What is the most appropriate initial test for a patient with non-diarrheal illness, nausea, cramping, diffuse abdominal pain, and fever?

Diagnostic Testing for Non-Diarrheal Abdominal Pain with Fever

For a 56-year-old patient with non-diarrheal abdominal pain, nausea, cramping, and low-grade fever, CT abdomen and pelvis with IV contrast is the most appropriate initial diagnostic test rather than stool cultures or fecal lactoferrin testing.

Clinical Assessment of the Case

This patient presents with:

• 24 hours of non-diarrheal illness
• Four episodes of abdominal pain since yesterday
• Nausea and cramping diffuse abdominal pain
• Low-grade fever (100°F)
• No recent travel, no antibiotic use
• No medical history
• Stable vital signs with moist mucous membranes

Why CT Abdomen/Pelvis is the Preferred Initial Test

The American College of Radiology (ACR) Appropriateness Criteria specifically addresses this clinical scenario under "Acute Nonlocalized Abdominal Pain and Fever" and recommends CT as the preferred imaging option 1:

• CT provides quick, definitive diagnosis in patients with nonlocalized abdominal pain and fever
• CT with IV contrast increases the spectrum of detectable pathology in patients with nonlocalized pain
• CT can identify potential causes including:
  • Intra-abdominal abscesses
  • Inflammatory conditions
  • Malignancies with secondary infections
  • Diverticulitis
  • Appendicitis
  • Other sources of infection

Why Stool Testing is Not Appropriate Initially

Stool testing (cultures or fecal lactoferrin) would be inappropriate as the initial test in this case for several reasons:

1. Absence of diarrhea: The patient has no diarrhea, which is a prerequisite for most stool-based diagnostic testing 1

2. IDSA guidelines focus: The Infectious Diseases Society of America guidelines for infectious diarrhea are not applicable to this non-diarrheal presentation 1

3. Fecal lactoferrin utility: Fecal lactoferrin is primarily used to detect intestinal inflammation in patients with diarrhea, particularly to differentiate inflammatory bowel disease from irritable bowel syndrome 2, 3

4. Clinical presentation mismatch: The patient's presentation with fever and diffuse abdominal pain without diarrhea suggests a potential intra-abdominal process requiring imaging rather than stool studies 1

Diagnostic Algorithm for Non-Diarrheal Abdominal Pain with Fever

1. Initial imaging: CT abdomen and pelvis with IV contrast

   • Provides comprehensive assessment of potential intra-abdominal pathology
   • Can identify abscesses, inflammatory conditions, bowel pathology

2. Secondary testing (based on CT findings):

   • If CT suggests inflammatory bowel pathology: Consider colonoscopy with biopsies
   • If CT suggests infectious process: Consider blood cultures and targeted antimicrobial therapy
   • If CT suggests obstruction: Consider surgical consultation

3. When to consider stool studies:

   • Only if diarrhea develops during the course of illness
   • If CT findings suggest colitis or enteritis
   • If other initial testing is negative but symptoms persist

Important Considerations

• Fecal lactoferrin and other stool biomarkers are valuable when diarrhea is present, as they can detect intestinal inflammation with high sensitivity and specificity 3, 4

• The absence of diarrhea in this patient makes inflammatory diarrheal conditions less likely and shifts the diagnostic focus toward other intra-abdominal processes that would be better visualized with CT imaging

• The low-grade fever suggests an inflammatory or infectious process that requires prompt evaluation with imaging to guide appropriate management

• While stool studies have high diagnostic value in diarrheal illnesses, they have limited utility in non-diarrheal presentations and would delay appropriate diagnosis in this case