What is the initial evaluation for a patient presenting with left abdominal pain?

Initial Evaluation for Left Abdominal Pain

For patients presenting with left abdominal pain, computed tomography (CT) with intravenous contrast is the recommended first-line imaging modality, with laboratory tests including complete blood count and C-reactive protein to evaluate for diverticulitis, which is the most common cause. 1

Clinical Assessment

Key History Elements

• Pain characteristics: onset, duration, severity, radiation
• Associated symptoms: fever, nausea, vomiting, change in bowel habits
• Previous episodes of similar pain
• Risk factors for diverticulitis: age >50, low-fiber diet, obesity

Physical Examination Focus

• Vital signs (especially for fever)
• Abdominal examination for:
  • Localized tenderness in left lower quadrant
  • Guarding or rebound tenderness
  • Abdominal distension
  • Presence of masses

Laboratory Evaluation

• Complete blood count (CBC) with differential
  • Leukocytosis suggests inflammation/infection
• C-reactive protein (CRP)
  • CRP >50 mg/L suggests diverticulitis
  • CRP >170 mg/L suggests severe diverticulitis 2
• Basic metabolic panel
• Urinalysis (to rule out urinary causes)
• Pregnancy test in women of reproductive age

Imaging Studies

First-Line Imaging

• CT abdomen and pelvis with IV contrast
  • Sensitivity 98-99%, specificity 99-100% 1
  • Can identify complications of diverticulitis (abscess, perforation)
  • Can detect alternative diagnoses

Alternative Imaging Options

• Ultrasonography:
  • Consider as initial study in premenopausal women to evaluate for gynecologic pathology
  • Sensitivity 61-90%, specificity 90-100% 1
  • Operator-dependent with variable results 2
• MRI:
  • For pregnant patients or those with contraindications to CT
  • Sensitivity 100% for diverticulitis 1

Plain Radiography

• Limited diagnostic value for abdominal pain 2
• May be appropriate only for suspected bowel obstruction, perforated viscus, or foreign bodies

Diagnostic Approach Based on Clinical Suspicion

For Suspected Diverticulitis

1. Assess for classic triad: left lower quadrant pain, fever, leukocytosis (present in only 25% of cases) 1
2. Order CBC and CRP
3. Proceed to CT abdomen/pelvis with IV contrast
4. Classify severity using WSES classification 2:
   • Uncomplicated: Diverticula, wall thickening, increased density of pericolic fat
   • Complicated: Stages 1A-4 based on presence of abscess, free air, or fluid

For Undifferentiated Left Abdominal Pain

1. Complete laboratory workup (CBC, CRP, electrolytes, urinalysis)
2. CT abdomen/pelvis with IV contrast as recommended by the American College of Radiology 2
3. Consider ultrasonography first in premenopausal women to evaluate for gynecologic causes

Management Considerations

• If diverticulitis is diagnosed:

  • Uncomplicated cases: Consider outpatient management if no systemic symptoms, increasing leukocytosis, age >80, immunocompromise, pregnancy, significant comorbidities 1
  • Complicated cases: Hospital admission, IV antibiotics, surgical consultation for abscesses ≥3-4 cm 1

• For other diagnoses, management will depend on specific findings

Pitfalls to Avoid

• Relying solely on clinical diagnosis without imaging (misdiagnosis rate 34-68%) 1
• Delaying imaging in elderly patients who may present with atypical symptoms and have higher risk of complications 1
• Overlooking gynecologic causes in women of reproductive age
• Failing to recognize that early CT can reduce hospital admissions by >50% and shorten hospital stays 1

Remember that prompt and accurate diagnosis is essential, as approximately 5% of uncomplicated diverticulitis cases can progress to complicated diverticulitis with higher morbidity and mortality 1.