What is the recommended approach to evaluating and managing a patient presenting with abdominal pain?

Approach to Abdominal Pain

For adults presenting with generalized abdominal pain, obtain CT abdomen/pelvis with IV contrast as the primary imaging modality after ensuring hemodynamic stability, as this changes diagnosis in 51-54% of cases and alters management in 25-42% of patients. 1

Immediate Assessment and Stabilization

Vital Signs and Hemodynamic Status

• Check vital signs immediately for fever, tachycardia, tachypnea, hypotension, and altered mental status, which indicate potential organ failure requiring immediate resuscitation. 2
• Establish IV access and initiate fluid resuscitation if signs of sepsis or shock are present. 2
• Administer low-molecular-weight heparin for VTE prophylaxis in all patients with acute abdominal pain, as this population carries high thrombotic risk. 1

Critical Life-Threatening Causes to Exclude First

• Obtain ECG immediately for all patients with epigastric pain to exclude myocardial infarction, especially in women, diabetics, and elderly. 3
• Consider mesenteric ischemia in elderly patients with atherosclerotic risk factors presenting with pain out of proportion to physical findings—this requires emergent vascular surgery consultation. 2, 3
• Obtain β-hCG in all women of reproductive age before imaging to exclude ectopic pregnancy. 3

Focused History Taking

Cardinal Features to Elicit

• Onset and duration of symptoms—acute onset suggests perforation, vascular event, or obstruction. 2
• Relationship between abdominal pain and bowel habit changes—pain relieved or exacerbated by defaecation or temporally associated with altered stool pattern suggests IBS. 2
• Location and migration of pain—migration to right lower quadrant with fever and positive psoas sign strongly suggests appendicitis. 1
• Vomiting before pain onset makes appendicitis less likely. 1

Key Historical Red Flags

• Recent surgery or prior abdominal operations raises concern for adhesive small bowel obstruction, which accounts for 55-75% of SBO cases. 1
• Recent acute enteric infection, antibiotic use, or psychological stress may trigger IBS in approximately 10% of patients. 2
• Age >60 years with atherosclerotic risk factors should prompt consideration of mesenteric ischemia. 2, 1

Associated Symptoms

• Presence of bloating with visible abdominal distension is highly suggestive of IBS. 2
• Nausea (44%), vomiting (35%), diarrhea (35%), and blood per rectum (16%) are common in acute mesenteric ischemia. 2
• Approximately one-third of patients with mesenteric ischemia present with the triad of abdominal pain, fever, and hemoccult-positive stools. 2

Physical Examination

Critical Examination Findings

• Abdominal rigidity suggests peritonitis and requires surgical consultation. 2
• Pain out of proportion to physical examination findings should be assumed to be acute mesenteric ischemia until disproven. 2
• Signs of peritonitis may be subtle—maintain high index of suspicion as these findings almost always predict intestinal infarction. 2
• Hypotension and hypoperfusion signs such as lactic acidosis, oliguria, and acute alteration of mental status indicate ongoing sepsis. 2

Laboratory Testing

Essential Initial Labs

• Full blood count, C-reactive protein or erythrocyte sedimentation rate, and coeliac serology. 2
• Serum lactate if concerned for bowel ischemia or sepsis. 1, 3
• Liver/renal function, amylase/lipase based on clinical presentation. 3
• Faecal calprotectin if diarrhea present and age <45 years. 2

Important Caveats

• Elderly patients may have normal labs despite serious infection—maintain high suspicion and rely on imaging. 1
• Complete blood count is basic but essential in limited-resource settings where imaging may be unavailable. 2

Imaging Strategy

Primary Imaging Modality

• CT abdomen/pelvis with IV contrast is the gold standard for non-localized abdominal pain, as recommended by the American College of Radiology. 2, 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 and slows ED throughput. 1

Alternative Imaging in Specific Scenarios

• In hemodynamically unstable patients with blunt abdominal trauma, bedside ultrasound should be the initial diagnostic modality to identify need for emergent laparotomy. 2
• Ultrasound is useful in pregnant patients, younger patients, and in limited-resource settings where CT is unavailable. 2
• Plain radiographs have limited diagnostic value and should generally be avoided, except when bowel obstruction is strongly suspected clinically. 2, 1

