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Aortic diameter >= 3.0 cm on bedside POCUS confirms aneurysm; transport to OR
Order biphasic CTA abdomen/pelvis immediately for pain out of proportion to exam
Upright CXR showing subdiaphragmatic free air; IV Pip-Tazo or Ceftriaxone/Flagyl + OR
Place large-bore Nasogastric (NG) tube to low intermittent suction; IV fluid repletion
RLQ tenderness, McBurney's point, Rovsing sign; IV Cefoxitin or Cefazolin + Flagyl
Bottom-Line Clinical Pearl
Acute mesenteric ischemia presents as severe abdominal pain out of proportion to physical examination; never wait for elevated lactate (a late sign of bowel gangrene) to order a biphasic CT mesenteric angiogram. In a patient > 50 with sudden back, flank, or abdominal pain and syncope/hypotension, obtain an immediate bedside POCUS of the aorta—it is a ruptured AAA until proven otherwise. Permissive hypotension (SBP 80–90 mmHg) and emergent vascular surgery consultation takes precedence over CT imaging in unstable patients.
Evaluation of acute abdominal pain begins with determining whether the patient has a surgical abdomen (peritonitis, hollow viscus perforation, bowel infarction, or vascular catastrophe) requiring emergent resuscitation and immediate operating room intervention:
| Life-Threatening Emergency | Hallmark Clinical Presentation | Physical Exam Findings | Definitive Diagnostic Modality | Immediate Management |
|---|---|---|---|---|
| Ruptured Abdominal Aortic Aneurysm (AAA) | Sudden severe back, flank, or abdominal pain; syncope, hypotension in patient > 50 yr | Pulsatile abdominal mass (50%), mottled lower extremities, flank ecchymosis (Grey Turner) | Bedside POCUS of Abdominal Aorta (Aorta >= 3.0 cm) | Permissive hypotension (SBP 80–90), activate MTP, emergency vascular surgery OR transport. |
| Acute Mesenteric Ischemia (SMA Embolus) | Sudden severe diffuse pain out of proportion to exam in elderly patient with Atrial Fibrillation | Soft, non-distended abdomen without focal peritonitis initially; gross/occult blood per rectum | Emergent biphasic CTA of Abdomen & Pelvis (arterial phase) | IV Heparin bolus, broad-spectrum antibiotics, emergent surgical embolectomy/revascularization. |
| Perforated Viscus (Peptic Ulcer/Diverticulum) | Sudden onset of explosive, severe epigastric or lower abdominal pain | Board-like abdominal rigidity, severe rebound tenderness, involuntary guarding | Upright Chest Radiograph (free air under diaphragm) | Bilateral large-bore IVs, IV Piperacillin-Tazobactam 4.5g, emergent laparotomy. |
| Strangulated Small Bowel Obstruction (SBO) | Colicky abdominal pain, bilious vomiting, obstipation in patient with prior abdominal surgeries | High-pitched hyperactive bowel sounds early, localized tenderness, fever, tachycardia | CT Abdomen/Pelvis with IV contrast (closed loop, transition point, pneumatosis) | NG tube decompression, fluid resuscitation, emergent surgical exploration. |
| Acute Ascending Cholangitis | Charcot's Triad (Fever, RUQ pain, Jaundice) or Reynolds' Pentad (+ Hypotension, Altered mental status) | RUQ tenderness, jaundice, scleral icterus, septic shock | RUQ Ultrasound (dilated common bile duct > 6 mm) + LFTs | IV broad-spectrum antibiotics (Pip-Tazo), emergent ERCP for biliary ductal decompression. |
A ruptured AAA is a true vascular catastrophe with 80–90% total mortality. Any patient over age 50 presenting with new back pain, flank pain, renal colic, or unexplained syncope must have a bedside aortic ultrasound before being evaluated for non-emergent conditions (e.g., nephrolithiasis or musculoskeletal strain).
