Snapshot A 30-year-old G0P0 woman presents to the emergency room for acute onset abdominal pain and nausea. She recently had unprotected sex with 2 different partners. On physical exam, she has involuntary guarding and tenderness to percussion. A urine pregnancy test is positive, and a transvaginal ultrasound shows a ruptured ectopic pregnancy. Introduction Overview acute abdomen is characterized by acute onset of severe abdominal pain that requires urgent surgical evaluation management depends on etiology Epidemiology Incidence Subtypes hemorrhage abdominal aortic aneurysm rupture bleeding gastric ulcer ruptured ectopic pregnancy ischemia ischemic bowel disease perforated bowel/peritonitis perforated peptic ulcer bowel obstruction diverticular disease inflammatory bowel disease perforated appendicitis ETIOLOGY Pathogenesis mechanism hemorrhage will often lead to hypovolemic shock, requiring swift intervention ischemia results in elevated lactate and also requires early intervention perforated bowel causes inflammation of the peritoneum or peritonitis Presentation Symptoms common symptoms dehydration sudden-onset abdominal pain pain out of proportion to exam ischemic bowel disease Physical exam inspection pallor hypovolemia tachycardia motion rigid abdomen tenderness to percussion involuntary guarding may have reduced or absent bowel sounds Imaging Chest radiograph indications to look for free air under the diaphragm findings free air under the diaphragm, indicating bowel perforation Abdominal radiograph indications if bowel obstruction is suspected findings dilated loops of bowel Abdominal ultrasound indications if biliary or hepatic etiology is suspected if tubo-ovarian pathology is suspected if appendicitis is suspected if aneurysm is suspected evaluate for hemorrhage CT abdomen and pelvis indications if mesenteric ischemia, diverticulitis, or bowel perforation are suspected Studies Serum labs lactate arterial blood gas urinalysis pregnancy test blood cultures to rule out infection amylase and lipase if pancreatitis is suspected complete blood count electrolytes liver function panel Differential Differential by Location of Abdominal PainGeneralizedBowel obstructionMesenteric ischemiaRight Upper QuadrantEpigastricLeft Upper QuadrantAcute cholecystitisHepatitisLiver abscessAcute cholangitisPeptic ulcer diseaseMyocardial infarctionPancreatitisGastric ulcerSplenic ruptureRight Lower QuadrantPeriumbilicalLeft Lower QuadrantAppendicitisBowel obstructionAppendicitisAbdominal aortic aneurysmDiverticulitisLower AbdomenInguinal herniaIBDUTIPelvic inflammatory diseaseEctopic pregnancyTesticular torsion Treatment Management approach depends on the etiology of acute abdomen Medical supportive care indications all patients modalities intravenous hydration analgesia anti-emetics nasogastric decompression if necessary bowel rest NPO blood transfusion if necessary Surgical surgical intervention indications irreversible pathologies such as appendicitis, mesenteric ischemia, and perforated bowel Complications Septic shock Death