What is the appropriate approach to evaluate and manage a patient presenting with abdominal pain?

Evaluation and Management of Abdominal Pain

Immediate Stabilization and Risk Stratification

Rapidly assess vital signs for fever, tachycardia, tachypnea, hypotension, or altered mental status to identify potential organ failure requiring immediate resuscitation. 1 Establish IV access and begin fluid resuscitation when clinical signs of sepsis or shock are present. 1 Hypotension with hypoperfusion indicators (elevated lactate, oliguria, altered consciousness) signals ongoing septic physiology and warrants aggressive support. 1 Administer low-molecular-weight heparin for VTE prophylaxis in all patients with acute abdominal pain. 1

Critical Red Flags Requiring Immediate Action

• Abdominal rigidity (guarding) indicates peritonitis and mandates prompt surgical consultation. 1
• Pain out of proportion to physical findings should be presumed to represent acute mesenteric ischemia until proven otherwise. 2, 1
• Hemodynamic instability (tachycardia, hypotension) suggests bleeding or sepsis. 2
• Peritoneal signs (rigid abdomen, rebound tenderness) indicate perforation or ischemia. 2
• Abdominal distension with vomiting indicates bowel obstruction. 2

Focused History - Key Discriminating Features

Characterize pain by location, onset, duration, quality, severity, and radiation to determine the underlying cause. 3 Acute onset of pain (minutes-to-hours) raises suspicion for perforation, vascular catastrophe, or bowel obstruction. 1

Location-Specific Considerations

• Right upper quadrant pain: Acute cholecystitis is the primary diagnostic consideration. 2 Consider hepatobiliary pathology including choledocholithiasis, cholangitis, hepatitis, or hepatic abscess. 2
• Right lower quadrant pain: Appendicitis is the most critical diagnosis to exclude. 2 Pain migration to right lower quadrant + fever + positive psoas sign strongly suggests appendicitis. 1 Vomiting before pain onset makes appendicitis less likely. 1 Consider ectopic pregnancy in women of reproductive age. 2
• Left lower quadrant pain: Diverticulitis is the leading consideration in older adults. 2 Consider sigmoid volvulus, especially with chronic constipation history. 2
• Epigastric or diffuse pain: Consider peptic ulcer disease, gastritis, acute pancreatitis, or perforated viscus. 2

Additional History Elements

• Recent surgery or prior abdominal operations: Raises concern for adhesive small bowel obstruction (accounts for 55-75% of SBO cases). 2, 1
• Age >60 years + atherosclerotic risk factors: Maintain high suspicion for mesenteric ischemia. 2, 1
• Pain improving/worsening with defecation + altered stool patterns: Characteristic of irritable bowel syndrome. 1
• Recent GI infection, antibiotic exposure, or significant stress: Can precipitate IBS in ~10% of patients. 1
• Medication history and recent antibiotic use should be documented. 3

Physical Examination Priorities

Examine for abdominal rigidity, rebound tenderness, and peritoneal signs. 2, 1 Do not overlook hernia orifices and surgical scars during examination, as this can miss incarcerated hernias. 2 Subtle peritoneal signs often precede intestinal infarction and should not be dismissed. 1

Mesenteric Ischemia Presentations

• Typical features: Nausea (44%), vomiting (35%), diarrhea (35%), hematochezia (16%). 1
• Classic triad: One-third present with abdominal pain, fever, and positive fecal occult blood. 1
• Arterial thrombosis: Often follows chronic post-prandial pain, weight loss, and prior revascularization. 1
• Embolic ischemia: ~50% have atrial fibrillation, ~33% have history of arterial embolus. 1
• Venous thrombosis: Commonly manifests with nausea, vomiting, diarrhea, and cramping. 1

Laboratory Evaluation

Obtain baseline complete blood count, C-reactive protein, and serology for celiac disease. 1 In limited-resource settings where imaging is unavailable, a complete blood count remains critical. 1 Order lactate if concerned for bowel ischemia or sepsis. 1

Special Testing

• β-hCG testing is mandatory in all women of reproductive age before imaging to avoid delayed diagnosis of ectopic pregnancy. 2
• Fecal calprotectin testing is indicated in patients with diarrhea who are younger than 45 years; values ≥250 µg/g strongly suggest inflammatory bowel disease and should trigger colonoscopy. 1

Imaging Strategy

Primary Imaging Modality

For non-localized or diffuse abdominal pain, contrast-enhanced CT of the abdomen and pelvis with IV contrast is the gold-standard imaging study, changing diagnosis in 51-54% of cases and altering management decisions in 25-42% of patients. 1 Single-phase IV contrast-enhanced CT is sufficient; pre-contrast and delayed phases are unnecessary. 1 Do NOT delay CT for oral contrast, as it delays diagnosis without improving accuracy. 1

