Sudden onset abdominal pain requiring urgent evaluation. Surgical vs medical cause is the critical distinction. CT is the workhorse imaging. Pain out of proportion to exam = mesenteric ischemia or vascular emergency.
Cannot-miss diagnoses: AAA rupture, mesenteric ischemia (pain out of proportion), ectopic pregnancy (all women of childbearing age get ฮฒ-hCG), testicular/ovarian torsion, perforated viscus.
Do NOT withhold pain medication while awaiting surgical evaluation. The old teaching that analgesics "mask" peritoneal signs and delay diagnosis is disproven. Pain control improves the physical exam by allowing the patient to cooperate Thomas, 2003. Give morphine 0.1 mg/kg IV while workup proceeds.
Pain control -Morphine (MS Contin) or Fentanyl (Sublimaze). Treating pain does NOT mask surgical findings.
NPO -if surgical cause suspected
Surgery consult -peritonitis, free air, hemodynamic instability
Surgical Emergencies (Cannot Wait)
Perforated viscus (free air under diaphragm)
AAA rupture
Mesenteric ischemia with infarction
Strangulated hernia/SBO
Testicular/ovarian torsion
Ectopic pregnancy with hemodynamic instability
Surgical vs Medical Acute Abdomen: Surgical emergencies requiring OR: perforated viscus (free air on CT), mesenteric ischemia with bowel necrosis, ruptured AAA, appendicitis, incarcerated hernia. Medical causes to consider: DKA (can mimic surgical abdomen), pancreatitis (usually medical), inferior MI (epigastric pain), adrenal crisis, sickle cell crisis, porphyria, C. diff colitis.
Antibiotics-first for uncomplicated appendicitis? The CODA 2020 trial showed antibiotics alone were noninferior to surgery for uncomplicated appendicitis at 30 days, but 29% eventually needed appendectomy within 90 days CODA, 2020. Surgery remains standard of care, but antibiotics-first is a shared decision option in select patients.
๐งช Workup
CT abdomen/pelvis with IV contrast -workhorse imaging for acute abdomen ACR Appropriateness Criteria, 2018
Upright CXR -free air under diaphragm (perforated viscus)
US -RUQ (biliary), pelvic (OB/GYN pathology), bedside FAST
CBC, BMP, lipase, LFTs, lactate, UA
ฮฒ-hCG -ALL women of childbearing age. Ectopic kills.
Type & screen if surgical candidate
Key Evidence: CT abdomen/pelvis with IV contrast is the most sensitive single test for acute abdomen (sensitivity > 95% for most surgical emergencies) Rosen, 2000. For suspected appendicitis, CT has 94% sensitivity and 95% specificity Doria, 2006. Ultrasound is first-line for biliary disease (sensitivity 95% for gallstones) and in pregnancy. MRI appendicitis protocol is safe and accurate in pregnancy Duke, 2016.
๐ Medications
Drug
Dose
Purpose
Morphine (MS Contin)
2โ4 mg IV q2โ4h
Pain control -does NOT mask surgical exam
Ketorolac (Toradol)
15โ30 mg IV
NSAID -good for renal colic, biliary colic
Ondansetron (Zofran)
4 mg IV
Anti-emetic
Piperacillin-Tazobactam (Zosyn)
3.375 g IV q6h
Broad-spectrum if peritonitis/perforation
IV NS/LR
Bolus 1โ2 L
Volume resuscitation
Clinical Examples
๐ Case 1, Perforated Peptic Ulcer
Patient: 55-year-old man with chronic NSAID use presents with sudden-onset severe epigastric pain radiating to the right shoulder (Kehr sign). Rigid abdomen, rebound tenderness, absent bowel sounds.
Key findings: Upright CXR shows free air under right hemidiaphragm. Lactate 3.2, WBC 18K. Tachycardic, BP 95/60.
Management:
NPO, IV fluids, broad-spectrum antibiotics (piperacillin-tazobactam)
Emergent surgery consult for exploratory laparotomy and repair
Pain control with IV fentanyl (does NOT mask surgical exam)
Teaching point: Free air under the diaphragm = perforated viscus until proven otherwise. This is a surgical emergency - surgical repair within 24 hours is associated with decreased mortality Soreide et al., 2015. Do not delay for CT if clinical picture is clear and patient is unstable.
๐ Case 2, Acute Mesenteric Ischemia
Patient: 72-year-old woman with atrial fibrillation (not on anticoagulation) presents with severe periumbilical pain for 6 hours. Pain is 10/10 but abdomen is soft and non-tender on palpation.
Key findings: Pain out of proportion to exam. Lactate 5.8. WBC 22K. CT angiography shows SMA thromboembolism with bowel wall thickening.
Management:
Emergent vascular surgery consult for embolectomy vs endovascular intervention
IV heparin anticoagulation
Aggressive IV fluid resuscitation, broad-spectrum antibiotics
If peritonitis develops, emergent laparotomy for bowel resection
Teaching point: Pain out of proportion to exam + atrial fibrillation + elevated lactate = mesenteric ischemia until proven otherwise. CTA abdomen is the study of choice Bala et al. (ACS Surgery), 2022. Mortality exceeds 60% if diagnosis is delayed beyond 12 hours.
๐ Case 3, Acute Appendicitis
Patient: 28-year-old woman presents with 18 hours of periumbilical pain that has migrated to the RLQ. Anorexia, nausea, low-grade fever (38.2C). Positive McBurney point tenderness, positive Rovsing sign.
Key findings: WBC 14K with left shift. Beta-hCG negative. CT abdomen/pelvis shows dilated appendix (12 mm) with periappendiceal fat stranding and an appendicolith.