| POCUS View | Technique & Landmark | Measurement Criteria | Diagnostic Utility |
|---|---|---|---|
| Transverse Proximal Aorta | Subxiphoid transverse, identify celiac trunk and SMA | Measure outer-to-outer diameter (including mural thrombus) | Normal caliber is < 2.0 cm. Aneurysm is diagnosed when >= 3.0 cm. |
| Transverse Mid/Distal Aorta | Umbilical level transverse above aortic bifurcation | Measure maximal transverse diameter | 90% of AAAs are infrarenal. Measure maximal outer-to-outer diameter. |
| Sagittal Longitudinal Aorta | Longitudinal midline view from diaphragm to bifurcation | Trace entire length of vessel; evaluate for saccular outpouchings | Demonstrates tortuosity and excludes false aneurysmal lumens. |
| Peritoneal Free Fluid View | Morison's pouch & retroperitoneal space | Anechoic fluid around aorta or in Morrison pouch | Rupture usually occurs into retroperitoneum; free peritoneal fluid indicates anterior intraperitoneal rupture (imminent death). |
Critical Pitfall / Contraindication
Permissive Hypotension in Ruptured AAA: In a suspected or confirmed ruptured AAA, do NOT aggressively resuscitate with fluids to normalize blood pressure. High blood pressure blows off the nascent retroperitoneal tamponade clot and accelerates fatal internal exsanguination. Maintain SBP at 80–90 mmHg (conscious, mentating patient) using small blood product aliquots until the vascular surgeon places an aortic cross-clamp or endovascular balloon in the operating room.
Mesenteric ischemia carries a mortality rate exceeding 60%, largely due to diagnostic delays. It results from superior mesenteric artery (SMA) embolism (50%, commonly from cardiac mural thrombus in atrial fibrillation), SMA thrombosis (25%, acute-on-chronic atherosclerotic disease), mesenteric venous thrombosis (10%), or non-occlusive mesenteric ischemia (NOMI, from low flow in cardiogenic/septic shock).
- The Classic Diagnostic Paradox: The patient experiences agonizing, writhing abdominal pain, but physical palpation reveals a soft, non-tender, non-distended abdomen without peritoneal signs. This 'pain out of proportion to exam' occurs because visceral mucosal ischemia causes severe visceral pain long before parietal peritoneal inflammation develops.
- The Lactate Fallacy: A normal serum lactate level does NOT rule out early mesenteric ischemia. Serum lactate elevates only AFTER transmural bowel gangrene and mucosal necrosis have already occurred. Ordering a lactate and waiting for an elevation guarantees delayed diagnosis.
- Diagnostic Gold Standard: Multidetector Biphasic CT Angiography (CTA) of the Abdomen and Pelvis with IV contrast. Evaluates SMA and celiac patency, bowel wall enhancement, focal mesenteric edema, and pneumatosis intestinalis.
- Emergency Management: Immediate systemic anticoagulation with Unfractionated Heparin (80 U/kg bolus, 18 U/kg/h); broad-spectrum IV antibiotics (Cefepime + Metronidazole); emergent consultation for endovascular catheter embolectomy or open surgical revascularization and bowel resection.
Postoperative adhesions cause 60–75% of small bowel obstructions, followed by incarcerated hernias (15%) and neoplasms (10%). The primary emergency task is distinguishing simple mechanical obstruction from closed-loop or strangulated obstruction requiring immediate operating room exploration.
| Diagnostic Feature | Simple Mechanical SBO | Strangulated/Closed-Loop SBO (Surgical Emergency) |
|---|---|---|
| Pain Character | Intermittent, cramping, colicky periumbilical pain | Continuous, severe, localized, sharp unremitting pain |
| Vital Signs | Normal or mild tachycardia due to dehydration | Tachycardia, fever, hypotension, marked leukocytosis with left shift |
| Physical Exam | Abdominal distension, high-pitched tinkling bowel sounds, diffuse mild tenderness | Focal exquisite tenderness, involuntary guarding, peritoneal signs, palpable tender mass |
| CT Findings | Dilated small bowel loops (> 2.5 cm) with air-fluid levels and clear transition point to collapsed bowel | C-shaped or U-shaped closed loop ('whirl sign'), thickened bowel wall (> 3 mm), lack of mucosal enhancement, pneumatosis intestinalis, portal venous gas |
Always Check the Hernia Orifices
In every patient presenting with nausea, vomiting, or abdominal pain, perform a dedicated physical examination of the inguinal, femoral, umbilical, and surgical incision sites. An incarcerated femoral hernia in an elderly patient is easily missed under hospital gowns and rapidly progresses to ischemic bowel necrosis.
