Approach to Diffuse Abdominal Pain Without Diarrhea or Vomiting
For a patient presenting with diffuse abdominal pain without diarrhea or vomiting, obtain a focused history and physical examination, check basic labs (CBC, CRP, metabolic panel), and proceed directly to CT abdomen/pelvis with IV contrast as your primary imaging modality 1, 2.
Initial Clinical Assessment
Key History Elements to Obtain:
- Pain characteristics: Onset (sudden vs. gradual), severity, progression over time
- Associated symptoms: Fever (suggests infection/abscess), anorexia, constipation (suggests obstruction)
- Past medical history: Recent surgery, immunocompromised status, cancer history, inflammatory bowel disease
- Age and sex: Elderly patients may have serious infection despite normal labs; women require consideration of gynecologic causes 1
Critical Physical Examination Findings:
- Peritoneal signs: Guarding, rigidity, rebound tenderness (indicate surgical emergency)
- Bowel sounds: Absent/decreased (obstruction), high-pitched (early obstruction)
- Vital signs: Fever, tachycardia, hypotension (sepsis/perforation)
- Abdominal distension: Suggests obstruction
Laboratory Evaluation
Order these tests immediately:
- CBC with differential: Leukocytosis suggests infection/inflammation
- C-reactive protein (CRP): Elevated in inflammatory processes
- Comprehensive metabolic panel: Assess electrolytes, renal function, liver enzymes
- Lactate: Elevated in bowel ischemia/sepsis
- Urinalysis: Rule out urinary tract infection/nephrolithiasis
- Pregnancy test (if applicable)
Critical decision point: If both WBC and CRP are normal, re-evaluate the patient in 12 hours rather than proceeding immediately to imaging 3. However, if either is elevated or clinical concern is high, proceed to imaging.
Imaging Strategy
CT Abdomen/Pelvis with IV Contrast - First-Line Imaging
This is your primary diagnostic tool for diffuse abdominal pain 1, 2. The evidence strongly supports CT as the initial imaging modality because:
- Diagnostic impact: CT changes the leading diagnosis in 51% of patients and alters management decisions in 42% of cases 1, 2
- Broad differential coverage: Can identify pneumonia, hepatobiliary disease, pancreatitis, nephrolithiasis, GI perforation, bowel obstruction/infarction, abscesses, and malignancy 1
- Speed and availability: Fast acquisition, widely available, provides definitive information 1
When NOT to Use CT First:
- Pregnant patients: Use ultrasound or MRI
- Young patients (<40) with clear right upper quadrant localization: Start with ultrasound for suspected cholecystitis 2
Plain Radiography - Limited Role
Do NOT routinely order plain abdominal X-rays 1, 2. Conventional radiography has limited diagnostic value and rarely changes management 2. Consider it only for:
- Suspected bowel obstruction (as a quick initial screen)
- Suspected perforated viscus (upright chest X-ray for free air)
- Suspected foreign body or urinary calculi
Plain films have only 49% sensitivity for bowel obstruction and low sensitivity for most causes of abdominal pain 1.
Common Diagnostic Pitfalls
The Elderly Patient
Exercise heightened suspicion in elderly patients - they may have serious intra-abdominal infection with normal or minimally elevated laboratory values 1. Proceed to CT imaging with lower threshold in this population.
The Immunocompromised Patient
Neutropenic or immunosuppressed patients may mask typical signs of abdominal sepsis, leading to delayed diagnosis and high mortality 1. Have a very low threshold for CT imaging in this population.
The "One-Third Rule"
Remember that among ED patients with abdominal pain: one-third have appendicitis, one-third have other documented pathology (cholecystitis, SBO, pancreatitis, renal colic, perforated ulcer, cancer, diverticulitis), and one-third never receive a definitive diagnosis 1.
Differential Diagnosis Priority
For diffuse abdominal pain, consider these life-threatening conditions first:
- Bowel obstruction or infarction
- Perforated viscus
- Intra-abdominal abscess
- Acute pancreatitis
- Ruptured abdominal aortic aneurysm (especially in elderly with vascular risk factors)
- Mesenteric ischemia
Disposition Algorithm
After CT results:
- Surgical pathology identified → Immediate surgical consultation
- Medical pathology identified (pancreatitis, pyelonephritis) → Admit for medical management
- Negative CT with high clinical suspicion → Consider observation, serial examinations, or diagnostic laparoscopy in select cases
- Negative CT with low clinical suspicion and normal labs → Discharge with strict return precautions and 24-48 hour follow-up
If imaging is delayed or unavailable: Serial physical examinations every 4-6 hours can help identify evolving peritonitis or worsening obstruction that requires surgical intervention 4.