Snapshot A 17-year-old boy is brought to the emergency room by his parents for increasing abdominal pain. He started having periumbilical pain last night but now reports increasing right lower quadrant pain. He reports that about an hour ago, the pain acutely intensified and was not responsive to ibuprofen or acetaminophen anymore. On physical exam, his abdomen is rigid with involuntary guarding and tenderness to light percussion. A right lower quadrant ultrasound shows an enlarged appendix with possible perforation. He is emergently taken to the operating room. Introduction Overview acute abdomen is characterized by acute onset of severe abdominal pain that requires urgent surgical evaluation management depends on etiology Epidemiology incidence etiologies 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 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 Pain Generalized Bowel obstruction Mesenteric ischemia Right Upper Quadrant Epigastric Left Upper Quadrant Acute cholecystitis Hepatitis Liver abscess Acute cholangitis Peptic ulcer disease Myocardial infarction Pancreatitis Gastric ulcer Splenic rupture Right Lower Quadrant Periumbilical Left Lower Quadrant Appendicitis Bowel obstruction Appendicitis Abdominal aortic aneurysm Diverticulitis Lower abdomen Inguinal hernia IBD UTI Pelvic inflammatory disease Ectopic pregnancy Testicular 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