What is the diagnosis and treatment for abdominal pain, diarrhea, leukocytosis with neutrophilia, and nonobstructive bowel gas pattern?

Diagnosis and Management of Acute Infectious Colitis

This presentation is most consistent with acute infectious colitis, likely bacterial enterocolitis, and requires immediate stool testing for bacterial pathogens (including C. difficile), empiric broad-spectrum antibiotics, and CT imaging to exclude complications such as toxic megacolon or perforation.

Clinical Assessment

The combination of abdominal pain, diarrhea, and leukocytosis (WBC 13.1 with neutrophilia 10.1) strongly suggests an invasive bacterial pathogen rather than viral or parasitic etiology 1. Neutrophilia with elevated total white blood cell count is characteristic of invasive bacterial pathogens, while viral etiologies typically present with normal WBC counts and lymphocytic predominance 1. The nonobstructive bowel gas pattern on X-ray does not exclude serious pathology but indicates the need for more sensitive imaging 1.

Key Diagnostic Considerations

• Bacterial enterocolitis (Salmonella, Shigella, Yersinia, Campylobacter) presents with watery, mucoid, or bloody diarrhea, abdominal tenderness, fever, and neutrophilia 1
• C. difficile infection (CDI) must be ruled out immediately, as it can present with abdominal pain, diarrhea, fever, and leukocytosis—even with minimal or absent diarrhea in severe cases 1, 2, 3
• Neutropenic enterocolitis is unlikely given the elevated (not decreased) neutrophil count, but should be considered if the patient has recent chemotherapy exposure 1

The association of neutrophil count >9.0 × 10⁹/L with the clinical presentation has 94.9% specificity for severe infectious or surgical illness requiring urgent intervention 4.

Immediate Diagnostic Workup

Laboratory Testing

• Stool studies should be collected immediately and include:

  • C. difficile toxin A and B testing (enzyme immunoassay or PCR) 1
  • Bacterial stool culture for Salmonella, Shigella, Yersinia, and Campylobacter 1
  • Fecal lactoferrin or microscopy for leukocytes to document colonic inflammation 1

• Additional blood work should include:

  • Complete metabolic panel to assess electrolyte disturbances and renal function 1
  • C-reactive protein and procalcitonin to assess severity of inflammation 1
  • Blood cultures if fever is present 1

Imaging Studies

Contrast-enhanced CT scan of the abdomen and pelvis is strongly recommended rather than relying on plain X-ray alone 1. CT imaging is critical to:

• Detect bowel wall thickening (>4-5 mm suggests colitis) 1
• Identify complications including toxic megacolon, perforation, or free intraperitoneal air 1
• Differentiate between infectious colitis and other causes (ischemic colitis, inflammatory bowel disease) 1

Plain abdominal radiographs have limited sensitivity and can miss significant pathology, particularly in early or moderate disease 1.

Empiric Treatment Strategy

Antibiotic Therapy

Empiric broad-spectrum antibiotics should be initiated immediately while awaiting culture results, given the leukocytosis and clinical presentation suggesting bacterial infection 1, 5:

• For suspected C. difficile infection with moderate-to-severe disease: Oral vancomycin 125 mg four times daily for 10 days OR oral fidaxomicin 200 mg twice daily for 10 days 1

  • If oral administration is not possible, IV metronidazole 500 mg three times daily can be used 1, 3

• For suspected bacterial enterocolitis (Salmonella, Shigella, Yersinia, Campylobacter):

  • Ciprofloxacin 500 mg twice daily OR azithromycin 500 mg daily (preferred for Campylobacter due to fluoroquinolone resistance) 1
  • For severe disease with systemic symptoms: Third-generation cephalosporin (ceftriaxone 1-2g daily) plus metronidazole 500 mg three times daily 1, 5

• If both CDI and bacterial enterocolitis cannot be excluded: Cover both empirically with vancomycin plus ciprofloxacin or ceftriaxone 1

Supportive Care

• Intravenous fluid resuscitation to correct dehydration and electrolyte abnormalities 1, 5
• Avoid antiperistaltic agents (loperamide, opiates) as they may precipitate toxic megacolon 1
• Bowel rest may be considered in severe cases 1

Critical Red Flags Requiring Urgent Intervention

Immediate surgical consultation is mandatory if any of the following develop 1, 6:

• Signs of peritonitis (rebound tenderness, guarding, rigidity)
• Bowel wall thickening >10 mm on imaging (associated with 60% mortality in neutropenic enterocolitis) 1
• Evidence of perforation (free air on imaging)
• Toxic megacolon (colonic dilation >6 cm with systemic toxicity)
• Persistent gastrointestinal bleeding despite correction of coagulopathy
• Clinical deterioration despite 24-48 hours of appropriate medical therapy

Common Pitfalls to Avoid

• Do not dismiss the diagnosis based on nonobstructive bowel gas pattern alone—plain X-rays are insensitive for early colitis and complications 1
• Do not delay CT imaging in patients with leukocytosis and abdominal pain—early detection of complications significantly improves outcomes 1
• Do not assume C. difficile is excluded by absence of severe diarrhea—CDI can present with minimal diarrhea but severe abdominal distention and systemic toxicity 1, 2, 3
• Do not withhold empiric antibiotics while awaiting culture results in patients with leukocytosis and systemic symptoms 1
• Do not use antiperistaltic agents as they increase risk of toxic megacolon and perforation 1

Follow-Up and De-escalation

Once culture and sensitivity results return, antibiotics should be narrowed to the most appropriate targeted therapy 1. Clinical improvement should be evident within 48-72 hours of appropriate treatment. If symptoms persist or worsen despite empiric therapy, consider:

• Repeat imaging to assess for complications 1
• Endoscopic evaluation (colonoscopy or sigmoidoscopy) to visualize mucosa and obtain biopsies—but colonoscopy is contraindicated if toxic megacolon or perforation is suspected 1
• Alternative diagnoses including inflammatory bowel disease, ischemic colitis, or medication-induced colitis 1