While emergency clinicians are rigorously trained to rule out surgical catastrophes (ruptured AAA, mesenteric ischemia, perforated viscus, and appendicitis), over 75% of emergency abdominal pain encounters represent non-emergent, benign, or ambulatory conditions. Distinguishing benign causes without over-ordering ionizing radiation or missing subtle surgical pathology is the core skill of modern emergency practice.
| Condition | What to Ask (Key History) | What to Look For (Physical Exam) | Diagnostic Testing (Choosing Wisely) | ED Management & Discharge Strategy |
|---|---|---|---|---|
| Viral Gastroenteritis | Diffuse crampy abdominal pain, nausea, vomiting preceding or concurrent with non-bloody watery diarrhea, sick contacts, contaminated food history. Absence of localized focal pain. | Soft, non-distended, diffuse mild tenderness without focal guarding or peritoneal signs; hyperactive high-pitched bowel sounds; moist mucous membranes or mild orthostasis. | Clinical diagnosis! Zero labs or CT scans indicated in young, healthy, non-toxic patients. Check basic metabolic panel only if severe dehydration, prolonged inability to tolerate fluids, or elderly. | Ondansetron (Zofran) 4–8 mg ODT, wait 15–20 minutes, then oral rehydration challenge (5–10 mL sips of electrolyte solution every 5 minutes). Discharge on oral rehydration and bland diet once fluid challenge tolerated. |
| GERD & Peptic Gastritis | Burning or gnawing epigastric pain radiating retrosternally, worse 30–60 minutes postprandially or when lying flat, sour taste/water brash, relieved by antacids. History of heavy NSAID, aspirin, or alcohol intake. | Mild epigastric tenderness to deep palpation; abdomen otherwise completely soft, non-tender, non-distended; normal bowel sounds; no peritoneal signs. | Check ECG and troponin in patients > 40 years old or with cardiovascular risk factors (inferior wall MI frequently mimics dyspepsia!). Fecal occult blood or CBC if chronic bleeding suspected. | GI Cocktail trial: 30 mL aluminum/magnesium hydroxide (Maalox) + 10 mL 2% viscous lidocaine provides prompt relief (note: relief does NOT exclude cardiac ischemia!). Discharge on oral PPI (Pantoprazole 40 mg daily) with primary care follow-up for H. pylori screening. |
| Constipation & Fecal Impaction | Dull, crampy LLQ or lower abdominal aching, bloating, no bowel movement for several days or passing hard Bristol Type 1 pellets, straining, tenesmus. Paradoxical 'overflow' liquid diarrhea in elderly impaction. Medication review: opioids, iron, anticholinergics. | Firm, non-tender, tubular palpable stool mass in left lower quadrant (sigmoid colon); tympanitic or dull percussion; digital rectal exam (DRE) reveals hard, packed fecal vault in the rectal ampulla. | Clinical diagnosis. Abdominal plain film (KUB) only if severe distension or fecal impaction vs pseudo-obstruction (Ogilvie syndrome) is in question. Zero CT imaging needed for routine constipation. | Digital disimpaction if hard low fecal shelf is reachable. Bowel cleanout protocol: Polyethylene glycol (MiraLAX) 17–34 g daily, Bisacodyl (Dulcolax) 10 mg PO or 10 mg suppository, and/or mineral oil or tap water enema. Increase dietary fiber and hydration. |
| Biliary Colic (Uncomplicated Cholelithiasis) | Episodic, severe, steady RUQ or epigastric pain radiating to the right infrascapular region, typically triggered by fatty or greasy meals, lasting 30 minutes to 4–6 hours, then resolving completely. History of identical prior self-resolving attacks. | Mild RUQ tenderness without peritoneal signs; NEGATIVE Murphy's sign (no inspiratory arrest on deep palpation); patient is afebrile, non-toxic, and comfortable between spasms. | Right Upper Quadrant (RUQ) Ultrasound: demonstrates acoustic shadowing gallstones WITHOUT gallbladder wall thickening (> 3 mm), pericholecystic fluid, or sonographic Murphy's sign. Normal LFTs, total bilirubin, and serum lipase. | Analgesia with IV Ketorolac (Toradol) 15 mg (NSAIDs block prostaglandin-mediated gallbladder contractility and are clinically superior to opioids for biliary colic). Discharge with outpatient elective surgical consultation; clear return precautions for fever, jaundice, or pain > 6 hours. |
| Irritable Bowel Syndrome (IBS) | Chronic recurrent abdominal cramping/pain (Rome IV criteria: >= 1 day/week for past 3 months) related to defecation, change in stool frequency or appearance. Absence of alarm features: no nocturnal pain, rectal bleeding, involuntary weight loss, or family history of IBD/colon cancer. | Mild diffuse lower abdominal discomfort, no peritoneal signs, normal bowel sounds, non-distended. | Basic metabolic panel and CBC normal. Zero CT imaging indicated in known IBS with typical baseline symptoms. | Reassurance, dicyclomine (Bentyl) 10–20 mg PO TID for acute spasm, low-FODMAP dietary counseling, PCP/gastroenterology outpatient referral. |