Imaging Pitfalls to Avoid

• Do not obtain repeat CT scans without clear clinical indication—diagnostic yield drops from 22% on initial CT to 5.9% on fourth or subsequent CTs. 1
• In rural areas of limited-resource countries with limited access to CT, plain X-ray abdomen and ultrasound can help identify surgical emergencies cost-effectively. 2

Diagnostic Algorithm Based on Clinical Presentation

Step-Up Approach

• Use a step-up approach from clinical and laboratory examination to imaging examination, tailored to hospital resources. 2
• In emergency departments of limited-resource hospitals, diagnosis is mainly clinical, supported by basic laboratory tests like complete blood count. 2
• Ultrasound use has increased worldwide, facilitated by machines becoming smaller, more reliable, and less expensive. 2

When Diagnosis Remains Uncertain

• If initial investigations are inconclusive, make a positive diagnosis of IBS if cardinal symptoms present (abdominal pain with altered bowel habit relationship) and red flags excluded. 2
• If faecal calprotectin is abnormal (≥250 μg/g), suspicion for IBD is high—proceed to colonoscopy. 2
• For indeterminate faecal calprotectin levels (100-249 μg/g), repeat testing or proceed to colonoscopy based on clinical judgment. 2

Pain Management

Analgesic Strategy

• 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, 3
• For IBS with pain as predominant symptom, consider antispasmodic (anticholinergic) medication, particularly when symptoms are exacerbated by meals. 2
• Tricyclic antidepressants may be considered if pain is frequent in IBS patients. 2

Antibiotic Administration

When to Initiate Antibiotics

• Do NOT routinely administer antibiotics for undifferentiated abdominal pain. 1
• Antibiotics are indicated only when intra-abdominal abscess is identified, clinical signs of sepsis are present, or specific infection is confirmed. 1
• Norepinephrine is the first-line vasopressor agent to correct hypotension in septic shock. 2

Surgical Consultation Criteria

Indications for Immediate Surgical Involvement

• Signs of peritonitis (abdominal rigidity, rebound tenderness). 2, 1
• Hemodynamic instability despite resuscitation. 1
• Free air on imaging indicating perforation. 1
• Complete bowel obstruction. 1
• Mesenteric ischemia. 1
• Ruptured abdominal aortic aneurysm. 1
• Failed conservative management of identified surgical pathology. 1

Timing and Adequacy of Source Control

• The timing and adequacy of source control are important in management of intra-abdominal infections—late and/or incomplete procedures may have severely adverse outcomes. 2

Common Differential Diagnoses

Most Common Causes in ED Patients

• Approximately one-third have no diagnosis established, one-third have appendicitis, and one-third have other documented pathology including small bowel obstruction, pancreatitis, renal colic, perforated peptic ulcer, and malignancy. 1, 3

Specific Phenotypes Based on History

• Patients with mesenteric arterial thrombosis often have history of chronic postprandial abdominal pain, progressive weight loss, and previous revascularization procedures. 2
• Patients with non-occlusive mesenteric ischemia have pain that is generally more diffuse and episodic, associated with poor cardiac performance. 2
• Patients with mesenteric venous thrombosis present with mixture of nausea, vomiting, diarrhea, and abdominal cramping. 2
• Nearly 50% of patients with embolic acute mesenteric ischemia have atrial fibrillation and approximately one-third have prior history of arterial embolus. 2

Common Pitfalls to Avoid

• Missing cardiac causes in patients presenting with epigastric pain—always obtain ECG. 3
• Failing to obtain β-hCG before imaging in reproductive-age women. 3
• Overlooking hernia orifices and surgical scars during examination. 3
• Dismissing atypical presentations in elderly patients who may not mount typical inflammatory responses. 3
• Prescribing opioids for functional gastrointestinal disorders, which worsens outcomes and risks narcotic bowel syndrome. 3
• Delaying presentation to hospital—in many countries worldwide, large proportion of patients with diffuse peritonitis present with unacceptable delay, reducing survival rates. 2