Diagnostic Approach to Abdominal Pain

Initial Imaging

The American College of Radiology recommends CT of the abdomen and pelvis with IV contrast as the optimal initial imaging choice for acute nonlocalized abdominal pain, particularly when fever is present or serious pathology is suspected 1, 2, 3
CT abdomen and pelvis with contrast is the preferred imaging option for nonlocalized abdominal pain with fever due to its broad differential and need for fast imaging 1, 2, 3

The American College of Radiology suggests that tachycardia is the most sensitive early warning sign of surgical complications and should trigger urgent investigation even before other symptoms develop 3
The combination of fever, tachycardia, and tachypnea predicts serious complications including anastomotic leak, perforation, or sepsis 3
Severe pain out of proportion to physical examination findings should raise immediate suspicion for acute mesenteric ischemia 3

Beta-hCG testing is mandatory in all women of reproductive age before any imaging 3, 4
Complete blood count to evaluate for leukocytosis suggesting infection or inflammation 3, 4
High C-reactive protein has superior sensitivity and specificity compared to white blood cell count for ruling in surgical disease 3

Elderly patients have a higher likelihood of malignancy, diverticulitis, and vascular causes 3
In elderly patients with fever and abdominal pain, many laboratory tests may be normal despite serious infection 1, 2
Post-bariatric surgery patients often present with atypical symptoms, and classic peritoneal signs are frequently absent 3

Right lower quadrant pain: Abdominal ultrasound is the most appropriate initial imaging 3
Pelvic pain: CT abdomen and pelvis with contrast 3
Right upper quadrant pain: Ultrasound for suspected cholecystitis 3, 4
Left lower quadrant pain: CT abdomen and pelvis with contrast for suspected diverticulitis 3
Suspected kidney stones: Non-contrast CT abdomen and pelvis 3

The absence of peritonitis on examination does not exclude bowel ischemia—patients with sigmoid volvulus often lack peritoneal signs despite established ischemia due to chronic distension masking the examination 3
Normal lactate does not exclude internal herniation or early ischemia 3
Normal laboratory tests in elderly patients do not exclude serious infection 1, 2