AP ↑ GGT
	Acute cholangitis	Charcot triad: RUQ pain, fever, and jaundice	↑ Bilirubin ↑ AP ↑ GGT
LUQ	Splenic rupture	History of recent trauma Shock	Anemia (late finding) Leukocytosis Thrombocytosis	Ultrasound (FAST exam)
RLQ	Appendicitis	Onset: periumbilical or epigastric pain Signs of appendicitis Fever		Ultrasound
LLQ	Sigmoid diverticulitis	Fever Possible constipation Elderly patients		CT
Epigastric	Gastric or duodenal ulcer perforation	History of NSAID or glucocorticoid use Dyspepsia		X-ray or CT
	Acute pancreatitis	Possibly fever Circumferential pain History of gallstones or alcoholism	↑ Lipase ↑ Amylase	Ultrasound or CT
	Acute coronary syndrome	Chest pain may be absent, especially in women, diabetics, and elderly patients History of atherosclerosis	Troponin CK-MB	ECG
Generalized	Intestinal obstruction	History of abdominal surgery Bloating No bowel activity Progressive nausea and vomiting (late finding)		Abdominal x-ray
	Mesenteric ischemia	Minimal tenderness to palpation History of atrial fibrillation or hypercoagulability Elderly patients	↑ Serum lactate	CT with angiography
Radiating to the flanks and back	Abdominal aortic aneurysm	History of arteriosclerosis, hypertension, or smoking Elderly patients Shock (if ruptured)		Ultrasound
Lower abdomen	Pelvic inflammatory disease	Cervical motion tenderness History of high-risk behavior/STD Purulent cervical/vaginal discharge		Ultrasound
	Ectopic pregnancy	Amenorrhea Vaginal bleeding Hypotension (if ruptured)	↑ hCG	Transvaginal ultrasound

Any woman of child-bearing age presenting with abdominal pain must have hCG checked!

References:^[1][2][3]

The differential diagnoses listed here are not exhaustive.