Management:
NPO, IV fluids, IV antibiotics (cefoxitin or ceftriaxone + metronidazole)
Surgery consult for appendectomy (laparoscopic preferred)
If perforated with abscess: percutaneous drainage + antibiotics, delayed interval appendectomy in 6-8 weeks
Teaching point: Classic appendicitis presents with visceral pain (periumbilical) migrating to somatic pain (RLQ) as inflammation involves the parietal peritoneum. Always check beta-hCG in women of childbearing age to rule out ectopic pregnancy. Laparoscopic appendectomy remains the gold standard WSES Guidelines, 2020.
๐ On Rounds
Pimp Questions
Why must every woman of childbearing age get a pregnancy test with abdominal pain?
Ectopic pregnancy can present as abdominal pain with or without vaginal bleeding and can rupture catastrophically โ hemorrhagic shock โ death in minutes. It is the #1 cause of first-trimester maternal death. A negative ฮฒ-hCG essentially rules it out. Cost of the test is trivial compared to the consequence of missing it.
Does giving opioids for abdominal pain mask surgical findings?
No. This is a persistent myth. Multiple studies (including a Cochrane review) show that analgesics do not impair diagnostic accuracy and may actually improve exam quality by allowing patients to cooperate. Withholding pain control is unethical. Treat pain while completing the workup.
What is the significance of pain out of proportion to physical exam?
Classic for mesenteric ischemia. Early mesenteric ischemia causes severe visceral pain but the abdomen may appear benign on exam (no peritoneal signs yet -ischemia hasn't progressed to infarction/necrosis). By the time peritonitis develops, bowel is dead. High lactate + pain out of proportion + risk factors (Afib, atherosclerosis, hypercoagulable) โ CTA abdomen STAT.
What are the Alvarado score components for appendicitis?
MANTRELS mnemonic: Migration of pain to RLQ (1), Anorexia (1), Nausea/vomiting (1), Tenderness in RLQ (2), Rebound (1), Elevated temp (1), Leukocytosis (2), Left shift (1). Total 10. Score 7+ = high probability, consider surgery. Score 5-6 = intermediate, get CT. Score 4 or less = low probability, observe.
When should you get a CT scan vs ultrasound for acute abdominal pain?
CT with IV contrast is the workhorse - sensitivity > 95% for most surgical emergencies. Preferred for: appendicitis in adults, diverticulitis, SBO, perforation, mesenteric ischemia. Ultrasound first-line for: RUQ pain/cholecystitis, pregnancy (avoid radiation), pediatric appendicitis, testicular torsion, AAA screening. Use MRI if US inconclusive in pregnancy.
What is the significance of "pain out of proportion to exam" beyond mesenteric ischemia?
Classic for mesenteric ischemia - severe pain but soft, nontender abdomen early on. Also seen in necrotizing fasciitis and compartment syndrome. In elderly with AFib or vascular disease + severe pain + benign exam, assume mesenteric ischemia until proven otherwise. CTA abdomen is diagnostic. Mortality > 60% if diagnosis delayed.
Clinical Examples
๐ Case 1, Perforated Peptic Ulcer
Patient: 55-year-old man with chronic NSAID use presents with sudden-onset severe epigastric pain radiating to the right shoulder (Kehr sign). Rigid abdomen, rebound tenderness, absent bowel sounds.
Key findings: Upright CXR shows free air under right hemidiaphragm. Lactate 3.2, WBC 18K. Tachycardic, BP 95/60.
Management:
NPO, IV fluids, broad-spectrum antibiotics (piperacillin-tazobactam)
Emergent surgery consult for exploratory laparotomy and repair
Pain control with IV fentanyl (does NOT mask surgical exam)
Teaching point: Free air under the diaphragm = perforated viscus until proven otherwise. This is a surgical emergency - surgical repair within 24 hours is associated with decreased mortality Soreide et al., 2015. Do not delay for CT if clinical picture is clear and patient is unstable.
๐ Case 2, Acute Mesenteric Ischemia
Patient: 72-year-old woman with atrial fibrillation (not on anticoagulation) presents with severe periumbilical pain for 6 hours. Pain is 10/10 but abdomen is soft and non-tender on palpation.
Key findings: Pain out of proportion to exam. Lactate 5.8. WBC 22K. CT angiography shows SMA thromboembolism with bowel wall thickening.
Management:
Emergent vascular surgery consult for embolectomy vs endovascular intervention
IV heparin anticoagulation
Aggressive IV fluid resuscitation, broad-spectrum antibiotics
If peritonitis develops, emergent laparotomy for bowel resection
Teaching point: Pain out of proportion to exam + atrial fibrillation + elevated lactate = mesenteric ischemia until proven otherwise. CTA abdomen is the study of choice Bala et al. (ACS Surgery), 2022. Mortality exceeds 60% if diagnosis is delayed beyond 12 hours.
๐ Case 3, Acute Appendicitis
Patient: 28-year-old woman presents with 18 hours of periumbilical pain that has migrated to the RLQ. Anorexia, nausea, low-grade fever (38.2C). Positive McBurney point tenderness, positive Rovsing sign.
Key findings: WBC 14K with left shift. Beta-hCG negative. CT abdomen/pelvis shows dilated appendix (12 mm) with periappendiceal fat stranding and an appendicolith.
Management:
NPO, IV fluids, IV antibiotics (cefoxitin or ceftriaxone + metronidazole)
Surgery consult for appendectomy (laparoscopic preferred)
If perforated with abscess: percutaneous drainage + antibiotics, delayed interval appendectomy in 6-8 weeks
Teaching point: Classic appendicitis presents with visceral pain (periumbilical) migrating to somatic pain (RLQ) as inflammation involves the parietal peritoneum. Always check beta-hCG in women of childbearing age to rule out ectopic pregnancy.