| Abdominal Wall Pain (Carnett's Sign) | Sharp, localized, superficial pain aggravated by movement, coughing, twisting, or lifting heavy objects. Patient can pinpoint the maximal tenderness with a single fingertip. | POSITIVE Carnett's Sign: Palpate the tender focal point while patient tenses abdominal wall (crosses arms and raises head/shoulders off gurney). If pain increases or remains identical, it is abdominal wall muscle strain or anterior cutaneous nerve entrapment. (If pain decreases, it is deep visceral pathology protected by the tensed rectus). | Zero laboratory or radiological imaging indicated. | Reassurance, topical lidocaine 5% patch, oral NSAIDs (ibuprofen/naproxen), heat/ice, avoidance of heavy lifting. |
| Non-Specific Abdominal Pain (NSAP) | Diffuse, vague, mild-to-moderate abdominal discomfort without clear localization, nausea without vomiting, normal bowel habits. Represents up to 40% of all ED abdominal pain visits! | Soft, non-distended, non-tender or mild diffuse tenderness without localized guarding or rebound; normal vital signs. | Urine pregnancy test in females of reproductive age (mandatory!), urinalysis. If exam remains benign and patient is young (< 50), observation and serial exams without advanced imaging are safe and evidence-based. | Symptomatic relief, clear liquid to bland diet advance, explicit return precautions. |
Physical Exam Maneuvers Every Clinician Must Know: Carnett's, Guarding & Peritoneal Signs
1. Carnett's Test: Palpate the tender spot while the patient crosses their arms and lifts their head and shoulders off the stretcher, contracting the rectus abdominis. If the pain increases or stays the same (Positive Carnett's), the pathology is in the abdominal wall (rectus hematoma, muscle tear, cutaneous nerve entrapment). If the pain decreases (Negative Carnett's), the pathology is intra-abdominal, as the tensed muscles shield the viscera.
2. Voluntary Guarding vs. Involuntary Rigidity: Voluntary guarding is patient anticipation/fear of pain; flexing the patient's knees or palpating gently during deep exhalation will cause the muscles to relax. Involuntary rigidity ('board-like abdomen') remains rock-hard even during exhalation and indicates true peritonitis.
3. The Gentle Peritoneal Vibration Tests: Never violently poke for 'rebound tenderness' (which traumatizes the patient and destroys rapport). Instead, use the Cough Test (ask patient to cough and point to where it hurts) or the Heel-Drop/Stretcher-Bump Test (tap the bottom of their heel or gently bump the stretcher). If a slight vibration elicits sharp focal agony, peritoneal irritation is present.
Bulletproof Discharge Criteria & The 24-Hour Return Script
Before discharging any patient with non-emergent or non-specific abdominal pain, ensure all four safety criteria are met:
1. Vital signs normalized (afebrile, heart rate < 100 bpm, normal blood pressure).
2. Oral hydration challenge tolerated (drank 8–12 oz of water/electrolyte solution without emesis over 30–60 minutes).
3. Pain controlled to mild baseline with oral non-opioid medications.
4. Ambulated safely without dizziness or orthostasis.
The Mandatory Return Script: 'Your exam and tests today are reassuring, but early appendicitis, gallbladder infection, or bowel inflammation can take 12 to 24 hours to declare itself. You must return immediately if you develop: a fever over 100.4°F, pain that shifts or localizes to the right lower belly, vomiting that prevents you from keeping water down, dark black or bloody bowel movements, or feeling faint or dizzy when standing.'
Test Your Acute Abdominal Pain & Surgical Emergencies Clinical Acumen
Directly launch an active-recall practice block from our validated question bank with comprehensive explanations and distractor analyses.
Distinguish primary life-threats from mimics. On board exams (COMLEX Level 1, 2-CE, 3 & USMLE), initial stabilizing interventions (airway, IV access, non-invasive ventilation, empiric reversal) always take precedence over diagnostic imaging.
Evaluate autonomic tone: Sympathetic viscerosomatics (T1–L2) cause acute paraspinal tissue texture changes (erythema, bogginess, hypertonicity). Suboccipital release (CN X Vagus) and rib raising normalize autonomic outflow and thoracic cage mechanics.