Location-Specific Imaging

• Right upper quadrant pain: Ultrasound is the initial imaging modality of choice for evaluating acute cholecystitis and hepatobiliary pathologies. 2, 4
• Right lower quadrant pain: CT abdomen/pelvis with contrast has 95% sensitivity and 94% specificity for appendicitis, identifying alternative diagnoses in 94% of cases. 2, 1
• Left lower quadrant pain: CT abdomen/pelvis with contrast has 98% diagnostic accuracy for diverticulitis and superior ability to detect complications. 2

Alternative Imaging

• Bedside focused ultrasound should be the initial test for hemodynamically unstable patients with blunt abdominal trauma to detect intra-abdominal bleeding. 1
• Point-of-care ultrasound is appropriate in pregnant patients, younger individuals, and settings where CT is not readily available. 1
• Plain abdominal radiographs have limited diagnostic yield and should be reserved for cases where bowel obstruction is strongly suspected clinically. 1, 5

Imaging Pitfalls

• Do not obtain repeat CT scans without clear clinical indication, as diagnostic yield drops from 22% on initial CT to 5.9% on fourth or subsequent CTs. 1
• CT has relatively low negative predictive value (64%) for upper abdominal pathology, commonly missing pancreaticobiliary inflammatory processes, gastritis, and duodenitis. 2

Antibiotic Administration

Do NOT routinely administer antibiotics for undifferentiated abdominal pain. 6, 1 Antibiotics are indicated only when intra-abdominal abscess is identified, clinical signs of sepsis are present, or specific infection is confirmed. 6, 1

When Antibiotics Are Indicated

• For intra-abdominal abscesses: Prompt antimicrobial therapy against Gram-negative aerobic/facultative bacilli, Gram-positive streptococci, and obligate anaerobic bacilli is needed. 6
• For abscesses >3 cm: Perform radiological percutaneous drainage associated with early empiric antibiotics, adapting to culture results. 6
• For abscesses <3 cm: Administer early empiric antimicrobial therapy in stable patients with close clinical and biochemical monitoring. 6

Pain Management

Provide early analgesia without compromising diagnostic accuracy. 1 Avoid opioids in chronic or functional abdominal pain, as they cause narcotic bowel syndrome, dependence, gut dysmotility, and increased mortality. 1

IBS-Specific Pain Management

• Antispasmodic (anticholinergic) agents are recommended for IBS patients whose pain worsens after meals. 1
• Tricyclic antidepressants may be considered for IBS patients with frequent pain. 1

Special Population Considerations

Elderly Patients

Atypical presentations are common in elderly patients, requiring more thorough evaluation even if laboratory tests are normal, with higher likelihood of malignancy, diverticulitis, and vascular causes. 2, 1 Elderly patients may have normal labs despite serious infection, so maintain high suspicion and rely on imaging. 1

Women of Reproductive Age

Transvaginal ultrasound is the first-line imaging modality when gynecologic pathology is suspected. 2 Mandatory β-hCG testing is recommended before imaging. 2

Immunocompromised Patients

Typical signs of abdominal sepsis may be masked in immunocompromised patients, and a more extensive workup is necessary to avoid delayed diagnosis and high mortality. 2 Delayed diagnosis is associated with high mortality risk. 2

Inflammatory Bowel Disease Patients

Optimal management of IBD patients presenting with acute abdominal pain is multidisciplinary, involving a gastroenterologist and an acute care surgeon. 6 All IBD patients should receive adequate IV fluids, low-molecular-weight heparin for thromboprophylaxis, and correction of electrolyte abnormalities and anemia. 6

When to Involve Surgery

Surgical consultation is needed for signs of peritonitis, hemodynamic instability despite resuscitation, free air on imaging, complete bowel obstruction, mesenteric ischemia, ruptured abdominal aortic aneurysm, and failed conservative management. 1 Surgery should be considered in the case of failure of percutaneous drainage and in patients with signs of septic shock. 6 Timely and complete source control is critical; delayed or incomplete procedures are associated with markedly worse outcomes. 1

Common Diagnostic Pitfalls to Avoid

• Failing to obtain β-hCG testing in all women of reproductive age before imaging can delay diagnosis of ectopic pregnancy. 2
• Overlooking hernia orifices and surgical scars during examination can miss incarcerated hernias. 2
• Dismissing atypical presentations in elderly patients can lead to missed diagnoses. 2
• Over-relying on normal laboratory values early in disease can lead to missed diagnoses. 2

Resource-Adapted Diagnostic Pathway

Adopt a step-up approach: begin with clinical assessment and basic labs, proceed to bedside ultrasound when appropriate, and reserve CT for cases where initial evaluation is inconclusive or when high-risk pathology is suspected. 1 In low-resource environments, reliance on thorough history, physical examination, and basic laboratory tests (CBC, CRP) is essential for safe decision-making. 1