What is the best approach to manage a patient with acute vague lower abdominal pain radiating to the back, without fever, urogenital or bowel symptoms, and normal vitals?

Management of Acute Vague Lower Abdominal Pain Radiating to Back

For a patient with acute vague lower abdominal pain radiating to the back without fever, urogenital symptoms, or bowel symptoms and normal vitals, obtain CT abdomen and pelvis with IV contrast as the initial imaging study to rule out serious intra-abdominal pathology including early diverticulitis, vascular causes, and occult perforation. 1

Initial Diagnostic Approach

Imaging is essential in this presentation because vague lower abdominal pain with back radiation in a hemodynamically stable patient requires exclusion of serious pathology that may not yet manifest with fever or peritoneal signs. 2

First-Line Imaging

• CT abdomen and pelvis with IV contrast is the optimal initial choice for acute nonlocalized abdominal pain, particularly when the differential diagnosis is broad and rapid, comprehensive evaluation is needed. 1
• This modality has superior sensitivity and specificity compared to ultrasound for detecting intra-abdominal pathology including early inflammatory processes, vascular abnormalities, and occult perforations. 2

Critical Laboratory Tests

• Complete blood count (CBC) to assess for leukocytosis suggesting occult infection or inflammation. 1
• C-reactive protein (CRP) has superior sensitivity and specificity compared to white blood cell count for ruling in surgical disease. 1
• Serum lactate to evaluate for mesenteric ischemia, though normal lactate does not exclude early ischemia. 1
• Lipase and amylase to evaluate for pancreatitis, which commonly presents with back radiation. 3
• Liver function tests and renal function tests to assess hepatobiliary and kidney pathology. 3

Key Clinical Considerations

Warning Signs Requiring Urgent Investigation

• Tachycardia is the most sensitive early warning sign of surgical complications and should trigger urgent investigation even before other symptoms develop. 1
• Pain out of proportion to physical examination should raise immediate suspicion for acute mesenteric ischemia, even with normal vitals. 1
• The absence of fever does not exclude serious intra-abdominal infection, particularly in elderly patients where laboratory tests may remain normal despite serious pathology. 1

Age-Specific Considerations

• In patients over 50 years, there is higher likelihood of malignancy, diverticulitis, and vascular causes requiring more aggressive imaging. 1
• For patients over 50 years with left lower quadrant pain, imaging is particularly important as diverticulitis may present without classic fever or leukocytosis initially. 2

Differential Diagnosis to Consider

Left Lower Quadrant Pain

• Diverticulitis can present with pain radiating to the back without initial fever, particularly in early stages. 2
• CT with IV contrast is rated 8/9 (usually appropriate) by the American College of Radiology for suspected diverticulitis. 2
• Imaging findings include intestinal wall thickening, pericolonic fat inflammation, and possible abscess formation. 2

Vascular Causes

• Abdominal aortic aneurysm must be excluded in patients with lower abdominal pain radiating to back, as this can present without hemodynamic instability initially. 4
• Elderly patients have higher risk for vascular causes. 1

Retroperitoneal Pathology

• Pain radiating to the back suggests possible retroperitoneal involvement including pancreatitis, renal pathology, or retroperitoneal abscess. 3

Common Pitfalls to Avoid

• Do not defer imaging based on normal vitals and absence of fever—serious pathology including early diverticulitis, vascular disease, and occult perforation can present without systemic signs. 2, 1
• Do not rely on physical examination alone—the absence of peritonitis on examination does not exclude bowel ischemia or other serious pathology. 1
• Do not assume normal laboratory tests exclude serious disease, particularly in elderly patients where many tests may be normal despite serious infection. 1
• Avoid plain radiography as it has limited diagnostic value for evaluating vague abdominal pain and should not be routinely used. 3

Management Algorithm After Imaging

If CT Shows Uncomplicated Diverticulitis

• Conservative management without antibiotics may be appropriate in immunocompetent patients with CT diagnosis of uncomplicated acute diverticulitis. 2
• Antibiotic therapy for no more than 7 days in immunocompromised or elderly patients. 2

If CT Shows Abscess

• Small diverticular abscesses: antibiotic therapy alone for 7 days. 2
• Large abscesses: percutaneous drainage combined with antibiotic therapy for 4 days. 2

If Imaging is Negative

• Consider diagnostic laparoscopy if symptoms persist and imaging is inconclusive, as it has diagnostic accuracy between 86-100%. 2
• Re-evaluate for functional disorders only after excluding structural pathology. 2