What is the appropriate initial evaluation and management for a patient presenting with diffuse abdominal pain and vomiting without diarrhea?

Initial Evaluation and Management of Diffuse Abdominal Pain with Vomiting

For a patient presenting with diffuse abdominal pain and vomiting without diarrhea, obtain CT abdomen and pelvis with IV contrast as the initial imaging study after ensuring hemodynamic stability and performing focused laboratory testing.

Immediate Assessment

First, ensure hemodynamic stability and assess for life-threatening conditions 1. Look specifically for:

• Signs of dehydration (dry mucous membranes, decreased skin turgor, orthostatic hypotension)
• Peritoneal signs (guarding, rigidity, rebound tenderness)
• Fever (raises suspicion for intra-abdominal infection or abscess)
• Acute abdomen requiring surgical intervention

Laboratory Workup

Order the following tests immediately 2:

• Complete blood count (evaluate for infection, anemia)
• Comprehensive metabolic panel (assess electrolytes, renal function, glucose)
• Lipase (rule out pancreatitis)
• Urinalysis (exclude urinary tract pathology)
• Pregnancy test in all women of childbearing age
• C-reactive protein (inflammatory marker)
• Hepatobiliary markers (AST, ALT, alkaline phosphatase, bilirubin)

Imaging Strategy

CT abdomen and pelvis with IV contrast is the preferred initial imaging modality for nonlocalized abdominal pain 3. This approach is justified because:

• Plain radiography has limited sensitivity for detecting sources of abdominal pain and fever, with only moderate sensitivity (49%) for bowel obstruction 3
• The differential diagnosis for diffuse pain with vomiting is broad and requires fast, definitive imaging 3
• CT can identify multiple etiologies including appendicitis, diverticulitis, bowel obstruction, pancreatitis, abscesses, and mesenteric ischemia 2

Avoid plain abdominal radiographs as the initial study—they have limited diagnostic yield and low-dose CT demonstrates superior diagnostic performance 3.

Common Etiologies to Consider

The most likely diagnoses in order of frequency are 2, 4:

1. Gastroenteritis (most common, though typically includes diarrhea)
2. Nonspecific abdominal pain (24-44% of cases)
3. Appendicitis (15.9-28.1%)
4. Cholelithiasis/cholecystitis (2.9-9.7%)
5. Bowel obstruction (especially in elderly or those with prior surgery)
6. Pancreatitis
7. Diverticulitis (in older patients)

Without diarrhea, consider mechanical obstruction, pancreatitis, or early appendicitis more prominently.

Symptomatic Management

Provide analgesia early—prospective randomized trials demonstrate that early analgesia reduces patient discomfort without impairing diagnostic accuracy 4. This is safe when used judiciously.

For vomiting management 5:

• Administer IV fluid resuscitation to correct dehydration and electrolyte imbalances
• Use 5-HT3 receptor antagonists (ondansetron) as first-line antiemetics—they act on both central and peripheral receptors
• Consider nasogastric decompression if obstruction is suspected or vomiting is intractable

Critical Pitfalls to Avoid

• Do not delay imaging in elderly patients—laboratory tests may be normal despite serious infection, and imaging is especially helpful in this population 3
• Do not withhold pain medication while awaiting diagnosis—this outdated practice causes unnecessary suffering without improving diagnostic accuracy 4
• Do not assume gastroenteritis without imaging when pain is severe or persistent—serious surgical conditions can present similarly 2
• Do not forget pregnancy testing—ectopic pregnancy and other obstetric emergencies must be excluded 2

When to Escalate Care

Consider surgical consultation immediately if:

• Peritoneal signs are present
• Hemodynamic instability persists despite resuscitation
• CT reveals surgical pathology (perforation, ischemia, appendicitis, etc.)
• Clinical deterioration occurs despite appropriate management

If CT is negative and symptoms persist, consider diagnostic laparoscopy as an alternative to prolonged observation 4.